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Panasci SE, Deretzis I, Schilirò E, La Magna A, Roccaforte F, Koos A, Nemeth M, Pécz B, Cannas M, Agnello S, Giannazzo F. Interface Properties of MoS 2 van der Waals Heterojunctions with GaN. Nanomaterials (Basel) 2024; 14:133. [PMID: 38251098 PMCID: PMC10818867 DOI: 10.3390/nano14020133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/27/2023] [Accepted: 01/03/2024] [Indexed: 01/23/2024]
Abstract
The combination of the unique physical properties of molybdenum disulfide (MoS2) with those of gallium nitride (GaN) and related group-III nitride semiconductors have recently attracted increasing scientific interest for the realization of innovative electronic and optoelectronic devices. A deep understanding of MoS2/GaN interface properties represents the key to properly tailor the electronic and optical behavior of devices based on this heterostructure. In this study, monolayer (1L) MoS2 was grown on GaN-on-sapphire substrates by chemical vapor deposition (CVD) at 700 °C. The structural, chemical, vibrational, and light emission properties of the MoS2/GaN heterostructure were investigated in detail by the combination of microscopic/spectroscopic techniques and ab initio calculations. XPS analyses on as-grown samples showed the formation of stoichiometric MoS2. According to micro-Raman spectroscopy, monolayer MoS2 domains on GaN exhibit an average n-type doping of (0.11 ± 0.12) × 1013 cm-2 and a small tensile strain (ε ≈ 0.25%), whereas an intense light emission at 1.87 eV was revealed by PL analyses. Furthermore, a gap at the interface was shown by cross-sectional TEM analysis, confirming the van der Waals (vdW) bond between MoS2 and GaN. Finally, density functional theory (DFT) calculations of the heterostructure were carried out, considering three different configurations of the interface, i.e., (i) an ideal Ga-terminated GaN surface, (ii) the passivation of Ga surface by a monolayer of oxygen (O), and (iii) the presence of an ultrathin Ga2O3 layer. This latter model predicts the formation of a vdW interface and a strong n-type doping of MoS2, in closer agreement with the experimental observations.
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Affiliation(s)
- Salvatore Ethan Panasci
- National Research Council-Institute for Microelectronics and Microsystems (CNR-IMM), Z.I. Strada VIII 5, 95121 Catania, Italy; (I.D.); (E.S.); (A.L.M.); (F.R.); (S.A.); (F.G.)
| | - Ioannis Deretzis
- National Research Council-Institute for Microelectronics and Microsystems (CNR-IMM), Z.I. Strada VIII 5, 95121 Catania, Italy; (I.D.); (E.S.); (A.L.M.); (F.R.); (S.A.); (F.G.)
| | - Emanuela Schilirò
- National Research Council-Institute for Microelectronics and Microsystems (CNR-IMM), Z.I. Strada VIII 5, 95121 Catania, Italy; (I.D.); (E.S.); (A.L.M.); (F.R.); (S.A.); (F.G.)
| | - Antonino La Magna
- National Research Council-Institute for Microelectronics and Microsystems (CNR-IMM), Z.I. Strada VIII 5, 95121 Catania, Italy; (I.D.); (E.S.); (A.L.M.); (F.R.); (S.A.); (F.G.)
| | - Fabrizio Roccaforte
- National Research Council-Institute for Microelectronics and Microsystems (CNR-IMM), Z.I. Strada VIII 5, 95121 Catania, Italy; (I.D.); (E.S.); (A.L.M.); (F.R.); (S.A.); (F.G.)
| | - Antal Koos
- HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege ut 29-33, 1121 Budapest, Hungary; (A.K.); (M.N.)
| | - Miklos Nemeth
- HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege ut 29-33, 1121 Budapest, Hungary; (A.K.); (M.N.)
| | - Béla Pécz
- HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege ut 29-33, 1121 Budapest, Hungary; (A.K.); (M.N.)
| | - Marco Cannas
- Department of Physics and Chemistry Emilio Segrè, University of Palermo, Via Archirafi 36, 90123 Palermo, Italy;
| | - Simonpietro Agnello
- National Research Council-Institute for Microelectronics and Microsystems (CNR-IMM), Z.I. Strada VIII 5, 95121 Catania, Italy; (I.D.); (E.S.); (A.L.M.); (F.R.); (S.A.); (F.G.)
- Department of Physics and Chemistry Emilio Segrè, University of Palermo, Via Archirafi 36, 90123 Palermo, Italy;
- ATEN Center, University of Palermo, Viale delle Scienze Ed. 18, 90128 Palermo, Italy
| | - Filippo Giannazzo
- National Research Council-Institute for Microelectronics and Microsystems (CNR-IMM), Z.I. Strada VIII 5, 95121 Catania, Italy; (I.D.); (E.S.); (A.L.M.); (F.R.); (S.A.); (F.G.)
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Španková M, Chromik Š, Dobročka E, Pribusová Slušná L, Talacko M, Gregor M, Pécz B, Koos A, Greco G, Panasci SE, Fiorenza P, Roccaforte F, Cordier Y, Frayssinet E, Giannazzo F. Large-Area MoS 2 Films Grown on Sapphire and GaN Substrates by Pulsed Laser Deposition. Nanomaterials (Basel) 2023; 13:2837. [PMID: 37947682 PMCID: PMC10647872 DOI: 10.3390/nano13212837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 10/19/2023] [Accepted: 10/24/2023] [Indexed: 11/12/2023]
Abstract
In this paper, we present the preparation of few-layer MoS2 films on single-crystal sapphire, as well as on heteroepitaxial GaN templates on sapphire substrates, using the pulsed laser deposition (PLD) technique. Detailed structural and chemical characterization of the films were performed using Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction measurements, and high-resolution transmission electron microscopy. According to X-ray diffraction studies, the films exhibit epitaxial growth, indicating a good in-plane alignment. Furthermore, the films demonstrate uniform thickness on large areas, as confirmed by Raman spectroscopy. The lateral electrical current transport of the MoS2 grown on sapphire was investigated by temperature (T)-dependent sheet resistance and Hall effect measurements, showing a high n-type doping of the semiconducting films (ns from ~1 × 1013 to ~3.4 × 1013 cm-2 from T = 300 K to 500 K), with a donor ionization energy of Ei = 93 ± 8 meV and a mobility decreasing with T. Finally, the vertical current injection across the MoS2/GaN heterojunction was investigated by means of conductive atomic force microscopy, showing the rectifying behavior of the I-V characteristics with a Schottky barrier height of ϕB ≈ 0.36 eV. The obtained results pave the way for the scalable application of PLD-grown MoS2 on GaN in electronics/optoelectronics.
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Affiliation(s)
- Marianna Španková
- Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 84104 Bratislava, Slovakia; (Š.C.); (E.D.); (L.P.S.); (M.T.)
| | - Štefan Chromik
- Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 84104 Bratislava, Slovakia; (Š.C.); (E.D.); (L.P.S.); (M.T.)
| | - Edmund Dobročka
- Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 84104 Bratislava, Slovakia; (Š.C.); (E.D.); (L.P.S.); (M.T.)
| | - Lenka Pribusová Slušná
- Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 84104 Bratislava, Slovakia; (Š.C.); (E.D.); (L.P.S.); (M.T.)
| | - Marcel Talacko
- Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 84104 Bratislava, Slovakia; (Š.C.); (E.D.); (L.P.S.); (M.T.)
| | - Maroš Gregor
- Faculty of Mathematics, Physics and Informatics, Comenius University Bratislava, 84248 Bratislava, Slovakia;
| | - Béla Pécz
- HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege ut 29-33, 1121 Budapest, Hungary; (B.P.); (A.K.)
| | - Antal Koos
- HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege ut 29-33, 1121 Budapest, Hungary; (B.P.); (A.K.)
| | - Giuseppe Greco
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (G.G.); (S.E.P.); (P.F.); (F.R.); (F.G.)
| | - Salvatore Ethan Panasci
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (G.G.); (S.E.P.); (P.F.); (F.R.); (F.G.)
| | - Patrick Fiorenza
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (G.G.); (S.E.P.); (P.F.); (F.R.); (F.G.)
| | - Fabrizio Roccaforte
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (G.G.); (S.E.P.); (P.F.); (F.R.); (F.G.)
| | - Yvon Cordier
- CNRS, CRHEA, Université Côte d’Azur, 06560 Valbonne, France; (Y.C.); (E.F.)
| | - Eric Frayssinet
- CNRS, CRHEA, Université Côte d’Azur, 06560 Valbonne, France; (Y.C.); (E.F.)
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (G.G.); (S.E.P.); (P.F.); (F.R.); (F.G.)
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Schilirò E, Fiorenza P, Lo Nigro R, Galizia B, Greco G, Di Franco S, Bongiorno C, La Via F, Giannazzo F, Roccaforte F. Al 2O 3 Layers Grown by Atomic Layer Deposition as Gate Insulator in 3C-SiC MOS Devices. Materials (Basel) 2023; 16:5638. [PMID: 37629929 PMCID: PMC10456437 DOI: 10.3390/ma16165638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 08/10/2023] [Accepted: 08/14/2023] [Indexed: 08/27/2023]
Abstract
Metal-oxide-semiconductor (MOS) capacitors with Al2O3 as a gate insulator are fabricated on cubic silicon carbide (3C-SiC). Al2O3 is deposited both by thermal and plasma-enhanced Atomic Layer Deposition (ALD) on a thermally grown 5 nm SiO2 interlayer to improve the ALD nucleation and guarantee a better band offset with the SiC. The deposited Al2O3/SiO2 stacks show lower negative shifts of the flat band voltage VFB (in the range of about -3 V) compared with the conventional single SiO2 layer (in the range of -9 V). This lower negative shift is due to the combined effect of the Al2O3 higher permittivity (ε = 8) and to the reduced amount of carbon defects generated during the short thermal oxidation process for the thin SiO2. Moreover, the comparison between thermal and plasma-enhanced ALD suggests that this latter approach produces Al2O3 layers possessing better insulating behavior in terms of distribution of the leakage current breakdown. In fact, despite both possessing a breakdown voltage of 26 V, the T-ALD Al2O3 sample is characterised by a higher current density starting from 15 V. This can be attributable to the slightly inferior quality (in terms of density and defects) of Al2O3 obtained by the thermal approach and, which also explains its non-uniform dC/dV distribution arising by SCM maps.
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Affiliation(s)
- Emanuela Schilirò
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, Zona Industriale, 95121 Catania, Italy; (P.F.); (R.L.N.); (B.G.); (G.G.); (S.D.F.); (C.B.); (F.L.V.); (F.G.); (F.R.)
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La Via F, Alquier D, Giannazzo F, Kimoto T, Neudeck P, Ou H, Roncaglia A, Saddow SE, Tudisco S. Emerging SiC Applications beyond Power Electronic Devices. Micromachines (Basel) 2023; 14:1200. [PMID: 37374785 DOI: 10.3390/mi14061200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 06/29/2023]
Abstract
In recent years, several new applications of SiC (both 4H and 3C polytypes) have been proposed in different papers. In this review, several of these emerging applications have been reported to show the development status, the main problems to be solved and the outlooks for these new devices. The use of SiC for high temperature applications in space, high temperature CMOS, high radiation hard detectors, new optical devices, high frequency MEMS, new devices with integrated 2D materials and biosensors have been extensively reviewed in this paper. The development of these new applications, at least for the 4H-SiC ones, has been favored by the strong improvement in SiC technology and in the material quality and price, due to the increasing market for power devices. However, at the same time, these new applications need the development of new processes and the improvement of material properties (high temperature packages, channel mobility and threshold voltage instability improvement, thick epitaxial layers, low defects, long carrier lifetime, low epitaxial doping). Instead, in the case of 3C-SiC applications, several new projects have developed material processes to obtain more performing MEMS, photonics and biomedical devices. Despite the good performance of these devices and the potential market, the further development of the material and of the specific processes and the lack of several SiC foundries for these applications are limiting further development in these fields.
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Affiliation(s)
| | - Daniel Alquier
- GREMAN, UMR 7347, Université de Tours, CNRS, 37071 Tours, France
| | | | - Tsunenobu Kimoto
- Department of Electronic Science and Engineering, Kyoto University, Nishikyo, Kyoto 615-8510, Japan
| | - Philip Neudeck
- NASA Glenn Research Center, 21000 Brookpark Rd., Cleveland, OH 44135, USA
| | - Haiyan Ou
- Department of Electrical and Photonics Engineering, Technical University of Denmark, Ørsteds Plads, Building 343, DK-2800 Kgs. Lyngby, Denmark
| | | | - Stephen E Saddow
- Electrical Engineering Department, University of South Florida, 4202 E. Fowler Avenue, ENG 030, Tampa, FL 33620, USA
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Panasci SE, Schilirò E, Greco G, Cannas M, Gelardi FM, Agnello S, Roccaforte F, Giannazzo F. Correction to "Strain, Doping, and Electronic Transport of Large Area Monolayer MoS 2 Exfoliated on Gold and Transferred to an Insulating Substrate". ACS Appl Mater Interfaces 2022; 14:36287. [PMID: 35905500 PMCID: PMC9376920 DOI: 10.1021/acsami.2c12608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Indexed: 06/15/2023]
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Shtepliuk I, Vagin M, Khan Z, Zakharov AA, Iakimov T, Giannazzo F, Ivanov IG, Yakimova R. Understanding of the Electrochemical Behavior of Lithium at Bilayer-Patched Epitaxial Graphene/4H-SiC. Nanomaterials 2022; 12:nano12132229. [PMID: 35808065 PMCID: PMC9268403 DOI: 10.3390/nano12132229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 06/27/2022] [Accepted: 06/28/2022] [Indexed: 02/01/2023]
Abstract
Novel two-dimensional materials (2DMs) with balanced electrical conductivity and lithium (Li) storage capacity are desirable for next-generation rechargeable batteries as they may serve as high-performance anodes, improving output battery characteristics. Gaining an advanced understanding of the electrochemical behavior of lithium at the electrode surface and the changes in interior structure of 2DM-based electrodes caused by lithiation is a key component in the long-term process of the implementation of new electrodes into to a realistic device. Here, we showcase the advantages of bilayer-patched epitaxial graphene on 4H-SiC (0001) as a possible anode material in lithium-ion batteries. The presence of bilayer graphene patches is beneficial for the overall lithiation process because it results in enhanced quantum capacitance of the electrode and provides extra intercalation paths. By performing cyclic voltammetry and chronoamperometry measurements, we shed light on the redox behavior of lithium at the bilayer-patched epitaxial graphene electrode and find that the early-stage growth of lithium is governed by the instantaneous nucleation mechanism. The results also demonstrate the fast lithium-ion transport (~4.7–5.6 × 10−7 cm2∙s−1) to the bilayer-patched epitaxial graphene electrode. Raman measurements complemented by in-depth statistical analysis and density functional theory calculations enable us to comprehend the lithiation effect on the properties of bilayer-patched epitaxial graphene and ascribe the lithium intercalation-induced Raman G peak splitting to the disparity between graphene layers. The current results are helpful for further advancement of the design of graphene-based electrodes with targeted performance.
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Affiliation(s)
- Ivan Shtepliuk
- Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden; (T.I.); (I.G.I.); (R.Y.)
- Correspondence: ; Tel.: +46-766-524-089
| | - Mikhail Vagin
- Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, SE-60174 Norrköping, Sweden; (M.V.); (Z.K.)
| | - Ziyauddin Khan
- Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, SE-60174 Norrköping, Sweden; (M.V.); (Z.K.)
| | - Alexei A. Zakharov
- MAX IV Laboratory, Lund University, Fotongatan 2, SE-22484 Lund, Sweden;
| | - Tihomir Iakimov
- Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden; (T.I.); (I.G.I.); (R.Y.)
| | | | - Ivan G. Ivanov
- Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden; (T.I.); (I.G.I.); (R.Y.)
| | - Rositsa Yakimova
- Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden; (T.I.); (I.G.I.); (R.Y.)
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Panasci SE, Koos A, Schilirò E, Di Franco S, Greco G, Fiorenza P, Roccaforte F, Agnello S, Cannas M, Gelardi FM, Sulyok A, Nemeth M, Pécz B, Giannazzo F. Multiscale Investigation of the Structural, Electrical and Photoluminescence Properties of MoS 2 Obtained by MoO 3 Sulfurization. Nanomaterials (Basel) 2022; 12:182. [PMID: 35055201 PMCID: PMC8778062 DOI: 10.3390/nano12020182] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 01/01/2022] [Accepted: 01/03/2022] [Indexed: 01/27/2023]
Abstract
In this paper, we report a multiscale investigation of the compositional, morphological, structural, electrical, and optical emission properties of 2H-MoS2 obtained by sulfurization at 800 °C of very thin MoO3 films (with thickness ranging from ~2.8 nm to ~4.2 nm) on a SiO2/Si substrate. XPS analyses confirmed that the sulfurization was very effective in the reduction of the oxide to MoS2, with only a small percentage of residual MoO3 present in the final film. High-resolution TEM/STEM analyses revealed the formation of few (i.e., 2-3 layers) of MoS2 nearly aligned with the SiO2 surface in the case of the thinnest (~2.8 nm) MoO3 film, whereas multilayers of MoS2 partially standing up with respect to the substrate were observed for the ~4.2 nm one. Such different configurations indicate the prevalence of different mechanisms (i.e., vapour-solid surface reaction or S diffusion within the film) as a function of the thickness. The uniform thickness distribution of the few-layer and multilayer MoS2 was confirmed by Raman mapping. Furthermore, the correlative plot of the characteristic A1g-E2g Raman modes revealed a compressive strain (ε ≈ -0.78 ± 0.18%) and the coexistence of n- and p-type doped areas in the few-layer MoS2 on SiO2, where the p-type doping is probably due to the presence of residual MoO3. Nanoscale resolution current mapping by C-AFM showed local inhomogeneities in the conductivity of the few-layer MoS2, which are well correlated to the lateral changes in the strain detected by Raman. Finally, characteristic spectroscopic signatures of the defects/disorder in MoS2 films produced by sulfurization were identified by a comparative analysis of Raman and photoluminescence (PL) spectra with CVD grown MoS2 flakes.
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Affiliation(s)
- Salvatore E. Panasci
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (S.E.P.); (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.); (S.A.)
- Department of Physics and Astronomy, University of Catania, 95123 Catania, Italy
| | - Antal Koos
- Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege ut 29-33, 1121 Budapest, Hungary; (A.K.); (A.S.); (M.N.)
| | - Emanuela Schilirò
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (S.E.P.); (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.); (S.A.)
| | - Salvatore Di Franco
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (S.E.P.); (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.); (S.A.)
| | - Giuseppe Greco
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (S.E.P.); (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.); (S.A.)
| | - Patrick Fiorenza
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (S.E.P.); (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.); (S.A.)
| | - Fabrizio Roccaforte
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (S.E.P.); (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.); (S.A.)
| | - Simonpietro Agnello
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (S.E.P.); (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.); (S.A.)
- Department of Physics and Chemistry Emilio Segrè, University of Palermo, 90123 Palermo, Italy; (M.C.); (F.M.G.)
- ATEN Center, University of Palermo, 90123 Palermo, Italy
| | - Marco Cannas
- Department of Physics and Chemistry Emilio Segrè, University of Palermo, 90123 Palermo, Italy; (M.C.); (F.M.G.)
| | - Franco M. Gelardi
- Department of Physics and Chemistry Emilio Segrè, University of Palermo, 90123 Palermo, Italy; (M.C.); (F.M.G.)
| | - Attila Sulyok
- Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege ut 29-33, 1121 Budapest, Hungary; (A.K.); (A.S.); (M.N.)
| | - Miklos Nemeth
- Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege ut 29-33, 1121 Budapest, Hungary; (A.K.); (A.S.); (M.N.)
| | - Béla Pécz
- Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege ut 29-33, 1121 Budapest, Hungary; (A.K.); (A.S.); (M.N.)
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche—Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, 95121 Catania, Italy; (S.E.P.); (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.); (S.A.)
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Vivona M, Giannazzo F, Roccaforte F. Materials and Processes for Schottky Contacts on Silicon Carbide. Materials (Basel) 2021; 15:ma15010298. [PMID: 35009445 PMCID: PMC8745973 DOI: 10.3390/ma15010298] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/15/2021] [Accepted: 12/22/2021] [Indexed: 11/25/2022]
Abstract
Silicon carbide (4H-SiC) Schottky diodes have reached a mature level of technology and are today essential elements in many applications of power electronics. In this context, the study of Schottky barriers on 4H-SiC is of primary importance, since a deeper understanding of the metal/4H-SiC interface is the prerequisite to improving the electrical properties of these devices. To this aim, over the last three decades, many efforts have been devoted to developing the technology for 4H-SiC-based Schottky diodes. In this review paper, after a brief introduction to the fundamental properties and electrical characterization of metal/4H-SiC Schottky barriers, an overview of the best-established materials and processing for the fabrication of Schottky contacts to 4H-SiC is given. Afterwards, besides the consolidated approaches, a variety of nonconventional methods proposed in literature to control the Schottky barrier properties for specific applications is presented. Besides the possibility of gaining insight into the physical characteristics of the Schottky contact, this subject is of particular interest for the device makers, in order to develop a new class of Schottky diodes with superior characteristics.
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Schilirò E, Giannazzo F, Di Franco S, Greco G, Fiorenza P, Roccaforte F, Prystawko P, Kruszewski P, Leszczynski M, Cora I, Pécz B, Fogarassy Z, Lo Nigro R. Highly Homogeneous Current Transport in Ultra-Thin Aluminum Nitride (AlN) Epitaxial Films on Gallium Nitride (GaN) Deposited by Plasma Enhanced Atomic Layer Deposition. Nanomaterials (Basel) 2021; 11:3316. [PMID: 34947665 PMCID: PMC8709117 DOI: 10.3390/nano11123316] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 11/19/2021] [Accepted: 12/03/2021] [Indexed: 11/25/2022]
Abstract
This paper reports an investigation of the structural, chemical and electrical properties of ultra-thin (5 nm) aluminum nitride (AlN) films grown by plasma enhanced atomic layer deposition (PE-ALD) on gallium nitride (GaN). A uniform and conformal coverage of the GaN substrate was demonstrated by morphological analyses of as-deposited AlN films. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) analyses showed a sharp epitaxial interface with GaN for the first AlN atomic layers, while a deviation from the perfect wurtzite stacking and oxygen contamination were detected in the upper part of the film. This epitaxial interface resulted in the formation of a two-dimensional electron gas (2DEG) with a sheet charge density ns ≈ 1.45 × 1012 cm-2, revealed by Hg-probe capacitance-voltage (C-V) analyses. Nanoscale resolution current mapping and current-voltage (I-V) measurements by conductive atomic force microscopy (C-AFM) showed a highly homogeneous current transport through the 5 nm AlN barrier, while a uniform flat-band voltage (VFB ≈ 0.3 V) for the AlN/GaN heterostructure was demonstrated by scanning capacitance microscopy (SCM). Electron transport through the AlN film was shown to follow the Fowler-Nordheim (FN) tunneling mechanism with an average barrier height of <ΦB> = 2.08 eV, in good agreement with the expected AlN/GaN conduction band offset.
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Affiliation(s)
- Emanuela Schilirò
- CNR-IMM, Strada VIII, 5, 95121 Catania, Italy; (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.)
| | - Filippo Giannazzo
- CNR-IMM, Strada VIII, 5, 95121 Catania, Italy; (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.)
| | - Salvatore Di Franco
- CNR-IMM, Strada VIII, 5, 95121 Catania, Italy; (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.)
| | - Giuseppe Greco
- CNR-IMM, Strada VIII, 5, 95121 Catania, Italy; (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.)
| | - Patrick Fiorenza
- CNR-IMM, Strada VIII, 5, 95121 Catania, Italy; (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.)
| | - Fabrizio Roccaforte
- CNR-IMM, Strada VIII, 5, 95121 Catania, Italy; (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.)
| | - Paweł Prystawko
- Top-GaN Ltd., Sokolowska 29/37, 01-142 Warsaw, Poland; (P.P.); (P.K.); (M.L.)
- Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw, Poland
| | - Piotr Kruszewski
- Top-GaN Ltd., Sokolowska 29/37, 01-142 Warsaw, Poland; (P.P.); (P.K.); (M.L.)
- Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw, Poland
| | - Mike Leszczynski
- Top-GaN Ltd., Sokolowska 29/37, 01-142 Warsaw, Poland; (P.P.); (P.K.); (M.L.)
- Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw, Poland
| | - Ildiko Cora
- Centre for Energy Research, Institute for Technical Physics and Materials Science Research, Konkoly-Thege, 29-33, 1121 Budapest, Hungary; (I.C.); (B.P.); (Z.F.)
| | - Béla Pécz
- Centre for Energy Research, Institute for Technical Physics and Materials Science Research, Konkoly-Thege, 29-33, 1121 Budapest, Hungary; (I.C.); (B.P.); (Z.F.)
| | - Zsolt Fogarassy
- Centre for Energy Research, Institute for Technical Physics and Materials Science Research, Konkoly-Thege, 29-33, 1121 Budapest, Hungary; (I.C.); (B.P.); (Z.F.)
| | - Raffaella Lo Nigro
- CNR-IMM, Strada VIII, 5, 95121 Catania, Italy; (E.S.); (S.D.F.); (G.G.); (P.F.); (F.R.)
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10
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Via FL, Zimbone M, Bongiorno C, La Magna A, Fisicaro G, Deretzis I, Scuderi V, Calabretta C, Giannazzo F, Zielinski M, Anzalone R, Mauceri M, Crippa D, Scalise E, Marzegalli A, Sarikov A, Miglio L, Jokubavicius V, Syväjärvi M, Yakimova R, Schuh P, Schöler M, Kollmuss M, Wellmann P. New Approaches and Understandings in the Growth of Cubic Silicon Carbide. Materials (Basel) 2021; 14:ma14185348. [PMID: 34576572 PMCID: PMC8465050 DOI: 10.3390/ma14185348] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 08/30/2021] [Accepted: 09/07/2021] [Indexed: 11/22/2022]
Abstract
In this review paper, several new approaches about the 3C-SiC growth are been presented. In fact, despite the long research activity on 3C-SiC, no devices with good electrical characteristics have been obtained due to the high defect density and high level of stress. To overcome these problems, two different approaches have been used in the last years. From one side, several compliance substrates have been used to try to reduce both the defects and stress, while from another side, the first bulk growth has been performed to try to improve the quality of this material with respect to the heteroepitaxial one. From all these studies, a new understanding of the material defects has been obtained, as well as regarding all the interactions between defects and several growth parameters. This new knowledge will be the basis to solve the main issue of the 3C-SiC growth and reach the goal to obtain a material with low defects and low stress that would allow for realizing devices with extremely interesting characteristics.
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Affiliation(s)
- Francesco La Via
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronice e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (M.Z.); (C.B.); (A.L.M.); (G.F.); (I.D.); (V.S.); (C.C.); (F.G.)
- Correspondence: (F.L.V.); (P.W.)
| | - Massimo Zimbone
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronice e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (M.Z.); (C.B.); (A.L.M.); (G.F.); (I.D.); (V.S.); (C.C.); (F.G.)
| | - Corrado Bongiorno
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronice e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (M.Z.); (C.B.); (A.L.M.); (G.F.); (I.D.); (V.S.); (C.C.); (F.G.)
| | - Antonino La Magna
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronice e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (M.Z.); (C.B.); (A.L.M.); (G.F.); (I.D.); (V.S.); (C.C.); (F.G.)
| | - Giuseppe Fisicaro
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronice e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (M.Z.); (C.B.); (A.L.M.); (G.F.); (I.D.); (V.S.); (C.C.); (F.G.)
| | - Ioannis Deretzis
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronice e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (M.Z.); (C.B.); (A.L.M.); (G.F.); (I.D.); (V.S.); (C.C.); (F.G.)
| | - Viviana Scuderi
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronice e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (M.Z.); (C.B.); (A.L.M.); (G.F.); (I.D.); (V.S.); (C.C.); (F.G.)
| | - Cristiano Calabretta
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronice e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (M.Z.); (C.B.); (A.L.M.); (G.F.); (I.D.); (V.S.); (C.C.); (F.G.)
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronice e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (M.Z.); (C.B.); (A.L.M.); (G.F.); (I.D.); (V.S.); (C.C.); (F.G.)
| | - Marcin Zielinski
- NOVASIC, Savoie Technolac—Arche Bat.4, Allée du Lac d’Aiguebelette, BP 267, 73375 Le Bourget du Lac CEDEX, France;
| | - Ruggero Anzalone
- STMicroelectronics, Stradale Primosole 50, 95121 Catania, Italy;
| | - Marco Mauceri
- LPE, Strada XVI, Pantano d’Arci, 95121 Catania, Italy; (M.M.); (D.C.)
| | - Danilo Crippa
- LPE, Strada XVI, Pantano d’Arci, 95121 Catania, Italy; (M.M.); (D.C.)
| | - Emilio Scalise
- L-NESS and Department of Materials Science, Università di Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, Italy; (E.S.); (A.S.); (L.M.)
| | - Anna Marzegalli
- L-NESS and Department of Physics, Politecnico di Milano, via Anzani 42, 22100 Como, Italy;
| | - Andrey Sarikov
- L-NESS and Department of Materials Science, Università di Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, Italy; (E.S.); (A.S.); (L.M.)
| | - Leo Miglio
- L-NESS and Department of Materials Science, Università di Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, Italy; (E.S.); (A.S.); (L.M.)
| | - Valdas Jokubavicius
- Department of Physics, Chemistry, and Biology (IFM), Linköping University, 581 83 Linköping, Sweden; (V.J.); (M.S.); (R.Y.)
| | - Mikael Syväjärvi
- Department of Physics, Chemistry, and Biology (IFM), Linköping University, 581 83 Linköping, Sweden; (V.J.); (M.S.); (R.Y.)
| | - Rositsa Yakimova
- Department of Physics, Chemistry, and Biology (IFM), Linköping University, 581 83 Linköping, Sweden; (V.J.); (M.S.); (R.Y.)
| | - Philipp Schuh
- Crystal Growth Lab, Materials Department 6 (i-MEET), Friedrich-Alexander University Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany; (P.S.); (M.S.); (M.K.)
| | - Michael Schöler
- Crystal Growth Lab, Materials Department 6 (i-MEET), Friedrich-Alexander University Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany; (P.S.); (M.S.); (M.K.)
| | - Manuel Kollmuss
- Crystal Growth Lab, Materials Department 6 (i-MEET), Friedrich-Alexander University Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany; (P.S.); (M.S.); (M.K.)
| | - Peter Wellmann
- Crystal Growth Lab, Materials Department 6 (i-MEET), Friedrich-Alexander University Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany; (P.S.); (M.S.); (M.K.)
- Correspondence: (F.L.V.); (P.W.)
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11
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Seravalli L, Bosi M, Fiorenza P, Panasci SE, Orsi D, Rotunno E, Cristofolini L, Rossi F, Giannazzo F, Fabbri F. Gold nanoparticle assisted synthesis of MoS 2 monolayers by chemical vapor deposition. Nanoscale Adv 2021; 3:4826-4833. [PMID: 36134320 PMCID: PMC9418562 DOI: 10.1039/d1na00367d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 06/30/2021] [Indexed: 06/16/2023]
Abstract
The use of metal nanoparticles is an established paradigm for the synthesis of semiconducting one-dimensional nanostructures. In this work we study their effect on the synthesis of two-dimensional semiconducting materials, by using gold nanoparticles for chemical vapor deposition growth of two-dimensional molybdenum disulfide (MoS2). In comparison with the standard method, the employment of gold nanoparticles allows us to obtain large monolayer MoS2 flakes, up to 20 μm in lateral size, even if they are affected by the localized overgrowth of MoS2 bilayer and trilayer islands. Important modifications of the optical and electronic properties of MoS2 triangular domains are reported, where the photoluminescence intensity of the A exciton is strongly quenched and a shift to a positive threshold voltage in back-gated field effect transistors is observed. These results indicate that the use of gold nanoparticles influences the flake growth and properties, indicating a method for possible localized synthesis of two-dimensional materials, improving the lateral size of monolayers and modifying their properties.
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Affiliation(s)
- L Seravalli
- Institute for Materials for Electronics and Magnetism (IMEM-CNR) Parco Area delle Scienze 37/a 43124 Parma Italy
| | - M Bosi
- Institute for Materials for Electronics and Magnetism (IMEM-CNR) Parco Area delle Scienze 37/a 43124 Parma Italy
| | - P Fiorenza
- Institute for Microelectronics and Microsystems (CNR-IMM) Z. I. VIII Strada 5 95121 Catania Italy
| | - S E Panasci
- Institute for Microelectronics and Microsystems (CNR-IMM) Z. I. VIII Strada 5 95121 Catania Italy
| | - D Orsi
- Department of Mathematical, Physical and Computer Sciences, University of Parma Parco Area delle Scienze 7/a 43124 Parma Italy
| | - E Rotunno
- Istituto Nanoscienze-CNR via G Campi 213/a 41125 Modena Italy
| | - L Cristofolini
- Department of Mathematical, Physical and Computer Sciences, University of Parma Parco Area delle Scienze 7/a 43124 Parma Italy
| | - F Rossi
- Institute for Materials for Electronics and Magnetism (IMEM-CNR) Parco Area delle Scienze 37/a 43124 Parma Italy
| | - F Giannazzo
- Institute for Microelectronics and Microsystems (CNR-IMM) Z. I. VIII Strada 5 95121 Catania Italy
| | - F Fabbri
- NEST, Istituto Nanoscienze - CNR, Scuola Normale Superiore Piazza San Silvestro 12 56127 Pisa Italy
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12
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Roccaforte F, Fiorenza P, Vivona M, Greco G, Giannazzo F. Selective Doping in Silicon Carbide Power Devices. Materials (Basel) 2021; 14:ma14143923. [PMID: 34300845 PMCID: PMC8307042 DOI: 10.3390/ma14143923] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 07/06/2021] [Accepted: 07/11/2021] [Indexed: 11/16/2022]
Abstract
Silicon carbide (SiC) is the most mature wide band-gap semiconductor and is currently employed for the fabrication of high-efficiency power electronic devices, such as diodes and transistors. In this context, selective doping is one of the key processes needed for the fabrication of these devices. This paper concisely reviews the main selective doping techniques for SiC power devices technology. In particular, due to the low diffusivity of the main impurities in SiC, ion implantation is the method of choice to achieve selective doping of the material. Hence, most of this work is dedicated to illustrating the main features of n-type and p-type ion-implantation doping of SiC and discussing the related issues. As an example, one of the main features of implantation doping is the need for post-implantation annealing processes at high temperatures (above 1500 °C) for electrical activation, thus having a notable morphological and structural impact on the material and, hence, on some device parameters. In this respect, some specific examples elucidating the relevant implications on devices’ performances are reported in the paper. Finally, a short overview of recently developed non-conventional doping and annealing techniques is also provided, although these techniques are still far from being applied in large-scale devices’ manufacturing.
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13
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Panasci S, Schilirò E, Greco G, Cannas M, Gelardi FM, Agnello S, Roccaforte F, Giannazzo F. Strain, Doping, and Electronic Transport of Large Area Monolayer MoS 2 Exfoliated on Gold and Transferred to an Insulating Substrate. ACS Appl Mater Interfaces 2021; 13:31248-31259. [PMID: 34165956 PMCID: PMC9280715 DOI: 10.1021/acsami.1c05185] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Gold-assisted mechanical exfoliation currently represents a promising method to separate ultralarge (centimeter scale) transition metal dichalcogenide (TMD) monolayers (1L) with excellent electronic and optical properties from the parent van der Waals (vdW) crystals. The strong interaction between Au and chalcogen atoms is key to achieving this nearly perfect 1L exfoliation yield. On the other hand, it may significantly affect the doping and strain of 1L TMDs in contact with Au. In this paper, we systematically investigated the morphology, strain, doping, and electrical properties of large area 1L MoS2 exfoliated on ultraflat Au films (0.16-0.21 nm roughness) and finally transferred to an insulating Al2O3 substrate. Raman mapping and correlative analysis of the E' and A1' peak positions revealed a moderate tensile strain (ε ≈ 0.2%) and p-type doping (n ≈ -0.25 × 1013 cm-2) of 1L MoS2 in contact with Au. Nanoscale resolution current mapping and current-voltage (I-V) measurements by conductive atomic force microscopy (C-AFM) showed direct tunneling across the 1L MoS2 on Au, with a broad distribution of tunneling barrier values (ΦB from 0.7 to 1.7 eV) consistent with p-type doping of MoS2. After the final transfer of 1L MoS2 on Al2O3/Si, the strain was converted to compressive strain (ε ≈ -0.25%). Furthermore, an n-type doping (n ≈ 0.5 × 1013 cm-2) was deduced by Raman mapping and confirmed by electrical measurements of an Al2O3/Si back-gated 1L MoS2 transistor. These results provide a deeper understanding of the Au-assisted exfoliation mechanism and can contribute to its widespread application for the realization of novel devices and artificial vdW heterostructures.
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Affiliation(s)
- Salvatore
Ethan Panasci
- CNR-IMM, Strada VIII, 5 95121, Catania, Italy
- Department
of Physics and Astronomy, University of
Catania, Via Santa Sofia
64, 95123 Catania, Italy
| | | | | | - Marco Cannas
- Department
of Physics and Chemistry Emilio Segrè, University of Palermo, Via Archirafi 36, 90123 Palermo, Italy
| | - Franco M. Gelardi
- Department
of Physics and Chemistry Emilio Segrè, University of Palermo, Via Archirafi 36, 90123 Palermo, Italy
| | - Simonpietro Agnello
- CNR-IMM, Strada VIII, 5 95121, Catania, Italy
- Department
of Physics and Chemistry Emilio Segrè, University of Palermo, Via Archirafi 36, 90123 Palermo, Italy
- ATeN
Center, Università degli Studi di
Palermo, Viale delle
Scienze, Edificio 18, 90128 Palermo, Italy
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14
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Kakanakova-Georgieva A, Ivanov IG, Suwannaharn N, Hsu CW, Cora I, Pécz B, Giannazzo F, Sangiovanni DG, Gueorguiev GK. MOCVD of AlN on epitaxial graphene at extreme temperatures. CrystEngComm 2021. [DOI: 10.1039/d0ce01426e] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Appearance of luminescent centers with narrow spectral emission at room temperature in nanometer thin AlN is reported.
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Affiliation(s)
| | - Ivan G. Ivanov
- Department of Physics
- Chemistry and Biology (IFM)
- Linköping University
- 581 83 Linköping
- Sweden
| | - Nattamon Suwannaharn
- Department of Physics
- Chemistry and Biology (IFM)
- Linköping University
- 581 83 Linköping
- Sweden
| | - Chih-Wei Hsu
- Department of Physics
- Chemistry and Biology (IFM)
- Linköping University
- 581 83 Linköping
- Sweden
| | - Ildikó Cora
- Centre for Energy Research
- Institute of Technical Physics and Materials Science
- Budapest
- Hungary
| | - Béla Pécz
- Centre for Energy Research
- Institute of Technical Physics and Materials Science
- Budapest
- Hungary
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche
- Istituto per la Microelettronica e Microsistemi
- Catania
- Italy
| | - Davide G. Sangiovanni
- Department of Physics
- Chemistry and Biology (IFM)
- Linköping University
- 581 83 Linköping
- Sweden
| | - Gueorgui K. Gueorguiev
- Department of Physics
- Chemistry and Biology (IFM)
- Linköping University
- 581 83 Linköping
- Sweden
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15
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Pécz B, Nicotra G, Giannazzo F, Yakimova R, Koos A, Kakanakova-Georgieva A. Indium Nitride at the 2D Limit. Adv Mater 2021; 33:e2006660. [PMID: 33225494 DOI: 10.1002/adma.202006660] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/01/2020] [Indexed: 06/11/2023]
Abstract
The properties of 2D InN are predicted to substantially differ from the bulk crystal. The predicted appealing properties relate to strong in- and out-of-plane excitons, high electron mobility, efficient strain engineering of their electronic and optical properties, and strong application potential in gas sensing. Until now, the realization of 2D InN remained elusive. In this work, the formation of 2D InN and measurements of its bandgap are reported. Bilayer InN is formed between graphene and SiC by an intercalation process in metal-organic chemical vapor deposition (MOCVD). The thickness uniformity of the intercalated structure is investigated by conductive atomic force microscopy (C-AFM) and the structural properties by atomic resolution transmission electron microscopy (TEM). The coverage of the SiC surface is very high, above 90%, and a major part of the intercalated structure is represented by two sub-layers of indium (In) bonded to nitrogen (N). Scanning tunneling spectroscopy (STS) measurements give a bandgap value of 2 ± 0.1 eV for the 2D InN. The stabilization of 2D InN with a pragmatic wide bandgap and high lateral uniformity of intercalation is demonstrated.
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Affiliation(s)
- Béla Pécz
- Centre for Energy Research, Institute for Technical Physics and Materials Science, Konkoly-Thege M. út 29-33, Budapest, 1121, Hungary
| | - Giuseppe Nicotra
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Strada VIII, n. 5, Zona Industriale, Catania, I-95121, Italy
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Strada VIII, n. 5, Zona Industriale, Catania, I-95121, Italy
| | - Rositsa Yakimova
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, 581 83, Sweden
| | - Antal Koos
- Centre for Energy Research, Institute for Technical Physics and Materials Science, Konkoly-Thege M. út 29-33, Budapest, 1121, Hungary
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16
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Giannazzo F, Dagher R, Schilirò E, Panasci SE, Greco G, Nicotra G, Roccaforte F, Agnello S, Brault J, Cordier Y, Michon A. Nanoscale structural and electrical properties of graphene grown on AlGaN by catalyst-free chemical vapor deposition. Nanotechnology 2021; 32:015705. [PMID: 33043906 DOI: 10.1088/1361-6528/abb72b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The integration of graphene (Gr) with nitride semiconductors is highly interesting for applications in high-power/high-frequency electronics and optoelectronics. In this work, we demonstrated the direct growth of Gr on Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition at a temperature of 1350 °C. After optimization of the C3H8 flow rate, a uniform and conformal Gr coverage was achieved, which proved beneficial to prevent degradation of AlGaN morphology. X-ray photoemission spectroscopy revealed Ga loss and partial oxidation of Al in the near-surface AlGaN region. Such chemical modification of a ∼2 nm thick AlGaN surface region was confirmed by cross-sectional scanning transmission electron microscopy combined with electron energy loss spectroscopy, which also showed the presence of a bilayer of Gr with partial sp2/sp3 hybridization. Raman spectra indicated that the deposited Gr is nanocrystalline (with domain size ∼7 nm) and compressively strained. A Gr sheet resistance of ∼15.8 kΩ sq-1 was evaluated by four-point-probe measurements, consistently with the nanocrystalline nature of these films. Furthermore, nanoscale resolution current mapping by conductive atomic force microscopy indicated local variations of the Gr carrier density at a mesoscopic scale, which can be ascribed to changes in the charge transfer from the substrate due to local oxidation of AlGaN or to the presence of Gr wrinkles.
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Affiliation(s)
- F Giannazzo
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 Zona Industriale, 95121, Catania, Italy
| | - R Dagher
- Université Côte d'Azur, CNRS, CRHEA, Rue Bernard Grégory, 06560, Valbonne, France
| | - E Schilirò
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 Zona Industriale, 95121, Catania, Italy
| | - S E Panasci
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 Zona Industriale, 95121, Catania, Italy
- Department of Physics and Astronomy, University of Catania, via Santa Sofia 64, 95123, Catania, Italy
| | - G Greco
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 Zona Industriale, 95121, Catania, Italy
| | - G Nicotra
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 Zona Industriale, 95121, Catania, Italy
| | - F Roccaforte
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 Zona Industriale, 95121, Catania, Italy
| | - S Agnello
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n. 5 Zona Industriale, 95121, Catania, Italy
- Department of Physics and Chemistry 'E. Segrè', University of Palermo, via Archirafi 36, 90123, Palermo, Italy
| | - J Brault
- Université Côte d'Azur, CNRS, CRHEA, Rue Bernard Grégory, 06560, Valbonne, France
| | - Y Cordier
- Université Côte d'Azur, CNRS, CRHEA, Rue Bernard Grégory, 06560, Valbonne, France
| | - A Michon
- Université Côte d'Azur, CNRS, CRHEA, Rue Bernard Grégory, 06560, Valbonne, France
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17
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Kakanakova-Georgieva A, Gueorguiev GK, Sangiovanni DG, Suwannaharn N, Ivanov IG, Cora I, Pécz B, Nicotra G, Giannazzo F. Nanoscale phenomena ruling deposition and intercalation of AlN at the graphene/SiC interface. Nanoscale 2020; 12:19470-19476. [PMID: 32960193 DOI: 10.1039/d0nr04464d] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The possibility for kinetic stabilization of prospective 2D AlN was explored by rationalizing metal organic chemical vapor deposition (MOCVD) processes of AlN on epitaxial graphene. From the wide range of temperatures which can be covered in the same MOCVD reactor, the deposition was performed at the selected temperatures of 700, 900, and 1240 °C. The characterization of the structures by atomic force microscopy, electron microscopy and Raman spectroscopy revealed a broad range of surface nucleation and intercalation phenomena. These phenomena included the abundant formation of nucleation sites on graphene, the fragmentation of the graphene layers which accelerated with the deposition temperature, the delivery of excess precursor-derived carbon adatoms to the surface, as well as intercalation of sub-layers of aluminum atoms at the graphene/SiC interface. The conceptual understanding of these nanoscale phenomena was supported by our previous comprehensive ab initio molecular dynamics (AIMD) simulations of the surface reaction of trimethylaluminum, (CH3)3Al, precursor with graphene. A case of applying trimethylindium, (CH3)3In, precursor to epitaxial graphene was considered in a comparative way.
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18
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Giannazzo F, Schilirò E, Greco G, Roccaforte F. Conductive Atomic Force Microscopy of Semiconducting Transition Metal Dichalcogenides and Heterostructures. Nanomaterials (Basel) 2020; 10:nano10040803. [PMID: 32331313 PMCID: PMC7221570 DOI: 10.3390/nano10040803] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/16/2020] [Accepted: 04/17/2020] [Indexed: 11/16/2022]
Abstract
Semiconducting transition metal dichalcogenides (TMDs) are promising materials for future electronic and optoelectronic applications. However, their electronic properties are strongly affected by peculiar nanoscale defects/inhomogeneities (point or complex defects, thickness fluctuations, grain boundaries, etc.), which are intrinsic of these materials or introduced during device fabrication processes. This paper reviews recent applications of conductive atomic force microscopy (C-AFM) to the investigation of nanoscale transport properties in TMDs, discussing the implications of the local phenomena in the overall behavior of TMD-based devices. Nanoscale resolution current spectroscopy and mapping by C-AFM provided information on the Schottky barrier uniformity and shed light on the mechanisms responsible for the Fermi level pinning commonly observed at metal/TMD interfaces. Methods for nanoscale tailoring of the Schottky barrier in MoS2 for the realization of ambipolar transistors are also illustrated. Experiments on local conductivity mapping in monolayer MoS2 grown by chemical vapor deposition (CVD) on SiO2 substrates are discussed, providing a direct evidence of the resistance associated to the grain boundaries (GBs) between MoS2 domains. Finally, C-AFM provided an insight into the current transport phenomena in TMD-based heterostructures, including lateral heterojunctions observed within MoxW1-xSe2 alloys, and vertical heterostructures made by van der Waals stacking of different TMDs (e.g., MoS2/WSe2) or by CVD growth of TMDs on bulk semiconductors.
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Fiorenza P, Alessandrino MS, Carbone B, Di Martino C, Russo A, Saggio M, Venuto C, Zanetti E, Giannazzo F, Roccaforte F. Understanding the role of threading dislocations on 4H-SiC MOSFET breakdown under high temperature reverse bias stress. Nanotechnology 2020; 31:125203. [PMID: 31816608 DOI: 10.1088/1361-6528/ab5ff6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The origin of dielectric breakdown was studied on 4H-SiC MOSFETs that failed after three months of high temperature reverse bias stress. A local inspection of the failed devices demonstrated the presence of a threading dislocation (TD) at the breakdown location. The nanoscale origin of the dielectric breakdown was highlighted with advanced high-spatial-resolution scanning probe microscopy (SPM) techniques. In particular, SPM revealed the conductive nature of the TD and a local increase of the minority carrier concentration close to the defect. Numerical simulations estimated a hole concentration 13 orders of magnitude larger than in the ideal 4H-SiC crystal. The hole injection in specific regions of the device explained the failure of the gate oxide under stress. In this way, the key role of the TD in the dielectric breakdown of 4H-SiC MOSFET was unambiguously demonstrated.
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Affiliation(s)
- P Fiorenza
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n.5 Zona Industriale, I-95121 Catania, Italy
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20
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Armano A, Buscarino G, Messina F, Sciortino A, Cannas M, Gelardi FM, Giannazzo F, Schilirò E, Agnello S. Dynamic Modification of Fermi Energy in Single-Layer Graphene by Photoinduced Electron Transfer from Carbon Dots. Nanomaterials (Basel) 2020; 10:nano10030528. [PMID: 32183471 PMCID: PMC7153610 DOI: 10.3390/nano10030528] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/06/2020] [Accepted: 03/11/2020] [Indexed: 12/20/2022]
Abstract
Graphene (Gr)—a single layer of two-dimensional sp2 carbon atoms—and Carbon Dots (CDs)—a novel class of carbon nanoparticles—are two outstanding nanomaterials, renowned for their peculiar properties: Gr for its excellent charge-transport, and CDs for their impressive emission properties. Such features, coupled with a strong sensitivity to the environment, originate the interest in bringing together these two nanomaterials in order to combine their complementary properties. In this work, the investigation of a solid-phase composite of CDs deposited on Gr is reported. The CD emission efficiency is reduced by the contact of Gr. At the same time, the Raman analysis of Gr demonstrates the increase of Fermi energy when it is in contact with CDs under certain conditions. The interaction between CDs and Gr is modeled in terms of an electron-transfer from photoexcited CDs to Gr, wherein an electron is first transferred from the carbon core to the surface states of CDs, and from there to Gr. There, the accumulated electrons determine a dynamical n-doping effect modulated by photoexcitation. The CD–graphene interaction unveiled herein is a step forward in the understanding of the mutual influence between carbon-based nanomaterials, with potential prospects in light conversion applications.
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Affiliation(s)
- Angelo Armano
- Dipartimento di Fisica e Chimica-Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy; (A.A.); (G.B.); (F.M.); (A.S.); (M.C.); (F.M.G.)
- Dipartimento di Fisica e Astronomia-Ettore Majorana, Università degli Studi di Catania, Via Santa Sofia 64, 95123 Catania, Italy
| | - Gianpiero Buscarino
- Dipartimento di Fisica e Chimica-Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy; (A.A.); (G.B.); (F.M.); (A.S.); (M.C.); (F.M.G.)
- ATeN Center, Università degli Studi di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo, Italy
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (F.G.); (E.S.)
| | - Fabrizio Messina
- Dipartimento di Fisica e Chimica-Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy; (A.A.); (G.B.); (F.M.); (A.S.); (M.C.); (F.M.G.)
- ATeN Center, Università degli Studi di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo, Italy
| | - Alice Sciortino
- Dipartimento di Fisica e Chimica-Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy; (A.A.); (G.B.); (F.M.); (A.S.); (M.C.); (F.M.G.)
| | - Marco Cannas
- Dipartimento di Fisica e Chimica-Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy; (A.A.); (G.B.); (F.M.); (A.S.); (M.C.); (F.M.G.)
| | - Franco Mario Gelardi
- Dipartimento di Fisica e Chimica-Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy; (A.A.); (G.B.); (F.M.); (A.S.); (M.C.); (F.M.G.)
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (F.G.); (E.S.)
| | - Emanuela Schilirò
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (F.G.); (E.S.)
| | - Simonpietro Agnello
- Dipartimento di Fisica e Chimica-Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy; (A.A.); (G.B.); (F.M.); (A.S.); (M.C.); (F.M.G.)
- ATeN Center, Università degli Studi di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo, Italy
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi, Strada VIII 5, 95121 Catania, Italy; (F.G.); (E.S.)
- Correspondence:
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Giannazzo F, Shtepliuk I, Ivanov IG, Iakimov T, Kakanakova-Georgieva A, Schilirò E, Fiorenza P, Yakimova R. Probing the uniformity of hydrogen intercalation in quasi-free-standing epitaxial graphene on SiC by micro-Raman mapping and conductive atomic force microscopy. Nanotechnology 2019; 30:284003. [PMID: 30913546 DOI: 10.1088/1361-6528/ab134e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this paper, micro-Raman mapping and conductive atomic force microscopy (C-AFM) were jointly applied to investigate the structural and electrical homogeneity of quasi-free-standing monolayer graphene (QFMLG), obtained by high temperature decomposition of 4H-SiC(0001) followed by hydrogen intercalation at 900 °C. Strain and doping maps, obtained by Raman data, showed the presence of sub-micron patches with reduced hole density correlated to regions with higher compressive strain, probably associated with a locally reduced hydrogen intercalation. Nanoscale resolution electrical maps by C-AFM also revealed the presence of patches with enhanced current injection through the QFMLG/SiC interface, indicating a locally reduced Schottky barrier height (ΦB). The ΦB values evaluated from local I-V curves by the thermionic emission model were in good agreement with the values calculated for the QFMLG/SiC interface using the Schottky-Mott rule and the graphene holes density from Raman maps. The demonstrated approach revealed a useful and non-invasive method to probe the structural and electrical homogeneity of QFMLG for future nano-electronics applications.
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Affiliation(s)
- F Giannazzo
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Strada VIII, n. 5, Zona Industriale, I-95121, Catania, Italy
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22
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Fiorenza P, Iucolano F, Nicotra G, Bongiorno C, Deretzis I, La Magna A, Giannazzo F, Saggio M, Spinella C, Roccaforte F. Electron trapping at SiO 2/4H-SiC interface probed by transient capacitance measurements and atomic resolution chemical analysis. Nanotechnology 2018; 29:395702. [PMID: 29972377 DOI: 10.1088/1361-6528/aad129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Studying the electrical and structural properties of the interface of the gate oxide (SiO2) with silicon carbide (4H-SiC) is a fundamental topic, with important implications for understanding and optimising the performances of metal-oxide-semiconductor field effect transistor (MOSFETs). In this paper, near interface oxide traps (NIOTs) in lateral 4H-SiC MOSFETs were investigated combining transient gate capacitance measurements (C-t) and state of the art scanning transmission electron microscopy in electron energy loss spectroscopy (STEM-EELS) with sub-nm resolution. The C-t measurements as a function of temperature indicated that the effective NIOTs discharge time is temperature independent and electrons from NIOTs are emitted toward the semiconductor via-tunnelling. The NIOTs discharge time was modelled also taking into account the interface state density in a tunnelling relaxation model and it allowed us to locate traps within a tunnelling distance of up to 1.3 nm from the SiO2/4H-SiC interface. On the other hand, sub-nm resolution STEM-EELS revealed the presence of a non-abrupt (NA) SiO2/4H-SiC interface. The NA interface shows the re-arrangement of the carbon atoms in a sub-stoichiometric SiO x matrix. A mixed sp2/sp3 carbon hybridization in the NA interface region suggests that the interfacial carbon atoms have lost their tetrahedral SiC coordination.
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Affiliation(s)
- Patrick Fiorenza
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII, n.5 Zona Industriale, I-95121 Catania, Italy
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23
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Greco G, Fiorenza P, Iucolano F, Severino A, Giannazzo F, Roccaforte F. Conduction Mechanisms at Interface of AlN/SiN Dielectric Stacks with AlGaN/GaN Heterostructures for Normally-off High Electron Mobility Transistors: Correlating Device Behavior with Nanoscale Interfaces Properties. ACS Appl Mater Interfaces 2017; 9:35383-35390. [PMID: 28920438 DOI: 10.1021/acsami.7b08935] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this work, the conduction mechanisms at the interface of AlN/SiN dielectric stacks with AlGaN/GaN heterostructures have been studied combining different macroscopic and nanoscale characterizations on bare materials and devices. The AlN/SiN stacks grown on the recessed region of AlGaN/GaN heterostructures have been used as gate dielectric of hybrid metal-insulator-semiconductor high electron mobility transistors (MISHEMTs), showing a normally-off behavior (Vth = +1.2 V), high channel mobility (204 cm2 V-1 s-1), and very good switching behavior (ION/IOFF current ratio of (5-6) × 108 and subthreshold swing of 90 mV/dec). However, the transistors were found to suffer from a positive shift of the threshold voltage during subsequent bias sweeps, which indicates electron trapping in the dielectric stack. To get a complete understanding of the conduction mechanisms and of the charge trapping phenomena in AlN/SiN films, nanoscale current and capacitance measurements by conductive atomic force microscopy (C-AFM) and scanning capacitance microscopy (SCM) have been compared with a macroscopic temperature-dependent characterization of gate current in MIS capacitors. The nanoscale electrical analyses showed the presence of a spatially uniform distribution of electrons trapping states in the insulator and the occurrence of a density of 7 × 108 cm-2 of local and isolated current spots at high bias values. These nanoscale conductive paths can be associated with electrically active defects responsible for the trap-assisted current transport mechanism through the dielectric, observed by the temperature-dependent characterization of the gate current. The results of this study can be relevant for future applications of AlN/SiN bilayers in GaN hybrid MISHEMT technology.
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Affiliation(s)
- Giuseppe Greco
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM) , Strada VIII, No. 5, Zona Industriale, 95121 Catania, Italy
| | - Patrick Fiorenza
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM) , Strada VIII, No. 5, Zona Industriale, 95121 Catania, Italy
| | | | - Andrea Severino
- STMicroelectronics , Stradale Primosole 50, 95121 Catania, Italy
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM) , Strada VIII, No. 5, Zona Industriale, 95121 Catania, Italy
| | - Fabrizio Roccaforte
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM) , Strada VIII, No. 5, Zona Industriale, 95121 Catania, Italy
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Giannazzo F, Fisichella G, Greco G, Di Franco S, Deretzis I, La Magna A, Bongiorno C, Nicotra G, Spinella C, Scopelliti M, Pignataro B, Agnello S, Roccaforte F. Ambipolar MoS 2 Transistors by Nanoscale Tailoring of Schottky Barrier Using Oxygen Plasma Functionalization. ACS Appl Mater Interfaces 2017; 9:23164-23174. [PMID: 28603968 DOI: 10.1021/acsami.7b04919] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
One of the main challenges to exploit molybdenum disulfide (MoS2) potentialities for the next-generation complementary metal oxide semiconductor (CMOS) technology is the realization of p-type or ambipolar field-effect transistors (FETs). Hole transport in MoS2 FETs is typically hampered by the high Schottky barrier height (SBH) for holes at source/drain contacts, due to the Fermi level pinning close to the conduction band. In this work, we show that the SBH of multilayer MoS2 surface can be tailored at nanoscale using soft O2 plasma treatments. The morphological, chemical, and electrical modifications of MoS2 surface under different plasma conditions were investigated by several microscopic and spectroscopic characterization techniques, including X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), conductive AFM (CAFM), aberration-corrected scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). Nanoscale current-voltage mapping by CAFM showed that the SBH maps can be conveniently tuned starting from a narrow SBH distribution (from 0.2 to 0.3 eV) in the case of pristine MoS2 to a broader distribution (from 0.2 to 0.8 eV) after 600 s O2 plasma treatment, which allows both electron and hole injection. This lateral inhomogeneity in the electrical properties was associated with variations of the incorporated oxygen concentration in the MoS2 multilayer surface, as shown by STEM/EELS analyses and confirmed by ab initio density functional theory (DFT) calculations. Back-gated multilayer MoS2 FETs, fabricated by self-aligned deposition of source/drain contacts in the O2 plasma functionalized areas, exhibit ambipolar current transport with on/off current ratio Ion/Ioff ≈ 103 and field-effect mobilities of 11.5 and 7.2 cm2 V-1 s-1 for electrons and holes, respectively. The electrical behavior of these novel ambipolar devices is discussed in terms of the peculiar current injection mechanisms in the O2 plasma functionalized MoS2 surface.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Michelangelo Scopelliti
- Dipartimento di Fisica e Chimica (DiFC), Università degli Studi di Palermo , Viale delle Scienze, Ed. 17, 90128 Palermo, Italy
- Aten Center, Università di Palermo , Ed. 18 V.le delle Scienze, Parco d'Orleans II, 90128 Palermo, Italy
- Consorzio Interuniversitario di Ricerca in Chimica dei Metalli nei Sistemi Biologici (C.I.R.C.M.S.B.) , 1, Piazza Umberto I, 70121 Bari, Italy
| | - Bruno Pignataro
- Dipartimento di Fisica e Chimica (DiFC), Università degli Studi di Palermo , Viale delle Scienze, Ed. 17, 90128 Palermo, Italy
- Aten Center, Università di Palermo , Ed. 18 V.le delle Scienze, Parco d'Orleans II, 90128 Palermo, Italy
| | - Simonpietro Agnello
- Dipartimento di Fisica e Chimica (DiFC), Università degli Studi di Palermo , Viale delle Scienze, Ed. 17, 90128 Palermo, Italy
- Aten Center, Università di Palermo , Ed. 18 V.le delle Scienze, Parco d'Orleans II, 90128 Palermo, Italy
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Fisichella G, Schilirò E, Di Franco S, Fiorenza P, Lo Nigro R, Roccaforte F, Ravesi S, Giannazzo F. Interface Electrical Properties of Al 2O 3 Thin Films on Graphene Obtained by Atomic Layer Deposition with an in Situ Seedlike Layer. ACS Appl Mater Interfaces 2017; 9:7761-7771. [PMID: 28135063 DOI: 10.1021/acsami.6b15190] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
High-quality thin insulating films on graphene (Gr) are essential for field-effect transistors (FETs) and other electronics applications of this material. Atomic layer deposition (ALD) is the method of choice to deposit high-κ dielectrics with excellent thickness uniformity and conformal coverage. However, to start the growth on the sp2 Gr surface, a chemical prefunctionalization or the physical deposition of a seed layer are required, which can effect, to some extent, the electrical properties of Gr. In this paper, we report a detailed morphological, structural, and electrical investigation of Al2O3 thin films grown by a two-steps ALD process on a large area Gr membrane residing on an Al2O3-Si substrate. This process consists of the H2O-activated deposition of a Al2O3 seed layer a few nanometers in thickness, performed in situ at 100 °C, followed by ALD thermal growth of Al2O3 at 250 °C. The optimization of the low-temperature seed layer allowed us to obtain a uniform, conformal, and pinhole-free Al2O3 film on Gr by the second ALD step. Nanoscale-resolution mapping of the current through the dielectric by conductive atomic force microscopy (CAFM) demonstrated an excellent laterally uniformity of the film. Raman spectroscopy measurements indicated that the ALD process does not introduce defects in Gr, whereas it produces a partial compensation of Gr unintentional p-type doping, as confirmed by the increase of Gr sheet resistance (from ∼300 Ω/sq in pristine Gr to ∼1100 Ω/sq after Al2O3 deposition). Analysis of the transfer characteristics of Gr field-effect transistors (GFETs) allowed us to evaluate the relative dielectric permittivity (ε = 7.45) and the breakdown electric field (EBD = 7.4 MV/cm) of the Al2O3 film as well as the transconductance and the holes field-effect mobility (∼1200 cm2 V-1 s-1). A special focus has been given to the electrical characterization of the Al2O3-Gr interface by the analysis of high frequency capacitance-voltage measurements, which allowed us to elucidate the charge trapping and detrapping phenomena due to near-interface and interface oxide traps.
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Affiliation(s)
- Gabriele Fisichella
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
| | - Emanuela Schilirò
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
| | - Salvatore Di Franco
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
| | - Patrick Fiorenza
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
| | - Raffaella Lo Nigro
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
| | - Fabrizio Roccaforte
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
| | - Sebastiano Ravesi
- STMicroelectronics , Stradale Primosole 50, Zona Industriale, 95121 Catania, Italy
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy
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Fisichella G, Lo Verso S, Di Marco S, Vinciguerra V, Schilirò E, Di Franco S, Lo Nigro R, Roccaforte F, Zurutuza A, Centeno A, Ravesi S, Giannazzo F. Advances in the fabrication of graphene transistors on flexible substrates. Beilstein J Nanotechnol 2017; 8:467-474. [PMID: 28326237 PMCID: PMC5331250 DOI: 10.3762/bjnano.8.50] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 01/24/2017] [Indexed: 05/29/2023]
Abstract
Graphene is an ideal candidate for next generation applications as a transparent electrode for electronics on plastic due to its flexibility and the conservation of electrical properties upon deformation. More importantly, its field-effect tunable carrier density, high mobility and saturation velocity make it an appealing choice as a channel material for field-effect transistors (FETs) for several potential applications. As an example, properly designed and scaled graphene FETs (Gr-FETs) can be used for flexible high frequency (RF) electronics or for high sensitivity chemical sensors. Miniaturized and flexible Gr-FET sensors would be highly advantageous for current sensors technology for in vivo and in situ applications. In this paper, we report a wafer-scale processing strategy to fabricate arrays of back-gated Gr-FETs on poly(ethylene naphthalate) (PEN) substrates. These devices present a large-area graphene channel fully exposed to the external environment, in order to be suitable for sensing applications, and the channel conductivity is efficiently modulated by a buried gate contact under a thin Al2O3 insulating film. In order to be compatible with the use of the PEN substrate, optimized deposition conditions of the Al2O3 film by plasma-enhanced atomic layer deposition (PE-ALD) at a low temperature (100 °C) have been developed without any relevant degradation of the final dielectric performance.
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Affiliation(s)
| | - Stella Lo Verso
- STMicroelectronics, Stradale Primosole 50, 95121 Catania, Italy
| | | | | | | | | | | | | | - Amaia Zurutuza
- Graphenea, Tolosa Hiribidea 76, Donostia-San Sebastian, Spain
| | - Alba Centeno
- Graphenea, Tolosa Hiribidea 76, Donostia-San Sebastian, Spain
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Piazza A, Giannazzo F, Buscarino G, Fisichella G, Magna AL, Roccaforte F, Cannas M, Gelardi FM, Agnello S. In-situ monitoring by Raman spectroscopy of the thermal doping of graphene and MoS 2 in O 2-controlled atmosphere. Beilstein J Nanotechnol 2017; 8:418-424. [PMID: 28326231 PMCID: PMC5331249 DOI: 10.3762/bjnano.8.44] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 01/24/2017] [Indexed: 05/07/2023]
Abstract
The effects of temperature and atmosphere (air and O2) on the doping of monolayers of graphene (Gr) on SiO2 and Si substrates, and on the doping of MoS2 multilayer flakes transferred on the same substrates have been investigated. The investigations were carried out by in situ micro-Raman spectroscopy during thermal treatments up to 430 °C, and by atomic force microscopy (AFM). The spectral positions of the G and 2D Raman bands of Gr undergo only minor changes during treatment, while their amplitude and full width at half maximum (FWHM) vary as a function of the temperature and the used atmosphere. The thermal treatments in oxygen atmosphere show, in addition to a thermal effect, an effect attributable to a p-type doping through oxygen. The thermal broadening of the line shape, found during thermal treatments by in situ Raman measurements, can be related to thermal phonon effects. The absence of a band shift results from the balance between a red shift due to thermal effects and a blue shift induced by doping. This shows the potential of in situ measurements to follow the doping kinetics. The treatment of MoS2 in O2 has evidenced a progressive erosion of the flakes without relevant spectral changes in their central zone during in situ measurements. The formation of MoO3 on the edges of the flakes is observed indicative of the oxygen-activated transformation.
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Affiliation(s)
- Aurora Piazza
- CNR-IMM, Strada VIII, 5, Zona Industriale, 95123 Catania, Italy
- Department of Physics and Chemistry, University of Palermo, Via Archirafi 36 - Palermo, 90123, Italy
- Department of Physics and Astronomy, University of Catania, Via Santa Sofia 64 - Catania, 95123, Italy
| | | | - Gianpiero Buscarino
- Department of Physics and Chemistry, University of Palermo, Via Archirafi 36 - Palermo, 90123, Italy
| | | | | | | | - Marco Cannas
- Department of Physics and Chemistry, University of Palermo, Via Archirafi 36 - Palermo, 90123, Italy
| | - Franco Mario Gelardi
- Department of Physics and Chemistry, University of Palermo, Via Archirafi 36 - Palermo, 90123, Italy
| | - Simonpietro Agnello
- Department of Physics and Chemistry, University of Palermo, Via Archirafi 36 - Palermo, 90123, Italy
- AteN Center, Universita’di Palermo, Viale delle Scienze, Ed.18 - Palermo, 90128, Italy
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Milazzo RG, Mio AM, D’Arrigo G, Smecca E, Alberti A, Fisichella G, Giannazzo F, Spinella C, Rimini E. Influence of hydrofluoric acid treatment on electroless deposition of Au clusters. Beilstein J Nanotechnol 2017; 8:183-189. [PMID: 28243555 PMCID: PMC5301911 DOI: 10.3762/bjnano.8.19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Accepted: 12/28/2016] [Indexed: 06/06/2023]
Abstract
The morphology of gold nanoparticles (AuNPs) deposited on a (100) silicon wafer by simple immersion in a solution containing a metal salt and hydrofluoric acid (HF) is altered by HF treatment both before and after deposition. The gold clusters are characterized by the presence of flat regions and quasispherical particles consistent with the layer-by-layer or island growth modes, respectively. The cleaning procedure, including HF immersion prior to deposition, affects the predominantly occurring gold structures. Flat regions, which are of a few tens of nanometers long, are present after immersion for 10 s. The three-dimensional (3D) clusters are formed after a cleaning procedure of 4 min, which results in a large amount of spherical particles with a diameter of ≈15 nm and in a small percentage of residual square layers of a few nanometers in length. The samples were also treated with HF after the deposition and we found out a general thickening of flat regions, as revealed by TEM and AFM analysis. This result is in contrast to the coalescence observed in similar experiments performed with Ag. It is suggested that the HF dissolves the silicon oxide layer formed on top of the thin flat clusters and promotes the partial atomic rearrangement of the layered gold atoms, driven by a reduction of the surface energy. The X-ray diffraction investigation indicated changes in the crystalline orientation of the flat regions, which partially lose their initially heteroepitaxial relationship with the substrate. A postdeposition HF treatment for almost 70 s has nearly the same effect of long duration, high temperature annealing. The process presented herein could be beneficial to change the spectral response of nanoparticle arrays and to improve the conversion efficiency of hybrid photovoltaic devices.
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Affiliation(s)
- Rachela G Milazzo
- CNR-IMM Institute for the Microelectronics and Microsystems, Z. I. VIII Strada 4, Catania, I-95121, Italy
| | - Antonio M Mio
- CNR-IMM Institute for the Microelectronics and Microsystems, Z. I. VIII Strada 4, Catania, I-95121, Italy
| | - Giuseppe D’Arrigo
- CNR-IMM Institute for the Microelectronics and Microsystems, Z. I. VIII Strada 4, Catania, I-95121, Italy
| | - Emanuele Smecca
- CNR-IMM Institute for the Microelectronics and Microsystems, Z. I. VIII Strada 4, Catania, I-95121, Italy
| | - Alessandra Alberti
- CNR-IMM Institute for the Microelectronics and Microsystems, Z. I. VIII Strada 4, Catania, I-95121, Italy
| | - Gabriele Fisichella
- CNR-IMM Institute for the Microelectronics and Microsystems, Z. I. VIII Strada 4, Catania, I-95121, Italy
| | - Filippo Giannazzo
- CNR-IMM Institute for the Microelectronics and Microsystems, Z. I. VIII Strada 4, Catania, I-95121, Italy
| | - Corrado Spinella
- CNR-IMM Institute for the Microelectronics and Microsystems, Z. I. VIII Strada 4, Catania, I-95121, Italy
| | - Emanuele Rimini
- CNR-IMM Institute for the Microelectronics and Microsystems, Z. I. VIII Strada 4, Catania, I-95121, Italy
- Department of Physics and Astronomy, v. S. Sofia 64, I-95123, Catania, Italy
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Giannazzo F, Fisichella G, Piazza A, Di Franco S, Greco G, Agnello S, Roccaforte F. Impact of contact resistance on the electrical properties of MoS 2 transistors at practical operating temperatures. Beilstein J Nanotechnol 2017; 8:254-263. [PMID: 28243564 PMCID: PMC5301949 DOI: 10.3762/bjnano.8.28] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 01/03/2017] [Indexed: 05/07/2023]
Abstract
Molybdenum disulphide (MoS2) is currently regarded as a promising material for the next generation of electronic and optoelectronic devices. However, several issues need to be addressed to fully exploit its potential for field effect transistor (FET) applications. In this context, the contact resistance, RC, associated with the Schottky barrier between source/drain metals and MoS2 currently represents one of the main limiting factors for suitable device performance. Furthermore, to gain a deeper understanding of MoS2 FETs under practical operating conditions, it is necessary to investigate the temperature dependence of the main electrical parameters, such as the field effect mobility (μ) and the threshold voltage (Vth). This paper reports a detailed electrical characterization of back-gated multilayer MoS2 transistors with Ni source/drain contacts at temperatures from T = 298 to 373 K, i.e., the expected range for transistor operation in circuits/systems, considering heating effects due to inefficient power dissipation. From the analysis of the transfer characteristics (ID-VG) in the subthreshold regime, the Schottky barrier height (ΦB ≈ 0.18 eV) associated with the Ni/MoS2 contact was evaluated. The resulting contact resistance in the on-state (electron accumulation in the channel) was also determined and it was found to increase with T as RC proportional to T3.1. The contribution of RC to the extraction of μ and Vth was evaluated, showing a more than 10% underestimation of μ when the effect of RC is neglected, whereas the effect on Vth is less significant. The temperature dependence of μ and Vth was also investigated. A decrease of μ proportional to 1/Tα with α = 1.4 ± 0.3 was found, indicating scattering by optical phonons as the main limiting mechanism for mobility above room temperature. The value of Vth showed a large negative shift (about 6 V) increasing the temperature from 298 to 373 K, which was explained in terms of electron trapping at MoS2/SiO2 interface states.
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Affiliation(s)
- Filippo Giannazzo
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e Microsistemi, Strada VIII, n 5, 95121 Catania, Italy
| | - Gabriele Fisichella
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e Microsistemi, Strada VIII, n 5, 95121 Catania, Italy
| | - Aurora Piazza
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e Microsistemi, Strada VIII, n 5, 95121 Catania, Italy
- Department of Physics and Chemistry, University of Palermo, Via Archirafi 36, 90143 Palermo, Italy
- Department of Physics and Astronomy, University of Catania, Via Santa Sofia, 64, 95123 Catania, Italy
| | - Salvatore Di Franco
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e Microsistemi, Strada VIII, n 5, 95121 Catania, Italy
| | - Giuseppe Greco
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e Microsistemi, Strada VIII, n 5, 95121 Catania, Italy
| | - Simonpietro Agnello
- Department of Physics and Chemistry, University of Palermo, Via Archirafi 36, 90143 Palermo, Italy
| | - Fabrizio Roccaforte
- Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e Microsistemi, Strada VIII, n 5, 95121 Catania, Italy
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Fiorenza P, Di Franco S, Giannazzo F, Roccaforte F. Nanoscale probing of the lateral homogeneity of donors concentration in nitridated SiO2/4H-SiC interfaces. Nanotechnology 2016; 27:315701. [PMID: 27324844 DOI: 10.1088/0957-4484/27/31/315701] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this paper, nanoscale resolution scanning capacitance microscopy (SCM) and local capacitance-voltage measurements were used to probe the interfacial donor concentration in SiO2/4H-SiC systems annealed in N2O. Such nitrogen-based annealings are commonly employed to passivate SiO2/SiC interface traps, and result both in the incorporation of N-related donors in SiC and in the increase of the mobility in the inversion layer in 4H-SiC MOS-devices. From our SCM measurements, a spatially inhomogeneous donor distribution was observed in the SiO2/4H-SiC system subjected to N2O annealing. Hence, the effect of a phosphorus implantation before the oxide deposition and N2O annealing was also evaluated. In this case, besides an increased average donor concentration, an improvement of the lateral homogeneity of the active doping was also detected. The possible implications of such a pre-implantation doping of the near-interface region on 4H-SiC MOS-devices are discussed.
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Affiliation(s)
- Patrick Fiorenza
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM) Strada VIII n. 5, Zona Industriale, I-95121, Catania, Italy
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Abstract
Graphene (Gr) is currently the object of intense research investigations, owing to its rich physics and wide potential for applications. In particular, epitaxial Gr on silicon carbide (SiC) holds great promise for the development of new device concepts based on the vertical current transport at Gr/SiC heterointerface. Precise tailoring of Gr workfunction (WF) represents a key requirement for these device structures. In this context, Günes et al (2015 Nanotechnology 26 445702) recently reported a straightforward approach for WF modulation in epitaxial Gr on silicon carbide by using nitric acid solutions at different dilutions. This paper provides a deep insight on the peculiar mechanisms of chemical doping of epitaxial Gr on 4H-SiC(0001), using several characterization techniques (Raman, UPS, AFM) and density functional theory calculations. The relevance of these findings and their perspective applications in emerging device concepts based on monolithic integration of Gr and SiC will be discussed.
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Alberti A, Deretzis I, Pellegrino G, Bongiorno C, Smecca E, Mannino G, Giannazzo F, Condorelli GG, Sakai N, Miyasaka T, Spinella C, La Magna A. Similar Structural Dynamics for the Degradation of CH3NH3PbI3in Air and in Vacuum. Chemphyschem 2015; 16:3064-71. [DOI: 10.1002/cphc.201500374] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Revised: 06/26/2015] [Indexed: 11/12/2022]
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Fisichella G, Greco G, Roccaforte F, Giannazzo F. Current transport in graphene/AlGaN/GaN vertical heterostructures probed at nanoscale. Nanoscale 2014; 6:8671-80. [PMID: 24946753 DOI: 10.1039/c4nr01150c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Vertical heterostructures combining two or more graphene (Gr) layers separated by ultra-thin insulating or semiconductor barriers represent very promising systems for next generation electronics devices, due to the combination of high speed operation with wide-range current modulation by a gate bias. They are based on the specific mechanisms of current transport between two-dimensional-electron-gases (2DEGs) in close proximity. In this context, vertical devices formed by Gr and semiconductor heterostructures hosting an "ordinary" 2DEG can be also very interesting. In this work, we investigated the vertical current transport in Gr/Al(0.25)Ga(0.75)N/GaN heterostructures, where Gr is separated from a high density 2DEG by a ∼ 24 nm thick AlGaN barrier layer. The current transport from Gr to the buried 2DEG was characterized at nanoscale using conductive atomic force microscopy (CAFM) and scanning capacitance microscopy (SCM). From these analyses, performed both on Gr/AlGaN/GaN and on AlGaN/GaN reference samples using AFM tips with different metal coatings, the Gr/AlGaN Schottky barrier height ΦB and its lateral uniformity were evaluated, as well as the variation of the carrier densities of graphene (ngr) and AlGaN/GaN 2DEG (ns) as a function of the applied bias. A low Schottky barrier (∼ 0.40 eV) with excellent spatial uniformity was found at the Gr/AlGaN interface, i.e., lower compared to the measured values for metal/AlGaN contacts, which range from ∼ 0.6 to ∼ 1.1 eV depending on the metal workfunction. The electrical behavior of the Gr/AlGaN contact has been explained by Gr interaction with AlGaN donor-like surface states located in close proximity, which are also responsible of high n-type Gr doping (∼ 1.3 × 10(13) cm(-2)). An effective modulation of ns by the Gr Schottky contact was demonstrated by capacitance analysis under reverse bias. From this basic understanding of transport properties in Gr/AlGaN/GaN heterostructures, novel vertical field effect transistor concepts with high operating speed and I(on)/I(off) ratio can be envisaged.
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Cataldo S, Sartorio C, Giannazzo F, Scandurra A, Pignataro B. Self-organization and nanostructural control in thin film heterojunctions. Nanoscale 2014; 6:3566-3575. [PMID: 24352800 DOI: 10.1039/c3nr05027k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In spite of more than two-decades of studies of molecular self-assembly, the achievement of low cost, easy-to-implement and multi-parameter bottom-up approaches to address the supramolecular morphology in three-dimensional (3D) systems is still missing. In the particular case of molecular thin films, the 3D nanoscale morphology and function are crucial for both fundamental and applied research. Here we show how it is possible to tune the 3D film structure (domain size, branching, etc.) of thin film heterojunctions with nanoscale accuracy together with the modulation of their optoelectronic properties by employing an easy two-step approach. At first we prepared multi-planar heterojunctions with a programmed sequence of nanoscopic layers. In a second step, thermal stimuli have been employed to induce the formation of bulk heterojunctions with bicontinuous and interdigitated phases having a size below the exciton diffusion length. Importantly, the study of luminescence quenching of these systems can be considered as a useful means for the accurate estimation of the exciton diffusion length of semiconductors in nanoscale blends. Finally, nearly a thousand times lower material consumption than spin coating allows a drastic reduction of material wasting and a low-cost implementation, besides the considerable possibility of preparing thin film blends also by employing materials soluble in different solvents.
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Affiliation(s)
- Sebastiano Cataldo
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, V.le delle Scienze, Ed.17 - 90100 Palermo, Italy.
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Greco G, Fiorenza P, Giannazzo F, Alberti A, Roccaforte F. Nanoscale electrical and structural modification induced by rapid thermal oxidation of AlGaN/GaN heterostructures. Nanotechnology 2014; 25:025201. [PMID: 24334374 DOI: 10.1088/0957-4484/25/2/025201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In this paper, the structural and electrical modifications induced, in the nanoscale, by a rapid thermal oxidation process on AlGaN/GaN heterostructures, are investigated. A local rapid oxidation (900 ° C in O2, 10 min) localized under the anode region of an AlGaN/GaN diode enabled a reduction of the leakage current with respect to a standard Schottky contact. The insulating properties of the near-surface oxidized layer were probed by a nanoscale electrical characterization using scanning probe microscopy techniques. The structural characterization indicated the formation of a thin uniform oxide layer on the surface, with preferential oxidation paths along V-shaped defects penetrating through the AlGaN/GaN interface. The oxidation process resulted in an expansion of the lattice parameters due to the incorporation of oxygen atoms, accompanied by an increase of the crystal mosaicity. As a consequence, a decrease of the sheet carrier density of the two-dimensional electron gas and a positive shift of the threshold voltage are observed. The results provide useful insights for a possible future integration of rapid oxidation processes during GaN device fabrication.
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Affiliation(s)
- Giuseppe Greco
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, Zona Industriale-I-95121 Catania, Italy
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36
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Nicotra G, Ramasse QM, Deretzis I, La Magna A, Spinella C, Giannazzo F. Delaminated graphene at silicon carbide facets: atomic scale imaging and spectroscopy. ACS Nano 2013; 7:3045-3052. [PMID: 23530467 DOI: 10.1021/nn305922u] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Atomic-resolution structural and spectroscopic characterization techniques (scanning transmission electron microscopy and electron energy loss spectroscopy) are combined with nanoscale electrical measurements (conductive atomic force microscopy) to study at the atomic scale the properties of graphene grown epitaxially through the controlled graphitization of a hexagonal SiC(0001) substrate by high temperature annealing. This growth technique is known to result in a pronounced electron-doping (∼10(13) cm(-2)) of graphene, which is thought to originate from an interface carbon buffer layer strongly bound to the substrate. The scanning transmission electron microscopy analysis, carried out at an energy below the knock-on threshold for carbon to ensure no damage is imparted to the film by the electron beam, demonstrates that the buffer layer present on the planar SiC(0001) face delaminates from it on the (112n) facets of SiC surface steps. In addition, electron energy loss spectroscopy reveals that the delaminated layer has a similar electronic configuration to purely sp2-hybridized graphene. These observations are used to explain the local increase of the graphene sheet resistance measured around the surface steps by conductive atomic force microscopy, which we suggest is due to significantly lower substrate-induced doping and a resonant scattering mechanism at the step regions. A first-principles-calibrated theoretical model is proposed to explain the structural instability of the buffer layer on the SiC facets and the resulting delamination.
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Fiorenza P, Giannazzo F, Swanson LK, Frazzetto A, Lorenti S, Alessandrino MS, Roccaforte F. A look underneath the SiO2/4H-SiC interface after N2O thermal treatments. Beilstein J Nanotechnol 2013; 4:249-254. [PMID: 23616945 PMCID: PMC3628548 DOI: 10.3762/bjnano.4.26] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 03/26/2013] [Indexed: 06/02/2023]
Abstract
The electrical compensation effect of the nitrogen incorporation at the SiO2/4H-SiC (p-type) interface after thermal treatments in ambient N2O is investigated employing both scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM). SSRM measurements on p-type 4H-SiC areas selectively exposed to N2O at 1150 °C showed an increased resistance compared to the unexposed ones; this indicates the incorporation of electrically active nitrogen-related donors, which compensate the p-type doping in the SiC surface region. Cross-sectional SCM measurements on SiO2/4H-SiC metal/oxide/semiconductor (MOS) devices highlighted different active carrier concentration profiles in the first 10 nm underneath the insulator-substrate interface depending on the SiO2/4H-SiC roughness. The electrically active incorporated nitrogen produces both a compensation of the acceptors in the substrate and a reduction of the interface state density (D it). This result can be correlated with the 4H-SiC surface configuration. In particular, lower D it values were obtained for a SiO2/SiC interface on faceted SiC than on planar SiC. These effects were explained in terms of the different surface configuration in faceted SiC that enables the simultaneous exposition at the interface of atomic planes with different orientations.
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Affiliation(s)
- Patrick Fiorenza
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM) Strada VIII n. 5, Zona Industriale, 95121, Catania, Italy
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM) Strada VIII n. 5, Zona Industriale, 95121, Catania, Italy
| | - Lukas K Swanson
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM) Strada VIII n. 5, Zona Industriale, 95121, Catania, Italy
| | - Alessia Frazzetto
- Scuola Superiore di Catania - Università degli Studi di Catania, Via Valdisavoia 9, 95123, Catania, Italy
- STMicroelectronics, Stadale Primosole 50, 95121, Catania, Italy
| | - Simona Lorenti
- STMicroelectronics, Stadale Primosole 50, 95121, Catania, Italy
| | | | - Fabrizio Roccaforte
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM) Strada VIII n. 5, Zona Industriale, 95121, Catania, Italy
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Fisichella G, Di Franco S, Fiorenza P, Lo Nigro R, Roccaforte F, Tudisco C, Condorelli GG, Piluso N, Spartà N, Lo Verso S, Accardi C, Tringali C, Ravesi S, Giannazzo F. Micro- and nanoscale electrical characterization of large-area graphene transferred to functional substrates. Beilstein J Nanotechnol 2013; 4:234-42. [PMID: 23616943 PMCID: PMC3628692 DOI: 10.3762/bjnano.4.24] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Accepted: 03/07/2013] [Indexed: 05/16/2023]
Abstract
Chemical vapour deposition (CVD) on catalytic metals is one of main approaches for high-quality graphene growth over large areas. However, a subsequent transfer step to an insulating substrate is required in order to use the graphene for electronic applications. This step can severely affect both the structural integrity and the electronic properties of the graphene membrane. In this paper, we investigated the morphological and electrical properties of CVD graphene transferred onto SiO2 and on a polymeric substrate (poly(ethylene-2,6-naphthalene dicarboxylate), briefly PEN), suitable for microelectronics and flexible electronics applications, respectively. The electrical properties (sheet resistance, mobility, carrier density) of the transferred graphene as well as the specific contact resistance of metal contacts onto graphene were investigated by using properly designed test patterns. While a sheet resistance R sh ≈ 1.7 kΩ/sq and a specific contact resistance ρc ≈ 15 kΩ·μm have been measured for graphene transferred onto SiO2, about 2.3× higher R sh and about 8× higher ρc values were obtained for graphene on PEN. High-resolution current mapping by torsion resonant conductive atomic force microscopy (TRCAFM) provided an insight into the nanoscale mechanisms responsible for the very high ρc in the case of graphene on PEN, showing a ca. 10× smaller "effective" area for current injection than in the case of graphene on SiO2.
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Affiliation(s)
- Gabriele Fisichella
- CNR-IMM, VIII Strada, 5, 95121, Catania, Italy
- Department of Electronic Engineering, University of Catania, Viale A. Doria 6, 95125 Catania, Italy
| | | | | | | | | | | | | | | | - Noemi Spartà
- STMicroelectronics, Stradale Primosole, 50, 95121, Catania, Italy
| | - Stella Lo Verso
- STMicroelectronics, Stradale Primosole, 50, 95121, Catania, Italy
| | - Corrado Accardi
- STMicroelectronics, Stradale Primosole, 50, 95121, Catania, Italy
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Musumeci C, Rosnes MH, Giannazzo F, Symes MD, Cronin L, Pignataro B. Smart high-κ nanodielectrics using solid supported polyoxometalate-rich nanostructures. ACS Nano 2011; 5:9992-9999. [PMID: 22066461 DOI: 10.1021/nn2037797] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Utilizing Langmuir-Blodgett deposition and scanning probe microscopy, we have investigated the extent to which cations alter the self-assembly processes of hybrid polyoxometalates (POMs) on surfaces. The well-defined 2D hexagonal nanostructures obtained were extensively characterized and their properties were studied, and this has revealed fascinating dielectric behavior and reversible capacitive properties. The nanostructures are extremely stable under ambient conditions, and yet exhibit fascinating self-patterning upon heating. These findings present POMs as effective smart nanodielectrics and open up a new field for future POM applications.
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Affiliation(s)
- Chiara Musumeci
- Superlab-Consorzio Catania Ricerche, Stradale Primosole 50, 95121 Catania, Italy
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Giannazzo F, Sonde S, Nigro RL, Rimini E, Raineri V. Mapping the density of scattering centers limiting the electron mean free path in graphene. Nano Lett 2011; 11:4612-8. [PMID: 21981146 DOI: 10.1021/nl2020922] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Recently, giant carrier mobility μ (>10(5) cm(2) V(-1) s(-1)) and micrometer electron mean free path (l) have been measured in suspended graphene or in graphene encapsulated between inert and ultraflat BN layers. Much lower μ values (10000-20000 cm(2) V(-1) s(-1)) are typically reported in graphene on common substrates (SiO(2), SiC) used for device fabrication. The debate on the factors limiting graphene electron mean free path is still open with charged impurities (CI) and resonant scatterers (RS) indicated as the most probable candidates. As a matter of fact, the inhomogeneous distribution of such scattering sources in graphene is responsible of nanoscale lateral inhomogeneities in the electronic properties, which could affect the behavior of graphene nanodevices. Hence, high resolution two-dimensional (2D) mapping of their density is very important. Here, we used scanning capacitance microscopy/spectroscopy to obtain 2D maps of l in graphene on substrates with different dielectric permittivities, that is, SiO(2) (κ(SiO2) = 3.9), 4H-SiC (0001) (κ(SiC) = 9.7) and the very-high-κ perovskite strontium titanate, SrTiO(3) (001), briefly STO (κ(STO) = 330). After measuring l versus the gate bias V(g) on an array of points on graphene, maps of the CI density (N(CI)) have been determined by the neutrality point shift from V(g) = 0 V in each curve, whereas maps of the RS density (N(RS)) have been extracted by fitting the dependence of l on the carrier density (n). Laterally inhomogeneous densities of CI and RS have been found. The RS distribution exhibits an average value ∼3 × 10(10) cm(-2) independently on the substrate. For the first time, a clear correlation between the minima in the l map and the maxima in the N(CI) map is obtained for graphene on SiO(2) and 4H-SiC, indicating that CI are the main source of the lateral inhomogeneity of l. On the contrary, the l and N(CI) maps are uncorrelated in graphene on STO, while a clear correlation is found between l and N(RS) maps. This demonstrates a very efficient dielectric screening of CI in graphene on STO and the role of RS as limiting factor for electron mean free path.
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Vecchio C, Sonde S, Bongiorno C, Rambach M, Yakimova R, Raineri V, Giannazzo F. Nanoscale structural characterization of epitaxial graphene grown on off-axis 4H-SiC (0001). Nanoscale Res Lett 2011; 6:269. [PMID: 21711803 PMCID: PMC3211332 DOI: 10.1186/1556-276x-6-269] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 03/29/2011] [Indexed: 05/27/2023]
Abstract
In this work, we present a nanometer resolution structural characterization of epitaxial graphene (EG) layers grown on 4H-SiC (0001) 8° off-axis, by annealing in inert gas ambient (Ar) in a wide temperature range (Tgr from 1600 to 2000°C). For all the considered growth temperatures, few layers of graphene (FLG) conformally covering the 100 to 200-nm wide terraces of the SiC surface have been observed by high-resolution cross-sectional transmission electron microscopy (HR-XTEM). Tapping mode atomic force microscopy (t-AFM) showed the formation of wrinkles with approx. 1 to 2 nm height and 10 to 20 nm width in the FLG film, as a result of the release of the compressive strain, which builds up in FLG during the sample cooling due to the thermal expansion coefficients mismatch between graphene and SiC. While for EG grown on on-axis 4H-SiC an isotropic mesh-like network of wrinkles interconnected into nodes is commonly reported, in the present case of a vicinal SiC surface, wrinkles are preferentially oriented in the direction perpendicular to the step edges of the SiC terraces. For each Tgr, the number of graphene layers was determined on very small sample areas by HR-XTEM and, with high statistics and on several sample positions, by measuring the depth of selectively etched trenches in FLG by t-AFM. Both the density of wrinkles and the number of graphene layers are found to increase almost linearly as a function of the growth temperature in the considered temperature range.
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Affiliation(s)
- Carmelo Vecchio
- CNR-IMM, Strada VIII, 5, Catania 95121, Italy
- Scuola Superiore di Catania, Via San Nullo, 5/i, Catania 95123, Italy
| | - Sushant Sonde
- CNR-IMM, Strada VIII, 5, Catania 95121, Italy
- Scuola Superiore di Catania, Via San Nullo, 5/i, Catania 95123, Italy
| | | | - Martin Rambach
- Centrotherm Thermal Solutions GmbH + Co. KG, Johannes-Schmid-Straße 8, Blaubeuren 89143, Germany
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Dózsa L, Lányi Š, Raineri V, Giannazzo F, Galkin NG. Microscopic study of electrical properties of CrSi2 nanocrystals in silicon. Nanoscale Res Lett 2011; 6:209. [PMID: 21711727 PMCID: PMC3211265 DOI: 10.1186/1556-276x-6-209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 03/09/2011] [Indexed: 05/31/2023]
Abstract
Semiconducting CrSi2 nanocrystallites (NCs) were grown by reactive deposition epitaxy of Cr onto n-type silicon and covered with a 50-nm epitaxial silicon cap. Two types of samples were investigated: in one of them, the NCs were localized near the deposition depth, and in the other they migrated near the surface. The electrical characteristics were investigated in Schottky junctions by current-voltage and capacitance-voltage measurements. Atomic force microscopy (AFM), conductive AFM and scanning probe capacitance microscopy (SCM) were applied to reveal morphology and local electrical properties. The scanning probe methods yielded specific information, and tapping-mode AFM has shown up to 13-nm-high large-area protrusions not seen in the contact-mode AFM. The electrical interaction of the vibrating scanning tip results in virtual deformation of the surface. SCM has revealed NCs deep below the surface not seen by AFM. The electrically active probe yielded significantly better spatial resolution than AFM. The conductive AFM measurements have shown that the Cr-related point defects near the surface are responsible for the leakage of the macroscopic Schottky junctions, and also that NCs near the surface are sensitive to the mechanical and electrical stress induced by the scanning probe.
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Affiliation(s)
- László Dózsa
- Research Institute for Technical Physics and Materials Science, P. O. Box 49, H-1525 Budapest, Hungary
| | - Štefan Lányi
- Institute of Physics of the Slovakian Academy of Sciences, Dúbravská Cesta 9, SK-854 11 Bratislava, Slovakia
| | | | | | - Nikolay Gennadevich Galkin
- Institute for Automation and Control Processes of Far Eastern Branch of Russian Academy of Sciences, 690041 Vladivostok Radio 5, Russia
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Frazzetto A, Giannazzo F, Lo Nigro R, Di Franco S, Bongiorno C, Saggio M, Zanetti E, Raineri V, Roccaforte F. Nanoscale electro-structural characterisation of ohmic contacts formed on p-type implanted 4H-SiC. Nanoscale Res Lett 2011; 6:158. [PMID: 21711667 PMCID: PMC3211209 DOI: 10.1186/1556-276x-6-158] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 02/21/2011] [Indexed: 05/31/2023]
Abstract
This work reports a nanoscale electro-structural characterisation of Ti/Al ohmic contacts formed on p-type Al-implanted silicon carbide (4H-SiC). The morphological and the electrical properties of the Al-implanted layer, annealed at 1700°C with or without a protective capping layer, and of the ohmic contacts were studied using atomic force microscopy [AFM], transmission line model measurements and local current measurements performed with conductive AFM.The characteristics of the contacts were significantly affected by the roughness of the underlying SiC. In particular, the surface roughness of the Al-implanted SiC regions annealed at 1700°C could be strongly reduced using a protective carbon capping layer during annealing. This latter resulted in an improved surface morphology and specific contact resistance of the Ti/Al ohmic contacts formed on these regions. The microstructure of the contacts was monitored by X-ray diffraction analysis and a cross-sectional transmission electron microscopy, and correlated with the electrical results.
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Affiliation(s)
- Alessia Frazzetto
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi-Strada VIII, n. 5, Zona Industriale, 95121, Catania, Italy
- Scuola Superiore di Catania, University of Catania, Via Valdisavoia, 9, 95123, Catania, Italy
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi-Strada VIII, n. 5, Zona Industriale, 95121, Catania, Italy
| | - Raffaella Lo Nigro
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi-Strada VIII, n. 5, Zona Industriale, 95121, Catania, Italy
| | - Salvatore Di Franco
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi-Strada VIII, n. 5, Zona Industriale, 95121, Catania, Italy
| | - Corrado Bongiorno
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi-Strada VIII, n. 5, Zona Industriale, 95121, Catania, Italy
| | - Mario Saggio
- STMicroelectronics, Stradale Primosole 50, 95121, Catania, Italy
| | - Edoardo Zanetti
- STMicroelectronics, Stradale Primosole 50, 95121, Catania, Italy
| | - Vito Raineri
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi-Strada VIII, n. 5, Zona Industriale, 95121, Catania, Italy
| | - Fabrizio Roccaforte
- Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi-Strada VIII, n. 5, Zona Industriale, 95121, Catania, Italy
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Dózsa L, Molnár G, Raineri V, Giannazzo F, Ferencz J, Lányi Š. Scanning tip measurement for identification of point defects. Nanoscale Res Lett 2011; 6:140. [PMID: 21711635 PMCID: PMC3211188 DOI: 10.1186/1556-276x-6-140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 02/14/2011] [Indexed: 05/31/2023]
Abstract
Self-assembled iron-silicide nanostructures were prepared by reactive deposition epitaxy of Fe onto silicon. Capacitance-voltage, current-voltage, and deep level transient spectroscopy (DLTS) were used to measure the electrical properties of Au/silicon Schottky junctions. Spreading resistance and scanning probe capacitance microscopy (SCM) were applied to measure local electrical properties. Using a preamplifier the sensitivity of DLTS was increased satisfactorily to measure transients of the scanning tip semiconductor junction. In the Fe-deposited area, Fe-related defects dominate the surface layer in about 0.5 μm depth. These defects deteriorated the Schottky junction characteristic. Outside the Fe-deposited area, Fe-related defect concentration was identified in a thin layer near the surface. The defect transients in this area were measured both in macroscopic Schottky junctions and by scanning tip DLTS and were detected by bias modulation frequency dependence in SCM.
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Affiliation(s)
- László Dózsa
- Research Institute for Technical Physics and Materials Sciences, P.O. 49, H-1525 Budapest, Hungary
| | - György Molnár
- Research Institute for Technical Physics and Materials Sciences, P.O. 49, H-1525 Budapest, Hungary
| | | | | | - János Ferencz
- Research Institute for Technical Physics and Materials Sciences, P.O. 49, H-1525 Budapest, Hungary
| | - Štefan Lányi
- Institue of Physics, Slovakian Academy of Sciences, Dúbravská cesta 9, SK-845 11 Bratislava, Slovakia
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Greco G, Giannazzo F, Frazzetto A, Raineri V, Roccaforte F. Near-surface processing on AlGaN/GaN heterostructures: a nanoscale electrical and structural characterization. Nanoscale Res Lett 2011; 6:132. [PMID: 21711655 PMCID: PMC3211179 DOI: 10.1186/1556-276x-6-132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 02/11/2011] [Indexed: 05/31/2023]
Abstract
The effects of near-surface processing on the properties of AlGaN/GaN heterostructures were studied, combining conventional electrical characterization on high-electron mobility transistors (HEMTs), with advanced characterization techniques with nanometer scale resolution, i.e., transmission electron microscopy, atomic force microscopy (AFM) and conductive atomic force microscopy (C-AFM). In particular, a CHF3-based plasma process in the gate region resulted in a shift of the threshold voltage in HEMT devices towards less negative values. Two-dimensional current maps acquired by C-AFM on the sample surface allowed us to monitor the local electrical modifications induced by the plasma fluorine incorporated in the material.The results are compared with a recently introduced gate control processing: the local rapid thermal oxidation process of the AlGaN layer. By this process, a controlled thin oxide layer on surface of AlGaN can be reliably introduced while the resistance of the layer below increase locally.
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Affiliation(s)
- Giuseppe Greco
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII n. 5, Zona Industriale, 95121 Catania, Italy
- Scuola Superiore di Catania, University of Catania, Piazza dell'Università, 2, 95124, Catania, Italy
| | - Filippo Giannazzo
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII n. 5, Zona Industriale, 95121 Catania, Italy
| | - Alessia Frazzetto
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII n. 5, Zona Industriale, 95121 Catania, Italy
| | - Vito Raineri
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII n. 5, Zona Industriale, 95121 Catania, Italy
| | - Fabrizio Roccaforte
- Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII n. 5, Zona Industriale, 95121 Catania, Italy
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Eriksson J, Roccaforte F, Reshanov S, Leone S, Giannazzo F, LoNigro R, Fiorenza P, Raineri V. Nanoscale characterization of electrical transport at metal/3C-SiC interfaces. Nanoscale Res Lett 2011; 6:120. [PMID: 21711619 PMCID: PMC3211166 DOI: 10.1186/1556-276x-6-120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 02/07/2011] [Indexed: 05/31/2023]
Abstract
In this work, the transport properties of metal/3C-SiC interfaces were monitored employing a nanoscale characterization approach in combination with conventional electrical measurements. In particular, using conductive atomic force microscopy allowed demonstrating that the stacking fault is the most pervasive, electrically active extended defect at 3C-SiC(111) surfaces, and it can be electrically passivated by an ultraviolet irradiation treatment. For the Au/3C-SiC Schottky interface, a contact area dependence of the Schottky barrier height (ΦB) was found even after this passivation, indicating that there are still some electrically active defects at the interface. Improved electrical properties were observed in the case of the Pt/3C-SiC system. In this case, annealing at 500°C resulted in a reduction of the leakage current and an increase of the Schottky barrier height (from 0.77 to 1.12 eV). A structural analysis of the reaction zone carried out by transmission electron microscopy [TEM] and X-ray diffraction showed that the improved electrical properties can be attributed to a consumption of the surface layer of SiC due to silicide (Pt2Si) formation. The degradation of Schottky characteristics at higher temperatures (up to 900°C) could be ascribed to the out-diffusion and aggregation of carbon into clusters, observed by TEM analysis.
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Affiliation(s)
- Jens Eriksson
- CNR-IMM, Strada VIII n. 5, Zona Industriale, 95121, Catania, Italy
- Scuola Superiore-Università di Catania, Via San Nullo 5/i, Catania, 95123, Italy
| | | | | | - Stefano Leone
- Department of Physics, Chemistry and Biology, Linköping University, Linköping, 58183, Sweden
| | | | | | - Patrick Fiorenza
- CNR-IMM, Strada VIII n. 5, Zona Industriale, 95121, Catania, Italy
| | - Vito Raineri
- CNR-IMM, Strada VIII n. 5, Zona Industriale, 95121, Catania, Italy
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Giannazzo F, Sonde S, Rimini E, Raineri V. Lateral homogeneity of the electronic properties in pristine and ion-irradiated graphene probed by scanning capacitance spectroscopy. Nanoscale Res Lett 2011; 6:109. [PMID: 21711643 PMCID: PMC3211153 DOI: 10.1186/1556-276x-6-109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 01/31/2011] [Indexed: 05/31/2023]
Abstract
In this article, a scanning probe method based on nanoscale capacitance measurements was used to investigate the lateral homogeneity of the electron mean free path both in pristine and ion-irradiated graphene. The local variations in the electronic transport properties were explained taking into account the scattering of electrons by charged impurities and point defects (vacancies). Electron mean free path is mainly limited by charged impurities in unirradiated graphene, whereas an important role is played by lattice vacancies after irradiation. The local density of the charged impurities and vacancies were determined for different irradiated ion fluences.
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Affiliation(s)
| | - Sushant Sonde
- CNR-IMM, Strada VIII, 5, Zona Industriale, 95121, Catania, Italy
- Scuola Superiore di Catania, Via San Nullo, 5/I, 95123, Catania, Italy
| | - Emanuele Rimini
- CNR-IMM, Strada VIII, 5, Zona Industriale, 95121, Catania, Italy
- Department of Physics and Astronomy, University of Catania, Via S. Sofia, 95123, Catania, Italy
| | - Vito Raineri
- CNR-IMM, Strada VIII, 5, Zona Industriale, 95121, Catania, Italy
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Giannazzo F, Eyben P, Baranowski J, Camassel J, Lányi S. Advanced materials nanocharacterization. Nanoscale Res Lett 2011; 6:107. [PMID: 21711622 PMCID: PMC3211151 DOI: 10.1186/1556-276x-6-107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 01/31/2011] [Indexed: 05/31/2023]
Abstract
This special issue of Nanoscale Research Letters contains scientific contributions presented at the Symposium D "Multidimensional Electrical and Chemical Characterization at the Nanometer-scale of Organic and Inorganic Semiconductors" of the E-MRS Fall Meeting 2010, which was held in Warsaw, Poland from 13th to 17th September, 2010.
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Affiliation(s)
| | | | - Jacek Baranowski
- Institute of experimental Physics, ul. Hoża 69 Warsaw 00-681, Poland
| | - Jean Camassel
- Groupe d'Etude des Semiconducteurs, Université Montpellier 2, 34095 Montpellier Cedex 5, France
| | - Stefan Lányi
- Institute of Physics, SAS Dúbravská cesta 9 845 11 Bratislava, Slovakia
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Giannazzo F, Sonde S, Raineri V, Patanè G, Compagnini G, Aliotta F, Ponterio R, Rimini E. Optical, morphological and spectro- scopic characterization of graphene on SiO2. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/pssc.200982967] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Ruffino F, Grimaldi M, Giannazzo F, Roccaforte F, Raineri V. Atomic Force Microscopy Study of the Kinetic Roughening in Nanostructured Gold Films on SiO2. Nanoscale Res Lett 2009; 4:262-8. [PMID: 20596386 PMCID: PMC2894129 DOI: 10.1007/s11671-008-9235-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Accepted: 12/18/2008] [Indexed: 05/29/2023]
Abstract
Dynamic scaling behavior has been observed during the room-temperature growth of sputtered Au films on SiO2using the atomic force microscopy technique. By the analyses of the dependence of the roughness, σ, of the surface roughness power,P(f), and of the correlation length,ξ, on the film thickness,h, the roughness exponent,α = 0.9 ± 0.1, the growth exponent,β = 0.3 ± 0.1, and the dynamic scaling exponent,z = 3.0 ± 0.1 were independently obtained. These values suggest that the sputtering deposition of Au on SiO2at room temperature belongs to a conservative growth process in which the Au grain boundary diffusion plays a dominant role.
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Affiliation(s)
- F Ruffino
- Dipartimento di Fisica e Astronomia, MATIS CNR-INFM, Università di Catania, via S, Sofia 64, I-95123, Catania, Italy.
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