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Dascalescu I, Palade C, Slav A, Stavarache I, Cojocaru O, Teodorescu VS, Maraloiu VA, Lepadatu AM, Ciurea ML, Stoica T. Enhancing SiGeSn nanocrystals SWIR photosensing by high passivation in nanocrystalline HfO 2 matrix. Sci Rep 2024; 14:3532. [PMID: 38347024 PMCID: PMC10861535 DOI: 10.1038/s41598-024-53845-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 02/06/2024] [Indexed: 02/15/2024] Open
Abstract
SiGeSn nanocrystals (NCs) in oxides are of considerable interest for photo-effect applications due to the fine-tuning of the optical bandgap by quantum confinement in NCs. We present a detailed study regarding the silicon germanium tin (SiGeSn) NCs embedded in a nanocrystalline hafnium oxide (HfO2) matrix fabricated by using magnetron co-sputtering deposition at room temperature and rapid thermal annealing (RTA). The NCs were formed at temperatures in the range of 500-800 °C. RTA was performed to obtain SiGeSn NCs with surfaces passivated by the embedding HfO2 matrix. The formation of NCs and β-Sn segregation were discussed in relation to the deposition and processing conditions by employing HRTEM, XRD and Raman spectroscopy studies. The spectral photosensitivity exhibited up to 2000 nm in short-wavelength infrared (SWIR) depending on the Sn composition was obtained. Comparing to similar results on GeSn NCs in SiO2 matrix, the addition of Si offers a better thermal stability of SiGeSn NCs, while the use of HfO2 matrix results in better passivation of NCs increasing the SWIR photosensitivity at room temperature. These results suggest that SiGeSn NCs embedded in an HfO2 matrix are a promising material for SWIR optoelectronic devices.
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Affiliation(s)
- Ioana Dascalescu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Catalin Palade
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Adrian Slav
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Ionel Stavarache
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Ovidiu Cojocaru
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Valentin Serban Teodorescu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
- Academy of Romanian Scientists, 54 Splaiul Independentei, 050094, Bucharest, Romania
| | | | - Ana-Maria Lepadatu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.
| | - Magdalena Lidia Ciurea
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.
- Academy of Romanian Scientists, 54 Splaiul Independentei, 050094, Bucharest, Romania.
| | - Toma Stoica
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.
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Yang CC, Cheng CH, Chen TH, Lin YH, He JH, Tsai DP, Lin GR. Synthesis of Nano-Structured Ge as Transmissive or Reflective Saturable Absorber for Mode-Locked Fiber Laser. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:nano13101697. [PMID: 37242115 DOI: 10.3390/nano13101697] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 05/08/2023] [Accepted: 05/19/2023] [Indexed: 05/28/2023]
Abstract
Amorphous-Ge (α-Ge) or free-standing nanoparticles (NPs) synthesized via hydrogen-free plasma-enhanced chemical vapor deposition (PECVD) were applied as transmissive or reflective saturable absorbers, respectively, for starting up passively mode-locked erbium-doped fiber lasers (EDFLs). Under a threshold pumping power of 41 mW for mode-locking the EDFL, the transmissive α-Ge film could serve as a saturable absorber with a modulation depth of 52-58%, self-starting EDFL pulsation with a pulsewidth of approximately 700 fs. Under a high power of 155 mW, the pulsewidth of the EDFL mode-locked by the 15 s-grown α-Ge was suppressed to 290 fs, with a corresponding spectral linewidth of 8.95 nm due to the soliton compression induced by intra-cavity self-phase modulation. The Ge-NP-on-Au (Ge-NP/Au) films could also serve as a reflective-type saturable absorber to passively mode-lock the EDFL with a broadened pulsewidth of 3.7-3.9 ps under a high-gain operation with 250 mW pumping power. The reflection-type Ge-NP/Au film was an imperfect mode-locker, owing to their strong surface-scattered deflection in the near-infrared wavelength region. From the abovementioned results, both ultra-thin α-Ge film and free-standing Ge NP exhibit potential as transmissive and reflective saturable absorbers, respectively, for ultrafast fiber lasers.
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Affiliation(s)
- Chi-Cheng Yang
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Chih-Hsien Cheng
- Optical Access Technology Laboratory, Photonic ICT Research Center, Network Research Institute, National Institute of Information and Communications Technology, Koganei 184-8795, Japan
| | - Ting-Hui Chen
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Yung-Hsiang Lin
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Jr-Hau He
- Department of Materials Science and Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China
| | - Din-Ping Tsai
- Department of Electronic and Information Engineering, Hong Kong Polytechnic University, Kowloon 999077, Hong Kong, China
| | - Gong-Ru Lin
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
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Capista D, Lozzi L, Pelella A, Di Bartolomeo A, Giubileo F, Passacantando M. Spatially Resolved Photo-Response of a Carbon Nanotube/Si Photodetector. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:650. [PMID: 36839018 PMCID: PMC9967656 DOI: 10.3390/nano13040650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/23/2023] [Accepted: 02/05/2023] [Indexed: 06/18/2023]
Abstract
Photodetectors based on vertical multi-walled carbon nanotube (MWCNT) film-Si heterojunctions are realized by growing MWCNTs on n-type Si substrates with a top surface covered by Si3N4 layers. Spatially resolved photocurrent measurements reveal that higher photo detection is achieved in regions with thinner MWCNT film, where nearly 100% external quantum efficiency is achieved. Hence, we propose a simple method based on the use of scotch tape with which to tune the thickness and density of as-grown MWCNT film and enhance device photo-response.
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Affiliation(s)
- Daniele Capista
- Department of Physical and Chemical Science, University of L’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, Italy
| | - Luca Lozzi
- Department of Physical and Chemical Science, University of L’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, Italy
| | - Aniello Pelella
- Department of Physics, University of Salerno, Via Giovanni Paolo II 132, Fisciano, 84084 Salerno, Italy
| | - Antonio Di Bartolomeo
- Department of Physics, University of Salerno, Via Giovanni Paolo II 132, Fisciano, 84084 Salerno, Italy
| | | | - Maurizio Passacantando
- Department of Physical and Chemical Science, University of L’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, Italy
- CNR-SPIN Via Vetoio, Coppito, 67100 L’Aquila, Italy
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Broadening the Action Spectrum of TiO2-Based Photocatalysts to Visible Region by Substituting Platinum with Copper. NANOMATERIALS 2022; 12:nano12091584. [PMID: 35564293 PMCID: PMC9105519 DOI: 10.3390/nano12091584] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 04/29/2022] [Accepted: 05/05/2022] [Indexed: 11/24/2022]
Abstract
In this study, TiO2-based photocatalysts modified with Pt and Cu/CuOx were synthesized and studied in the photocatalytic reduction of CO2. The morphology and chemical states of synthesized photocatalysts were studied using UV-Vis diffuse reflectance spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. A series of light-emitting diodes (LEDs) with maximum intensity in the range of 365–450 nm was used to determine the action spectrum of photocatalysts. It is shown for, the first time, that the pre-calcination of TiO2 at 700 °C and the use of Cu/CuOx instead of Pt allow one to design a highly efficient photocatalyst for CO2 transformation shifting the working range to the visible light (425 nm). Cu/CuOx/TiO2 (calcined at 700 °C) shows a rate of CH4 formation of 1.2 ± 0.1 µmol h−1 g−1 and an overall CO2 reduction rate of 11 ± 1 µmol h−1 g−1 (at 425 nm).
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Nanocrystallized Ge-Rich SiGe-HfO 2 Highly Photosensitive in Short-Wave Infrared. MATERIALS 2021; 14:ma14227040. [PMID: 34832440 PMCID: PMC8623256 DOI: 10.3390/ma14227040] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/16/2021] [Accepted: 11/18/2021] [Indexed: 11/29/2022]
Abstract
Group IV nanocrystals (NCs), in particular from the Si–Ge system, are of high interest for Si photonics applications. Ge-rich SiGe NCs embedded in nanocrystallized HfO2 were obtained by magnetron sputtering deposition followed by rapid thermal annealing at 600 °C for nanostructuring. The complex characterization of morphology and crystalline structure by X-ray diffraction, μ-Raman spectroscopy, and cross-section transmission electron microscopy evidenced the formation of Ge-rich SiGe NCs (3–7 nm diameter) in a matrix of nanocrystallized HfO2. For avoiding the fast diffusion of Ge, the layer containing SiGe NCs was cladded by very thin top and bottom pure HfO2 layers. Nanocrystallized HfO2 with tetragonal/orthorhombic structure was revealed beside the monoclinic phase in both buffer HfO2 and SiGe NCs–HfO2 layers. In the top part, the film is mainly crystallized in the monoclinic phase. High efficiency of the photocurrent was obtained in a broad spectral range of curves of 600–2000 nm at low temperatures. The high-quality SiGe NC/HfO2 matrix interface together with the strain induced in SiGe NCs by nanocrystallization of both HfO2 matrix and SiGe nanoparticles explain the unexpectedly extended photoelectric sensitivity in short-wave infrared up to about 2000 nm that is more than the sensitivity limit for Ge, in spite of the increase of bandgap by well-known quantum confinement effect in SiGe NCs.
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Cojocaru O, Lepadatu AM, Nemnes GA, Stoica T, Ciurea ML. Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals. Sci Rep 2021; 11:13582. [PMID: 34193909 PMCID: PMC8245600 DOI: 10.1038/s41598-021-92936-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 05/31/2021] [Indexed: 11/17/2022] Open
Abstract
We present a detailed study regarding the bandgap dependence on diameter and composition of spherical Ge-rich GexSi1−x nanocrystals (NCs). For this, we conducted a series of atomistic density functional theory (DFT) calculations on H-passivated NCs of Ge-rich GeSi random alloys, with Ge atomic concentration varied from 50 to 100% and diameters ranging from 1 to 4 nm. As a result of the dominant confinement effect in the DFT computations, a composition invariance of the line shape of the bandgap diameter dependence was found for the entire computation range, the curves being shifted for different Ge concentrations by ΔE(eV) = 0.651(1 − x). The shape of the dependence of NCs bandgap on the diameter is well described by a power function 4.58/d1.25 for 2–4 nm diameter range, while for smaller diameters, there is a tendency to limit the bandgap to a finite value. By H-passivation of the NC surface, the effect of surface states near the band edges is excluded aiming to accurately determine the NC bandgap. The number of H atoms necessary to fully passivate the spherical GexSi1−x NC surface reaches the total number atoms of the Ge + Si core for smallest NCs and still remains about 25% from total number of atoms for bigger NC diameters of 4 nm. The findings are in line with existing theoretical and experimental published data on pure Ge NCs and allow the evaluation of the GeSi NCs behavior required by desired optical sensor applications for which there is a lack of DFT simulation data in literature.
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Affiliation(s)
- Ovidiu Cojocaru
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.,Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125, Magurele, Romania
| | - Ana-Maria Lepadatu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - George Alexandru Nemnes
- Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125, Magurele, Romania
| | - Toma Stoica
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.
| | - Magdalena Lidia Ciurea
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania. .,Academy of Romanian Scientists, 54 Splaiul Independentei, 050094, Bucharest, Romania.
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Slav A, Dascalescu I, Lepadatu AM, Palade C, Zoita NC, Stroescu H, Iftimie S, Lazanu S, Gartner M, Buca D, Teodorescu VS, Ciurea ML, Braic M, Stoica T. GeSn/SiO 2 Multilayers by Magnetron Sputtering Deposition for Short-Wave Infrared Photonics. ACS APPLIED MATERIALS & INTERFACES 2020; 12:56161-56171. [PMID: 33275429 DOI: 10.1021/acsami.0c15887] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The development of short-wave infrared (SWIR) photonics based on GeSn alloys is of high technological interest for many application fields, such as the Internet of things or pollution monitoring. The manufacture of crystalline GeSn is a major challenge, mainly because of the low miscibility of Ge and Sn. The use of embedded GeSn nanocrystals (NCs) by magnetron sputtering is a cost-effective and efficient method to relax the growth conditions. We report on the use of GeSn/SiO2 multilayer deposition as a way to control the NC size and their insulation. The in situ prenucleation of NCs during deposition was followed by ex situ rapid thermal annealing. The nanocrystallization of 20×(11nm_Ge0.865Sn0.135/1.5nm_SiO2) multilayers leads to formation of GeSn NCs with ∼16% Sn concentration and ∼9 nm size. Formation of GeSn domes that are vertically correlated contributes to the nanocrystallization process. The absorption limit of ∼0.4 eV in SWIR found by ellipsometry is in agreement with the spectral photosensitivity. The ITO/20×(GeSn NC/SiO2)/p-Si/Al diodes show a maximum value of the SWIR photosensitivity at a reverse voltage of 0.5 V, with extended sensitivity to wavelengths longer than 2200 nm. The multilayer diodes have higher photocurrent efficiency compared to diodes based on a thick monolayer of GeSn NCs.
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Affiliation(s)
- Adrian Slav
- National Institute of Materials Physics, 405A Atomistilor Street, Magurele 077125, Romania
| | - Ioana Dascalescu
- National Institute of Materials Physics, 405A Atomistilor Street, Magurele 077125, Romania
- Faculty of Physics, University of Bucharest, 405 Atomistilor Street, Magurele 077125, Romania
| | - Ana-Maria Lepadatu
- National Institute of Materials Physics, 405A Atomistilor Street, Magurele 077125, Romania
| | - Catalin Palade
- National Institute of Materials Physics, 405A Atomistilor Street, Magurele 077125, Romania
| | - Nicolae C Zoita
- National Institute for Research and Development in Optoelectronics, 409 Atomistilor Street, Magurele 077125, Romania
| | - Hermine Stroescu
- Institute of Physical Chemistry of the Romanian Academy, 202 Splaiul Independentei, Bucharest 060021, Romania
| | - Sorina Iftimie
- Faculty of Physics, University of Bucharest, 405 Atomistilor Street, Magurele 077125, Romania
| | - Sorina Lazanu
- National Institute of Materials Physics, 405A Atomistilor Street, Magurele 077125, Romania
| | - Mariuca Gartner
- Institute of Physical Chemistry of the Romanian Academy, 202 Splaiul Independentei, Bucharest 060021, Romania
| | - Dan Buca
- Peter Grünberg Institut 9 (PGI 9) and JARA Fundamentals of Future Information Technologies, Forschungszentrum Jülich, Jülich 52425, Germany
| | - Valentin S Teodorescu
- National Institute of Materials Physics, 405A Atomistilor Street, Magurele 077125, Romania
- Academy of Romanian Scientists, 54 Splaiul Independentei, Bucharest 050094, Romania
| | - Magdalena L Ciurea
- National Institute of Materials Physics, 405A Atomistilor Street, Magurele 077125, Romania
- Academy of Romanian Scientists, 54 Splaiul Independentei, Bucharest 050094, Romania
| | - Mariana Braic
- National Institute for Research and Development in Optoelectronics, 409 Atomistilor Street, Magurele 077125, Romania
| | - Toma Stoica
- National Institute of Materials Physics, 405A Atomistilor Street, Magurele 077125, Romania
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GeSi Nanocrystals Photo-Sensors for Optical Detection of Slippery Road Conditions Combining Two Classification Algorithms. SENSORS 2020; 20:s20216395. [PMID: 33182467 PMCID: PMC7665139 DOI: 10.3390/s20216395] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 10/29/2020] [Accepted: 11/05/2020] [Indexed: 02/06/2023]
Abstract
One of the key elements in assessing traffic safety on the roads is the detection of asphalt conditions. In this paper, we propose an optical sensor based on GeSi nanocrystals embedded in SiO2 matrix that discriminates between different slippery road conditions (wet and icy asphalt and asphalt covered with dirty ice) in respect to dry asphalt. The sensor is fabricated by magnetron sputtering deposition followed by rapid thermal annealing. The photodetector has spectral sensitivity in the 360–1350 nm range and the signal-noise ratio is 102–103. The working principle of sensor setup for detection of road conditions is based on the photoresponse (photocurrent) of the sensor under illumination with the light reflected from the asphalt having different reflection coefficients for dry, wet, icy and dirty ice coatings. For this, the asphalt is illuminated sequentially with 980 and 1064 nm laser diodes. A database of these photocurrents is obtained for the different road conditions. We show that the use of both k-nearest neighbor and artificial neural networks classification algorithms enables a more accurate recognition of the class corresponding to a specific road state than in the case of using only one algorithm. This is achieved by comparing the new output sensor data with previously classified data for each algorithm and then by performing an intersection of the algorithms’ results.
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Dascalescu I, Zoita NC, Slav A, Matei E, Iftimie S, Comanescu F, Lepadatu AM, Palade C, Lazanu S, Buca D, Teodorescu VS, Ciurea ML, Braic M, Stoica T. Epitaxial GeSn Obtained by High Power Impulse Magnetron Sputtering and the Heterojunction with Embedded GeSn Nanocrystals for Shortwave Infrared Detection. ACS APPLIED MATERIALS & INTERFACES 2020; 12:33879-33886. [PMID: 32633935 DOI: 10.1021/acsami.0c06212] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
GeSn alloys have the potential of extending the Si photonics functionality in shortwave infrared (SWIR) light emission and detection. Epitaxial GeSn layers were deposited on a relaxed Ge buffer on Si(100) wafer by using high power impulse magnetron sputtering (HiPI-MS). Detailed X-ray reciprocal space mapping and HRTEM investigations indicate higher crystalline quality of GeSn epitaxial layers deposited by Ge HiPI-MS compared to commonly used radio frequency magnetron sputtering (RF-MS). To obtain a rectifying heterostructure for SWIR light detection, a layer of GeSn nanocrystals (NCs) embedded in oxide was deposited on the epitaxial GeSn one. Embedded GeSn NCs are obtained by cosputtering deposition of (Ge1-xSnx)1-y(SiO2)y layers and subsequent rapid thermal annealing at a low temperature of 400 °C. Intrinsic GeSn structural defects give p-type behavior, while the presence of oxygen leads to the n-character of the embedded GeSn NCs. Such an embedded NCs/epitaxial GeSn p-n heterostructure shows superior photoelectrical response up to 3 orders of magnitude increase in the 1.2-2.5 μm range, as compared to performances of diode based only on embedded NCs.
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Affiliation(s)
- Ioana Dascalescu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
- Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125 Magurele, Romania
| | - Nicolae C Zoita
- National Institute for Research and Development in Optoelectronics, 409 Atomistilor Street, 077125 Magurele, Romania
| | - Adrian Slav
- National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
| | - Elena Matei
- National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
| | - Sorina Iftimie
- Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125 Magurele, Romania
| | - Florin Comanescu
- National Institute for Research and Development in Microtechnologies, 077190 Voluntari, Romania
| | - Ana-Maria Lepadatu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
| | - Catalin Palade
- National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
| | - Sorina Lazanu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
| | - Dan Buca
- Peter Grünberg Institut 9 (PGI 9) and JARA Fundamentals of Future Information Technologies, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Valentin S Teodorescu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
- Academy of Romanian Scientists, Bucharest, 050094 Bucharest, Romania
| | - Magdalena L Ciurea
- National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
- Academy of Romanian Scientists, Bucharest, 050094 Bucharest, Romania
| | - Mariana Braic
- National Institute for Research and Development in Optoelectronics, 409 Atomistilor Street, 077125 Magurele, Romania
| | - Toma Stoica
- National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
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SiGe nanocrystals in SiO 2 with high photosensitivity from visible to short-wave infrared. Sci Rep 2020; 10:3252. [PMID: 32094361 PMCID: PMC7040041 DOI: 10.1038/s41598-020-60000-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 01/30/2020] [Indexed: 11/26/2022] Open
Abstract
Films of SiGe nanocrystals (NCs) in oxide have the advantage of tuning the energy band gap by adjusting SiGe NCs composition and size. In this study, SiGe-SiO2 amorphous films were deposited by magnetron sputtering on Si substrate followed by rapid thermal annealing at 700, 800 and 1000 °C. We investigated films with Si:Ge:SiO2 compositions of 25:25:50 vol.% and 5:45:50 vol.%. TEM investigations reveal the major changes in films morphology (SiGe NCs with different sizes and densities) produced by Si:Ge ratio and annealing temperature. XPS also show that the film depth profile of SiGe content is dependent on the annealing temperature. These changes strongly influence electrical and photoconduction properties. Depending on annealing temperature and Si:Ge ratio, photocurrents can be 103 times higher than dark currents. The photocurrent cutoff wavelength obtained on samples with 25:25 vol% SiGe ratio decreases with annealing temperature increase from 1260 nm in SWIR for 700 °C annealed films to 1210 nm for those at 1000 °C. By increasing Ge content in SiGe (5:45 vol%) the cutoff wavelength significantly shifts to 1345 nm (800 °C annealing). By performing measurements at 100 K, the cutoff wavelength extends in SWIR to 1630 nm having high photoresponsivity of 9.35 AW−1.
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11
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Sultan MT, Maraloiu AV, Stavarache I, Gudmundsson JT, Manolescu A, Teodorescu VS, Ciurea ML, Svavarsson HG. Fabrication and characterization of Si 1- x Ge x nanocrystals in as-grown and annealed structures: a comparative study. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2019; 10:1873-1882. [PMID: 31598453 PMCID: PMC6774067 DOI: 10.3762/bjnano.10.182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 08/28/2019] [Indexed: 05/28/2023]
Abstract
Multilayer structures comprising of SiO2/SiGe/SiO2 and containing SiGe nanoparticles were obtained by depositing SiO2 layers using reactive direct current magnetron sputtering (dcMS), whereas, Si and Ge were co-sputtered using dcMS and high-power impulse magnetron sputtering (HiPIMS). The as-grown structures subsequently underwent rapid thermal annealing (550-900 °C for 1 min) in N2 ambient atmosphere. The structures were investigated using X-ray diffraction, high-resolution transmission electron microscopy together with spectral photocurrent measurements, to explore structural changes and corresponding properties. It is observed that the employment of HiPIMS facilitates the formation of SiGe nanoparticles (2.1 ± 0.8 nm) in the as-grown structure, and that presence of such nanoparticles acts as a seed for heterogeneous nucleation, which upon annealing results in the periodically arranged columnar self-assembly of SiGe core-shell nanocrystals. An increase in photocurrent intensity by more than an order of magnitude was achieved by annealing. Furthermore, a detailed discussion is provided on strain development within the structures, the consequential interface characteristics and its effect on the photocurrent spectra.
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Affiliation(s)
- Muhammad Taha Sultan
- Reykjavik University, School of Science and Engineering, IS-101 Reykjavik, Iceland
| | | | - Ionel Stavarache
- National Institute of Materials Physics, 077125 Magurele, Romania
| | - Jón Tómas Gudmundsson
- Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland
- Department of Space and Plasma Physics, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, SE-100 44, Stockholm, Sweden
| | - Andrei Manolescu
- Reykjavik University, School of Science and Engineering, IS-101 Reykjavik, Iceland
| | - Valentin Serban Teodorescu
- National Institute of Materials Physics, 077125 Magurele, Romania
- Academy of Romanian Scientists, 050094 Bucharest, Romania
| | - Magdalena Lidia Ciurea
- National Institute of Materials Physics, 077125 Magurele, Romania
- Academy of Romanian Scientists, 050094 Bucharest, Romania
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Sultan MT, Gudmundsson JT, Manolescu A, Teodorescu VS, Ciurea ML, Svavarsson HG. Efficacy of annealing and fabrication parameters on photo-response of SiGe in TiO 2 matrix. NANOTECHNOLOGY 2019; 30:365604. [PMID: 31151130 DOI: 10.1088/1361-6528/ab260e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
SiGe nanoparticles dispersed in a dielectric matrix exhibit properties different from those of bulk and have shown great potential in devices for application in advanced optoelectronics. Annealing is a common fabrication step used to increase crystallinity and to form nanoparticles in such a system. A frequent downside of such annealing treatment is the formation of insulating SiO2 layer at the matrix/SiGe interface, degrading the optical properties of the structure. An annealing process that could bypass this downside would therefore be of great interest. In this work, a short-time furnace annealing of a SiGe/TiO2 system is applied to obtain SiGe nanoparticles without formation of the undesired SiO2 layer between the dielectric matrix (TiO2) and SiGe. The structures were prepared by depositing alternate layers of TiO2 and SiGe films, using direct-current magnetron sputtering technique. A wide range spectral response with a response-threshold up to ∼1300 nm was obtained, accompanied with an increase in photo-response of more than two-orders of magnitude. Scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy and grazing incidence x-ray diffraction were used to analyze the morphological changes in respective structures. Photoconductive properties were studied by measuring photocurrent spectra using applied dc-voltages at various temperatures.
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Affiliation(s)
- M T Sultan
- Reykjavik University, School of Science and Engineering, IS-101 Reykjavik, Iceland
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Stavarache I, Teodorescu VS, Prepelita P, Logofatu C, Ciurea ML. Ge nanoparticles in SiO 2 for near infrared photodetectors with high performance. Sci Rep 2019; 9:10286. [PMID: 31312003 PMCID: PMC6635504 DOI: 10.1038/s41598-019-46711-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 06/27/2019] [Indexed: 02/07/2023] Open
Abstract
In this work we prepared films of amorphous germanium nanoparticles embedded in SiO2 deposited by magnetron sputtering on Si and quartz heated substrates at 300, 400 and 500 °C. Structure, morphology, optical, electrical and photoconduction properties of all films were investigated. The Ge concentration in the depth of the films is strongly dependent on the deposition temperature. In the films deposited at 300 °C, the Ge content is constant in the depth, while films deposited at 500 °C show a significant decrease of Ge content from interface of the film with substrate towards the film free surface. From the absorption curves we obtained the Ge band gap of 1.39 eV for 300 °C deposited films and 1.44 eV for the films deposited at 500 °C. The photocurrents are higher with more than one order of magnitude than the dark ones. The photocurrent spectra present different cutoff wavelengths depending on the deposition temperature, i.e. 1325 nm for 300 °C and 1267 nm for 500 °C. These films present good responsivities of 2.42 AW−1 (52 μW incident power) at 300 °C and 0.69 AW−1 (57 mW) at 500 °C and high internal quantum efficiency of ∼445% for 300 °C and ∼118% for 500 °C.
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Affiliation(s)
- Ionel Stavarache
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Ilfov, Romania.
| | | | - Petronela Prepelita
- National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, 077125, Magurele, Ilfov, Romania
| | - Constantin Logofatu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Ilfov, Romania
| | - Magdalena Lidia Ciurea
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Ilfov, Romania. .,Academy of Romanian Scientists, 050094, Bucharest, Romania.
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