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Han B, Zhao Y, Ma C, Wang C, Tian X, Wang Y, Hu W, Samorì P. Asymmetric Chemical Functionalization of Top-Contact Electrodes: Tuning the Charge Injection for High-Performance MoS 2 Field-Effect Transistors and Schottky Diodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2109445. [PMID: 35061928 DOI: 10.1002/adma.202109445] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 01/11/2022] [Indexed: 06/14/2023]
Abstract
The fabrication of high-performance (opto-)electronic devices based on 2D channel materials requires the optimization of the charge injection at electrode-semiconductor interfaces. While chemical functionalization with chemisorbed self-assembled monolayers has been extensively exploited to adjust the work function of metallic electrodes in bottom-contact devices, such a strategy has not been demonstrated for the top-contact configuration, despite the latter being known to offer enhanced charge-injection characteristics. Here, a novel contact engineering method is developed to functionalize gold electrodes in top-contact field-effect transistors (FETs) via the transfer of chemically pre-modified electrodes. The source and drain Au electrodes of the molybdenum disulfide (MoS2 ) FETs are functionalized with thiolated molecules possessing different dipole moments. While the modification of the electrodes with electron-donating molecules yields a marked improvement of device performance, the asymmetric functionalization of the source and drain electrodes with different molecules with opposed dipole moment enables the fabrication of a high-performance Schottky diode with a rectification ratio of ≈103 . This unprecedented strategy to tune the charge injection in top-contact MoS2 FETs is of general applicability for the fabrication of high-performance (opto-)electronic devices, in which asymmetric charge injection is required, enabling tailoring of the device characteristics on demand.
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Affiliation(s)
- Bin Han
- Université de Strasbourg, CNRS, ISIS, 8 allée Gaspard Monge, Strasbourg, 67000, France
| | - Yuda Zhao
- Université de Strasbourg, CNRS, ISIS, 8 allée Gaspard Monge, Strasbourg, 67000, France
| | - Chun Ma
- Université de Strasbourg, CNRS, ISIS, 8 allée Gaspard Monge, Strasbourg, 67000, France
| | - Can Wang
- Université de Strasbourg, CNRS, ISIS, 8 allée Gaspard Monge, Strasbourg, 67000, France
| | - Xinzi Tian
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, China
| | - Ye Wang
- Université de Strasbourg, CNRS, ISIS, 8 allée Gaspard Monge, Strasbourg, 67000, France
| | - Wenping Hu
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, China
| | - Paolo Samorì
- Université de Strasbourg, CNRS, ISIS, 8 allée Gaspard Monge, Strasbourg, 67000, France
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Nanofabrication Techniques in Large-Area Molecular Electronic Devices. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10176064] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The societal impact of the electronics industry is enormous—not to mention how this industry impinges on the global economy. The foreseen limits of the current technology—technical, economic, and sustainability issues—open the door to the search for successor technologies. In this context, molecular electronics has emerged as a promising candidate that, at least in the short-term, will not likely replace our silicon-based electronics, but improve its performance through a nascent hybrid technology. Such technology will take advantage of both the small dimensions of the molecules and new functionalities resulting from the quantum effects that govern the properties at the molecular scale. An optimization of interface engineering and integration of molecules to form densely integrated individually addressable arrays of molecules are two crucial aspects in the molecular electronics field. These challenges should be met to establish the bridge between organic functional materials and hard electronics required for the incorporation of such hybrid technology in the market. In this review, the most advanced methods for fabricating large-area molecular electronic devices are presented, highlighting their advantages and limitations. Special emphasis is focused on bottom-up methodologies for the fabrication of well-ordered and tightly-packed monolayers onto the bottom electrode, followed by a description of the top-contact deposition methods so far used.
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Liu Y, Zhong M, Downey EF, Chen X, Li T, Nørgaard K, Wei Z. Temperature dependence of charge transport in solid-state molecular junctions based on oligo(phenylene ethynylene)s. NANOTECHNOLOGY 2020; 31:164001. [PMID: 31891933 DOI: 10.1088/1361-6528/ab6681] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The ultimate goal of molecular electronics is to achieve practical applications. For approaching the target, we have successfully fabricated solid-state junctions based on oligo(phenylene ethynylene)s (OPEs) and cruciform OPEs with extended tetrathiafulvalene (TTF) (OPE3 and OPE3-TTF) self-assembled monolayers (SAMs) with a diamine anchoring group. SAMs were confined in micropores with gold substrates to ensure well-defined device surface areas. The transport properties were conducted on a double-junction layout, which the rGO films used for top contacts and interconnects between adjacent SAMs. The solid-state devices based on OPE3-TTF SAMs showed the expected higher conductance under ambient conditions because of the incorporation of a TTF moiety. The two devices displayed varying degrees of temperature dependence with decreasing temperature, which resulted from the cross-conjugated OPE3-TTF molecule exhibiting quantum interference while the linear-conjugated OPE3 molecule did not. This study shows the temperature dependence of the electrical properties of molecular devices based on cruciform OPEs, further enriching the research results of functional molecular devices.
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Affiliation(s)
- Yuqing Liu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences & Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100083, People's Republic of China. Sino-Danish College, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China. Nano-Science Center and Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
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Using Polarized Spectroscopy to Investigate Order in Thin-Films of Ionic Self-Assembled Materials Based on Azo-Dyes. NANOMATERIALS 2018; 8:nano8020109. [PMID: 29462883 PMCID: PMC5853740 DOI: 10.3390/nano8020109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 02/08/2018] [Accepted: 02/12/2018] [Indexed: 12/04/2022]
Abstract
Three series of ionic self-assembled materials based on anionic azo-dyes and cationic benzalkonium surfactants were synthesized and thin films were prepared by spin-casting. These thin films appear isotropic when investigated with polarized optical microscopy, although they are highly anisotropic. Here, three series of homologous materials were studied to rationalize this observation. Investigating thin films of ordered molecular materials relies to a large extent on advanced experimental methods and large research infrastructure. A statement that in particular is true for thin films with nanoscopic order, where X-ray reflectometry, X-ray and neutron scattering, electron microscopy and atom force microscopy (AFM) has to be used to elucidate film morphology and the underlying molecular structure. Here, the thin films were investigated using AFM, optical microscopy and polarized absorption spectroscopy. It was shown that by using numerical method for treating the polarized absorption spectroscopy data, the molecular structure can be elucidated. Further, it was shown that polarized optical spectroscopy is a general tool that allows determination of the molecular order in thin films. Finally, it was found that full control of thermal history and rigorous control of the ionic self-assembly conditions are required to reproducibly make these materials of high nanoscopic order. Similarly, the conditions for spin-casting are shown to be determining for the overall thin film morphology, while molecular order is maintained.
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Li T, Jevric M, Hauptmann JR, Hviid R, Wei Z, Wang R, Reeler NEA, Thyrhaug E, Petersen S, Meyer JAS, Bovet N, Vosch T, Nygård J, Qiu X, Hu W, Liu Y, Solomon GC, Kjaergaard HG, Bjørnholm T, Nielsen MB, Laursen BW, Nørgaard K. Ultrathin reduced graphene oxide films as transparent top-contacts for light switchable solid-state molecular junctions. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:4164-4170. [PMID: 23765569 DOI: 10.1002/adma.201300607] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 04/09/2013] [Indexed: 06/02/2023]
Abstract
A new type of solid-state molecular junction is introduced, which employs reduced graphene oxide as a transparent top contact that permits a self-assembled molecular monolayer to be photoswitched in situ, while simultaneously enabling charge-transport measurements across the molecules. The electrical switching behavior of a less-studied molecular switch, dihydroazulene/vinylheptafulvene, is described, which is used as a test case.
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Affiliation(s)
- Tao Li
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen, Denmark
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Neuhold A, Brandner H, Ausserlechner SJ, Lorbek S, Neuschitzer M, Zojer E, Teichert C, Resel R. X-ray based tools for the investigation of buried interfaces in organic electronic devices. ORGANIC ELECTRONICS 2013; 14:479-487. [PMID: 23565069 PMCID: PMC3608035 DOI: 10.1016/j.orgel.2012.11.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 11/15/2012] [Accepted: 11/19/2012] [Indexed: 05/29/2023]
Abstract
X-ray reflectivity combined with grazing incidence diffraction is a valuable tool for investigating organic multilayer structures that can be used in devices. We focus on a bilayer stack consisting of two materials (poly-(3-hexylthiophene)) (P3HT) and poly-(4-styrenesulfonic acid) (PSSA) spin cast from orthogonal solvents (water in the case of PSSA and chloroform or toluene for P3HT). X-ray reflectivity is used to determine the thickness of all layers as well as the roughness of the organic-organic hetero-interface and the P3HT surface. The surface roughness is found to be consistent with the results of atomic force microscopy measurements. For the roughness of P3HT/PSSA interface, we observe a strong dependence on the solvent used for P3HT deposition. The solvent also strongly impacts the texturing of the P3HT crystallites as revealed by grazing incidence diffraction. When applying the various PSSA/P3HT multilayers in organic thin-film transistors, we find an excellent correlation between the determined interface morphology, structure and the device performance.
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Affiliation(s)
- Alfred Neuhold
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Hannes Brandner
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Simon J. Ausserlechner
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Stefan Lorbek
- Institute of Physics, Montan Universität Leoben, 8700 Leoben, Austria
| | - Markus Neuschitzer
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Egbert Zojer
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | | | - Roland Resel
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
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Ren L, Gao H, Gao S, Liu J, Zhang W. Determination of multilayer thicknesses of GaAs/AlAs
superlattice by grazing incidence X-ray reflectivity. INTERNATIONAL JOURNAL OF METROLOGY AND QUALITY ENGINEERING 2013. [DOI: 10.1051/ijmqe/2013040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
The grazing incidence X-ray reflectivity is used to determine the multilayer thickness of
GaAs/AlAs supperlattice. The measurement process includes the fitting model and the
measurement conditions (different powers of 45 kV × 40 mA, 40 kV × 40 mA and 35 kV × 40
mA, different step sizes of 0.005°, 0.008° and 0.010°,
and different times per step of 1 s, 2 s, 3 s). In order to obtain the valid measurement
process, the combined standard deviation is used as the normal of the fitting results
selection. As a result, the measurement condition of 0.008° step size and 2 s
time per step with the power 40 kV × 40 mA is selectable with the operation stability of
facilities and smaller error.
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Petersen S, Glyvradal M, Bøggild P, Hu W, Feidenhans'l R, Laursen BW. Graphene oxide as a monoatomic blocking layer. ACS NANO 2012; 6:8022-8029. [PMID: 22891605 DOI: 10.1021/nn302628q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Monolayer graphene oxide (mGO) is shown to effectively protect molecular thin films from reorganization and function as an atomically thin barrier for vapor-deposited Ti/Al metal top electrodes. Fragile organic Langmuir-Blodgett (LB) films of C(22) fatty acid cadmium salts (cadmium(II) behenate) were covered by a compressed mosaic LB film of mGO flakes. These hybrid LB films were examined with atomic force microscopy (AFM) and X-ray reflectivity, both with and without the metal top electrodes. While the AFM enabled surface and morphology analysis, the X-ray reflectivity allowed for a detailed structural depth profiling of the organic film and mGO layer below the metal top layers. The structure of the mGO-protected LB films was found to be perfectly preserved; in contrast, it has previously been shown that metal deposition completely destroys the first two LB layers of unprotected films. This study provides clear evidence of the efficient protection offered by a single atomic layer of GO.
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Affiliation(s)
- Søren Petersen
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
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Li T, Hauptmann JR, Wei Z, Petersen S, Bovet N, Vosch T, Nygård J, Hu W, Liu Y, Bjørnholm T, Nørgaard K, Laursen BW. Solution-processed ultrathin chemically derived graphene films as soft top contacts for solid-state molecular electronic junctions. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:1333-1339. [PMID: 22311594 DOI: 10.1002/adma.201104550] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Indexed: 05/31/2023]
Abstract
A novel method using solution-processed ultrathin chemically derived graphene films as soft top contacts for the non-destructive fabrication of molecular junctions is demonstrated. We believe this protocol will greatly enrich the solid-state test beds for molecular electronics due to its low-cost, easy-processing and flexible nature.
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Affiliation(s)
- Tao Li
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen, Denmark
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Hauptmann JR, Li T, Petersen S, Nygård J, Hedegård P, Bjørnholm T, Laursen BW, Nørgaard K. Electrical annealing and temperature dependent transversal conduction in multilayer reduced graphene oxide films for solid-state molecular devices. Phys Chem Chem Phys 2012; 14:14277-81. [DOI: 10.1039/c2cp41723e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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