WorldWideScience

Sample records for amorphous silicon films

  1. Film adhesion in amorphous silicon solar cells

    Indian Academy of Sciences (India)

    A R M Yusoff; M N Syahrul; K Henkel

    2007-08-01

    A major issue encountered during fabrication of triple junction -Si solar cells on polyimide substrates is the adhesion of the solar cell thin films to the substrates. Here, we present our study of film adhesion in amorphous silicon solar cells made on different polyimide substrates (Kapton VN, Upilex-S and Gouldflex), and the effect of tie coats on film adhesion.

  2. Amorphous silicon for thin-film transistors

    NARCIS (Netherlands)

    Schropp, Rudolf Emmanuel Isidore

    1987-01-01

    Hydrogenated amorphous silicon (a-Si:H) has considerable potential as a semiconducting material for large-area photoelectric and photovoltaic applications. Moreover, a-Si:H thin-film transistors (TFT’s) are very well suited as switching devices in addressable liquid crystal display panels and addres

  3. Amorphous molybdenum silicon superconducting thin films

    Directory of Open Access Journals (Sweden)

    D. Bosworth

    2015-08-01

    Full Text Available Amorphous superconductors have become attractive candidate materials for superconducting nanowire single-photon detectors due to their ease of growth, homogeneity and competitive superconducting properties. To date the majority of devices have been fabricated using WxSi1−x, though other amorphous superconductors such as molybdenum silicide (MoxSi1−x offer increased transition temperature. This study focuses on the properties of MoSi thin films grown by magnetron sputtering. We examine how the composition and growth conditions affect film properties. For 100 nm film thickness, we report that the superconducting transition temperature (Tc reaches a maximum of 7.6 K at a composition of Mo83Si17. The transition temperature and amorphous character can be improved by cooling of the substrate during growth which inhibits formation of a crystalline phase. X-ray diffraction and transmission electron microscopy studies confirm the absence of long range order. We observe that for a range of 6 common substrates (silicon, thermally oxidized silicon, R- and C-plane sapphire, x-plane lithium niobate and quartz, there is no variation in superconducting transition temperature, making MoSi an excellent candidate material for SNSPDs.

  4. Tunable plasticity in amorphous silicon carbide films.

    Science.gov (United States)

    Matsuda, Yusuke; Kim, Namjun; King, Sean W; Bielefeld, Jeff; Stebbins, Jonathan F; Dauskardt, Reinhold H

    2013-08-28

    Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold.

  5. Raman and ellipsometric characterization of hydrogenated amorphous silicon thin films

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Hydrogenated amorphous silicon (a-Si:H) thin films were deposited by plasma-enhanced vapor deposition (PECVD) at different silane temperatures (Tg) before glow-discharge. The effect of Tg on the amorphous network and optoelectronic properties of the films has been investigated by Raman scattering spectra, ellipsometric transmittance spectra, and dark conductivity measurement, respectively. The results show that the increase in Tg leads to an improved ordering of amorphous network on the short and intermediate scales and an increase of both refractive index and absorption coefficient in a-Si:H thin films. It is indicated that the dark conductivity increases by two orders of magnitude when Tg is raised from room temperature (RT) to 433 K. The continuous ordering of amorphous network of a-Si:H thin films deposited at a higher Tg is the main cause for the increase of dark conductivity.

  6. Silicon nanocrystals on amorphous silicon carbide alloy thin films: Control of film properties and nanocrystals growth

    Energy Technology Data Exchange (ETDEWEB)

    Barbe, Jeremy, E-mail: jeremy.barbe@hotmail.com [CEA, Liten, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Universite de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, 31062 Toulouse (France); Xie, Ling; Leifer, Klaus [Department of Engineering Sciences, Uppsala University, Box 534, S-751 21 Uppsala (Sweden); Faucherand, Pascal; Morin, Christine; Rapisarda, Dario; De Vito, Eric [CEA, Liten, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Makasheva, Kremena; Despax, Bernard [Universite de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, 31062 Toulouse (France); CNRS, LAPLACE, F-31062 Toulouse (France); Perraud, Simon [CEA, Liten, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2012-11-01

    The present study demonstrates the growth of silicon nanocrystals on amorphous silicon carbide alloy thin films. Amorphous silicon carbide films [a-Si{sub 1-x}C{sub x}:H (with x < 0.3)] were obtained by plasma enhanced chemical vapor deposition from a mixture of silane and methane diluted in hydrogen. The effect of varying the precursor gas-flow ratio on the film properties was investigated. In particular, a wide optical band gap (2.3 eV) was reached by using a high methane-to-silane flow ratio during the deposition of the a-Si{sub 1-x}C{sub x}:H layer. The effect of short-time annealing at 700 Degree-Sign C on the composition and properties of the layer was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It was observed that the silicon-to-carbon ratio in the layer remains unchanged after short-time annealing, but the reorganization of the film due to a large dehydrogenation leads to a higher density of SiC bonds. Moreover, the film remains amorphous after the performed short-time annealing. In a second part, it was shown that a high density (1 Multiplication-Sign 10{sup 12} cm{sup -2}) of silicon nanocrystals can be grown by low pressure chemical vapor deposition on a-Si{sub 0.8}C{sub 0.2} surfaces at 700 Degree-Sign C, from silane diluted in hydrogen. The influence of growth time and silane partial pressure on nanocrystals size and density was studied. It was also found that amorphous silicon carbide surfaces enhance silicon nanocrystal nucleation with respect to SiO{sub 2}, due to the differences in surface chemical properties. - Highlights: Black-Right-Pointing-Pointer Silicon nanocrystals (Si-NC) growth on amorphous silicon carbide alloy thin films Black-Right-Pointing-Pointer Plasma deposited amorphous silicon carbide films with well-controlled properties Black-Right-Pointing-Pointer Study on the thermal effect of 700 Degree-Sign C short-time annealing on the layer properties Black-Right-Pointing-Pointer Low pressure

  7. Pyrolytic transformation from polydihydrosilane to hydrogenated amorphous silicon film

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Takashi, E-mail: mtakashi@jaist.ac.jp [Japan Science and Technology Agency, ERATO, Shimoda Nano-Liquid Process Project, 2-13 Asahidai, Nomi, Ishikawa, 923-1211 (Japan); Matsuki, Yasuo [Japan Science and Technology Agency, ERATO, Shimoda Nano-Liquid Process Project, 2-13 Asahidai, Nomi, Ishikawa, 923-1211 (Japan); Yokkaichi Research Center, JSR Corporation, 100 Kawajiri-cho, Yokkaichi, Mie, 510-8552 (Japan); Shimoda, Tatsuya [Japan Science and Technology Agency, ERATO, Shimoda Nano-Liquid Process Project, 2-13 Asahidai, Nomi, Ishikawa, 923-1211 (Japan); School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292 (Japan)

    2012-08-31

    The fabrication of thin film silicon devices based on solution processes rather than on conventional vacuum processes is of substantial interest since cost reductions may result. Using a solution process, we coated substrates with polydihydrosilane solution and studied the pyrolytic transformation of the material into hydrogenated amorphous silicon (a-Si:H). From thermal gravimetry and differential thermal analysis data a significant reduction in weight of the material and a construction of Si-Si bonds are concluded for the pyrolysis temperature T{sub p} = 270 to 360 Degree-Sign C. The appearance of amorphous silicon phonon bands in Raman spectra for films prepared at T{sub p} {>=} 330 Degree-Sign C suggests the construction of a three-dimensional amorphous silicon network. Films prepared at T{sub p} {>=} 360 Degree-Sign C exhibit a hydrogen content near 10 at.% and an optical gap near 1.6 eV similar to device-grade vacuum processed a-Si:H. However, the infrared microstructure factor, the spin density, and the photosensitivity require significant improvements. - Highlights: Black-Right-Pointing-Pointer We fabricate hydrogenated amorphous silicon (a-Si:H) films by a solution process. Black-Right-Pointing-Pointer The a-Si:H films are prepared by pyrolytic transformation in polysilane solution. Black-Right-Pointing-Pointer We investigate basic properties in relation to the pyrolysis temperature. Black-Right-Pointing-Pointer Raman spectra, hydrogen content, and optical gap are similar to device-grade a-Si:H. Black-Right-Pointing-Pointer Microstructure factor, spin density, and photoconductivity show poor quality.

  8. High thermal conductivity of a hydrogenated amorphous silicon film.

    Science.gov (United States)

    Liu, Xiao; Feldman, J L; Cahill, D G; Crandall, R S; Bernstein, N; Photiadis, D M; Mehl, M J; Papaconstantopoulos, D A

    2009-01-23

    We measured the thermal conductivity kappa of an 80 microm thick hydrogenated amorphous silicon film prepared by hot-wire chemical-vapor deposition with the 3omega (80-300 K) and the time-domain thermo-reflectance (300 K) methods. The kappa is higher than any of the previous temperature dependent measurements and shows a strong phonon mean free path dependence. We also applied a Kubo based theory using a tight-binding method on three 1000 atom continuous random network models. The theory gives higher kappa for more ordered models, but not high enough to explain our results, even after extrapolating to lower frequencies with a Boltzmann approach. Our results show that this material is more ordered than any amorphous silicon previously studied.

  9. Infrared analysis of thin films amorphous, hydrogenated carbon on silicon

    CERN Document Server

    Jacob, W; Schwarz-Selinger, T

    2000-01-01

    The infrared analysis of thin films on a thick substrate is discussed using the example of plasma-deposited, amorphous, hydrogenated carbon layers (a-C:H) on silicon substrates. The framework for the optical analysis of thin films is presented. The main characteristic of thin film optics is the occurrence of interference effects due to the coherent superposition of light multiply reflected at the various internal and external interfaces of the optical system. These interference effects lead to a sinusoidal variation of the transmitted and reflected intensity. As a consequence, the Lambert-Beer law is not applicable for the determination of the absorption coefficient of thin films. Furthermore, observable changes of the transmission and reflection spectra occur in the vicinity of strong absorption bands due to the Kramers-Kronig relation. For a sound data evaluation these effects have to be included in the analysis. To be able to extract the full information contained in a measured optical thin film spectrum, ...

  10. Enhanced crystallization of amorphous silicon thin films using embedded silicon nanocrystals

    Science.gov (United States)

    Anderson, Curtis Michael

    This thesis is concerned with the production of silicon thin films for photovoltaic applications. Much research has been carried out to find a stable, more efficient alternative to amorphous silicon, resulting in a number of various amorphous/crystalline mixed-phase film structures with properties superior to amorphous silicon. This thesis work details a completely new approach to mixed-phase film deposition, focusing on the fast crystallization of these films. The deposition of amorphous silicon films with embedded nanocrystals was carried out via a dual-plasma system. It is known that plasma conditions to produce high quality films are much different from those to produce particles. Hence the experimental system used here involved two separate plasmas to allow the optimum production of the crystalline nanoparticles and the amorphous film. Both plasmas use 13.56 MHz excitation voltage with diluted silane as the silicon precursor. The nanoparticle production reactor is a flow-through device that can be altered to control the size of the particles from around 5--30 nm average diameter. The film production reactor is a parallel-plate capacitively-coupled plasma system, into which the aerosol-suspended nanoparticles were injected. The nanocrystals could either be "co-deposited" simultaneously with the amorphous film, or be deposited separately in a layer-by-layer technique; both approaches are discussed in detail. Measurements of the film conductivity provide for the first time unambiguous evidence that the presence of nanocrystallites above 5 nm in the amorphous film have a direct impact on the electronic properties of co-deposited films. Further measurements of the film structure by transmission electron microscopy (TEM) and Raman spectroscopy demonstrate clearly the effect of embedded nanocrystals on the annealed crystallization process; the immediate growth of the crystal seeds has been observed. Additionally, a newly discovered mechanism of film crystallization

  11. Electronic properties of intrinsic and doped amorphous silicon carbide films

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, M. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain)]. E-mail: mvetter@eel.upc.edu; Voz, C. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Ferre, R. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Martin, I. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Orpella, A. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Puigdollers, J. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Andreu, J. [Departament de Fisica Aplicada i Optica, Universitat de Barcelona, Av. Diagonal 647, E-08028 Barcelona (Spain); Alcubilla, R. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain)

    2006-07-26

    Hydrogenated amorphous silicon carbide (a-SiC{sub x} : H) films have shown excellent surface passivation of crystalline silicon. With the aim of large area deposition of these films the influence of the rf plasma power was investigated. It is found that homogenous deposition with effective surface recombination velocity lower than 100 cms{sup -1} is possible up to 6'' diameter in a simple parallel plate reactor by optimizing deposition parameters. For application in solar cell processes the conductivity of these a-SiC{sub x} : H films might become of importance since good surface passivation results from field-effect passivation which needs an insulating dielectric layer. Therefore, the temperature dependence of the dark dc conductivity of these films was investigated in the temperature range from - 20 to 260 deg. C. Two transition temperatures, T {sub s}{approx}80 deg. C and T {sub s}{approx}170 deg. C, were found where conductivity increases, resp. decreases over-exponential. From Arrhenius plots activation energy (E {sub a}) and conductivity pre-factor ({sigma} {sub 0}) were calculated for a large number of samples with different composition. A correlation between E {sub a} and {sigma} {sub 0} was found giving a Meyer-Neldel relation with a slope of 59 mV, corresponding to a material characteristic temperature T {sub m} = 400 deg. C, and an intercept at {sigma} {sub 00} = 0.1 {omega}{sup -1}cm{sup -1}.

  12. Femtosecond Laser Crystallization of Boron-doped Amorphous Hydrogenated Silicon Films

    Directory of Open Access Journals (Sweden)

    P.D. Rybalko

    2016-10-01

    Full Text Available Crystallization of amorphous hydrogenated silicon films with femtosecond laser pulses is one of the promising ways to produce nanocrystalline silicon for photovoltaics. The structure of laser treated films is the most important factor determining materials' electric and photoelectric properties. In this work we investigated the effect of femtosecond laser irradiation of boron doped amorphous hydrogenated silicon films with different fluences on crystalline volume fraction and electrical properties of this material. A sharp increase of conductivity and essential decrease of activation energy of conductivity temperature dependences accompany the crystallization process. The results obtained are explained by increase of boron doping efficiency in crystalline phase of modified silicon film.

  13. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Abdulraheem, Yaser, E-mail: yaser.abdulraheem@kuniv.edu.kw [Electrical Engineering Department, College of Engineering and Petroleum, Kuwait University. P.O. Box 5969, 13060 Safat (Kuwait); Gordon, Ivan; Bearda, Twan; Meddeb, Hosny; Poortmans, Jozef [IMEC, Kapeldreef 75, 3001, Leuven (Belgium)

    2014-05-15

    An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H) layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si) wafers by plasma enhanced chemical vapor deposition (PECVD). The layer thicknesses along with their optical properties –including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE) in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc) bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause of the observed

  14. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    Directory of Open Access Journals (Sweden)

    Yaser Abdulraheem

    2014-05-01

    Full Text Available An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si wafers by plasma enhanced chemical vapor deposition (PECVD. The layer thicknesses along with their optical properties –including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause

  15. Characteristics of Disorder and Defect in Hydrogenated Amorphous Silicon Nitride Thin Films Containing Silicon Nanograins

    Institute of Scientific and Technical Information of China (English)

    DING Wen-ge; YU Wei; ZHANG Jiang-yong; HAN Li; FU Guang-sheng

    2006-01-01

    The hydrogenated amorphous silicon nitride (SiNx) thin films embedded with nano-structural silicon were prepared and the microstructures at the interface of silicon nano-grains/SiNx were identified by the optical absorption and Raman scattering measurements. Characterized by the exponential tail of optical absorption and the band-width of the Raman scattering TO mode, the disorder in the interface region increases with the gas flow ratio increasing. Besides, as reflected by the sub-gap absorption coefficients, the density of interface defect states decreases, which can be attributed to the structural mismatch in the interface region and also the changes of hydrogen content in the deposited films. Additional annealing treatment results in a significant increase of defects and degree of disorder, for which the hydrogen out-diffusion in the annealing process would be responsible.

  16. Research on high-efficiency, single-junction, monolithic, thin-film amorphous silicon solar cells

    Science.gov (United States)

    Wiesmann, H.; Dolan, J.; Fricano, G.; Danginis, V.

    1987-02-01

    A study was undertaken of the optoelectronic properties of amorphous silicon-hydrogen thin films deposited from disilane at high deposition rates. The information derived from this study was used to fabricate amorphous silicon solar cells with efficiencies exceeding 7%. The intrinsic layer of these solar cells was deposited at 15 angstroms/second. Material properties investigated included dark conductivity, photoconductivity, minority carrier diffusion length, and density of states. The solar cells properties characterized were absolute quantum yield and simulated global AM 1.5 efficiencies. Investigations were undertaken utilizing optical and infrared spectroscopy to optimize the microstructures of the intrinsic amorphous silicon. That work was sponsored by the New York State Energy Research and Development Authority. The information was used to optimize the intrinsic layer of amorphous silicon solar cells, resulting in AM 1.5 efficiencies exceeding 7%.

  17. CW laser induced crystallization of thin amorphous silicon films deposited by EBE and PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Said-Bacar, Z., E-mail: zabardjade@yahoo.fr [InESS (UMR 7163 CNRS-UDS), 23 rue de Loess, 67037 Strasbourg Cedex 2 (France); Prathap, P. [InESS (UMR 7163 CNRS-UDS), 23 rue de Loess, 67037 Strasbourg Cedex 2 (France); Cayron, C. [CEA, LITEN, DEHT, Minatec, 17 rue des Martyrs, 38054 Cedex 9 (France); Mermet, F. [IREPA LASER, Pole API - Parc d' Innovation, 67400 Illkirch (France); Leroy, Y.; Antoni, F.; Slaoui, A.; Fogarassy, E. [InESS (UMR 7163 CNRS-UDS), 23 rue de Loess, 67037 Strasbourg Cedex 2 (France)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer The effect of hydrogen in CW laser crystallization of hydrogenated amorphous silicon thin films has been investigated. Black-Right-Pointing-Pointer Large hydrogen content results in decohesion of the films due to hydrogen effusion. Black-Right-Pointing-Pointer Very low hydrogen content or hydrogen free amorphous silicon film are suitable for crystallization induced by CW laser. Black-Right-Pointing-Pointer Grains of size between 20 and 100 {mu}m in width and about 200 {mu}m in long in scanning direction are obtained with these latter films. - Abstract: This work presents the Continuous Wave (CW) laser crystallization of thin amorphous silicon (a-Si) films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and by Electron Beam Evaporation (EBE) on low cost glass substrate. The films are characterized by Elastic Recoil Detection Analysis (ERDA) and by Fourier-Transform Infrared (FTIR) spectroscopy to evaluate the hydrogen content. Analysis shows that the PECVD films contain a high hydrogen concentration ({approx}10 at.%) while the EBE films are almost hydrogen-free. It is found that the hydrogen is in a bonding configuration with the a-Si network and in a free form, requiring a long thermal annealing for exodiffusion before the laser treatment to avoid explosive effusion. The CW laser crystallization process of the amorphous silicon films was operated in liquid phase regime. We show by Electron Backscatter Diffraction (EBSD) that polysilicon films with large grains can be obtained with EBE as well as for the PECVD amorphous silicon provided that for the latest the hydrogen content is lower than 2 at.%.

  18. Amorphous Silicon-Germanium Films with Embedded Nanocrystals for Thermal Detectors with Very High Sensitivity

    Directory of Open Access Journals (Sweden)

    Cesar Calleja

    2016-01-01

    Full Text Available We have optimized the deposition conditions of amorphous silicon-germanium films with embedded nanocrystals in a plasma enhanced chemical vapor deposition (PECVD reactor, working at a standard frequency of 13.56 MHz. The objective was to produce films with very large Temperature Coefficient of Resistance (TCR, which is a signature of the sensitivity in thermal detectors (microbolometers. Morphological, electrical, and optical characterization were performed in the films, and we found optimal conditions for obtaining films with very high values of thermal coefficient of resistance (TCR = 7.9% K−1. Our results show that amorphous silicon-germanium films with embedded nanocrystals can be used as thermosensitive films in high performance infrared focal plane arrays (IRFPAs used in commercial thermal cameras.

  19. N-type crystalline silicon films free of amorphous silicon deposited on glass by HCl addition using hot wire chemical vapour deposition.

    Science.gov (United States)

    Chung, Yung-Bin; Park, Hyung-Ki; Lee, Sang-Hoon; Song, Jean-Ho; Hwang, Nong-Moon

    2011-09-01

    Since n-type crystalline silicon films have the electric property much better than those of hydrogenated amorphous and microcrystalline silicon films, they can enhance the performance of advanced electronic devices such as solar cells and thin film transistors (TFTs). Since the formation of amorphous silicon is unavoidable in the low temperature deposition of microcrystalline silicon on a glass substrate at temperatures less than 550 degrees C in the plasma-enhanced chemical vapour deposition and hot wire chemical vapour deposition (HWCVD), crystalline silicon films have not been deposited directly on a glass substrate but fabricated by the post treatment of amorphous silicon films. In this work, by adding the HCl gas, amorphous silicon-free n-type crystalline silicon films could be deposited directly on a glass substrate by HWCVD. The resistivity of the n-type crystalline silicon film for the flow rate ratio of [HCl]/[SiH4] = 7.5 and [PH3]/[SiH4] = 0.042 was 5.31 x 10(-4) ohms cm, which is comparable to the resistivity 1.23 x 10(-3) ohms cm of films prepared by thermal annealing of amorphous silicon films. The absence of amorphous silicon in the film could be confirmed by high resolution transmission electron microscopy.

  20. Anode properties of silicon-rich amorphous silicon suboxide films in all-solid-state lithium batteries

    Science.gov (United States)

    Miyazaki, Reona; Ohta, Narumi; Ohnishi, Tsuyoshi; Takada, Kazunori

    2016-10-01

    This paper reports the effects of introducing oxygen into amorphous silicon films on their anode properties in all-solid-state lithium batteries. Although poor cycling performance is a critical issue in silicon anodes, it has been effectively improved by introducing even a small amount of oxygen, that is, even in Si-rich amorphous silicon suboxide (a-SiOx) films. Because of the small amount of oxygen in the films, high cycling performance has been achieved without lowering the capacity and power density: an a-Si film delivers discharge capacity of 2500 mAh g-1 under high discharge current density of 10 mA cm-2 (35 C). These results demonstrate that a-SiOx is a promising candidate for high-capacity anode materials in solid-state batteries.

  1. Method of forming semiconducting amorphous silicon films from the thermal decomposition of fluorohydridodisilanes

    Science.gov (United States)

    Sharp, Kenneth G.; D'Errico, John J.

    1988-01-01

    The invention relates to a method of forming amorphous, photoconductive, and semiconductive silicon films on a substrate by the vapor phase thermal decomposition of a fluorohydridodisilane or a mixture of fluorohydridodisilanes. The invention is useful for the protection of surfaces including electronic devices.

  2. Infrared Insight into the Network of Hydrogenated Amorphous and Polycrystalline Silicon thin Films

    Directory of Open Access Journals (Sweden)

    Jarmila Mullerova

    2006-01-01

    Full Text Available IR measurements were carried out on both amorphous and polycrystalline silicon samples deposited by PECVDon glass substrate. The transition from amorphous to polycrystalline phase was achieved by increasing dilution of silaneplasma at the deposition process. The samples were found to be mixed phase materials. Commonly, infrared spectra ofhydrogenated silicon thin films yield information about microstructure, hydrogen content and hydrogen bonding to silicon. Inthis paper, additional understanding was retrieved from infrared response. Applying standard optical laws, effective mediatheory and Clausius-Mossoti approach concerning the Si-Si and Si-H bonds under IR irradiation as individual oscillators,refractive indices in the long wavelength limit, crystalline, amorphous and voids volume fractions and the mass density of thefilms were determined. The mass density was found to decrease with increasing crystalline volume fraction, which can beattributed to the void-dominated mechanism of network formation.

  3. Electronic transport in mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films

    Science.gov (United States)

    Wienkes, Lee Raymond

    Interest in mixed-phase silicon thin film materials, composed of an amorphous semiconductor matrix in which nanocrystalline inclusions are embedded, stems in part from potential technological applications, including photovoltaic and thin film transistor technologies. Conventional mixed-phase silicon films are produced in a single plasma reactor, where the conditions of the plasma must be precisely tuned, limiting the ability to adjust the film and nanoparticle parameters independently. The films presented in this thesis are deposited using a novel dual-plasma co-deposition approach in which the nanoparticles are produced separately in an upstream reactor and then injected into a secondary reactor where an amorphous silicon film is being grown. The degree of crystallinity and grain sizes of the films are evaluated using Raman spectroscopy and X-ray diffraction respectively. I describe detailed electronic measurements which reveal three distinct conduction mechanisms in n-type doped mixed-phase amorphous/nanocrystalline silicon thin films over a range of nanocrystallite concentrations and temperatures, covering the transition from fully amorphous to ~30% nanocrystalline. As the temperature is varied from 470 to 10 K, we observe activated conduction, multiphonon hopping (MPH) and Mott variable range hopping (VRH) as the nanocrystal content is increased. The transition from MPH to Mott-VRH hopping around 100K is ascribed to the freeze out of the phonon modes. A conduction model involving the parallel contributions of these three distinct conduction mechanisms is shown to describe both the conductivity and the reduced activation energy data to a high accuracy. Additional support is provided by measurements of thermal equilibration effects and noise spectroscopy, both done above room temperature (>300 K). This thesis provides a clear link between measurement and theory in these complex materials.

  4. Silicon and aluminum doping effects on the microstructure and properties of polymeric amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaoqiang, E-mail: lxq_suse@sina.com [Material Corrosion and Protection Key Laboratory of Sichuan province, Sichuan University of Science and Engineering, Zigong 643000 (China); Hao, Junying, E-mail: jyhao@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Xie, Yuntao [Material Corrosion and Protection Key Laboratory of Sichuan province, Sichuan University of Science and Engineering, Zigong 643000 (China)

    2016-08-30

    Highlights: • Evolution of nanostructure and properties of the polymeric amorphous carbon films were firstly studied. • Si doping enhanced polymerization of the hydrocarbon chains and Al doping resulted in increase in the ordered carbon clusters of polymeric amorphous carbon films. • Soft polymeric amorphous carbon films exhibited an unconventional frictional behaviors with a superior wear resistance. • The mechanical and vacuum tribological properties of the polymeric amorphous carbon films were significantly improved by Si and Al co-doping. - Abstract: Polymeric amorphous carbon films were prepared by radio frequency (R.F. 13.56 MHz) magnetron sputtering deposition. The microstructure evolution of the deposited polymeric films induced by silicon (Si) and aluminum(Al) doping were scrutinized through infrared spectroscopy, multi-wavelength Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The comparative results show that Si doping can enhance polymerization and Al doping results in an increase in the ordered carbon clusters. Si and Al co-doping into polymeric films leads to the formation of an unusual dual nanostructure consisting of cross-linked polymer-like hydrocarbon chains and fullerene-like carbon clusters. The super-high elasticity and super-low friction coefficients (<0.002) under a high vacuum were obtained through Si and Al co-doping into the films. Unconventionally, the co-doped polymeric films exhibited a superior wear resistance even though they were very soft. The relationship between the microstructure and properties of the polymeric amorphous carbon films with different elements doping are also discussed in detail.

  5. Surface plasmon enhanced photoluminescence in amorphous silicon carbide films by adjusting Ag island film sizes

    Institute of Scientific and Technical Information of China (English)

    Yu Wei; Wang Xin-Zhan; Dai Wan-Lei; Lu Wan-Bing; Liu Yu-Mei; Fu Guang-Sheng

    2013-01-01

    Ag island films with different sizes are deposited on hydrogenated amorphous silicon carbide (α-SiC∶H) films,and the influences of Ag island films on the optical properties of the α-SiC∶H films are investigated.Atomic force microscope images show that Ag nanoislands are formed after Ag coating,and the size of the Ag islands increases with increasing Ag deposition time.The extinction spectra indicate that two resonance absorption peaks which correspond to out-of-plane and in-plane surface plasmon modes of the Ag island films are obtained,and the resonance peak shifts toward longer wavelength with increasing Ag island size.The photoluminescence (PL) enhancement or quenching depends on the size of Ag islands,and PL enhancement by 1.6 times on the main PL band is obtained when the sputtering time is 10 min.Analyses show that the influence of surface plasmons on the PL of α-SiC:H is determined by the competition between the scattering and absorption of Ag islands,and PL enhancement is obtained when scattering is the main interaction between the Ag islands and incident light.

  6. Deposition and characterization of amorphous silicon with embedded nanocrystals and microcrystalline silicon for thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, R., E-mail: rambrosi@uacj.mx [Instituto Nacional de Astrofísica, Óptica y Electrónica, INAOE, Puebla (Mexico); Instituto de Ingeniería y Tecnología, Universidad Autónoma de Ciudad Juárez, UACJ, C.J., Chihuahua (Mexico); Moreno, M.; Torres, A. [Instituto Nacional de Astrofísica, Óptica y Electrónica, INAOE, Puebla (Mexico); Carrillo, A. [Instituto de Ingeniería y Tecnología, Universidad Autónoma de Ciudad Juárez, UACJ, C.J., Chihuahua (Mexico); Vivaldo, I.; Cosme, I. [Instituto Nacional de Astrofísica, Óptica y Electrónica, INAOE, Puebla (Mexico); Heredia, A. [Universidad Popular Autónoma del Estado de Puebla, Puebla (Mexico)

    2015-09-15

    Highlights: • Nanostructured silicon thin films were deposited by PECVD. • Polymorphous and microcrystalline were obtained varying the pressure and power. • Structural and optoelectronics properties were studied. • The σ{sub dark} changed by 5 order of magnitude under illumination, V{sub d} was at 2.5 A/s. • The evidence of embedded nanocrystals into the amorphous matrix was investigated. - Abstract: Amorphous silicon thin films with embedded nanocrystals and microcrystalline silicon were deposited by the standard Radio Frequency (RF) Plasma Enhanced Chemical Vapor Deposition (PECVD) technique, from SiH{sub 4}, H{sub 2}, Ar gas mixture at substrate temperature of 200 °C. Two series of films were produced varying deposition parameters as chamber pressure and RF power density. The chemical bonding in the films was characterized by Fourier transform infrared spectroscopy, where it was observed a correlation between the hydrogen content and the morphological and electrical properties in the films. Electrical and optical parameters were extracted in both series of films, as room temperature conductivity (σ{sub RT}), activation energy (E{sub a}), and optical band gap (E{sub g}). As well, structural analysis in the films was performed by Raman spectroscopy and Atomic Force Microscopy (AFM), which gives an indication of the films crystallinity. The photoconductivity changed in a range of 2 and 6 orders of magnitude from dark to AM 1.5 illumination conditions, which is of interest for thin film solar cells applications.

  7. Depth profile study on Raman spectra of high-energy-electron-irradiated hydrogenated amorphous silicon films

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    According to the different penetration depths for the incident lights of 472 nm and 532 nm in hydrogenated amorphous silicon (a-Si:H) thin films, the depth profile study on Raman spectra of a-Si:H films was carried out. The network ordering evolution in the near surface and interior region of the unirradiated and irradiated a-Si:H films was investigated. The results show that there is a structural improvement in the shortand intermediate-range order towards the surface of the unirradiated a-Si:H films. The amorphous silicon network in the near and interior region becomes more disordered on the shortand intermediate-range scales after being irradiated with high energy electrons. However, the surface of the irradiated films becomes more disordered in comparison with their interior region, indicating that the created defects caused by electron irradiation are concentrated in the near surface of the irradiated films. Annealing eliminates the irradiation effects on a-Si:H thin films and the structural order of the irradiated films is similar to that of the unirradiated ones after being annealed. There exists a structural improvement in the shortand intermediate-range order towards the surface of the irradiated a-Si:H films after being annealed.

  8. Modeling the Crystallization of Amorphous Silicon Thin Films Using a High Repetition Rate Scanning Laser

    Directory of Open Access Journals (Sweden)

    R. Černý

    2000-01-01

    Full Text Available An optimum design of experimental setup for the preparation of polycrystalline silicon (pc-Si films from amorphous layers applicable in the solar cell production is analyzed in the paper. In the computational simulations, the influence of basic characteristic parameters of the experimental procedure on the mechanisms of pc-Si lateral growth is studied. Among these parameters, the energy density of the applied laser and the thickness of the amorphous silicon (a-Si layer are identified as the most significant. As an optimum solution, the mechanism of pc-Si growth consisting in repeated melting of a part of already crystallized pc-Si layer by the scanning laser is proposed.

  9. Highly efficient ultrathin-film amorphous silicon solar cells on top of imprinted periodic nanodot arrays

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Wensheng, E-mail: yws118@gmail.com; Gu, Min, E-mail: mgu@swin.edu.au [Centre for Micro-Photonics, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Tao, Zhikuo [College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Ong, Thiam Min Brian [Plasma Sources and Application Center, NIE, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore); Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)

    2015-03-02

    The addressing of the light absorption and conversion efficiency is critical to the ultrathin-film hydrogenated amorphous silicon (a-Si:H) solar cells. We systematically investigate ultrathin a-Si:H solar cells with a 100 nm absorber on top of imprinted hexagonal nanodot arrays. Experimental evidences are demonstrated for not only notable silver nanodot arrays but also lower-cost ITO and Al:ZnO nanodot arrays. The measured external quantum efficiency is explained by the simulation results. The J{sub sc} values are 12.1, 13.0, and 14.3 mA/cm{sup 2} and efficiencies are 6.6%, 7.5%, and 8.3% for ITO, Al:ZnO, and silver nanodot arrays, respectively. Simulated optical absorption distribution shows high light trapping within amorphous silicon layer.

  10. Aluminium-induced crystallization of amorphous silicon films deposited by DC magnetron sputtering on glasses

    Energy Technology Data Exchange (ETDEWEB)

    Kezzoula, F., E-mail: kezzoula@usa.com [UDTS 2Bd Frantz Fanon 7 merveilles Algiers (Algeria); Laboratory of Materials, Mineral and Composite (LMMC), Boumerdes University (Algeria); Hammouda, A. [UPR CNRS 3079 CEMHTI - 1D Avenue de la Recherche Scientifique, 45071 Orleans Cedex 2 (France); Equipe Couches Minces, Laboratoire de Physique des Materiaux, Faculte de Physique, USTHB, Algiers (Algeria); Universite d' Orleans, 45067 Orleans Cedex 2 (France); Kechouane, M. [Equipe Couches Minces, Laboratoire de Physique des Materiaux, Faculte de Physique, USTHB, Algiers (Algeria); Simon, P. [UPR CNRS 3079 CEMHTI - 1D Avenue de la Recherche Scientifique, 45071 Orleans Cedex 2 (France); Universite d' Orleans, 45067 Orleans Cedex 2 (France); Abaidia, S.E.H. [Laboratory of Materials, Mineral and Composite (LMMC), Boumerdes University (Algeria); Keffous, A. [UDTS 2Bd Frantz Fanon 7 merveilles Algiers (Algeria); Cherfi, R. [Equipe Couches Minces, Laboratoire de Physique des Materiaux, Faculte de Physique, USTHB, Algiers (Algeria); Menari, H.; Manseri, A. [UDTS 2Bd Frantz Fanon 7 merveilles Algiers (Algeria)

    2011-09-15

    Amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) films were deposited by DC magnetron sputtering technique with argon and hydrogen plasma mixture on Al deposited by thermal evaporation on glass substrates. The a-Si/Al and a-Si:H/Al thin films were annealed at different temperatures ranging from 250 to 550 deg. C during 4 h in vacuum-sealed bulb. The effects of annealing temperature on optical, structural and morphological properties of as-grown as well as the vacuum-annealed a-Si/Al and a-Si:H/Al thin films are presented in this contribution. The averaged transmittance of a-Si:H/Al film increases upon increasing the annealing temperature. XRD measurements clearly evidence that crystallization is initiated at 450 deg. C. The number and intensity of diffraction peaks appearing in the diffraction patterns are more important in a-Si:H/Al than that in a-Si/Al layers. Results show that a-Si:H films deposited on Al/glass crystallize above 450 deg. C and present better crystallization than the a-Si layers. The presence of hydrogen induces an improvement of structural properties of poly-Si prepared by aluminium-induced crystallization (AIC).

  11. A Comparison of Photo-Induced Hysteresis Between Hydrogenated Amorphous Silicon and Amorphous IGZO Thin-Film Transistors.

    Science.gov (United States)

    Ha, Tae-Jun; Cho, Won-Ju; Chung, Hong-Bay; Koo, Sang-Mo

    2015-09-01

    We investigate photo-induced instability in thin-film transistors (TFTs) consisting of amorphous indium-gallium-zinc-oxide (a-IGZO) as active semiconducting layers by comparing with hydrogenated amorphous silicon (a-Si:H). An a-IGZO TFT exhibits a large hysteresis window in the illuminated measuring condition but no hysteresis window in the dark condition. On the contrary, a large hysteresis window measured in the dark condition in a-Si:H was not observed in the illuminated condition. Even though such materials possess the structure of amorphous phase, optical responses or photo instability in TFTs looks different from each other. Photo-induced hysteresis results from initially trapped charges at the interface between semiconductor and dielectric films or in the gate dielectric which possess absorption energy to interact with deep trap-states and affect the movement of Fermi energy level. In order to support our claim, we also perform CV characteristics in photo-induced hysteresis and demonstrate thermal-activated hysteresis. We believe that this work can provide important information to understand different material systems for optical engineering which includes charge transport and band transition.

  12. Silicon nitride and intrinsic amorphous silicon double antireflection coatings for thin-film solar cells on foreign substrates

    Energy Technology Data Exchange (ETDEWEB)

    Li, Da; Kunz, Thomas [Bavarian Center for Applied Energy Research (ZAE Bayern), Division: Photovoltaics and Thermosensoric, Haberstr. 2a, 91058 Erlangen (Germany); Wolf, Nadine [Bavarian Center for Applied Energy Research (ZAE Bayern), Division: Energy Efficiency, Am Galgenberg 87, 97074 Wuerzburg (Germany); Liebig, Jan Philipp [Materials Science and Engineering, Institute I, University of Erlangen-Nuremberg, Martensstr. 5, 91058 Erlangen (Germany); Wittmann, Stephan; Ahmad, Taimoor; Hessmann, Maik T.; Auer, Richard [Bavarian Center for Applied Energy Research (ZAE Bayern), Division: Photovoltaics and Thermosensoric, Haberstr. 2a, 91058 Erlangen (Germany); Göken, Mathias [Materials Science and Engineering, Institute I, University of Erlangen-Nuremberg, Martensstr. 5, 91058 Erlangen (Germany); Brabec, Christoph J. [Bavarian Center for Applied Energy Research (ZAE Bayern), Division: Photovoltaics and Thermosensoric, Haberstr. 2a, 91058 Erlangen (Germany); Institute of Materials for Electronics and Energy Technology, University of Erlangen-Nuremberg, Martensstr. 7, 91058 Erlangen (Germany)

    2015-05-29

    Hydrogenated intrinsic amorphous silicon (a-Si:H) was investigated as a surface passivation method for crystalline silicon thin film solar cells on graphite substrates. The results of the experiments, including quantum efficiency and current density-voltage measurements, show improvements in cell performance. This improvement is due to surface passivation by an a-Si:H(i) layer, which increases the open circuit voltage and the fill factor. In comparison with our previous work, we have achieved an increase of 0.6% absolute cell efficiency for a 40 μm thick 4 cm{sup 2} aperture area on the graphite substrate. The optical properties of the SiN{sub x}/a-Si:H(i) stack were studied using spectroscopic ellipsometer techniques. Scanning transmission electron microscopy inside a scanning electron microscope was applied to characterize the cross section of the SiN{sub x}/a-Si:H(i) stack using focus ion beam preparation. - Highlights: • We report a 10.8% efficiency for thin-film silicon solar cell on graphite. • Hydrogenated intrinsic amorphous silicon was applied for surface passivation. • SiN{sub x}/a-Si:H(i) stacks were characterized by spectroscopic ellipsometer techniques. • Cross-section micrograph was obtained by scanning transmission electron microscopy. • Quantum efficiency and J-V measurements show improvements in the cell performance.

  13. Efficient visible luminescence of nanocrystalline silicon prepared from amorphous silicon films by thermal annealing and stain etching

    Directory of Open Access Journals (Sweden)

    Nikulin Valery

    2011-01-01

    Full Text Available Abstract Films of nanocrystalline silicon (nc-Si were prepared from hydrogenated amorphous silicon (a-Si:H by using rapid thermal annealing. The formed nc-Si films were subjected to stain etching in hydrofluoric acid solutions in order to passivate surfaces of nc-Si. The optical reflectance spectroscopy revealed the nc-Si formation as well as the high optical quality of the formed films. The Raman scattering spectroscopy was used to estimate the mean size and volume fraction of nc-Si in the annealed films, which were about 4 to 8 nm and 44 to 90%, respectively, depending on the annealing regime. In contrast to as-deposited a-Si:H films, the nc-Si films after stain etching exhibited efficient photoluminescence in the spectral range of 600 to 950 nm at room temperature. The photoluminescence intensity and lifetimes of the stain etched nc-Si films were similar to those for conventional porous Si formed by electrochemical etching. The obtained results indicate new possibilities to prepare luminescent thin films for Si-based optoelectronics.

  14. Investigation of the degradation of a thin-film hydrogenated amorphous silicon photovoltaic module

    Energy Technology Data Exchange (ETDEWEB)

    van Dyk, E.E.; Audouard, A.; Meyer, E.L. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Woolard, C.D. [Department of Chemistry, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2007-01-23

    The degradation of a thin-film hydrogenated single-junction amorphous silicon (a-Si:H) photovoltaic (PV) module has been studied. We investigated the different modes of electrical and physical degradation of a-Si:H PV modules by employing a degradation and failure assessment procedure used in conjunction with analytical techniques, including, scanning electron microscopy (SEM) and thermogravimetry. This paper reveals that due to their thickness, thin films are very sensitive to the type of degradation observed. Moreover, this paper deals with the problems associated with the module encapsulant, poly(ethylene-co-vinylacetate) (EVA). The main objective of this study was to establish the influence of outdoor environmental conditions on the performance of a thin-film PV module comprising a-Si:H single-junction cells. (author)

  15. Direct measurement of free-energy barrier to nucleation of crystallites in amorphous silicon thin films

    Science.gov (United States)

    Shi, Frank G.

    1994-01-01

    A method is introduced to measure the free-energy barrier W(sup *), the activation energy, and activation entropy to nucleation of crystallites in amorphous solids, independent of the energy barrier to growth. The method allows one to determine the temperature dependence of W(sup *), and the effect of the preparation conditions of the initial amorphous phase, the dopants, and the crystallization methds on W(sup *). The method is applied to determine the free-energy barrier to nucleation of crystallites in amorphous silicon (a-Si) thin films. For thermally induced nucleation in a-Si thin films with annealing temperatures in the range of from 824 to 983 K, the free-energy barrier W(sup *) to nucleation of silicon crystals is about 2.0 - 2.1 eV regardless of the preparation conditions of the films. The observation supports the idea that a-Si transforms into an intermediate amorphous state through the structural relaxation prior to the onset of nucleation of crystallites in a-Si. The observation also indicates that the activation entropy may be an insignificant part of the free-energy barrier for the nucleation of crystallites in a-Si. Compared with the free-energy barrier to nucleation of crystallites in undoped a-Si films, a significant reduction is observed in the free-energy barrier to nucleation in Cu-doped a-Si films. For a-Si under irradiation of Xe(2+) at 10(exp 5) eV, the free-energy barrier to ion-induced nucleation of crystallites is shown to be about half of the value associated with thermal-induced nucleation of crystallites in a-Si under the otherwise same conditions, which is much more significant than previously expected. The present method has a general kinetic basis; it thus should be equally applicable to nucleation of crystallites in any amorphous elemental semiconductors and semiconductor alloys, metallic and polymeric glasses, and to nucleation of crystallites in melts and solutions.

  16. Absorption enhancement in amorphous silicon thin films via plasmonic resonances in nickel silicide nanoparticles

    Science.gov (United States)

    Hachtel, Jordan; Shen, Xiao; Pantelides, Sokrates; Sachan, Ritesh; Gonzalez, Carlos; Dyck, Ondrej; Fu, Shaofang; Kalnayaraman, Ramki; Rack, Phillip; Duscher, Gerd

    2013-03-01

    Silicon is a near ideal material for photovoltaics due to its low cost, abundance, and well documented optical properties. The sole detriment of Si in photovoltaics is poor absorption in the infrared. Nanoparticle surface plasmon resonances are predicted to increase absorption by scattering to angles greater than the critical angle for total internal reflection (16° for a Si/air interface), trapping the light in the film. Experiments confirm that nickel silicide nanoparticles embedded in amorphous silicon increases absorption significantly in the infrared. However, it remains to be seen if electron-hole pair generation is increased in the solar cell, or whether the light is absorbed by the nanoparticles themselves. The nature of the absorption is explored by a study of the surface plasmon resonances through electron energy loss spectrometry and scanning transmission electron microscopy experiments, as well as first principles density functional theory calculations. Initial experimental results do not show strong plasmon resonances on the nanoparticle surfaces. Calculations of the optical properties of the nickel silicide particles in amorphous silicon are performed to understand why this resonance is suppressed. Work supported by NSF EPS 1004083 (TN-SCORE).

  17. Phosphorus- and boron-doped hydrogenated amorphous silicon films prepared using vaporized liquid cyclopentasilane

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Takashi, E-mail: mtakashi@jaist.ac.jp [Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, 923-1292 (Japan); Takagishi, Hideyuki; Shen, Zhongrong; Ohdaira, Keisuke; Shimoda, Tatsuya [Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, 923-1292 (Japan); Japan Science and Technology Agency, ALCA, Nomi, Ishikawa, 923-1211 (Japan)

    2015-08-31

    A simple, inexpensive method for fabricating a hydrogenated amorphous silicon (a-Si:H) film using thermal chemical vapor deposition from cyclopentasilane (CPS) at atmospheric pressure with a substrate temperature of 370 °C is described. The reactant gas was generated from liquid CPS by vaporization in the deposition chamber. The vaporized CPS gas was transformed immediately into a-Si:H film on a heated substrate. The a-Si:H films could be doped either n- or p-type by dissolving appropriate amounts of white phosphorus or decaborane, respectively, in the liquid CPS before vaporization. This process allows deposition of doped a-Si:H films of photovoltaic device-quality without the need for handling, storage, or transportation of large amounts of gaseous reactants. - Highlights: • B and P doped a-Si:H films made from liquid materials is presented. • Decaborane and white phosphorus is dissolved in the liquid materials. • A simple, inexpensive method for fabricating a-Si:H films using non-vacuum process. • The doped a-Si:H films with usable quality for photovoltaic devices are deposited.

  18. Photoelectronic properties of hydrogenated amorphous silicon films deposited by R. F sputtering and glow discharge methods

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Rahman, M.; Madkour, H. (Faculty of Science, Aswan (Egypt)); Hassan, H.H.; El-Desouki, S. (Cairo Univ., Giza (Egypt))

    1989-09-01

    Hydrogenated amorphous silicon films a-Si:H were deposited by both R.F. sputtering in a planar magnetron configuration and glow discharge methods on Corning glass substrates at different substrate temperatures. The dc and ac photoconductivities of the deposited films were extensively studied as a function of temperature, photon energy and photo-excitation intensity. The results showed that, the dark and photoconductivities have different dependency regions on temperature with different activation energies in the range of 0.08-0.20 eV. It has been also found that the photoconductivity is influenced by the method of deposition and the deposition parameters, indicating that the density of gap states is sensitive to the deposition conditions. The photoconductivity ({sigma}{sub ph}) has a power dependence on the illumination intensity (I) of the form {sigma}{sub ph} {alpha} I {sup {nu}}, where {nu} is a constant and was found also to be increase with temperature.

  19. Room Temperature Growth of Hydrogenated Amorphous Silicon Films by Dielectric Barrier Discharge Enhanced CVD

    Institute of Scientific and Technical Information of China (English)

    GUO Yu; ZHANG Xiwen; HAN Gaorong

    2007-01-01

    Hydrogenated amorphous silicon (a-Si:H) films were deposited on Si (100) and glass substrates by dielectric barrier discharge enhanced chemical vapour deposition (DBD-CVD)in (SiH4+H2) atmosphere at room temperature.Results of the thickness measurement,SEM (scanning electron microscope),Raman,and FTIR (Fourier transform infrared spectroscopy) show that with the increase in the applied peak voltage,the deposition rate and network order of the films increase,and the hydrogen bonding configurations mainly in di-hydrogen (Si-H2) and poly hydrogen (SiH2)n are introduced into the films.The UV-visible transmission spectra show that with the decrease in Sill4/ (SiH4+H2) the thin films'band gap shifts from 1.92 eV to 2.17 eV.These experimental results are in agreement with the theoretic analysis of the DBD discharge.The deposition of a-Si:H films by the DBD-CVD method as reported here for the first time is attractive because it allows fast deposition of a-Si:H films on large-area low-melting-point substrates and requires only a low cost of production without additional heating or pumping equipment.

  20. Low temperature plasma deposition of silicon thin films: From amorphous to crystalline

    OpenAIRE

    Roca i Cabarrocas, Pere; Cariou, Romain; Labrune, Martin

    2012-01-01

    International audience; We report on the epitaxial growth of crystalline silicon films on (100) oriented crystalline silicon substrates by standard plasma enhanced chemical vapor deposition at 175 °C. Such unexpected epitaxial growth is discussed in the context of deposition processes of silicon thin films, based on silicon radicals and nanocrystals. Our results are supported by previous studies on plasma synthesis of silicon nanocrystals and point toward silicon nanocrystals being the most p...

  1. Synthesis of Poly-Silicon Thin Films on Glass Substrate Using Laser Initiated Metal Induced Crystallization of Amorphous Silicon for Space Power Application

    Science.gov (United States)

    Abu-Safe, Husam H.; Naseem, Hameed A.; Brown, William D.

    2007-01-01

    Poly-silicon thin films on glass substrates are synthesized using laser initiated metal induced crystallization of hydrogenated amorphous silicon films. These films can be used to fabricate solar cells on low cost glass and flexible substrates. The process starts by depositing 200 nm amorphous silicon films on the glass substrates. Following this, 200 nm of sputtered aluminum films were deposited on top of the silicon layers. The samples are irradiated with an argon ion cw laser beam for annealing. Laser power densities ranging from 4 to 9 W/cm2 were used in the annealing process. Each area on the sample is irradiated for a different exposure time. Optical microscopy was used to examine any cracks in the films and loss of adhesion to the substrates. X-Ray diffraction patterns from the initial results indicated the crystallization in the films. Scanning electron microscopy shows dendritic growth. The composition analysis of the crystallized films was conducted using Energy Dispersive x-ray Spectroscopy. The results of poly-silicon films synthesis on space qualified flexible substrates such as Kapton are also presented.

  2. Optical Properties of Amorphous AlN Thin Films on Glass and Silicon Substrates Grown by Single Ion Beam Sputtering

    Science.gov (United States)

    Hajakbari, Fatemeh; Mojtahedzadeh Larijani, Majid; Ghoranneviss, Mahmood; Aslaninejad, Morteza; Hojabri, Alireza

    2010-09-01

    The structural and optical properties of aluminum nitride (AlN) films deposited on glass and silicon substrates by single ion beam sputtering technique have been investigated. The X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) study revealed the formation of the amorphous phase of AlN. The optical characteristics of films, such as refractive index, extinction coefficient, and average thickness, were calculated by Swanepoel's method using transmittance measurements. The refractive index and average roughness values of the films increased with film thickness. Moreover, it was found that thickness augmentation leads to a decrease in optical band gap energy calculated using Tauc's relation.

  3. Enhanced photocurrent in thin-film amorphous silicon solar cells via shape controlled three-dimensional nanostructures.

    Science.gov (United States)

    Hilali, Mohamed M; Yang, Shuqiang; Miller, Mike; Xu, Frank; Banerjee, Sanjay; Sreenivasan, S V

    2012-10-12

    In this paper, we have explored manufacturable approaches to sub-wavelength controlled three-dimensional (3D) nano-patterns with the goal of significantly enhancing the photocurrent in amorphous silicon solar cells. Here we demonstrate efficiency enhancement of about 50% over typical flat a-Si thin-film solar cells, and report an enhancement of 20% in optical absorption over Asahi textured glass by fabricating sub-wavelength nano-patterned a-Si on glass substrates. External quantum efficiency showed superior results for the 3D nano-patterned thin-film solar cells due to enhancement of broadband optical absorption. The results further indicate that this enhanced light trapping is achieved with minimal parasitic absorption losses in the deposited transparent conductive oxide for the nano-patterned substrate thin-film amorphous silicon solar cell configuration. Optical simulations are in good agreement with experimental results, and also show a significant enhancement in optical absorption, quantum efficiency and photocurrent.

  4. Band engineering of amorphous silicon ruthenium thin film and its near-infrared absorption enhancement combined with nano-holes pattern on back surface of silicon substrate

    Science.gov (United States)

    Guo, Anran; Zhong, Hao; Li, Wei; Gu, Deen; Jiang, Xiangdong; Jiang, Yadong

    2016-10-01

    Silicon is widely used in semiconductor industry but has poor performance in near-infrared photoelectronic devices because of its bandgap limit. In this study, a narrow bandgap silicon rich semiconductor is achieved by introducing ruthenium (Ru) into amorphous silicon (a-Si) to form amorphous silicon ruthenium (a-Si1-xRux) thin films through co-sputtering. The increase of Ru concentration leads to an enhancement of light absorption and a narrower bandgap. Meanwhile, a specific light trapping technique is employed to realize high absorption of a-Si1-xRux thin film in a finite thickness to avoid unnecessary carrier recombination. A double-layer absorber comprising of a-Si1-xRux thin film and silicon random nano-holes layer is formed on the back surface of silicon substrates, and significantly improves near-infrared absorption while the leaky light intensity is less than 5%. This novel absorber, combining narrow bandgap thin film with light trapping structure, may have a potential application in near-infrared photoelectronic devices.

  5. Improvement of small-area, amorphous-silicon thin-film photovoltaics on polymer substrate

    Energy Technology Data Exchange (ETDEWEB)

    Weber, M.F. (Minnesota Mining and Mfg. Co., St. Paul, MN (USA). Applied Technologies Lab.)

    1990-02-01

    This report describes a contract to produce, using roll-to-roll deposition on polyamide substrate, a small-area amorphous-silicon p-i-n photovoltaic (PV) cell with an energy conversion efficiency of 10% under air mass 1.5 insolation. Three improvements were attempted to achieve this goal: (1) zinc oxide, a transparent conducting oxide, was used as a top contact; the zinc oxide conductivity was improved to 8--9 ohms/square sheet resistance with less than 8% average optical absorption. (2) The red light response was improved with dielectric enhanced metal reflecting electrodes, which increased the short-circuit current density by more than 1 mA/Cm{sup 2}; a three-layer dielectric mirror coating was also designed that can increase the current density by another 1 mA/cm{sup 2}. (3) Improving the fill factor of the n-i-p (reverse structured) devices was also achieved in a multichamber deposition system. The overall energy conversion efficiency of the PV cell was 8.36%. Major obstacles to higher efficiencies are (1) controlling the thin-film defects that cause electrical shunts in devices fabricated on enhanced reflection electrodes, and (2) controlling impurities and introducing dopant profiles near the p/i interface in a continuous web deposition system.

  6. Amorphous Silicon Film Deposition from SiH4 by Chemical Vapor Deposition with Argon Excimer Lamp

    Science.gov (United States)

    Toshikawa, Kiyohiko; Yokotani, Atsushi; Kurosawa, Kou

    2005-11-01

    We have deposited amorphous silicon thin films from monosilane (SiH4) gas by photochemical vapor deposition using a vacuum ultraviolet excimer lamp (VUV-CVD). We used an argon excimer lamp (λ=126 nm, hν=9.8 eV) whose photons are strongly absorbed by SiH4 gas. The substrate temperatures were changed from 25 to 300°C. When the temperature was lower than 150°C, the films included H--Si--H units and H2 molecules in its structure. When it was higher than 150°C, the main structural unit was Si--H.

  7. Behavioral data of thin-film single junction amorphous silicon (a-Si) photovoltaic modules under outdoor long term exposure.

    Science.gov (United States)

    Kichou, Sofiane; Silvestre, Santiago; Nofuentes, Gustavo; Torres-Ramírez, Miguel; Chouder, Aissa; Guasch, Daniel

    2016-06-01

    Four years׳ behavioral data of thin-film single junction amorphous silicon (a-Si) photovoltaic (PV) modules installed in a relatively dry and sunny inland site with a Continental-Mediterranean climate (in the city of Jaén, Spain) are presented in this article. The shared data contributes to clarify how the Light Induced Degradation (LID) impacts the output power generated by the PV array, especially in the first days of exposure under outdoor conditions. Furthermore, a valuable methodology is provided in this data article permitting the assessment of the degradation rate and the stabilization period of the PV modules. Further discussions and interpretations concerning the data shared in this article can be found in the research paper "Characterization of degradation and evaluation of model parameters of amorphous silicon photovoltaic modules under outdoor long term exposure" (Kichou et al., 2016) [1].

  8. Fabrication of hydrogenated amorphous silicon carbide films by decomposition of hexamethyldisilane with microwave discharge flow of Ar

    Science.gov (United States)

    Ito, Haruhiko; Kumakura, Motoki; Suzuki, Tsuneo; Niibe, Masahito; Kanda, Kazuhiro; Saitoh, Hidetoshi

    2016-06-01

    Hydrogenated amorphous silicon carbide films have been fabricated by the decomposition of hexamethyldisilane with a microwave discharge flow of Ar. Mechanically hard films were obtained by applying radio-frequency (RF) bias voltages to the substrate. The atomic compositions of the films were analyzed by a combination of Rutherford backscattering and elastic recoil detection, X-ray photoelectron spectroscopy (XPS), and glow discharge optical emission spectroscopy. The chemical structure was analyzed by carbon-K near-edge X-ray absorption fine structure spectroscopy, high-resolution XPS, and Fourier transform infrared absorption spectroscopy. The structural changes upon the application of RF bias were investigated, and the concentration of O atoms near the film surface was found to play a key role in the mechanical hardness of the present films.

  9. Investigation on Silicon Thin Film Solar Cells

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The preparation, current status and trends are investigated for silicon thin film solar cells. The advantages and disadvantages of amorphous silicon thin film, polycrystalline silicon thin film and mono-crystalline silicon thin film solar cells are compared. The future development trends are pointed out. It is found that polycrystalline silicon thin film solar cells will be more promising for application with great potential.

  10. Spectroscopy and structural properties of amorphous and nanocrystalline silicon carbide thin films

    NARCIS (Netherlands)

    Halindintwali, Sylvain; Knoesen, D.; Julies, B.A.; Arendse, C.J.; Muller, T.; Gengler, Régis Y.N.; Rudolf, P.; Loosdrecht, P.H.M. van

    2011-01-01

    Amorphous SiC:H thin films were grown by hot wire chemical vapour deposition from a SiH4/CH4/H2 mixture at a substrate temperature below 400 °C. Thermal annealing in an argon environment up to 900 °C shows that the films crystallize as μc-Si:H and SiC with a porous microstructure that favours an oxi

  11. Band engineering of amorphous silicon ruthenium thin film and its near-infrared absorption enhancement combined with nano-holes pattern on back surface of silicon substrate

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Anran; Zhong, Hao [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Li, Wei, E-mail: wli@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Gu, Deen; Jiang, Xiangdong [School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Jiang, Yadong [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2016-10-30

    Highlights: • The increase of Ru concentration leads to a narrower bandgap of a-Si{sub 1-x}Ru{sub x} thin film. • The absorption coefficient of a-Si{sub 1-x}Ru{sub x} is higher than that of SiGe. • A double-layer absorber comprising of a-Si{sub 1-x}Ru{sub x} film and Si nano-holes layer is achieved. - Abstract: Silicon is widely used in semiconductor industry but has poor performance in near-infrared photoelectronic devices because of its bandgap limit. In this study, a narrow bandgap silicon rich semiconductor is achieved by introducing ruthenium (Ru) into amorphous silicon (a-Si) to form amorphous silicon ruthenium (a-Si{sub 1-x}Ru{sub x}) thin films through co-sputtering. The increase of Ru concentration leads to an enhancement of light absorption and a narrower bandgap. Meanwhile, a specific light trapping technique is employed to realize high absorption of a-Si{sub 1-x}Ru{sub x} thin film in a finite thickness to avoid unnecessary carrier recombination. A double-layer absorber comprising of a-Si{sub 1-x}Ru{sub x} thin film and silicon random nano-holes layer is formed on the back surface of silicon substrates, and significantly improves near-infrared absorption while the leaky light intensity is less than 5%. This novel absorber, combining narrow bandgap thin film with light trapping structure, may have a potential application in near-infrared photoelectronic devices.

  12. Low Cost Amorphous Silicon Intrinsic Layer for Thin-Film Tandem Solar Cells

    Directory of Open Access Journals (Sweden)

    Ching-In Wu

    2013-01-01

    Full Text Available The authors propose a methodology to improve both the deposition rate and SiH4 consumption during the deposition of the amorphous silicon intrinsic layer of the a-Si/μc-Si tandem solar cells prepared on Gen 5 glass substrate. It was found that the most important issue is to find out the saturation point of deposition rate which guarantees saturated utilization of the sourcing gas. It was also found that amorphous silicon intrinsic layers with the same k value will result in the same degradation of the fabricated modules. Furthermore, it was found that we could significantly reduce the production cost of the a-Si/μc-Si tandem solar cells prepared on Gen 5 glass substrate by fine-tuning the process parameters.

  13. Amorphous silicon carbon films prepared by hybrid plasma enhanced chemical vapor/sputtering deposition system: Effects of r.f. power

    Energy Technology Data Exchange (ETDEWEB)

    Rashid, Nur Maisarah Abdul, E-mail: nurmaisarahrashid@gmail.com [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ritikos, Richard; Othman, Maisara; Khanis, Noor Hamizah; Gani, Siti Meriam Ab. [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Muhamad, Muhamad Rasat [Chancellery Office, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia); Rahman, Saadah Abdul, E-mail: saadah@um.edu.my [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Chancellery Office, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia)

    2013-02-01

    Silicon carbon films were deposited using a hybrid radio frequency (r.f.) plasma enhanced chemical vapor deposition (PECVD)/sputtering deposition system at different r.f. powers. This deposition system combines the advantages of r.f. PECVD and sputtering techniques for the deposition of silicon carbon films with the added advantage of eliminating the use of highly toxic silane gas in the deposition process. Silicon (Si) atoms were sputtered from a pure amorphous silicon (a-Si) target by argon (Ar) ions and carbon (C) atoms were incorporated into the film from C based growth radicals generated through the discharge of methane (CH{sub 4}) gas. The effects of r.f. powers of 60, 80, 100, 120 and 150 W applied during the deposition process on the structural and optical properties of the films were investigated. Raman spectroscopic studies showed that the silicon carbon films contain amorphous silicon carbide (SiC) and amorphous carbon (a-C) phases. The r.f. power showed significant influence on the C incorporation in the film structure. The a-C phases became more ordered in films with high C incorporation in the film structure. These films also produced high photoluminescence emission intensity at around 600 nm wavelength as a result of quantum confinement effects from the presence of sp{sup 2} C clusters embedded in the a-SiC and a-C phases in the films. - Highlights: ► Effects of radio frequency (r.f.) power on silicon carbon (SiC) films were studied. ► Hybrid plasma enhanced chemical vapor deposition/sputtering technique was used. ► r.f. power influences C incorporation in the film structure. ► High C incorporation results in higher ordering of the amorphous C phase. ► These films produced high photoluminescence emission intensity.

  14. Study on the effect of process conditions on the thermo-optic coefficient of amorphous silicon films

    Science.gov (United States)

    Zhou, Xiang; Liu, Shuang; Tang, Haihua; Zhong, Zhiyong; Liu, Yong

    2016-05-01

    A thermo-optical coefficient (TOC) test platform based on FILMeasure-20 was designed and the thermal coefficient of hydrogenated amorphous silicon (a-Si:H) thin films material at 1330 nm was tested. a-Si:H were deposited on the quartz glass using a plasma-enhanced chemical vapor deposition (PECVD) system. Fourier transform infrared spectrometer (FTIR) was used to characterize the infrared spectral feature of films. The hydrogen content of films was influenced by different radio frequency (RF) power and deposition pressure conditions according to the FTIR spectra and theoretical analysis, and the thermo-optic effect of a-Si:H varied with temperature characteristics. Experimental results indicated that selecting the appropriate process conditions to prepare a-Si:H films can effectively increase or avoid the impact of thermo-optical effect on the optical devices.

  15. Amorphous silicon films with high deposition rate prepared using argon and hydrogen diluted silane for stable solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Gogoi, Purabi; Agarwal, Pratima [Department of Physics, IIT Guwahati, Guwahati 781039 (India); Dixit, P.N. [Plasma Processed Materials Division, National Physical Laboratory, New Delhi 110012 (India)

    2007-08-15

    Hydrogenated amorphous silicon films with high deposition rate (4-5 Aa/s) and reduced Staebler-Wronski effect are prepared using a mixture of silane (SiH{sub 4}), hydrogen and argon. The films show an improvement in short and medium range order. The structural, transport and stability studies on the films are done using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman scattering studies, electrical conductivity and diffusion length measurement. Presence of both atomic hydrogen and Ar{sup *} in the plasma causes breaking of weak Si-Si bonds and subsequent reconstruction of strong bonds resulting in improvement of short and medium range order. The improved structural order enhances the stability of these films against light soaking. High deposition rate is due to the lesser etching of growing surface compared to the case of only hydrogen diluted silane. (author)

  16. Uniform dehydrogenation of amorphous silicon thin films using a wide thermal annealing system

    Science.gov (United States)

    Jung, Yong Chan; Seong, Sejong; Lee, Taehoon; Ahn, Jinho; Kim, Tae Hyun; Yeo, Won-Jae; Park, In-Sung

    2017-02-01

    To prevent ablation caused by sudden hydrogen eruption during crystallization of hydrogenated amorphous Si (a-Si:H) thin films, a wide dehydrogenation thermal annealing (wDTA) system was developed to reduce hydrogen content in a-Si:H film prior to its crystallization process. The annealed a-Si:H films were fully dehydrogenated and nanocrystallized by the wDTA system. Raman scattering measurement revealed that the dehydrogenation process lowers the hydrogen content through disappearance of the peak intensity at 2000 cm-1. The a-Si:H film was transformed into nanocrystallized Si with lower residual stress. The major advantage of this wDTA was the large area uniformity of the thermal and the resulting material properties for 8 generation display. The uniform material characteristics of the hydrogen content, thickness, energy bandgap, and transmittance of the annealed Si films in the overall area was confirmed by Raman spectroscopy, spectroscopic ellipsometry, and UV-vis spectrometer measurement.

  17. PHOTO- AND ELECTRO-LUMINESCENCE FROM HYDROGENATED AMORPHOUS SILICON CARBIDE FILMS PREPARED BY USING ORGANIC CARBON SOURCE

    Institute of Scientific and Technical Information of China (English)

    Xu Jun; Ma Tian-fu; Li Wei; Chen Kun-ji; Li Zhi-feng; Lu Wei

    2000-01-01

    Hydrogenated amorphous silicon carbide (a-SiC:H) films were grown byusing an organic source, xylene (C8H{10), instead of methane(CH4) in a conventional plasma enhanced chemical vapor depositionsystem. The optical band gap of these samples was increased gradually bychanging the gas ratio of C8H10 to SiH4. The film with highoptical band gap was soft and polymer-like and intense photoluminescencewere obtained. Room temperature electro-luminescence was also achievedwith peak energy at 2.05 eV (600 nm) for the a-SiC:H film withoptical band gap of 3.2 eV.1.8mm

  18. Fabrication and Modeling of Ambipolar Hydrogenated Amorphous Silicon Thin Film Transistors.

    Science.gov (United States)

    1986-08-01

    that over 150 die can be fabricated on a single 2in Si wafer. Individual die are 4 -- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ - -- rM M- ri- PA NX RA "’K Kno ’--tx...Kusian, and B. Bullemer, "An Ambipolar Amorphous- Silicon Field-Effect Transistor," Siemens Forsch.-u. Entwickl.-Ber., vol. 14, no. 3, pp. 114-119...1985. 99. H. Pfleiderer, W. Kusian, and B. Bullemer, "An Ambipolar Field-Effect Transistor Model," Siemens Forsch.-u. Entwicki.-Ber., vol. 14, no. 2, pp

  19. Laser fabrication of crystalline silicon nanoresonators from an amorphous film for low-loss all-dielectric nanophotonics

    CERN Document Server

    Dmitriev, P A; Milichko, V A; Mukhin, I S; Gudovskikh, A S; Sitnikova, A A; Samusev, A K; Krasnok, A E; Belov, P A

    2015-01-01

    The concept of high refractive index subwavelength dielectric nanoresonators, supporting electric and magnetic optical resonances, is a promising platform for waveguiding, sensing, and nonlinear nanophotonic devices. However, high concentration of defects in the nanoresonators diminishes their resonant properties, which are crucially dependent on their internal losses. Therefore, it seems to be inevitable to use initially crystalline materials for fabrication of the nanoresonators. Here, we show that the fabrication of crystalline (low-loss) resonant silicon nanoparticles by femtosecond laser ablation of amorphous (high-loss) silicon thin films is possible. We apply two conceptually different approaches: recently proposed laser-induced transfer and a novel laser writing technique for large-scale fabrication of the crystalline nanoparticles. The crystallinity of the fabricated nanoparticles is proven by Raman spectroscopy and electron transmission microscopy, whereas optical resonant properties of the nanopart...

  20. Laser fabrication of crystalline silicon nanoresonators from an amorphous film for low-loss all-dielectric nanophotonics

    Science.gov (United States)

    Dmitriev, P. A.; Makarov, S. V.; Milichko, V. A.; Mukhin, I. S.; Gudovskikh, A. S.; Sitnikova, A. A.; Samusev, A. K.; Krasnok, A. E.; Belov, P. A.

    2016-02-01

    The concept of high refractive index subwavelength dielectric nanoresonators, supporting electric and magnetic optical resonance, is a promising platform for waveguiding, sensing, and nonlinear nanophotonic devices. However, high concentration of defects in the nanoresonators diminishes their resonant properties, which are crucially dependent on their internal losses. Therefore, it seems to be inevitable to use initially crystalline materials for fabrication of the nanoresonators. Here, we show that the fabrication of crystalline (low-loss) resonant silicon nanoparticles by femtosecond laser ablation of amorphous (high-loss) silicon thin films is possible. We apply two conceptually different approaches: recently proposed laser-induced transfer and a novel laser writing technique for large-scale fabrication of the crystalline nanoparticles. The crystallinity of the fabricated nanoparticles is proven by Raman spectroscopy and electron transmission microscopy, whereas optical resonant properties of the nanoparticles are studied using dark-field optical spectroscopy and full-wave electromagnetic simulations.

  1. Impact of contamination on hydrogenated amorphous silicon thin films and solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Woerdenweber, Jan

    2011-09-26

    This thesis deals with atmospheric contamination and cross-contamination of boron (single-chamber process) of the intrinsic absorber layer (i-layer) of p-i-n thin film solar cells based on hydrogenated amorphous silicon. The atmospheric contaminations were introduced by means of intentional leaks. Hereby, the focus is on the influence of contamination species (oxygen and nitrogen), quantity of contamination (leak flow), source of contamination (leaks at chamber wall or in the process gas pipe), and plasma power on the properties of solar cells. Thereby, the minimum requirements for the purity of vacuum and process gas as well as leak conditions of the recipient and gas pipe system have been determined. Additionally, deposition regimes were developed, where the incorporation of impurities is significantly suppressed. For standard processes critical levels of nitrogen and oxygen contamination are determined to be {proportional_to} 4 x 10{sup 18} cm{sup -3} and {proportional_to} 2 x 10{sup 19} cm{sup -3}, respectively, for a leak situated at the chamber wall. Above these concentrations the solar cell efficiency deteriorates. In literature, incorporation of oxygen and nitrogen in doping configuration is assumed to be the reason for the cell deterioration. This assumption is supported by additional material studies of contaminated absorber layers done in this work. The difference in critical concentration is due to the higher doping efficiency of nitrogen compared to that for oxygen. Nevertheless, applying an air leak the critical concentrations of O and N are reached almost simultaneously since the incorporation probability of oxygen is about one order of magnitude higher compared to that for nitrogen. Applying a leak in the process gas pipe the critical oxygen contamination level increases to {proportional_to} 2 x 10{sup 20} cm{sup -3} whereas the critical nitrogen level remains unchanged compared to a chamber wall leak. Applying a deposition regime with a very high

  2. Amorphization and recrystallization processes in monocrystalline beta silicon carbide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Edmond, J.A.; Withrow, S.P.; Kong, H.S.; Davis, R.F.

    1985-01-01

    Individual, as well as multiple doses of /sup 27/Al/sup +/, /sup 31/P/sup +/, /sup 28/Si/sup +/, and /sup 28/Si/sup +/ and /sup 12/C/sup +/, were implanted into (100) oriented monocrystalline ..beta..-SiC films. The critical energy of approx. =16 eV/atom required for the amorphization of ..beta..-SiC via implantation of /sup 27/Al/sup +/ and /sup 31/P/sup +/ was determined using the TRIM84 computer program for calculation of the damage-energy profiles coupled with the results of RBS/ion channeling analyses. In order to recrystallize amorphized layers created by the individual implantation of all four ion species, thermal annealing at 1600, 1700, or 1800/sup 0/C was employed. Characterization of the recrystallized layers was performed using XTEM. Examples of SPE regrown layers containing precipitates and dislocation loops, highly faulted-microtwinned regions, and random crystallites were observed.

  3. Atmospheric Pressure Plasma CVD of Amorphous Hydrogenated Silicon Carbonitride (a-SiCN:H) Films Using Triethylsilane and Nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan Guruvenket; Steven Andrie; Mark Simon; Kyle W. Johnson; Robert A. Sailer

    2011-10-04

    Amorphous hydrogenated silicon carbonitride (a-SiCN:H) thin films are synthesized by atmospheric pressure plasma enhanced chemical vapor (AP-PECVD) deposition using the Surfx Atomflow{trademark} 250D APPJ source with triethylsilane (HSiEt{sub 3}, TES) and nitrogen as the precursor and the reactive gases, respectively. The effect of the substrate temperature (T{sub s}) on the growth characteristics and the properties of a-SiCN:H films was evaluated. The properties of the films were investigated via scanning electron microscopy (SEM), atomic force microscopy (AFM) for surface morphological analyses, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) for chemical and compositional analyses; spectroscopic ellipsometry for optical properties and thickness determination and nanoindentation to determine the mechanical properties of the a-SiCN:H films. Films deposited at low T{sub s} depict organic like features, while the films deposited at high T{sub s} depict ceramic like features. FTIR and XPS studies reveal that an increases in T{sub s} helps in the elimination of organic moieties and incorporation of nitrogen in the film. Films deposited at T{sub s} of 425 C have an index of refraction (n) of 1.84 and hardness (H) of 14.8 GPa. A decrease in the deposition rate between T{sub s} of 25 and 250 C and increase in deposition rate between T{sub s} of 250 and 425 C indicate that the growth of a-SiCN:H films at lower T{sub s} are surface reaction controlled, while at high temperatures film growth is mass-transport controlled. Based on the experimental results, a potential route for film growth is proposed.

  4. Spatially-Resolved Crystallization of Amorphous Silicon Films on the Glass Substrate by Multi-beam Laser Interference

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Laser interference induced crystallization of amorphous silicon (a-Si) on the glass substrate was performed using a Q-switched Nd:YAG (yttrium aluminum garnet) laser. White light interferometer (WLI) and atomic force microscope (AFM) were used to characterize the morphology of the structured films, while X-ray diffraction (XRD), combined with the AFM, was used to analyse the crystalline structure of the film. The experimental results show that the laser energy density above a certain threshold, in the range of 400-500 mJ/cm2,triggers the patterned crystallizations which take the form similar to the laser intensity distribution. For the patterned crystallization under multipulse exposure, a definite polycrystalline structure with individual phases was observed by XRD. The difference in feature form, e.g., deepened craters or heightened lines, is related to the laser energy density relative to the threshold of evaporation of the material.

  5. 非晶硅锗电池性能的调控研究%Modification to the performance of hydrogenated amorphous silicon germanium thin film solar cell

    Institute of Scientific and Technical Information of China (English)

    刘伯飞; 白立沙; 魏长春; 孙建; 侯国付; 赵颖; 张晓丹

    2013-01-01

    采用射频等离子体增强化学气相沉积技术,研究了非晶硅锗薄膜太阳电池。针对非晶硅锗薄膜材料的本身特性,通过调控硅锗合金中硅锗的比例,实现了对硅锗薄膜太阳电池中开路电压和短路电流密度的分别控制。借助于本征层硅锗材料帯隙梯度的设计,获得了可有效用于多结叠层电池中的非晶硅锗电池。%In this paper, we study hydrogenated amorphous silicon germanium thin film solar cells prepared by the radio frequency plasma-enhanced chemical vapor deposition. In the light of the inherent characteristics of hydrogenated amorphous silicon germanium mate-rial, the modulation of the germanium/silicon ratio in silicon germanium alloys can separately control open circuit voltage (Voc) and short circuit current density (Jsc) of a-SiGe:H thin film solar cells. By the structural design of band gap profiling in the amorphous silicon germanium intrinsic layer, hydrogenated amorphous silicon germanium thin film solar cells, which can be used efficiently as the component cell of multi-junction solar cells, are obtained.

  6. Noise and degradation of amorphous silicon devices

    NARCIS (Netherlands)

    Bakker, J.P.R.

    2003-01-01

    Electrical noise measurements are reported on two devices of the disordered semiconductor hydrogenated amorphous silicon (a-Si:H). The material is applied in sandwich structures and in thin-film transistors (TFTs). In a sandwich configuration of an intrinsic layer and two thin doped layers, the obse

  7. Study of the effect of boron doping on the solid phase crystallisation of hydrogenated amorphous silicon films

    Energy Technology Data Exchange (ETDEWEB)

    Westra, J.M.; Swaaij, R.A.C.M.M. van [Photovoltaic Materials and Devices, Department of Sustainable Electrical Energy, Delft University of Technology, Delft (Netherlands); Šutta, P. [New Technologies-Research Centre, University of West Bohemia, Plzen (Czech Republic); Sharma, K.; Creatore, M. [Department of Applied Physics, Eindhoven University of Technology, Eindhoven (Netherlands); Zeman, M. [Photovoltaic Materials and Devices, Department of Sustainable Electrical Energy, Delft University of Technology, Delft (Netherlands)

    2014-10-01

    Thin-film polycrystalline silicon on glass obtained by crystallization of hydrogenated amorphous silicon (a-Si:H) films is an interesting alternative for thin-film silicon solar cells. Although the solar-cell efficiencies are still limited, this technique offers excellent opportunity to study the influence of B-doping on the crystallisation process of a-Si:H. Our approach is to slowly crystallize B-doped a-Si:H films by solid phase crystallization in the temperature range 580–600°C. We use plasma-enhanced chemical vapour deposition (PECVD) and expanding thermal plasma chemical vapour deposition (ETPCVD) for the B-doped a-Si:H deposition. In this work we show the first in-situ study of the crystallization process of B-doped a-Si:H films produced by ETPCVD and make a comparison to the crystallization of intrinsic ETPCVD deposited a-Si:H as well as intrinsic and B-doped a-Si:H films deposited by PECVD. The crystallization process is investigated by in-situ x-ray diffraction, using a high temperature chamber for the annealing procedure. The study shows a strong decrease in the time required for full crystallisation for B-doped a-Si:H films compared to the intrinsic films. The time before the onset of crystallisation is reduced by the incorporation of B as is the grain growth velocity. The time to full crystallisation can be manipulated by the B{sub 2}H{sub 6}-to-SiH{sub 4} ratio used during the deposition and by the microstructure of the as-deposited a-Si:H films. - Highlights: • Solid-phase crystallization of B-doped a-Si:H films is presented. • Crystallization study of B-doped and intrinsic a-Si:H by in-situ x-ray diffraction • The microstructure and B-doping of a-Si:H influences the crystallisation process. • B enhances the grain growth rate, but the effect on the nucleation rate is limited.

  8. Amorphous silicon pixel radiation detectors and associated thin film transistor electronics readout

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Mendez, V.; Drewery, J.; Hong, W.S.; Jing, T.; Kaplan, S.N.; Lee, H.; Mireshghi, A.

    1994-10-01

    We describe the characteristics of thin (1 {mu}m) and thick (>30 {mu}m) hydrogenated amorphous silicon p-i-n diodes which are optimized for detecting and recording the spatial distribution of charged particles, x-rays and {gamma} rays. For x-ray, {gamma} ray, and charged particle detection we can use thin p-i-n photosensitive diode arrays coupled to evaporated layers of suitable scintillators. For direct detection of charged particles with high resistance to radiation damage, we use the thick p-i-n diode arrays. Deposition techniques using helium dilution, which produce samples with low stress are described. Pixel arrays for flux exposures can be readout by transistor, single diode or two diode switches. Polysilicon charge sensitive pixel amplifiers for single event detection are described. Various applications in nuclear, particle physics, x-ray medical imaging, neutron crystallography, and radionuclide chromatography are discussed.

  9. Picosecond and nanosecond laser annealing and simulation of amorphous silicon thin films for solar cell applications

    Science.gov (United States)

    Theodorakos, I.; Zergioti, I.; Vamvakas, V.; Tsoukalas, D.; Raptis, Y. S.

    2014-01-01

    In this work, a picosecond diode pumped solid state laser and a nanosecond Nd:YAG laser have been used for the annealing and the partial nano-crystallization of an amorphous silicon layer. These experiments were conducted as an alternative/complementary to plasma-enhanced chemical vapor deposition method for fabrication of micromorph tandem solar cell. The laser experimental work was combined with simulations of the annealing process, in terms of temperature distribution evolution, in order to predetermine the optimum annealing conditions. The annealed material was studied, as a function of several annealing parameters (wavelength, pulse duration, fluence), as far as it concerns its structural properties, by X-ray diffraction, SEM, and micro-Raman techniques.

  10. Structural and optical properties of thin films porous amorphous silicon carbide formed by Ag-assisted photochemical etching

    Energy Technology Data Exchange (ETDEWEB)

    Boukezzata, A., E-mail: assiab2006@yahoo.fr [Silicon Technology Development Unit (UDTS), 02 Bd. Frantz FANON, B.P. 140 Algiers (Algeria); Keffous, A., E-mail: keffousa@yahoo.fr [Silicon Technology Development Unit (UDTS), 02 Bd. Frantz FANON, B.P. 140 Algiers (Algeria); Cheriet, A.; Belkacem, Y.; Gabouze, N.; Manseri, A. [Silicon Technology Development Unit (UDTS), 02 Bd. Frantz FANON, B.P. 140 Algiers (Algeria); Nezzal, G. [Houari Boumediene University (USTHB), Chemical Faculty, Algiers (Algeria); Kechouane, M.; Bright, A. [Houari Boumediene University, Physical Faculty, Algiers (Algeria); Guerbous, L. [Algerian Nuclear Research Center (CRNA), Algiers (Algeria); Menari, H. [Silicon Technology Development Unit (UDTS), 02 Bd. Frantz FANON, B.P. 140 Algiers (Algeria)

    2010-07-01

    In this work, we present the formation of porous layers on hydrogenated amorphous SiC (a-SiC: H) by Ag-assisted photochemical etching using HF/K{sub 2}S{sub 2}O{sub 8} solution under UV illumination at 254 nm wavelength. The amorphous films a-SiC: H were elaborated by d.c. magnetron sputtering using a hot pressed polycrystalline 6H-SiC target. Because of the high resistivity of the SiC layer, around 1.6 M{Omega} cm and in order to facilitate the chemical etching, a thin metallic film of high purity silver (Ag) has been deposited under vacuum onto the thin a-SiC: H layer. The etched surface was characterized by scanning electron microscopy, secondary ion mass spectroscopy, infrared spectroscopy and photoluminescence. The results show that the morphology of etched a-SiC: H surface evolves with etching time. For an etching time of 20 min the surface presents a hemispherical crater, indicating that the porous SiC layer is perforated. Photoluminescence characterization of etched a-SiC: H samples for 20 min shows a high and an intense blue PL, whereas it has been shown that the PL decreases for higher etching time. Finally, a dissolution mechanism of the silicon carbide in 1HF/1K{sub 2}S{sub 2}O{sub 8} solution has been proposed.

  11. Towards upconversion for amorphous silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    de Wild, J.; Rath, J.K.; Schropp, R.E.I. [Utrecht University, Faculty of Science, Debye Institute for Nanomaterials Science, Nanophotonics, P.O. Box 80000, 3508 TA Utrecht (Netherlands); Meijerink, A. [Utrecht University, Faculty of Science, Debye Institute for Nanomaterials Science, Condensed Matter and Interfaces, P.O. Box 80000, 3508 TA Utrecht (Netherlands); van Sark, W.G.J.H.M. [Utrecht University, Copernicus Institute for Sustainable Development and Innovation, Science, Technology and Society, Heidelberglaan 2, 3584 CS Utrecht (Netherlands)

    2010-11-15

    Upconversion of subbandgap light of thin film single junction amorphous silicon solar cells may enhance their performance in the near infrared (NIR). In this paper we report on the application of the NIR-vis upconverter {beta}-NaYF{sub 4}:Yb{sup 3+}(18%) Er{sup 3+}(2%) at the back of an amorphous silicon solar cell in combination with a white back reflector and its response to infrared irradiation. Current-voltage measurements and spectral response measurements were done on experimental solar cells. An enhancement of 10 {mu}A/cm{sup 2} was measured under illumination with a 980 nm diode laser (10 mW). A part of this was due to defect absorption in localized states of the amorphous silicon. (author)

  12. Innovative Characterization of Amorphous and Thin-Film Silicon for Improved Module Performance: 1 February 2005 - 31 July 2008

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, P. C.; Williams, G. A.

    2009-09-01

    Electron spin resonance and nuclear magnetic resonance was done on amorphous silicon samples (modules with a-Si:H and a-SixGe1-x:H intrinsic layer) to study defects that contribute to Staebler-Wronski effect.

  13. Development of Thin Film Amorphous Silicon Tandem Junction Based Photocathodes Providing High Open-Circuit Voltages for Hydrogen Production

    Directory of Open Access Journals (Sweden)

    F. Urbain

    2014-01-01

    Full Text Available Hydrogenated amorphous silicon thin film tandem solar cells (a-Si:H/a-Si:H have been developed with focus on high open-circuit voltages for the direct application as photocathodes in photoelectrochemical water splitting devices. By temperature variation during deposition of the intrinsic a-Si:H absorber layers the band gap energy of a-Si:H absorber layers, correlating with the hydrogen content of the material, can be adjusted and combined in a way that a-Si:H/a-Si:H tandem solar cells provide open-circuit voltages up to 1.87 V. The applicability of the tandem solar cells as photocathodes was investigated in a photoelectrochemical cell (PEC measurement set-up. With platinum as a catalyst, the a-Si:H/a-Si:H based photocathodes exhibit a high photocurrent onset potential of 1.76 V versus the reversible hydrogen electrode (RHE and a photocurrent of 5.3 mA/cm2 at 0 V versus RHE (under halogen lamp illumination. Our results provide evidence that a direct application of thin film silicon based photocathodes fulfills the main thermodynamic requirements to generate hydrogen. Furthermore, the presented approach may provide an efficient and low-cost route to solar hydrogen production.

  14. Large Polycrystalline Silicon Grains Prepared by Excimer Laser Crystallization of Sputtered Amorphous Silicon Film with Process Temperature at 100 °C

    Science.gov (United States)

    He, Ming; Ishihara, Ryoichi; Neihof, Ellen J. J.; van Andel, Yvonne; Schellevis, Hugo; Metselaar, Wim; Beenakker, Kees

    2007-03-01

    Large polycrystalline silicon (poly-Si) grains with a diameter of 1.8 μm are successfully prepared by excimer laser crystallization (ELC) of a sputtered amorphous silicon (α-Si) film at a maximum process temperature of 100 °C. By pulsed DC magnetron sputtering, α-Si is deposited on a non-structured oxidized wafer. It is found that the α-Si film deposited with a bias is easily ablated during ELC, even at an energy density below the super lateral growth (SLG) region. However, the α-Si film deposited without a bias can endure an energy density well beyond the SLG region without ablation. This zero-bias sputtered α-Si film with a high compressive stress has a low Ar content and a high density, which is beneficial for the suppression of ablation. Large grains with a petal-like shape can be obtained in a wide energy density window, which can be a result from some fine crystallites in the α-Si matrix. These large grains with a low process temperature are promising for the direct formation of system circuits as well as a high-quality display on a plastic foil.

  15. Amorphous Silicon Single-Junction Thin-Film Solar Cell Exceeding 10% Efficiency by Design Optimization

    Directory of Open Access Journals (Sweden)

    Mohammed Ikbal Kabir

    2012-01-01

    Full Text Available The conversion efficiency of a solar cell can substantially be increased by improved material properties and associated designs. At first, this study has adopted AMPS-1D (analysis of microelectronic and photonic structures simulation technique to design and optimize the cell parameters prior to fabrication, where the optimum design parameters can be validated. Solar cells of single junction based on hydrogenated amorphous silicon (a-Si:H have been analyzed by using AMPS-1D simulator. The investigation has been made based on important model parameters such as thickness, doping concentrations, bandgap, and operating temperature and so forth. The efficiency of single junction a-Si:H can be achieved as high as over 19% after parametric optimization in the simulation, which might seem unrealistic with presently available technologies. Therefore, the numerically designed and optimized a-SiC:H/a-SiC:H-buffer/a-Si:H/a-Si:H solar cells have been fabricated by using PECVD (plasma-enhanced chemical vapor deposition, where the best initial conversion efficiency of 10.02% has been achieved ( V,  mA/cm2 and for a small area cell (0.086 cm2. The quantum efficiency (QE characteristic shows the cell’s better spectral response in the wavelength range of 400 nm–650 nm, which proves it to be a potential candidate as the middle cell in a-Si-based multijunction structures.

  16. Formation of iron disilicide on amorphous silicon

    Science.gov (United States)

    Erlesand, U.; Östling, M.; Bodén, K.

    1991-11-01

    Thin films of iron disilicide, β-FeSi 2 were formed on both amorphous silicon and on crystalline silicon. The β-phase is reported to be semiconducting with a direct band-gap of about 0.85-0.89 eV. This phase is known to form via a nucleation-controlled growth process on crystalline silicon and as a consequence a rather rough silicon/silicide interface is usually formed. In order to improve the interface a bilayer structure of amorphous silicon and iron was sequentially deposited on Czochralski silicon in an e-gun evaporation system. Secondary ion mass spectrometry profiling (SIMS) and scanning electron micrographs revealed an improvement of the interface sharpness. Rutherford backscattering spectrometry (RBS) and X-ray diffractiometry showed β-FeSi 2 formation already at 525°C. It was also observed that the silicide growth was diffusion-controlled, similar to what has been reported for example in the formation of NiSi 2 for the reaction of nickel on amorphous silicon. The kinetics of the FeSi 2 formation in the temperature range 525-625°C was studied by RBS and the activation energy was found to be 1.5 ± 0.1 eV.

  17. Carrier collection losses in interface passivated amorphous silicon thin-film solar cells

    Science.gov (United States)

    Neumüller, A.; Bereznev, S.; Ewert, M.; Volobujeva, O.; Sergeev, O.; Falta, J.; Vehse, M.; Agert, C.

    2016-07-01

    In silicon thin-film solar cells the interface between the i- and p-layer is the most critical. In the case of back diffusion of photogenerated minority carriers to the i/p-interface, recombination occurs mainly on the defect states at the interface. To suppress this effect and to reduce recombination losses, hydrogen plasma treatment (HPT) is usually applied. As an alternative to using state of the art HPT we apply an argon plasma treatment (APT) before the p-layer deposition in n-i-p solar cells. To study the effect of APT, several investigations were applied to compare the results with HPT and no plasma treatment at the interface. Carrier collection losses in resulting solar cells were examined with spectral response measurements with and without bias voltage. To investigate single layers, surface photovoltage and X-ray photoelectron spectroscopy (XPS) measurements were conducted. The results with APT at the i/p-interface show a beneficial contribution to the carrier collection compared with HPT and no plasma treatment. Therefore, it can be concluded that APT reduces the recombination centers at the interface. Further, we demonstrate that carrier collection losses of thin-film solar cells are significantly lower with APT.

  18. Improving the organic/Si heterojunction hybrid solar cell property by optimizing PEDOT:PSS film and with amorphous silicon as back surface field

    Science.gov (United States)

    Wen, Hongbin; Cai, Hongkun; Du, Yangyang; Dai, Xiaowan; Sun, Yun; Ni, Jian; Li, Juan; Zhang, Dexian; Zhang, Jianjun

    2017-01-01

    Organic/Si hybrid heterojunction hybrid solar cells have got a great progress. The hybrid device may be promising in terms of reducing cost due to its simple technological process. It is crucial for high efficiency solar cells to form better coating films on the Si substrate. Here, the performance of organic/Si heterojunction hybrid solar cells is obviously enhanced by adding surfactant (FS300) into poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) film and the device with amorphous silicon as back surface field is successfully fabricated. The proper amount of surfactant addition improves the uniformity and homogeneous of the polymer film that can be reflected by scanning electron microscope and atomic force microscope, which allows good contact on the texture-Si substrate resulting in excellent device property. Also, the power conversion efficiency of cells is boosted to 9.37 from 7.31% displayed a 28% enhancement by embedding amorphous silicon thin film layer at rear interface as holes blocking layer. The insertion layer of amorphous silicon enhances the extraction of photon-generated carrier and suppresses the recombination of hole-electron at the rear cathode. Which results all improvement in the short-circuit current density, the open-circuit voltage and the fill factor. By optimizing the polymer film property and inserting the hole blocking layer, the performance of hybrid Si/organic hybrid solar cells is greatly improved.

  19. High Growth Rate Deposition of Hydrogenated Amorphous Silicon-Germanium Films and Devices Using ECR-PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yong [Iowa State Univ., Ames, IA (United States)

    2002-01-01

    Hydrogenated amorphous silicon germanium films (a-SiGe:H) and devices have been extensively studied because of the tunable band gap for matching the solar spectrum and mature the fabrication techniques. a-SiGe:H thin film solar cells have great potential for commercial manufacture because of very low cost and adaptability to large-scale manufacturing. Although it has been demonstrated that a-SiGe:H thin films and devices with good quality can be produced successfully, some issues regarding growth chemistry have remained yet unexplored, such as the hydrogen and inert-gas dilution, bombardment effect, and chemical annealing, to name a few. The alloying of the SiGe introduces above an order-of-magnitude higher defect density, which degrades the performance of the a-SiGe:H thin film solar cells. This degradation becomes worse when high growth-rate deposition is required. Preferential attachment of hydrogen to silicon, clustering of Ge and Si, and columnar structure and buried dihydride radicals make the film intolerably bad. The work presented here uses the Electron-Cyclotron-Resonance Plasma-Enhanced Chemical Vapor Deposition (ECR-PECVD) technique to fabricate a-SiGe:H films and devices with high growth rates. Helium gas, together with a small amount of H2, was used as the plasma species. Thickness, optical band gap, conductivity, Urbach energy, mobility-lifetime product, I-V curve, and quantum efficiency were characterized during the process of pursuing good materials. The microstructure of the a-(Si,Ge):H material was probed by Fourier-Transform Infrared spectroscopy. They found that the advantages of using helium as the main plasma species are: (1) high growth rate--the energetic helium ions break the reactive gas more efficiently than hydrogen ions; (2) homogeneous growth--heavy helium ions impinging on the surface promote the surface mobility of the reactive radicals, so that heteroepitaxy growth as clustering of Ge and Si, columnar structure are

  20. Dual-Layer Nanostructured Flexible Thin-Film Amorphous Silicon Solar Cells with Enhanced Light Harvesting and Photoelectric Conversion Efficiency.

    Science.gov (United States)

    Lin, Yinyue; Xu, Zhen; Yu, Dongliang; Lu, Linfeng; Yin, Min; Tavakoli, Mohammad Mahdi; Chen, Xiaoyuan; Hao, Yuying; Fan, Zhiyong; Cui, Yanxia; Li, Dongdong

    2016-05-04

    Three-dimensional (3-D) structures have triggered tremendous interest for thin-film solar cells since they can dramatically reduce the material usage and incident light reflection. However, the high aspect ratio feature of some 3-D structures leads to deterioration of internal electric field and carrier collection capability, which reduces device power conversion efficiency (PCE). Here, we report high performance flexible thin-film amorphous silicon solar cells with a unique and effective light trapping scheme. In this device structure, a polymer nanopillar membrane is attached on top of a device, which benefits broadband and omnidirectional performances, and a 3-D nanostructure with shallow dent arrays underneath serves as a back reflector on flexible titanium (Ti) foil resulting in an increased optical path length by exciting hybrid optical modes. The efficient light management results in 42.7% and 41.7% remarkable improvements of short-circuit current density and overall efficiency, respectively. Meanwhile, an excellent flexibility has been achieved as PCE remains 97.6% of the initial efficiency even after 10 000 bending cycles. This unique device structure can also be duplicated for other flexible photovoltaic devices based on different active materials such as CdTe, Cu(In,Ga)Se2 (CIGS), organohalide lead perovskites, and so forth.

  1. Light emission in forward and reverse bias operation in OLED with amorphous silicon carbon nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Reyes, R [Facultad de Ingenieria Quimica y Textil, Universidad Nacional de Ingenieria, Av. Tupac Amaru SN, Lima (Peru); Cremona, M [Departamento de Fisica, PontifIcia Universidade Catolica de Rio de Janeiro, PUC-Rio, Cx. Postal 38071, Rio de Janeiro, RJ, CEP 22453-970 (Brazil); Achete, C A, E-mail: rreyes@uni.edu.pe [Departamento de Engenheria Metalurgica e de Materiais, Universidade Federal do Rio de Janeiro, Cx. Postal 68505, Rio de Janeiro, RJ, CEP 21945-970 (Brazil)

    2011-01-01

    Amorphous silicon carbon nitride (a-SiC:N) thin films deposited by magnetron sputtering were used in the structure of an organic light emitting diode (OLED), obtaining an OLED operating in forward and reverse bias mode. The device consist of the heterojunction structure ITO/a-SiC:N/Hole Transport Layer (HTL)/ Electron Transport Layer (ETL)/a-SiC:N/Al. As hole transporting layer was used a thin film of 1-(3-methylphenyl)-1,2,3,4 tetrahydroquinoline - 6 - carboxyaldehyde - 1,1'- diphenylhydrazone (MTCD), while the tris(8-hydroxyquinoline aluminum) (Alq{sub 3}) is used as electron transport and emitting layer. A significant increase in the voltage operation compared to the conventional ITO/MTCD/Alq{sub 3}/Al structure was observed, so the onset of electroluminescence occurs at about 22 V in the forward and reverse bias mode of operation. The electroluminescence spectra is similar in both cases, only slightly shifted 0.14 eV to lower energies in relation to the conventional device.

  2. Nickel-induced crystallization of amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, J A; Arce, R D; Buitrago, R H [INTEC (CONICET-UNL), Gueemes 3450, S3000GLN Santa Fe (Argentina); Budini, N; Rinaldi, P, E-mail: jschmidt@intec.unl.edu.a [FIQ - UNL, Santiago del Estero 2829, S3000AOM Santa Fe (Argentina)

    2009-05-01

    The nickel-induced crystallization of hydrogenated amorphous silicon (a-Si:H) is used to obtain large grained polycrystalline silicon thin films on glass substrates. a-Si:H is deposited by plasma enhanced chemical vapour deposition at 200 deg. C, preparing intrinsic and slightly p-doped samples. Each sample was divided in several pieces, over which increasing Ni concentrations were sputtered. Two crystallization methods are compared, conventional furnace annealing (CFA) and rapid thermal annealing (RTA). The crystallization was followed by optical microscopy and scanning electron microscopy observations, X-ray diffraction, and reflectance measurements in the UV region. The large grain sizes obtained - larger than 100{mu}m for the samples crystallized by CFA - are very encouraging for the preparation of low-cost thin film polycrystalline silicon solar cells.

  3. Atomic-scale characterization of hydrogenated amorphous-silicon films and devices. Annual subcontract report, 15 April 1994--14 March 1998

    Energy Technology Data Exchange (ETDEWEB)

    Gallagher, A.; Barzen, S.; Childs, M.; Laracuente, A. [National Inst. of Standards and Technology, Boulder, CO (United States)

    1998-06-01

    The research is concerned with improving the electronic properties of hydrogenated amorphous silicon (a-Si:H) films and of photovoltaic (PV) cells that use these films. Two approaches toward this goal are being taken. One is to establish the character of silicon particle growth in the rf glow discharges that are used to make the films and PV cells, and to understand the particle incorporation into the films. The ultimate goal of this effort is to find mitigation techniques that minimize the particle incorporation. During this contract period the authors have developed a novel particle light-scattering technique that provides a detailed and sensitive diagnostic of small (8-60 nm diameter) particles suspended in the discharge. The authors have used this to measure the particle growth rates and densities, versus conditions in pure-silane discharges. The second program is directed toward measuring the electronic properties of thin-film PV cells, as a function of depth within the cell. The approach being taken is to use a scanning tunneling microscope (STM) to measure the depth-dependent electronic properties of cross-sectioned PV cells. During the present period, measurements on single and tandem amorphous silicon cells have been carried out. Using STM current-voltage spectroscopy, these measurements distinguish the boundaries between the highly-conducting and intrinsic layers, as well as the chemical potential versus depth in the cell.

  4. Scattering effect of the high-index dielectric nanospheres for high performance hydrogenated amorphous silicon thin-film solar cells

    Science.gov (United States)

    Yang, Zhenhai; Gao, Pingqi; Zhang, Cheng; Li, Xiaofeng; Ye, Jichun

    2016-07-01

    Dielectric nanosphere arrays are considered as promising light-trapping designs with the capability of transforming the freely propagated sunlight into guided modes. This kinds of designs are especially beneficial to the ultrathin hydrogenated amorphous silicon (a-Si:H) solar cells due to the advantages of using lossless material and easily scalable assembly. In this paper, we demonstrate numerically that the front-sided integration of high-index subwavelength titanium dioxide (TiO2) nanosphere arrays can significantly enhance the light absorption in 100 nm-thick a-Si:H thin films and thus the power conversion efficiencies (PCEs) of related solar cells. The main reason behind is firmly attributed to the strong scattering effect excited by TiO2 nanospheres in the whole waveband, which contributes to coupling the light into a-Si:H layer via two typical ways: 1) in the short-waveband, the forward scattering of TiO2 nanospheres excite the Mie resonance, which focuses the light into the surface of the a-Si:H layer and thus provides a leaky channel; 2) in the long-waveband, the transverse waveguided modes caused by powerful scattering effectively couple the light into almost the whole active layer. Moreover, the finite-element simulations demonstrate that photocurrent density (Jph) can be up to 15.01 mA/cm2, which is 48.76% higher than that of flat system.

  5. Microspot-based ELISA in microfluidics: chemiluminescence and colorimetry detection using integrated thin-film hydrogenated amorphous silicon photodiodes.

    Science.gov (United States)

    Novo, Pedro; Prazeres, Duarte Miguel França; Chu, Virginia; Conde, João Pedro

    2011-12-07

    Microfluidic technology has the potential to decrease the time of analysis and the quantity of sample and reactants required in immunoassays, together with the potential of achieving high sensitivity, multiplexing, and portability. A lab-on-a-chip system was developed and optimized using optical and fluorescence microscopy. Primary antibodies are adsorbed onto the walls of a PDMS-based microchannel via microspotting. This probe antibody is then recognised using secondary FITC or HRP labelled antibodies responsible for providing fluorescence or chemiluminescent and colorimetric signals, respectively. The system incorporated a micron-sized thin-film hydrogenated amorphous silicon photodiode microfabricated on a glass substrate. The primary antibody spots in the PDMS-based microfluidic were precisely aligned with the photodiodes for the direct detection of the antibody-antigen molecular recognition reactions using chemiluminescence and colorimetry. The immunoassay takes ~30 min from assay to the integrated detection. The conditions for probe antibody microspotting and for the flow-through ELISA analysis in the microfluidic format with integrated detection were defined using antibody solutions with concentrations in the nM-μM range. Sequential colorimetric or chemiluminescence detection of specific antibody-antigen molecular recognition was quantitatively detected using the photodiode. Primary antibody surface densities down to 0.182 pmol cm(-2) were detected. Multiplex detection using different microspotted primary antibodies was demonstrated.

  6. Formation of ion tracks in amorphous silicon nitride films with MeV C{sub 60} ions

    Energy Technology Data Exchange (ETDEWEB)

    Kitayama, T.; Morita, Y.; Nakajima, K. [Department of Micro Engineering, Kyoto University, Kyoto 606-8501 (Japan); Narumi, K.; Saitoh, Y. [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki-machi, Takasaki, Gunma 370-1292 (Japan); Matsuda, M.; Sataka, M. [Nuclear Science Research Institute, Japan Atomic Energy Agency, Tokai, Naka, Ibaraki 319-1195 (Japan); Tsujimoto, M.; Isoda, S. [Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8501 (Japan); Toulemonde, M. [CIMAP-GANIL (CEA-CNRS-ENSICAEN-Université de Caen Basse Normandie), Bd. H. Becquerel, 14070 Caen (France); Kimura, K., E-mail: kimura@kues.kyoto-u.ac.jp [Department of Micro Engineering, Kyoto University, Kyoto 606-8501 (Japan)

    2015-08-01

    Amorphous silicon nitride (a-SiN) films (thickness 5–100 nm) were irradiated with 0.12–5 MeV C{sub 60}, 100 MeV Xe, 200 MeV Kr, and 200 and 420 MeV Au ions. Ion tracks were clearly observed using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) except for 100 MeV Xe and 200 MeV Kr. The observed HAADF-STEM images showed that the ion tracks consist of a low density core (0.5–2 nm in radius) and a high density shell (several nm in radius). The observed core and shell radii are not simply correlated with the electronic energy loss indicating that the nuclear energy loss plays an important role in the both core and shell formations. The observed track radii were well reproduced by the unified thermal spike model with two thresholds for shell and core formations.

  7. Conduction Mechanism of Amorphous Hydrogenated Silicon Nitride Films%a-SiNx∶H薄膜的导电机制

    Institute of Scientific and Technical Information of China (English)

    王燕; 岳瑞峰

    2001-01-01

    研究了a-SiNx∶H薄膜的电导激活能与氮含量的关系。结果表明,随氮含量增加,样品表现出两种并行的电导机制:欧姆机制与Poole-Frenkel机制。采用两种电导机制拟合电流随温度变化曲线后得到了不同氮含量样品的电导激活能。由于氮在非晶硅中为施主类杂质,且具有特殊的结构组态,因而提出了一种调制掺杂模型解释了实验现象。%Dependence of conductivity activated energy on nitrogen contents in amorphous hydrogenated silicon nitride (a-SiNx∶H)films was studied.The results show that both Ohmic mechanism and Poole-Frenkel mechanism are responsible for the variations in the conductivity activated energies.Temperature dependence of the current can be analytically evaluated by means of the two mechanisms and the conductivity activated energies can be calculated for samples with different nitrogen contents.Since nitrogen is a donor-type impurity with special stoichiometry in a-SiNx∶H,we propose a modulated doping model to understand the dependence of the conductivity activated energy on N contents.

  8. Investigation of the crystallization process of amorphous silicon thin films%非晶硅薄膜晶化过程的研究

    Institute of Scientific and Technical Information of China (English)

    黄木香; 杨琳; 刘玉琪; 王江涌

    2012-01-01

    Polycrystalline silicon thin film is a high quality material for micro - electronic components, thin film transistors and large flat-panel LCD displays because of its high electrical mobility and stable photoelectric properties. Moreover, it has been regarded as a candidate material for making high efficiency, lower energy consumption and optimized thin film solar cells. Therefore, how to fabricate polycrystalline silicon thin film is a very meaningful research topic. Solid phase crystallization is a usual method to fabricate polycrystalline silicon thin film, by high temperature annealing to transfer amorphous film to polycrystalline phase, In this paper, the solid phase crystallization process of amorphous silicon thin films fabricated by different techniques are studied systematically by XRD and Raman spectroscopy.%多晶硅薄膜具有较高的电迁移率和稳定的光电性能,是制备微电子器件、薄膜晶体管、大面积平板液晶显示的优质材料.多晶硅薄膜被公认为是制备高效、低耗、最理想的薄膜太阳能电池的材料.因此,如何制备多晶硅薄膜是一个非常有意义的研究课题.固相法是制备多晶硅薄膜的一种常用方法,它是在高温退火的条件下,使非晶硅薄膜通过固相相变而成为多晶硅薄膜.本文采用固相法,利用X-ray衍射及拉曼光谱,对用不同方法制备的非晶硅薄膜的晶化过程进行了系统地研究.

  9. Preferred orientations of laterally grown silicon films over amorphous substrates using the vapor–liquid–solid technique

    Energy Technology Data Exchange (ETDEWEB)

    LeBoeuf, J. L., E-mail: jerome.leboeuf@mail.mcgill.ca; Brodusch, N.; Gauvin, R.; Quitoriano, N. J. [Department of Mining and Materials Engineering, McGill University, Montreal (Canada)

    2014-12-28

    A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor–liquid–solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30% single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the (1 0 0) surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° Σ3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning.

  10. Colloidal Photoluminescent Amorphous Porous Silicon, Methods Of Making Colloidal Photoluminescent Amorphous Porous Silicon, And Methods Of Using Colloidal Photoluminescent Amorphous Porous Silicon

    KAUST Repository

    Chaieb, Sahraoui

    2015-04-09

    Embodiments of the present disclosure provide for a colloidal photoluminescent amorphous porous silicon particle suspension, methods of making a colloidal photoluminescent amorphous porous silicon particle suspension, methods of using a colloidal photoluminescent amorphous porous silicon particle suspension, and the like.

  11. RF Sputtering for preparing substantially pure amorphous silicon monohydride

    Science.gov (United States)

    Jeffrey, Frank R.; Shanks, Howard R.

    1982-10-12

    A process for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicon produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous silicon hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

  12. Thin-film amorphous silicon alloy research partnership, Phase I. Annual technical progress report, February 2, 1995--February 1, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Guha, S. [United Solar Systems Corp., Troy, MI (United States)

    1996-04-01

    The principal objective of this R&D program is to expand, enhance and accelerate knowledge and capabilities for the development of high-performance, two-terminal multifunction amorphous silicon (a-Si) alloy modules. The near-term goal of the program is to achieve 12% stable module efficiency by 1998 using the multifunction approach. This report describes research on back reflectors of Ag/TiO{sub 2}/ZnO.

  13. Surface morphology and grain analysis of successively industrially grown amorphous hydrogenated carbon films (a-C:H) on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Catena, Alberto [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany); McJunkin, Thomas [Department of Physics, The Ohio State University, 43210 Columbus, Ohio (United States); Agnello, Simonpietro; Gelardi, Franco M. [Department of Physics and Chemistry, University of Palermo, 90100 Palermo (Italy); Wehner, Stefan [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany); Fischer, Christian B., E-mail: chrbfischer@uni-koblenz.de [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany)

    2015-08-30

    Graphical abstract: - Highlights: • Two different a-C:H coatings in various thicknesses on Si (1 0 0) have been studied. • For both types no significant difference in surface morphology is detectable. • The grain number with respect to their height appears randomly distributed. • In average no grain higher than 14 nm and larger than 0.05 μm{sup 2} was observed. • A height to area correlation confines all detected grains to a limited region. - Abstract: Silicon (1 0 0) has been gradually covered by amorphous hydrogenated carbon (a-C:H) films via an industrial process. Two types of these diamond-like carbon (DLC) coatings, one more flexible (f-DLC) and one more robust (r-DLC), have been investigated. Both types have been grown by a radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique with acetylene plasma. Surface morphologies have been studied in detail by atomic force microscopy (AFM) and Raman spectroscopy has been used to investigate the DLC structure. Both types appeared to have very similar morphology and sp{sup 2} carbon arrangement. The average height and area for single grains have been analyzed for all depositions. A random distribution of grain heights was found for both types. The individual grain structures between the f- and r-type revealed differences: the shape for the f-DLC grains is steeper than for the r-DLC grains. By correlating the average grain heights to the average grain areas for all depositions a limited region is identified, suggesting a certain regularity during the DLC deposition mechanisms that confines both values. A growth of the sp{sup 2} carbon entities for high r-DLC depositions is revealed and connected to a structural rearrangement of carbon atom hybridizations and hydrogen content in the DLC structure.

  14. Preparation of high-quality hydrogenated amorphous silicon film with a new microwave electron cyclotron resonance chemical vapour deposition system assisted with hot wire

    Institute of Scientific and Technical Information of China (English)

    Zhu Xiu-Hong; Chen Guang-Hua; Yin Sheng-Yi; Rong Yan-Dong; Zhang Wen-Li; Hu Yue-Hui

    2005-01-01

    The preparation of high-quality hydrogenated amorphous silicon (a-Si:H) film with a new microwave electron cyclotron resonance-chemical vapour deposition (MWECR-CVD) system assisted with hot wire is presented. In this system the hot wire plays an important role in perfecting the microstructure as well as improving the stability and the optoelectronic properties of the a-Si:H film. The experimental results indicate that in the microstructure of the a-Si:H film, the concentration of dihydride is decreased and a trace of microcrystalline occurs, which is useful to improve its stability, and that in the optoelectronic properties of the a-Si:H film, the deposition rate reaches above 2.0nm/s and the photosensitivity increases up to 4.71× 105.

  15. Application of metal nanowire networks on hydrogenated amorphous silicon thin film solar cells.

    Science.gov (United States)

    Xie, Shouyi; Hou, Guofu; Chen, Peizhuan; Jia, Baohua; Gu, Min

    2017-02-24

    We demonstrate the application of metal nanowire (NW) networks as a transparent electrode on hydrogenated amorphous Si (a-Si:H) solar cells. We first systematically investigate the optical performances of the metal NW networks on a-Si:H solar cells in different electrode configurations through numerical simulations to fully understand the mechanisms to guide the experiments. The theoretically optimized configuration is discovered to be metal NWs sandwiched between a 40 nm indium tin oxide (ITO) layer and a 20 nm ITO layer. The overall performances of the solar cells integrated with the metal NW networks are experimentally studied. It has been found the experimentally best performing NW integrated solar cell deviates from the theoretically predicated design due to the performance degradation induced by the fabrication complicity. A 6.7% efficiency enhancement was achieved for the solar cell with metal NW network integrated on top of a 60 nm thick ITO layer compared to the cell with only the ITO layer due to enhanced electrical conductivity by the metal NW network.

  16. Application of metal nanowire networks on hydrogenated amorphous silicon thin film solar cells

    Science.gov (United States)

    Xie, Shouyi; Hou, Guofu; Chen, Peizhuan; Jia, Baohua; Gu, Min

    2017-02-01

    We demonstrate the application of metal nanowire (NW) networks as a transparent electrode on hydrogenated amorphous Si (a-Si:H) solar cells. We first systematically investigate the optical performances of the metal NW networks on a-Si:H solar cells in different electrode configurations through numerical simulations to fully understand the mechanisms to guide the experiments. The theoretically optimized configuration is discovered to be metal NWs sandwiched between a 40 nm indium tin oxide (ITO) layer and a 20 nm ITO layer. The overall performances of the solar cells integrated with the metal NW networks are experimentally studied. It has been found the experimentally best performing NW integrated solar cell deviates from the theoretically predicated design due to the performance degradation induced by the fabrication complicity. A 6.7% efficiency enhancement was achieved for the solar cell with metal NW network integrated on top of a 60 nm thick ITO layer compared to the cell with only the ITO layer due to enhanced electrical conductivity by the metal NW network.

  17. Threshold-Voltage-Shift Compensation and Suppression Method Using Hydrogenated Amorphous Silicon Thin-Film Transistors for Large Active Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Oh, Kyonghwan; Kwon, Oh-Kyong

    2012-03-01

    A threshold-voltage-shift compensation and suppression method for active matrix organic light-emitting diode (AMOLED) displays fabricated using a hydrogenated amorphous silicon thin-film transistor (TFT) backplane is proposed. The proposed method compensates for the threshold voltage variation of TFTs due to different threshold voltage shifts during emission time and extends the lifetime of the AMOLED panel. Measurement results show that the error range of emission current is from -1.1 to +1.7% when the threshold voltage of TFTs varies from 1.2 to 3.0 V.

  18. Experimental study of the hysteresis in hydrogenated amorphous silicon thin-film transistors for an active matrix organic light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae-Hoon; Shin, Kwang-Sub; Park, Joong-Hyun; Han, Min-Koo [Seoul National University, Seoul (Korea, Republic of)

    2006-01-15

    An experimental scheme for validating the cause of the hysteresis phenomenon in hydrogenated amorphous-silicon-thin-film transistors (a-Si:H TFTs) is reported. A different gate starting voltage to the desired gate voltage has been considered to prove an effect of filling an acceptor-like or donor-like state in the interface. The integration time of the semiconductor parameter analyzer has also been controlled to investigate the effect between the de-trapping rate and hysteresis. The experimental results show that the previous data voltage in the (n-1)th frame affects the OLED current in the (n)th frame.

  19. Silicon heterojunction solar cell and crystallization of amorphous silicon

    Science.gov (United States)

    Lu, Meijun

    The rapid growth of photovoltaics in the past decade brings on the soaring price and demand for crystalline silicon. Hence it becomes necessary and also profitable to develop solar cells with over 20% efficiency, using thin (˜100mum) silicon wafers. In this respect, diffused junction cells are not the best choice, since the inescapable heating in the diffusion process not only makes it hard to handle thin wafers, but also reduces carriers' bulk lifetime and impairs the crystal quality of the substrate, which could lower cell efficiency. An alternative is the heterojunction cells, such as amorphous silicon/crystalline silicon heterojunction (SHJ) solar cell, where the emitter layer can be grown at low temperature (solar cell, including the importance of intrinsic buffer layer; the discussion on the often observed anomalous "S"-shaped J-V curve (low fill factor) by using band diagram analysis; the surface passivation quality of intrinsic buffer and its relationship to the performance of front-junction SHJ cells. Although the a-Si:H is found to help to achieve high efficiency in c-Si heterojuntion solar cells, it also absorbs short wavelength (cells. Considering this, heterojunction with both a-Si:H emitter and base contact on the back side in an interdigitated pattern, i.e. interdigitated back contact silicon heterojunction (IBC-SHJ) solar cell, is developed. This dissertation will show our progress in developing IBC-SHJ solar cells, including the structure design; device fabrication and characterization; two dimensional simulation by using simulator Sentaurus Device; some special features of IBC-SHJ solar cells; and performance of IBC-SHJ cells without and with back surface buffer layers. Another trend for solar cell industry is thin film solar cells, since they use less materials resulting in lower cost. Polycrystalline silicon (poly-Si) is one promising thin-film material. It has the potential advantages to not only retain the performance and stability of c

  20. Optimization of Recombination Layer in the Tunnel Junction of Amorphous Silicon Thin-Film Tandem Solar Cells

    Directory of Open Access Journals (Sweden)

    Yang-Shin Lin

    2011-01-01

    Full Text Available The amorphous silicon/amorphous silicon (a-Si/a-Si tandem solar cells have attracted much attention in recent years, due to the high efficiency and low manufacturing cost compared to the single-junction a-Si solar cells. In this paper, the tandem cells are fabricated by high-frequency plasma-enhanced chemical vapor deposition (HF-PECVD at 27.1 MHz. The effects of the recombination layer and the i-layer thickness matching on the cell performance have been investigated. The results show that the tandem cell with a p+ recombination layer and i2/i1 thickness ratio of 6 exhibits a maximum efficiency of 9.0% with the open-circuit voltage (Voc of 1.59 V, short-circuit current density (Jsc of 7.96 mA/cm2, and a fill factor (FF of 0.70. After light-soaking test, our a-Si/a-Si tandem cell with p+ recombination layer shows the excellent stability and the stabilized efficiency of 8.7%.

  1. The investigation of ZnO:Al2O3/metal composite back reflectors in amorphous silicon germanium thin film solar cells

    Institute of Scientific and Technical Information of China (English)

    Wang Guang-Hong; Zhao Lei; Yan Bao-Jun; Chen Jing-Wei; Wang Ge; Diao Hong-Wei; Wang Wen-Jing

    2013-01-01

    Different aluminum-doped ZnO (AZO)/metal composite thin films,including AZO/Ag/Al,AZO/Ag/nickelchromium alloy (NiCr),and AZO/Ag/NiCr/Al,are utilized as the back reflectors of p-i-n amorphous silicon germanium thin film solar cells.NiCr is used as diffusion barrier layer between Ag and Al to prevent mutual diffusion,which increases the short circuit current density of solar cell.NiCr and NiCr/Al layers are used as protective layers of Ag layer against oxidation and sulfurization,the higher efficiency of solar cell is achieved.The experimental results show that the performance of a-SiGe solar cell with AZO/Ag/NiCr/Al back reflector is best.The initial conversion efficiency is achieved to be 8.05%.

  2. High quality crystalline silicon surface passivation by combined intrinsic and n-type hydrogenated amorphous silicon

    NARCIS (Netherlands)

    Schuttauf, J.A.; van der Werf, C.H.M.; Kielen, I.M.; van Sark, W.G.J.H.M.; Rath, J.K.

    2011-01-01

    We investigate the influence of thermal annealing on the passivation quality of crystalline silicon (c-Si) surfaces by intrinsic and n-type hydrogenated amorphous silicon (a-Si:H) films. For temperatures up to 255 C, we find an increase in surface passivation quality, corresponding to a decreased da

  3. Electrical and optical properties of hydrogenated amorphous silicon-germanium (a-Si1 - xGexH) films prepared by reactive ion beam sputtering

    Science.gov (United States)

    Bhan, Mohan Krishan; Malhotra, L. K.; Kashyap, Subhash C.

    1989-09-01

    Thin films of hydrogenated amorphous silicon-germanium (a-Si1-xGex: H) alloys have been prepared by reactive ion beam sputtering of a composite target of silicon and germanium. The dependence of the deposition rate, conductivity-temperature variation, optical absorption coefficient, refractive index, imaginary part of the dielectric constant, hydrogen content, and infrared (IR) absorption spectra on germanium content (x) are reported and analyzed. For a typical composition—a-Si28Ge72:H (x=0.72), the effect of beam voltage, H2:Ar flow ratio, and substrate temperature on the material properties have also been investigated. For the films prepared with increasing x, the expected behavior of a decrease in both hydrogen content and band gap and an increase in the electrical conductivity have been observed. The films prepared at x>0.80 are found to be more homogeneous than the films deposited at 0.0disorder introduced by the random mixing of Si and Ge atoms in the a-Si1-xGex: H network in the latter case. The a-Si28Ge72:H films exhibiting minimum conductivity (1.7×10-7 Ω-1 cm-1) have been obtained for an H2:Ar flow ratio of 10:1 and a beam voltage and substrate temperature of 1500 V and 300 °C, respectively. These films contain a hydrogen concentration of 10.2 at. % and show an optical band gap of 1.25 eV. The IR studies have shown that a-Si28Ge72:H films prepared both at low beam voltages and at low substrate temperatures show the unusual preferential attachment of hydrogen to Ge rather than to Si.

  4. Nanostructural characterization of amorphous diamondlike carbon films

    Energy Technology Data Exchange (ETDEWEB)

    SIEGAL,MICHAEL P.; TALLANT,DAVID R.; MARTINEZ-MIRANDA,L.J.; BARBOUR,J. CHARLES; SIMPSON,REGINA L.; OVERMYER,DONALD L.

    2000-01-27

    Nanostructural characterization of amorphous diamondlike carbon (a-C) films grown on silicon using pulsed-laser deposition (PLD) is correlated to both growth energetic and film thickness. Raman spectroscopy and x-ray reflectivity probe both the topological nature of 3- and 4-fold coordinated carbon atom bonding and the topographical clustering of their distributions within a given film. In general, increasing the energetic of PLD growth results in films becoming more ``diamondlike'', i.e. increasing mass density and decreasing optical absorbance. However, these same properties decrease appreciably with thickness. The topology of carbon atom bonding is different for material near the substrate interface compared to material within the bulk portion of an a-C film. A simple model balancing the energy of residual stress and the free energies of resulting carbon topologies is proposed to provide an explanation of the evolution of topographical bonding clusters in a growing a-C film.

  5. Nanoscale Transformations in Metastable, Amorphous, Silicon-Rich Silica.

    Science.gov (United States)

    Mehonic, Adnan; Buckwell, Mark; Montesi, Luca; Munde, Manveer Singh; Gao, David; Hudziak, Stephen; Chater, Richard J; Fearn, Sarah; McPhail, David; Bosman, Michel; Shluger, Alexander L; Kenyon, Anthony J

    2016-09-01

    Electrically biasing thin films of amorphous, substoichiometric silicon oxide drives surprisingly large structural changes, apparent as density variations, oxygen movement, and ultimately, emission of superoxide ions. Results from this fundamental study are directly relevant to materials that are increasingly used in a range of technologies, and demonstrate a surprising level of field-driven local reordering of a random oxide network.

  6. Tritiated amorphous silicon for micropower applications

    Energy Technology Data Exchange (ETDEWEB)

    Kherani, N.P. [Ontario Hydro Technologies, Toronto, Ontario (Canada)]|[Univ. of Toronto, Ontario (Canada); Kosteski, T.; Zukotynski, S. [Univ. of Toronto, Ontario (Canada); Shmayda, W.T. [Ontario Hydro Technologies, Toronto, Ontario (Canada)

    1995-10-01

    The application of tritiated amorphous silicon as an intrinsic energy conversion semiconductor for radioluminescent structures and betavoltaic devices is presented. Theoretical analysis of the betavoltaic application shows an overall efficiency of 18% for tritiated amorphous silicon. This is equivalent to a 330 Ci intrinsic betavoltaic device producing 1 mW of power for 12 years. Photoluminescence studies of hydrogenated amorphous silicon, a-Si:H, show emission in the infra-red with a maximum quantum efficiency of 7.2% at 50 K; this value drops by 3 orders of magnitude at a temperature of 300 K. Similar studies of hydrogenated amorphous carbon show emission in the visible with an estimated quantum efficiency of 1% at 300 K. These results suggest that tritiated amorphous carbon may be the more promising candidate for room temperature radioluminescence in the visible. 18 refs., 5 figs.

  7. Raman Amplifier Based on Amorphous Silicon Nanoparticles

    Directory of Open Access Journals (Sweden)

    M. A. Ferrara

    2012-01-01

    Full Text Available The observation of stimulated Raman scattering in amorphous silicon nanoparticles embedded in Si-rich nitride/silicon superlattice structures (SRN/Si-SLs is reported. Using a 1427 nm continuous-wavelength pump laser, an amplification of Stokes signal up to 0.9 dB/cm at 1540.6 nm and a significant reduction in threshold power of about 40% with respect to silicon are experimentally demonstrated. Our results indicate that amorphous silicon nanoparticles are a great promise for Si-based Raman lasers.

  8. Electron energy-loss spectroscopy of boron-doped layers in amorphous thin film silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Duchamp, M.; Boothroyd, C.B.; Dunin-Borkowski, R.E. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C) and Peter Gruenberg Institute (PGI), Forschungszentrum Juelich, D-52425 Juelich (Germany); Moreno, M.S. [Centro Atomico Bariloche, 8400 - S. C. de Bariloche (Argentina); Van Aken, B.B.; Soppe, W.J. [ECN Solar Energy, High Tech Campus, Building 5, 5656 AE Eindhoven (Netherlands)

    2013-03-07

    Electron energy-loss spectroscopy (EELS) is used to study p-doped layers in n-i-p amorphous thin film Si solar cells grown on steel foil substrates. For a solar cell in which an intrinsic amorphous hydrogenated Si (a-Si-H) layer is sandwiched between 10-nm-thick n-doped and p-doped a-Si:H layers, we assess whether core-loss EELS can be used to quantify the B concentration. We compare the shape of the measured B K edge with real space ab initio multiple scattering calculations and show that it is possible to separate the weak B K edge peak from the much stronger Si L edge fine structure by using log-normal fitting functions. The measured B concentration is compared with values obtained from secondary ion mass spectrometry, as well as with EELS results obtained from test samples that contain ?200-nm-thick a-Si:H layers co-doped with B and C. We also assess whether changes in volume plasmon energy can be related to the B concentration and/or to the density of the material and whether variations of the volume plasmon line-width can be correlated with differences in the scattering of valence electrons in differently doped a-Si:H layers.

  9. Driving Method for Compensating Reliability Problem of Hydrogenated Amorphous Silicon Thin Film Transistors and Image Sticking Phenomenon in Active Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Shin, Min-Seok; Jo, Yun-Rae; Kwon, Oh-Kyong

    2011-03-01

    In this paper, we propose a driving method for compensating the electrical instability of hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) and the luminance degradation of organic light-emitting diode (OLED) devices for large active matrix OLED (AMOLED) displays. The proposed driving method senses the electrical characteristics of a-Si:H TFTs and OLEDs using current integrators and compensates them by an external compensation method. Threshold voltage shift is controlled a using negative bias voltage. After applying the proposed driving method, the measured error of the maximum emission current ranges from -1.23 to +1.59 least significant bit (LSB) of a 10-bit gray scale under the threshold voltage shift ranging from -0.16 to 0.17 V.

  10. Electron energy-loss spectroscopy study of hydrogenated amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Burnham, N.A.; Fisher, R.F.; Asher, S.E.; Kazmerski, L.L.

    1987-07-01

    Electron energy-loss spectroscopy is used to study hydrogenated amorphous silicon (a-Si:H). Core-level and plasma excitations were examined as a function of hydrogen content. This technique and its interpretation reveals a consistent picture of the electron excitations within this important material. The a-Si:H thin films were fabricated by rf sputtering. Their hydrogen concentrations ranged from 0% to 15%. Hydrogen content was determined by infrared spectroscopy and secondary ion mass spectroscopy. X-ray photoelectron spectroscopy and inspection of the silicon Auger-KLL peak confirmed the silicon core levels.

  11. Flexible amorphous metal films with high stability

    Science.gov (United States)

    Liu, M.; Cao, C. R.; Lu, Y. M.; Wang, W. H.; Bai, H. Y.

    2017-01-01

    We report the formation of amorphous Cu50Zr50 films with a large-area of more than 100 cm2. The films were fabricated by ion beam assisted deposition with a slow deposition rate at moderate temperature. The amorphous films have markedly enhanced thermal stability, excellent flexibility, and high reflectivity with atomic level smoothness. The multifunctional properties of the amorphous films are favorites in the promising applications of smart skin or wearable devices. The method of preparing highly stable amorphous metal films by tuning the deposition rate instead of deposition temperature could pave a way for exploring amorphous metal films with unique properties.

  12. Optical characterization and density of states determination of silicon nanocrystals embedded in amorphous silicon based matrix

    Science.gov (United States)

    van Sebille, M.; Vasudevan, R. A.; Lancee, R. J.; van Swaaij, R. A. C. M. M.; Zeman, M.

    2015-08-01

    We present a non-destructive measurement and simple analysis method for obtaining the absorption coefficient of silicon nanocrystals (NCs) embedded in an amorphous matrix. This method enables us to pinpoint the contribution of silicon NCs to the absorption spectrum of NC containing films. The density of states (DOS) of the amorphous matrix is modelled using the standard model for amorphous silicon while the NCs are modelled using one Gaussian distribution for the occupied states and one for the unoccupied states. For laser annealed a-Si0.66O0.34:H films, our analysis shows a reduction of the NC band gap from approximately 2.34-2.08 eV indicating larger mean NC size for increasing annealing laser fluences, accompanied by a reduction in NC DOS distribution width from 0.28-0.26 eV, indicating a narrower size distribution.

  13. On the effect of the amorphous silicon microstructure on the grain size of solid phase crystallized polycrystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Kashish; Branca, Annalisa; Illiberi, Andrea; Creatore, Mariadriana; Sanden, Mauritius C.M. van de [Department of Applied Physics, Eindhoven University of Technology (Netherlands); Tichelaar, Frans D. [Kavli Institute of Nanoscience, Delft University of Technology (Netherlands)

    2011-05-15

    In this paper the effect of the microstructure of remote plasma-deposited amorphous silicon films on the grain size development in polycrystalline silicon upon solid-phase crystallization is reported. The hydrogenated amorphous silicon films are deposited at different microstructure parameter values R* (which represents the distribution of SiH{sub x} bonds in amorphous silicon), at constant hydrogen content. Amorphous silicon films undergo a phase transformation during solid-phase crystallization and the process results in fully (poly-)crystallized films. An increase in amorphous film structural disorder (i.e., an increase in R*), leads to the development of larger grain sizes (in the range of 700-1100 nm). When the microstructure parameter is reduced, the grain size ranges between 100 and 450 nm. These results point to the microstructure parameter having a key role in controlling the grain size of the polycrystalline silicon films and thus the performance of polycrystalline silicon solar cells. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Temperature of thermal spikes in amorphous silicon nitride films produced by 1.11 MeV C{sub 60}{sup 3+} impacts

    Energy Technology Data Exchange (ETDEWEB)

    Kitayama, T.; Nakajima, K.; Suzuki, M. [Department of Micro Engineering, Kyoto University, Kyoto 615-8540 (Japan); Narumi, K.; Saitoh, Y. [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki-machi, Takasaki, Gunma 370-1292 (Japan); Matsuda, M.; Sataka, M. [Nuclear Science Research Institute, Japan Atomic Energy Agency, Tokai, Naka, Ibaraki 319-1195 (Japan); Tsujimoto, M.; Isoda, S. [Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8501 (Japan); Kimura, K., E-mail: kimura@kues.kyoto-u.ac.jp [Department of Micro Engineering, Kyoto University, Kyoto 615-8540 (Japan)

    2015-07-01

    Gold nanoparticles with an average diameter of 3.6 nm were deposited on amorphous silicon nitride (a-SiN) films. These samples were irradiated with 1.11 MeV C{sub 60}{sup 3+} ions to a fluence of ∼5 × 10{sup 10} ions/cm{sup 2} and observed using transmission electron microscopy (TEM). The ion tracks were clearly seen as bright spots and the gold nanoparticles disappeared from a surface area with a diameter of ∼20 nm around each ion track. The disappeared nanoparticles were collected by a foil placed in front of the sample. Gold particles of circular shape with a diameter of several nm were observed on the collector foil using TEM, suggesting that the gold nanoparticles were emitted as liquid droplets from the a-SiN film upon impact of the C{sub 60} ion. In view of the previous molecular dynamics simulations (Anders et al., 2009), this indicates that the surface temperature rises above the melting point of gold in the region with a diameter of ∼20 nm around the ion impact position.

  15. Neutron irradiation induced amorphization of silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Snead, L.L.; Hay, J.C. [Oak Ridge National Lab., TN (United States)

    1998-09-01

    This paper provides the first known observation of silicon carbide fully amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60 C to a total fast neutron fluence of 2.6 {times} 10{sup 25} n/m{sup 2}. Amorphization was seen in both materials, as evidenced by TEM, electron diffraction, and x-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density ({minus}10.8%), elastic modulus as measured using a nanoindentation technique ({minus}45%), hardness as measured by nanoindentation ({minus}45%), and standard Vickers hardness ({minus}24%). Similar property changes are observed for the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C.

  16. Research and development of photovoltaic power system. Study on growth mechanism of a-Si:H and preparation of the stable, high quality films; Taiyoko hatsuden system no kenkyu kaihatsu. Amorphous silicon no seimaku kiko to kohinshitsuka

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, M. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering

    1994-12-01

    This paper reports the result obtained during fiscal 1994 on research on a film forming mechanism for amorphous silicon for solar cells and its quality improvement. In in-situ observation on plasma CVD surface reaction by using the total reflection infrared absorbing spectroscopy, an observation on a real time basis was performed on the reaction process of an a-Si:H surface in contact with gas mixture plasma composed of SiH4 + CH4. In microscopic observation on initial processes of amorphous silicon growth, surface morphological change before and after a-Si:H deposition at 200{degree}C was observed by using an inter-atomic force microscope. The observation verified that a-Si:H has grown to an atomic layer. In research on defect density in a-Si:H fabricated under high-speed film forming conditions, analysis was made on correlation between the film forming speed at 250{degree}C and defect density in the film. Other research works include those on a high-quality a-SiGe:H film fabricated by using the nanometer film forming/hydrogen plasma annealing method, modulated doping into multi-layer films of a-Si:H/a-Ge:H, and thin film transistor using very thin multi layer films of a-Si:H/a-Ge:H. 5 refs., 12 figs.

  17. Excimer laser crystallization of amorphous silicon on metallic substrate

    Science.gov (United States)

    Delachat, F.; Antoni, F.; Slaoui, A.; Cayron, C.; Ducros, C.; Lerat, J.-F.; Emeraud, T.; Negru, R.; Huet, K.; Reydet, P.-L.

    2013-06-01

    An attempt has been made to achieve the crystallization of silicon thin film on metallic foils by long pulse duration excimer laser processing. Amorphous silicon thin films (100 nm) were deposited by radiofrequency magnetron sputtering on a commercial metallic alloy (N42-FeNi made of 41 % of Ni) coated by a tantalum nitride (TaN) layer. The TaN coating acts as a barrier layer, preventing the diffusion of metallic impurities in the silicon thin film during the laser annealing. An energy density threshold of 0.3 J cm-2, necessary for surface melting and crystallization of the amorphous silicon, was predicted by a numerical simulation of laser-induced phase transitions and witnessed by Raman analysis. Beyond this fluence, the melt depth increases with the intensification of energy density. A complete crystallization of the layer is achieved for an energy density of 0.9 J cm-2. Scanning electron microscopy unveils the nanostructuring of the silicon after laser irradiation, while cross-sectional transmission electron microscopy reveals the crystallites' columnar growth.

  18. FEM numerical analysis of excimer laser induced modification in alternating multi-layers of amorphous and nano-crystalline silicon films

    Energy Technology Data Exchange (ETDEWEB)

    Conde, J.C., E-mail: jconde@uvigo.es [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Martin, E. [Dpto. Mecanica, Maquinas, Motores Termicos y Fluidos, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Stefanov, S. [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Alpuim, P. [Departamento de Fisica, Universidade do Minho, 4800-058 Guimaraes (Portugal); Chiussi, S. [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer nc-Si:H is a material with growing importance for a large-area of nano-electronic, photovoltaic or biomedical devices. Black-Right-Pointing-Pointer UV-ELA technique causes a rapid heating that provokes the H{sub 2} desorption from the Si surface and bulk material. Black-Right-Pointing-Pointer Next, diffusion of P doped nc-Si films and eventually, for high energy densities would be possible to reach the melting point. Black-Right-Pointing-Pointer These multilayer structures consisting of thin alternating a-Si:H(10 nm) and n-doped nc-Si:H(60 nm) films deposited on SiO{sub 2}. Black-Right-Pointing-Pointer To optimize parameters involved in this processing, FEM numerical analysis of multilayer structures have been performed. Black-Right-Pointing-Pointer The numerical results are compared with exhaustive characterization of the experimental results. - Abstract: UV excimer laser annealing (UV-ELA) is an alternative annealing process that, during the last few years, has gained enormous importance for the CMOS nano-electronic technologies, with the ability to provide films and alloys with electrical and optical properties to fit the desired device performance. The UV-ELA of amorphous (a-) and/or doped nano-crystalline (nc-) silicon films is based on the rapid (nanoseconds) formation of temperature profiles caused by laser radiation that is absorbed in the material and lead to crystallisation, diffusion in solid or even in liquid phase. To achieve the desired temperature profiles and to optimize the parameters involved in the processing of hydrogenated nanocrystalline silicon (nc-Si:H) films with the UV-ELA, a numerical analysis by finite element method (FEM) of a multilayer structure has been performed. The multilayer structures, consisting of thin alternating a-Si:H(10 nm) and n-doped nc-Si:H(60 nm) layers, deposited on a glass substrate, has also been experimentally analyzed. Temperature profiles caused by 193 nm radiation with 25

  19. Hydrogen effusion from tritiated amorphous silicon

    Science.gov (United States)

    Kherani, N. P.; Liu, B.; Virk, K.; Kosteski, T.; Gaspari, F.; Shmayda, W. T.; Zukotynski, S.; Chen, K. P.

    2008-01-01

    Results for the effusion and outgassing of tritium from tritiated hydrogenated amorphous silicon (a-Si:H:T) films are presented. The samples were grown by dc-saddle field glow discharge at various substrate temperatures between 150 and 300°C. The tracer property of radioactive tritium is used to detect tritium release. Tritium effusion measurements are performed in a nonvacuum ion chamber and are found to yield similar results as reported for standard high vacuum technique. The results suggest for decreasing substrate temperature the growth of material with an increasing concentration of voids. These data are corroborated by analysis of infrared absorption data in terms of microstructure parameters. For material of low substrate temperature (and high void concentration) tritium outgassing in air at room temperature was studied, and it was found that after 600h about 0.2% of the total hydrogen (hydrogen+tritium) content is released. Two rate limiting processes are identified. The first process, fast tritium outgassing with a time constant of 15h, seems to be related to surface desorption of tritiated water (HTO) with a free energy of desorption of 1.04eV. The second process, slow tritium outgassing with a time constant of 200-300h, appears to be limited by oxygen diffusivity in a growing oxide layer. This material of lowest H stability would lose half of the hydrogen after 60years.

  20. Elastic Properties of Several Silicon Nitride Films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X.; Metcalf, T. H.; Wang, Q.; Photiadis, D. M.

    2007-01-01

    We have measured the internal friction (Q{sup -1}) of amorphous silicon nitride (a-SiN{sub x}) films prepared by a variety of methods, including low-pressure chemical-vapor deposition (LPCVD), plasma-enhanced chemical-vapor deposition (PECVD), and hot-wire chemical-vapor deposition (HWCVD) from 0.5 K to room temperature. The measurements are made by depositing the films onto extremely high-Q silicon double paddle oscillator substrates with a resonant frequency of {approx}5500 Hz. We find the elastic properties of these a-SiN{sub x} films resemble those of amorphous silicon (a-Si) films, demonstrating considerable variation which depends on the film growth methods and post deposition annealing. The internal friction for most of the films shows a broad temperature-independent plateau below 30 K, characteristic of amorphous solids. The values of Q{sup -1}, however, vary from film to film in this plateau region by more than one order of magnitude. This has been observed in tetrehedrally covalent-bonded amorphous thin films, like a-Si, a-Ge, and a-C. The PECVD films have the highest Q{sup -1} just like a normal amorphous solid, while LPCVD films have an internal friction more than one order of magnitude lower. All the films show a reduction of Q{sup -1} after annealing at 800 C, even for the LPCVD films which were prepared at 850 C. This can be viewed as a reduction of structural disorder.

  1. Transmission Electron Microscopy of Amorphous Tandem Thin-Film Silicon Modules Produced by A Roll-to-Roll Process on Plastic Foil

    DEFF Research Database (Denmark)

    Couty, P.; Duchamp, Martial; Söderström, K.;

    2011-01-01

    An improvement of the photo-current is expected when amorphous silicon solar cells are grown on a ZnO texture. A full understanding of the relationship between cell structure and electrical performance is essential for the rapid development of high efficiency VHF-tandem cells on textured substrates...

  2. FTIR study of silicon carbide amorphization by heavy ion irradiations

    Science.gov (United States)

    Costantini, Jean-Marc; Miro, Sandrine; Pluchery, Olivier

    2017-03-01

    We have measured at room temperature (RT) the Fourier-transform infra-red (FTIR) absorption spectra of ion-irradiated thin epitaxial films of cubic silicon carbide (3C–SiC) with 1.1 µm thickness on a 500 µm thick (1 0 0) silicon wafer substrate. Irradiations were carried out at RT with 2.3 MeV 28Si+ ions and 3.0 MeV 84Kr+ ions for various fluences in order to induce amorphization of the SiC film. Ion projected ranges were adjusted to be slightly larger than the film thickness so that the whole SiC layers were homogeneously damaged. FTIR spectra of virgin and irradiated samples were recorded for various incidence angles from normal incidence to Brewster’s angle. We show that the amorphization process in ion-irradiated 3C–SiC films can be monitored non-destructively by FTIR absorption spectroscopy without any major interference of the substrate. The compared evolutions of TO and LO peaks upon ion irradiation yield valuable information on the damage process. Complementary test experiments were also performed on virgin silicon nitride (Si3N4) self-standing films for similar conditions. Asymmetrical shapes were found for TO peaks of SiC, whereas Gaussian profiles are found for LO peaks. Skewed Gaussian profiles, with a standard deviation depending on wave number, were used to fit asymmetrical peaks for both materials. A new methodology for following the amorphization process is proposed on the basis of the evolution of fitted IR absorption peak parameters with ion fluence. Results are discussed with respect to Rutherford backscattering spectrometry channeling and Raman spectroscopy analysis.

  3. Methane Flow Rate Effects On The Optical Properties of Amorphous Silicon Carbon (a-SiC:H Films Deposited By DC Sputtering Methods

    Directory of Open Access Journals (Sweden)

    Rosari Saleh

    2002-04-01

    Full Text Available We have investigated the refractive index (n and the optical absorption coeffi cient (α from refl ection and transmission measurements on hydrogenated amorphous silicon carbon (a-SiC:H fi lms. The a-SiC:H fi lms were prepared by dc sputtering method using silicon target in argon and methane gas mixtures. The refractive index (n decreases as the methane fl ow rate increase. The optical absorption coeffi cient (α shifts to higher energy with increasing methane fl ow rate. At higher methane fl ow rate, the fi lms tend to be more disorder and have wider optical gap. The relation of the optical properties and the disorder amorphous network with the compositional properties will be discussed.

  4. Atomic structure of the amorphous nonstoichiometric silicon oxides and nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Gritsenko, V A [Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2008-07-31

    In addition to amorphous SiO{sub 2} and Si{sub 3}N{sub 4}, the two key dielectric film materials used in modern silicon devices, the fabrication technology of nonstoichiometric SiO{sub x}N{sub y}, SiN{sub x}, and SiO{sub x} compounds is currently under development. Varying the chemical composition of these compounds allows a wide range of control over their physical - specifically, optical and electrical - properties. The development of technology for synthesizing such films requires a detailed understanding of their atomic structure. Current views on the atomic structure of nonstoichiometric silicon nitrides and oxides are reviewed and summarized. (reviews of topical problems)

  5. Recent developments in amorphous silicon-based solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Beneking, C.; Rech, B.; Foelsch, J.; Wagner, H. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Schicht- und Ionentechnik

    1996-03-01

    Two examples of recent advances in the field of thin-film, amorphous hydrogenated silicon (a-Si:H) pin solar cells are described: the improved understanding and control of the p/i interface, and the improvement of wide-bandgap a-Si:H material deposited at low substrate temperature as absorber layer for cells with high stabilized open-circuit voltage. Stacked a-Si:H/a-Si:H cells incorporating these concepts exhibit less than 10% (relative) efficiency degradation and show stabilized efficiencies as high as 9 to 10% (modules 8 to 9%). The use of low-gap a-Si:H and its alloys like a-SiGe:H as bottom cell absorber materials in multi-bandgap stacked cells offers additional possibilities. The combination of a-Si:H based top cells with thin-film crystalline silicon-based bottom cells appears as a promising new trend. It offers the perspective to pass significantly beyond the present landmark of 10% module efficiency reached by the technology utilizing exclusively amorphous silicon-based absorber layers, while keeping its advantages of potentially low-cost production. (orig.) 47 refs.

  6. Development of Amorphous/Microcrystalline Silicon Tandem Thin-Film Solar Modules with Low Output Voltage, High Energy Yield, Low Light-Induced Degradation, and High Damp-Heat Reliability

    Directory of Open Access Journals (Sweden)

    Chin-Yi Tsai

    2014-01-01

    Full Text Available In this work, tandem amorphous/microcrystalline silicon thin-film solar modules with low output voltage, high energy yield, low light-induced degradation, and high damp-heat reliability were successfully designed and developed. Several key technologies of passivation, transparent-conducting-oxide films, and cell and segment laser scribing were researched, developed, and introduced into the production line to enhance the performance of these low-voltage modules. A 900 kWp photovoltaic system with these low-voltage panels was installed and its performance ratio has been simulated and projected to be 92.1%, which is 20% more than the crystalline silicon and CdTe counterparts.

  7. Anomalous hopping conduction in nanocrystalline/amorphous composites and amorphous semiconductor thin films

    Science.gov (United States)

    Kakalios, James; Bodurtha, Kent

    Composite nanostructured materials consisting of nanocrystals (nc) embedded within a thin film amorphous matrix can exhibit novel opto-electronic properties. Composite films are synthesized in a dual-chamber co-deposition PECVD system capable of producing nanocrystals of material A and embedding then within a thin film matrix of material B. Electronic conduction in composite thin films of hydrogenated amorphous silicon (a-Si:H) containing nc-germanium or nc-silicon inclusions, as well as in undoped a-Si:H, does not follow an Arrhenius temperature dependence, but rather is better described by an anomalous hopping expression (exp[-(To/T)3/4) , as determined from the ``reduced activation energy'' proposed by Zabrodskii and Shlimak. This temperature dependence has been observed in other thin film resistive materials, such as ultra-thin disordered films of Ag, Bi, Pb and Pd; carbon-black polymer composites; and weakly coupled Au and ZnO quantum dot arrays. There is presently no accepted theoretical understanding of this expression. The concept of a mobility edge, accepted for over four decades, appears to not be necessary to account for charge transport in amorphous semiconductors. Supported by NSF-DMR and the Minnesota Nano Center.

  8. Similarities in the electrical conduction processes in hydrogenated amorphous silicon oxynitride and silicon nitride

    CERN Document Server

    Kato, H; Ohki, Y; Seol, K S; Noma, T

    2003-01-01

    Electrical conduction at high fields was examined in a series of hydrogenated amorphous silicon oxynitride and silicon nitride films with different nitrogen contents deposited by plasma-enhanced chemical vapour deposition. It was shown that the conduction is attributable to the Poole-Frenkel (PF) emission in the two materials. The energy depths of the PF sites and the dependences on the sample's chemical composition are quite similar for the two samples. It is considered that the PF sites in the two materials are identical.

  9. Three-Terminal Amorphous Silicon Solar Cells

    OpenAIRE

    Cheng-Hung Tai; Chu-Hsuan Lin; Chih-Ming Wang; Chun-Chieh Lin

    2011-01-01

    Many defects exist within amorphous silicon since it is not crystalline. This provides recombination centers, thus reducing the efficiency of a typical a-Si solar cell. A new structure is presented in this paper: a three-terminal a-Si solar cell. The new back-to-back p-i-n/n-i-p structure increased the average electric field in a solar cell. A typical a-Si p-i-n solar cell was also simulated for comparison using the same thickness and material parameters. The 0.28 μm-thick three-terminal a-Si...

  10. Development of Tandem Amorphous/Microcrystalline Silicon Thin-Film Large-Area See-Through Color Solar Panels with Reflective Layer and 4-Step Laser Scribing for Building-Integrated Photovoltaic Applications

    Directory of Open Access Journals (Sweden)

    Chin-Yi Tsai

    2014-01-01

    Full Text Available In this work, tandem amorphous/microcrystalline silicon thin-film large-area see-through color solar modules were successfully designed and developed for building-integrated photovoltaic applications. Novel and key technologies of reflective layers and 4-step laser scribing were researched, developed, and introduced into the production line to produce solar panels with various colors, such as purple, dark blue, light blue, silver, golden, orange, red wine, and coffee. The highest module power is 105 W and the highest visible light transmittance is near 20%.

  11. Performance improvement in amorphous silicon based uncooled microbolometers through pixel design and materials development

    Science.gov (United States)

    Ajmera, Sameer; Brady, John; Hanson, Charles; Schimert, Tom; Syllaios, A. J.; Taylor, Michael

    2011-06-01

    Uncooled amorphous silicon microbolometers have been established as a field-worthy technology for a broad range of applications where performance and form factor are paramount, such as soldier-borne systems. Recent developments in both bolometer materials and pixel design at L-3 in the 17μm pixel node have further advanced the state-of-the-art. Increasing the a-Si material temperature coefficient of resistance (TCR) has the impact of improving NETD sensitivity without increasing thermal time constant (TTC), leading to an improvement in the NETD×TTC product. By tuning the amorphous silicon thin-film microstructure using hydrogen dilution during deposition, films with high TCR have been developed. The electrical properties of these films have been shown to be stable even after thermal cycling to temperatures greater than 300oC enabling wafer-level vacuum packaging currently performed at L-3 to reduce the size and weight of the vacuum packaged unit. Through appropriate selection of conditions during deposition, amorphous silicon of ~3.4% TCR has been integrated into the L-3 microbolometer manufacturing flow. By combining pixel design enhancements with improvements to amorphous silicon thin-film technology, L-3's amorphous silicon microbolometer technology will continue to provide the performance required to meet the needs to tomorrow's war-fighter.

  12. On the use of a charged tunnel layer as a hole collector to improve the efficiency of amorphous silicon thin-film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ke, Cangming; Sahraei, Nasim; Aberle, Armin G. [Solar Energy Research Institute of Singapore, National University of Singapore, Singapore 117574 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583 (Singapore); Stangl, Rolf [Solar Energy Research Institute of Singapore, National University of Singapore, Singapore 117574 (Singapore); Peters, Ian Marius

    2015-06-28

    A new concept, using a negatively charged tunnel layer as a hole collector, is proposed and theoretically investigated for application in amorphous silicon thin-film solar cells. The concept features a glass/transparent conductive oxide/ultra-thin negatively charged tunnel layer/intrinsic a-Si:H/n-doped a-Si:H/metal structure. The key feature of this so called t{sup +}-i-n structure is the introduction of a negatively charged tunnel layer (attracting holes from the intrinsic absorber layer), which substitutes the highly recombination active p-doped a-Si:H layer in a conventional p-i-n configuration. Atomic layer deposited aluminum oxide (ALD AlO{sub x}) is suggested as a potential candidate for such a tunnel layer. Using typical ALD AlO{sub x} parameters, a 27% relative efficiency increase (i.e., from 9.7% to 12.3%) is predicted theoretically for a single-junction a-Si:H solar cell on a textured superstrate. This prediction is based on parameters that reproduce the experimentally obtained external quantum efficiency and current-voltage characteristics of a conventional processed p-i-n a-Si:H solar cell, reaching 9.7% efficiency and serving as a reference. Subsequently, the p-doped a-Si:H layer is replaced by the tunnel layer (studied by means of numerical device simulation). Using a t{sup +}-i-n configuration instead of a conventional p-i-n configuration will not only increase the short-circuit current density (from 14.4 to 14.9 mA/cm{sup 2}, according to our simulations), it also enhances the open-circuit voltage and the fill factor (from 917 mV to 1.0 V and from 74% to 83%, respectively). For this concept to work efficiently, a high work function front electrode material or a high interface charge is needed.

  13. Role of SiNx Barrier Layer on the Performances of Polyimide Ga2O3-doped ZnO p-i-n Hydrogenated Amorphous Silicon Thin Film Solar Cells

    Directory of Open Access Journals (Sweden)

    Fang-Hsing Wang

    2014-02-01

    Full Text Available In this study, silicon nitride (SiNx thin films were deposited on polyimide (PI substrates as barrier layers by a plasma enhanced chemical vapor deposition (PECVD system. The gallium-doped zinc oxide (GZO thin films were deposited on PI and SiNx/PI substrates at room temperature (RT, 100 and 200 °C by radio frequency (RF magnetron sputtering. The thicknesses of the GZO and SiNx thin films were controlled at around 160 ± 12 nm and 150 ± 10 nm, respectively. The optimal deposition parameters for the SiNx thin films were a working pressure of 800 × 10−3 Torr, a deposition power of 20 W, a deposition temperature of 200 °C, and gas flowing rates of SiH4 = 20 sccm and NH3 = 210 sccm, respectively. For the GZO/PI and GZO-SiNx/PI structures we had found that the GZO thin films deposited at 100 and 200 °C had higher crystallinity, higher electron mobility, larger carrier concentration, smaller resistivity, and higher optical transmittance ratio. For that, the GZO thin films deposited at 100 and 200 °C on PI and SiNx/PI substrates with thickness of ~1000 nm were used to fabricate p-i-n hydrogenated amorphous silicon (α-Si thin film solar cells. 0.5% HCl solution was used to etch the surfaces of the GZO/PI and GZO-SiNx/PI substrates. Finally, PECVD system was used to deposit α-Si thin film onto the etched surfaces of the GZO/PI and GZO-SiNx/PI substrates to fabricate α-Si thin film solar cells, and the solar cells’ properties were also investigated. We had found that substrates to get the optimally solar cells’ efficiency were 200 °C-deposited GZO-SiNx/PI.

  14. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Boccard, Mathieu; Holman, Zachary C. [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706 (United States)

    2015-08-14

    Amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphous silicon carbide being shown to surpass amorphous silicon for temperatures above 300 °C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.

  15. Energy landscape of relaxed amorphous silicon

    Science.gov (United States)

    Valiquette, Francis; Mousseau, Normand

    2003-09-01

    We analyze the structure of the energy landscape of a well-relaxed 1000-atom model of amorphous silicon using the activation-relaxation technique (ART nouveau). Generating more than 40 000 events starting from a single minimum, we find that activated mechanisms are local in nature, that they are distributed uniformly throughout the model, and that the activation energy is limited by the cost of breaking one bond, independently of the complexity of the mechanism. The overall shape of the activation-energy-barrier distribution is also insensitive to the exact details of the configuration, indicating that well-relaxed configurations see essentially the same environment. These results underscore the localized nature of relaxation in this material.

  16. Dynamics of hydrogen in hydrogenated amorphous silicon

    Indian Academy of Sciences (India)

    Ranber Singh; S Prakash

    2003-07-01

    The problem of hydrogen diffusion in hydrogenated amorphous silicon (a-Si:H) is studied semiclassically. It is found that the local hydrogen concentration fluctuations-induced extra potential wells, if intense enough, lead to the localized electronic states in a-Si:H. These localized states are metastable. The trapping of electrons and holes in these states leads to the electrical degradation of the material. These states also act as recombination centers for photo-generated carriers (electrons and holes) which in turn may excite a hydrogen atom from a nearby Si–H bond and breaks the weak (strained) Si–Si bond thereby apparently enhancing the hydrogen diffusion and increasing the light-induced dangling bonds.

  17. Three-Terminal Amorphous Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Cheng-Hung Tai

    2011-01-01

    Full Text Available Many defects exist within amorphous silicon since it is not crystalline. This provides recombination centers, thus reducing the efficiency of a typical a-Si solar cell. A new structure is presented in this paper: a three-terminal a-Si solar cell. The new back-to-back p-i-n/n-i-p structure increased the average electric field in a solar cell. A typical a-Si p-i-n solar cell was also simulated for comparison using the same thickness and material parameters. The 0.28 μm-thick three-terminal a-Si solar cell achieved an efficiency of 11.4%, while the efficiency of a typical a-Si p-i-n solar cell was 9.0%. Furthermore, an efficiency of 11.7% was achieved by thickness optimization of the three-terminal solar cell.

  18. Amorphous Dielectric Thin Films with Extremely Low Mechanical Loss

    Directory of Open Access Journals (Sweden)

    Liu X.

    2015-04-01

    Full Text Available The ubiquitous low-energy excitations are one of the universal phenomena of amorphous solids. These excitations dominate the acoustic, dielectric, and thermal properties of structurally disordered solids. One exception has been a type of hydrogenated amorphous silicon (a-Si:H with 1 at.% H. Using low temperature elastic and thermal measurements of electron-beam evap-orated amorphous silicon (a-Si, we show that TLS can be eliminated in this system as the films become denser and more structurally ordered under certain deposition conditions. Our results demonstrate that TLS are not intrinsic to the glassy state but instead reside in low density regions of the amorphous network. This work obviates the role hydrogen was previously thought to play in removing TLS in a-Si:H and favors an ideal four-fold covalently bonded amorphous structure as the cause for the disappearance of TLS. Our result supports the notion that a-Si can be made a “perfect glass” with “crystal-like” properties, thus offering an encouraging opportunity to use it as a simple crystal dielectric alternative in applications, such as in modern quantum devices where TLS are the source of dissipation, decoherence and 1/f noise.

  19. Microcavity effects in the photoluminescence of hydrogenated amorphous silicon nitride

    Science.gov (United States)

    Serpenguzel, Ali; Aydinli, Atilla; Bek, Alpan

    1998-07-01

    Fabry-Perot microcavities are used for the alteration of photoluminescence in hydrogenated amorphous silicon nitride grown with and without ammonia. The photoluminescence is red-near-infrared for the samples grown without ammonia, and blue-green for the samples grown with ammonia. In the Fabry- Perot microcavities, the amplitude of the photoluminescence is enhanced, while its linewidth is reduced with respect to the bulk hydrogenated amorphous silicon nitride. The microcavity was realized by a metallic back mirror and a hydrogenated amorphous silicon nitride--air or a metallic front mirror. The transmittance, reflectance, and absorbance spectra were also measured and calculated. The calculated spectra agree well with the experimental spectra. The hydrogenated amorphous silicon nitride microcavity has potential for becoming a versatile silicon based optoelectronic device such as a color flat panel display, a resonant cavity enhanced light emitting diode, or a laser.

  20. Stability of deuterated amorphous silicon solar cells

    CERN Document Server

    Munyeme, G; Van der Meer, L F G; Dijkhuis, J I; Van der Weg, W F; Schropp, R

    2004-01-01

    In order to elucidate the microscopic mechanism for the earlier observed enhanced stability of deuterated amorphous silicon solar cells we conducted a side by-side study of fully deuterated intrinsic layers on crystalline silicon substrates using the free-electron laser facility at Nieuwegein (FELIX) to resonantly excite the Si-D stretching vibration and measure the various relaxation channels available to these modes, and of p-i-n solar cells with identical intrinsic absorber layers on glass/TCO substrates to record the degradation and stabilization of solar cell parameters under prolonged light soaking treatments. From our comparative study it is shown that a-Si:D has a superior resistance against light-induced defect creation as compared to a-Si:H and that this can now be explained in the light of the 'H collision model' since the initial step in the process, the release of H, is more likely than that of D. Thus, a natural explanation for the stability as observed in a-Si:D solar cells is provided.

  1. Effect of surface irradiation during the photo-CVD deposition of a-Si:H thin films. Hikari CVD ho ni yoru amorphous silicon sakuseiji no kiban hikari reiki koka

    Energy Technology Data Exchange (ETDEWEB)

    Tasaka, K.; Doering, H.; Hashimoto, K.; Fujishima, A. (The University of Tokyo, Tokyo (Japan))

    1990-12-06

    This paper shows the impact of the irradiation from an additional light source during the deposition of hydrogenated amorphous silicon by photo-CVD deposition. Using a mercury sensitized photo-CVD process from Disilan (Si {sub 2} H {sub 6}) and hydrogen, silicon was deposited. A 40W low pressure mercury lamp was applied as the light source. A portion of the substrate was in addition irradiated using an Xg-He lamp through a thermal filter. Irradiation of the substrate using only Xg-He lamp produced no deposition, since this light has a wavelength which is too long to produce the SiH {sub 3}-radicals needed for Si deposition. The additional Xg-He light source was discovered to cause an increased thickness of deposited a-Si:H film and a transmission of the band structure. The reasons of these are considered that the influence of irradiation is not limited to film thickness, but that irradiation also impacts the composition of the a-Si:H film so as to cause a reduction in the hydrogen content. 10 figs., 1 tab.

  2. Proton irradiation effects of amorphous silicon solar cell for solar power satellite

    Energy Technology Data Exchange (ETDEWEB)

    Morita, Yousuke; Oshima, Takeshi [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Sasaki, Susumu; Kuroda, Hideo; Ushirokawa, Akio

    1997-03-01

    Flexible amorphous silicon(fa-Si) solar cell module, a thin film type, is regarded as a realistic power generator for solar power satellite. The radiation resistance of fa-Si cells was investigated by the irradiations of 3,4 and 10 MeV protons. The hydrogen gas treatment of the irradiated fa-Si cells was also studied. The fa-Si cell shows high radiation resistance for proton irradiations, compared with a crystalline silicon solar cell. (author)

  3. Nanocavity Shrinkage and Preferential Amorphization during Irradiation in Silicon

    Institute of Scientific and Technical Information of China (English)

    ZHU Xian-Fang; WANG Zhan-Guo

    2005-01-01

    @@ We model the recent experimental results and demonstrate that the internal shrinkage of nanocavities in silicon is intrinsically associated with preferential amorphization as induced by self-ion irradiation.

  4. Si-H bond dynamics in hydrogenated amorphous silicon

    Science.gov (United States)

    Scharff, R. Jason; McGrane, Shawn D.

    2007-08-01

    The ultrafast structural dynamics of the Si-H bond in the rigid solvent environment of an amorphous silicon thin film is investigated using two-dimensional infrared four-wave mixing techniques. The two-dimensional infrared (2DIR) vibrational correlation spectrum resolves the homogeneous line shapes ( 4ps waiting times. The Si-H stretching mode anharmonic shift is determined to be 84cm-1 and decreases slightly with vibrational frequency. The 1→2 linewidth increases with vibrational frequency. Frequency dependent vibrational population times measured by transient grating spectroscopy are also reported. The narrow homogeneous line shape, large inhomogeneous broadening, and lack of spectral diffusion reported here present the ideal backdrop for using a 2DIR probe following electronic pumping to measure the transient structural dynamics implicated in the Staebler-Wronski degradation [Appl. Phys. Lett. 31, 292 (1977)] in a-Si:H based solar cells.

  5. Progress in amorphous silicon solar cells produced by reactive sputtering

    Science.gov (United States)

    Moustakas, T. D.

    The photovoltaic properties of reactively sputtered amorphous silicon are reviewed and it is shown that efficient PIN solar cells can be fabricated by the method of sputtering. The photovoltaic properties of the intrinsic films correlate with their structural and compositional inhomogeneities. Hydrogen incorporation and small levels of phosphorus and boron impurities also affect the photovoltaic properties through reduction of residual dangling bond related defects and modification of their occupation. The optical and transport properties of the doped P and N-films were found to depend sensitively on the amount of hydrogen and boron or phosphorus incorporation into the films as well as on their degree of crystallinity. Combination of the best intrinsic and doped films leads to PIN solar cell structures generating J(sc) of 13 mA/sq cm and V(oc) of between 0.85 to 0.95 volts. The efficiency of these devices, 5 to 6 percent, is limited by the low FF, typically about 50 percent. As a further test to the potential of this technology efficient tandem solar cell structures were fabricated, and device design concepts, such as the incorporation of optically reflective back contacts were tested.

  6. The model of solid phase crystallization of amorphous silicon under elastic stress

    OpenAIRE

    2000-01-01

    Solid phase crystallization of an amorphous silicon (a-Si) film stressed by a Si3N4 cap was studied by laser Raman spectroscopy. The a-Si films were deposited on Si3N4 (50 nm)/Si(100) substrate by rf sputtering. The stress in an a-Si film was controlled by thickness of a Si3N4 cap layer. The Si3N4 films were also deposited by rf sputtering. It was observed that the crystallization was affected by the stress in a-Si films introduced by the Si3N4 cap layer. The study suggests that the elastic s...

  7. Polarization effects in femtosecond laser induced amorphization of monocrystalline silicon

    Science.gov (United States)

    Bai, Feng; Li, Hong-Jin; Huang, Yuan-Yuan; Fan, Wen-Zhong; Pan, Huai-Hai; Wang, Zhuo; Wang, Cheng-Wei; Qian, Jing; Li, Yang-Bo; Zhao, Quan-Zhong

    2016-10-01

    We have used femtosecond laser pulses to ablate monocrystalline silicon wafer. Raman spectroscopy and X-ray diffraction analysis of ablation surface indicates horizontally polarized laser beam shows an enhancement in amorphization efficiency by a factor of 1.6-1.7 over the circularly polarized laser ablation. This demonstrates that one can tune the amorphization efficiency through the polarization of irradiation laser.

  8. Substrate and Passivation Techniques for Flexible Amorphous Silicon-Based X-ray Detectors

    Science.gov (United States)

    Marrs, Michael A.; Raupp, Gregory B.

    2016-01-01

    Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium. A dark current of 0.5 pA/mm2 and photodiode quantum efficiency of 74% are possible with a pixelated diode structure with a silicon nitride/SU-8 bilayer passivation structure on a 20 µm-thick polyimide substrate. PMID:27472329

  9. Substrate and Passivation Techniques for Flexible Amorphous Silicon-Based X-ray Detectors

    Directory of Open Access Journals (Sweden)

    Michael A. Marrs

    2016-07-01

    Full Text Available Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium. A dark current of 0.5 pA/mm2 and photodiode quantum efficiency of 74% are possible with a pixelated diode structure with a silicon nitride/SU-8 bilayer passivation structure on a 20 µm-thick polyimide substrate.

  10. Substrate and Passivation Techniques for Flexible Amorphous Silicon-Based X-ray Detectors.

    Science.gov (United States)

    Marrs, Michael A; Raupp, Gregory B

    2016-07-26

    Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium. A dark current of 0.5 pA/mm² and photodiode quantum efficiency of 74% are possible with a pixelated diode structure with a silicon nitride/SU-8 bilayer passivation structure on a 20 µm-thick polyimide substrate.

  11. Improved stability of hydrogenated amorphous-silicon photosensitivity by ultraviolet illumination

    Science.gov (United States)

    Branz, Howard M.; Xu, Yueqin; Heck, Stephan; Gao, Wei

    2002-10-01

    Postdeposition ultraviolet (UV) illumination, followed by etching, improves the stability of hydrogenated amorphous-silicon thin films against subsequent light-induced degradation of photosensitivity. The etch removes a heavily damaged layer extending about 100 nm below the surface, but beneath the damage, the UV has improved the stability of 200 to 300 nm of bulk film. The open-circuit voltage of Schottky solar cells is also stabilized by UV-etch treatment. Possible mechanisms are discussed.

  12. 一种增加光吸收的非晶硅薄膜太阳能电池的设计%Design of An Amorphous Silicon Thin-film Sloar Cell with Absorption Enhancement

    Institute of Scientific and Technical Information of China (English)

    沈宏君; 张瑞; 卢辉东

    2013-01-01

    分别设计与优化了非晶薄膜太阳能电池的上表层和电池底部结构,采用严格耦合波方法(RCWA)数值计算了电池的光吸收.计算结果表明:在仅考虑TM偏振的情况下,优化后的增透膜与无增透膜相比,300~840 nm波长范围内的吸收平均提高了35%左右;优化后的背反射器与无背反射器相比,700~840 nm波长范围内的吸收平均提高了23%左右.该非晶硅薄膜太阳能电池结构在全角宽频范围内有较高吸收,可以提高太阳能电池的转化效率.%The front-surface and the bottom of amorphous silicon (a-Si) thin-film solar cell are designed respectively.Light absorption is calculated by using the rigorous coupled wave analysis (RCWA).In TM polarization,the absorption of solar cells with optimized AR coating can be increased by an average of 35% compared with that without AR coating in the range of 300 ~ 840 nm.Furthermore,the absorption of solar cells with optimized back reflector can be increased by an average of 23% compared with that without back reflector in the range of 700 ~ 840 nm.The amorphous silicon(a-Si) thin-film solar cell that we design has broadband and omnidirectional absorption,so that it can improve the conversion efficiency of solar cells.

  13. Wide-Gap p-μc-Si1-xOx:H Films and Their Application to Amorphous Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Taweewat Krajangsang

    2013-01-01

    Full Text Available Optimization of p-type hydrogenated microcrystalline silicon oxide thin films (p-μc-Si1-xOx:H by very high frequency plasma enhanced chemical vapor deposition 40 MHz method for use as a p-layer of a-Si:H solar cells was performed. The properties of p-μc-Si1-xOx:H films were characterized by conductivity, Raman scattering spectroscopy, and spectroscopic ellipsometry. The wide optical band gap p-μc-Si1-xOx:H films were optimized by CO2/SiH4 ratio and H2/SiH4 dilution. Besides, the effects of wide-gap p-μc-Si1-xOx:H layer on the performance of a-Si:H solar cells with various optical band gaps of p-layer were also investigated. Furthermore, improvements of open circuit voltage, short circuit current, and performance of the solar cells by using the effective wide-gap p-μc-Si1-xOx:H were observed in this study. These results indicate that wide-gap p-μc-Si1-xOx:H is promising to use as window layer in a-Si:H solar cells.

  14. In situ probing of surface hydrides on hydrogenated amorphous silicon using attenuated total reflection infrared spectroscopy

    CERN Document Server

    Kessels, W M M; Sanden, M C M; Aydil, E S

    2002-01-01

    An in situ method based on attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) is presented for detecting surface silicon hydrides on plasma deposited hydrogenated amorphous silicon (a-Si:H) films and for determining their surface concentrations. Surface silicon hydrides are desorbed by exposing the a-Si:H films to low energy ions from a low density Ar plasma and by comparing the infrared spectrum before and after this low energy ion bombardment, the absorptions by surface hydrides can sensitively be separated from absorptions by bulk hydrides incorporated into the film. An experimental comparison with other methods that utilize isotope exchange of the surface hydrogen with deuterium showed good agreement and the advantages and disadvantages of the different methods are discussed. Furthermore, the determination of the composition of the surface hydrogen bondings on the basis of the literature data on hydrogenated crystalline silicon surfaces is presented, and quantification of the h...

  15. On the crystallization of amorphous germanium films

    Science.gov (United States)

    Edelman, F.; Komem, Y.; Bendayan, M.; Beserman, R.

    1993-06-01

    The incubation time for crystallization of amorphous Ge (a-Ge) films, deposited by e-gun, was studied as a function of temperature between 150 and 500°C by means of both in situ transmission electron microscopy and Raman scattering spectroscopy. The temperature dependence of t0 follows an Arrhenius curve with an activation energy of 2.0 eV for free-sustained a-Ge films. In the case where the a-Ge films were on Si 3N 4 substrate, the activation energy of the incubation process was 1.3 eV.

  16. Nickel-disilicide-assisted excimer laser crystallization of amorphous silicon

    Institute of Scientific and Technical Information of China (English)

    Liao Yan-Ping; Shao Xi-Bin; Gao Feng-Li; Luo Wen-Sheng; Wu Yuan; Fu Guo-Zhu; Jing Hai; Ma Kai

    2006-01-01

    Polycrystalline silicon (poly-Si) thin film has been prepared by means of nickel-disilicide (NiSi2) assisted excimer laser crystallization (ELC). The process to prepare a sample includes two steps. One step consists of the formation of NiSi2 precipitates by heat-treating the dehydrogenated amorphous silicon (a-Si) coated with a thin layer of Ni. And the other step consists of the formation of poly-Si grains by means of ELC. According to the test results of scanning electron microscopy (SEM), another grain growth model named two-interface grain growth has been proposed to contrast with the conventional Ni-metal-induced lateral crystallization (Ni-MILC) model and the ELC model. That is, an additional grain growth interface other than that in conventional ELC is formed, which consists of NiSi2 precipitates and a-Si.The processes for grain growth according to various excimer laser energy densities delivered to the a-Si film have been discussed. It is discovered that grains with needle shape and most of a uniform orientation are formed which grow up with NiSi2 precipitates as seeds. The reason for the formation of such grains which are different from that of Ni-MILCwithout migration of Ni atoms is not clear. Our model and analysis point out a method to prepare grains with needle shape and mostly of a uniform orientation. If such grains are utilized to make thin-film transistor, its characteristics may be improved.

  17. A fast method to diagnose phase transition from amorphous to microcrystalline silicon

    Institute of Scientific and Technical Information of China (English)

    HOU; GuoFu

    2007-01-01

    A series of hydrogenated silicon thin films were prepared by the radio frequency plasma enhanced chemical vapor deposition method (RF-PECVD) with various silane concentrations. The influence of silane concentration on structural and electrical characteristics of these films was investigated to study the phase transition region from amorphous to microcrystalline phase. At the same time, optical emission spectra (OES) from the plasma during the deposition process were monitored to get information about the plasma properties, Raman spectra were measured to study the structural characteristics of the deposited films. The combinatorial analysis of OES and Raman spectra results demonstrated that the OES can be used as a fast method to diagnose phase transition from amorphous to microcrystalline silicon. At last the physical mechanism, why both OES and Raman can be used to diagnose the phase transition, was analyzed theoretically.……

  18. On the effect of the underlying ZnO:Al layer on the crystallization kinetics of hydrogenated amorphous silicon

    NARCIS (Netherlands)

    Sharma, K.; Ponomarev, M. V.; M. C. M. van de Sanden,; Creatore, M.

    2013-01-01

    In this contribution, we analyze the thickness effect of the underlying aluminum doped-zinc oxide (ZnO:Al) layers on the structural properties and crystallization kinetics of hydrogenated amorphous silicon (a-Si:H) thin films. It is shown that the disorder in as-deposited a-Si:H films, as probed by

  19. Nanostructured silicon carbon thin films grown by plasma enhanced chemical vapour deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Coscia, U. [Dipartimento di Fisica, Università di Napoli “Federico II” Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); CNISM Unita' di Napoli, Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); Ambrosone, G., E-mail: ambrosone@na.infn.it [Dipartimento di Fisica, Università di Napoli “Federico II” Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); SPIN-CNR, Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); Basa, D.K. [Department of Physics, Utkal University, Bhubaneswar 751004 (India); Rigato, V. [INFN Laboratori Nazionali Legnaro, 35020 Legnaro (Padova) (Italy); Ferrero, S.; Virga, A. [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino (Italy)

    2013-09-30

    Nanostructured silicon carbon thin films, composed of Si nanocrystallites embedded in hydrogenated amorphous silicon carbon matrix, have been prepared by varying rf power in ultra high vacuum plasma enhanced chemical vapour deposition system using silane and methane gas mixtures diluted in hydrogen. In this paper we have studied the compositional, structural and electrical properties of these films as a function of rf power. It is shown that with increasing rf power the atomic densities of carbon and hydrogen increase while the atomic density of silicon decreases, resulting in a reduction in the mass density. Further, it is demonstrated that carbon is incorporated into amorphous matrix and it is mainly bonded to silicon. The study has also revealed that the crystalline volume fraction decreases with increase in rf power and that the films deposited with low rf power have a size distribution of large and small crystallites while the films deposited with relatively high power have only small crystallites. Finally, the enhanced transport properties of the nanostructured silicon carbon films, as compared to amorphous counterpart, have been attributed to the presence of Si nanocrystallites. - Highlights: • The mass density of silicon carbon films decreases from 2.3 to 2 g/cm{sup 3}. • Carbon is incorporated in the amorphous phase and it is mainly bonded to silicon. • Nanostructured silicon carbon films are deposited at rf power > 40 W. • Si nanocrystallites in amorphous silicon carbon enhance the electrical properties.

  20. The specific heat of pure and hydrogenated amorphous silicon

    Science.gov (United States)

    Queen, Daniel Robert

    At low temperature, amorphous materials have low energy excitations that result in a heat capacity that is in excess of the Debye heat capacity calculated from the sound velocity. These excitations are ubiquitous to the glassy state and occur with roughly the same density for all glasses. The specific heat has a linear temperature dependence below 1K that has been described by the phenomenological two-level systems (TLS) model in addition to a T 3 temperature dependence which is in excess of the T3 Debye specific heat. It is still unknown what exact mechanism gives rise to the TLS but it is assumed that groups of atoms have configurations that are close in energy and, at low temperature, these atoms can change configurations by tunneling through the energy barrier separating them. It has been an open question as to whether tetrahedrally bonded materials, like amorphous silicon, can support TLS due to the over-constrained nature of their bonding. It is shown in this work that amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) have specific heat CP in excess of the Debye specific heat which depends on the details of the growth process. There is a linear term that is due to TLS in addition to an excess T3 contribution. We find that the TLS density depends on number density of atoms in the a-Si film and that the presence of hydrogen in a-Si:H increases CP further. We suggest that regions of low density are sufficiently under-constrained to support tunneling between structural configurations at low temperature as described by the TLS model. The presence of H further lowers the energy barriers for the tunneling process resulting in an increase in TLS density in a-Si:H. The presence of H in a-Si:H network is found to be metastable. Annealing causes H to diffuse away from clustered regions which reduces the density of TLS. A low temperature anomaly is found in the a-Si:H films in their as prepared state that is of unknown origin but appears to take the

  1. Passivation of c-Si surfaces by sub-nm amorphous silicon capped with silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Yimao, E-mail: yimao.wan@anu.edu.au; Yan, Di; Bullock, James; Zhang, Xinyu; Cuevas, Andres [Research School of Engineering, The Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

    2015-12-07

    A sub-nm hydrogenated amorphous silicon (a-Si:H) film capped with silicon nitride (SiN{sub x}) is shown to provide a high level passivation to crystalline silicon (c-Si) surfaces. When passivated by a 0.8 nm a-Si:H/75 nm SiN{sub x} stack, recombination current density J{sub 0} values of 9, 11, 47, and 87 fA/cm{sup 2} are obtained on 10 Ω·cm n-type, 0.8 Ω·cm p-type, 160 Ω/sq phosphorus-diffused, and 120 Ω/sq boron-diffused silicon surfaces, respectively. The J{sub 0} on n-type 10 Ω·cm wafers is further reduced to 2.5 ± 0.5 fA/cm{sup 2} when the a-Si:H film thickness exceeds 2.5 nm. The passivation by the sub-nm a-Si:H/SiN{sub x} stack is thermally stable at 400 °C in N{sub 2} for 60 min on all four c-Si surfaces. Capacitance–voltage measurements reveal a reduction in interface defect density and film charge density with an increase in a-Si:H thickness. The nearly transparent sub-nm a-Si:H/SiN{sub x} stack is thus demonstrated to be a promising surface passivation and antireflection coating suitable for all types of surfaces encountered in high efficiency c-Si solar cells.

  2. Facile fabrication of boron nitride nanosheets-amorphous carbon hybrid film for optoelectronic applications

    KAUST Repository

    Wan, Shanhong

    2015-01-01

    A novel boron nitride nanosheets (BNNSs)-amorphous carbon (a-C) hybrid film has been deposited successfully on silicon substrates by simultaneous electrochemical deposition, and showed a good integrity of this B-C-N composite film by the interfacial bonding. This synthesis can potentially provide the facile control of the B-C-N composite film for the potential optoelectronic devices. This journal is

  3. Synthesis of silicon carbide thin films with polycarbosilane (PCS)

    Energy Technology Data Exchange (ETDEWEB)

    Colombo, P. [Univ. di Padova (Italy). Dept. di Ingegneria Meccanica-Settore Materiali; Paulson, T.E.; Pantano, C.G. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

    1997-09-01

    Polycarbosilane (PCS) thin films were deposited on silicon (and other) substrates and heat treated under vacuum ({approximately}10{sup {minus}6} torr) at temperatures in the range of 200--1,200 C. At temperatures in the range of 1,000--1,200 C, the initially amorphous PCS films transformed to polycrystalline {beta}-silicon carbide ({beta}-SiC). Although PCS films could be deposited at thickness up to 2 {micro}m, the films with thicknesses >1 {micro}m could not be transformed to SiC without extensive cracking. The resulting SiC coatings were characterized using Fourier transform infrared spectroscopy, glancing-angle X-ray diffractometry, secondary-ion mass spectroscopy, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. The temperature and time dependence of the amorphous-to-crystalline transition could be associated with the evolution of free carbon, oxygen, and hydrogen in the films.

  4. Amorphous microcellular polytetrafluoroethylene foam film

    Science.gov (United States)

    Tang, Chongzheng

    1991-11-01

    We report herein the preparation of novel low-density ultramicrocellular fluorocarbon foams and their application. These fluorocarbon foams are of interest for the biochemistry arena in numerous applications including foodstuff, pharmacy, wine making, beer brewery, fermentation medical laboratory, and other processing factories. All of those require good quality processing programs in which, after eliminating bacterium and virus, compressed air is needed. Ordinarily, compressed air contains bacterium and virus, its size is 0.01 - 2 micrometers fluorocarbon foam films. Having average porous diameter 0.04 - 0.1 micrometers , these are stable to high temperature (280 degree(s)C) and chemical environments, and generally have good engineering and mechanical properties (e.g., low coefficient of thermal expansion, high modulus, and good dimensional stability). Our new process for preparing low density fluorocarbon foams provides materials with unique properties. As such, they offer the possibility for being superior to earlier materials for a number of the filter applications mentioned.

  5. Raman spectroscopy of thin-film silicon on woven polyester

    Energy Technology Data Exchange (ETDEWEB)

    Lind, Helena; Wilson, John [Department of Physics, School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS (United Kingdom); Mather, Robert [Power Textiles Limited, Upland House, Ettrick Road, Selkirk TD7 5AJ (United Kingdom)

    2011-12-15

    Thin-film silicon deposited by plasma-enhanced chemical vapour deposition (PECVD), encompasses both hydrogenated amorphous silicon (a-Si:H) and 'nanocrystalline silicon' (nc-Si), the latter being a two-phase mixture of discrete nanocrystallites in an amorphous matrix. It is distinguished from a-Si:H by a characteristic Raman spectrum. As the film structure moves from amorphous to more crystalline, the Raman TO phonon spectral region no longer consists of a broad amorphous peak at {proportional_to}480 cm{sup -1} but instead has an obvious narrower peak located at higher wavenumber. The accepted signature peak for nc-Si lies between these two and most probably arises from the hexagonal, wurtzite structure of the nanocrystals. Here we use Raman spectroscopy to show how the structure of thin-film silicon on woven polyester is influenced by the substrate as well as by the deposition conditions. We find that the rough surface of the textile substrate enables nc-Si formation, provided that the correct deposition conditions are employed and that the substrate temperature does not exceed 210 C. Although the gas mixture is the dominant parameter for determining the film structure, and input power also has a significant effect, we find that a specific combination of these interrelated parameters is essential to control the final structure. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Understanding the Structure of Amorphous Thin Film Hafnia - Final Paper

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Andre [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-27

    Hafnium Oxide (HfO2) amorphous thin films are being used as gate oxides in transistors because of their high dielectric constant (κ) over Silicon Dioxide. The present study looks to find the atomic structure of HfO2 thin films which hasn’t been done with the technique of this study. In this study, two HfO2 samples were studied. One sample was made with thermal atomic layer deposition (ALD) on top of a Chromium and Gold layer on a silicon wafer. The second sample was made with plasma ALD on top of a Chromium and Gold layer on a Silicon wafer. Both films were deposited at a thickness of 50nm. To obtain atomic structure information, Grazing Incidence X-ray diffraction (GIXRD) was carried out on the HfO2 samples. Because of this, absorption, footprint, polarization, and dead time corrections were applied to the scattering intensity data collected. The scattering curves displayed a difference in structure between the ALD processes. The plasma ALD sample showed the broad peak characteristic of an amorphous structure whereas the thermal ALD sample showed an amorphous structure with characteristics of crystalline materials. This appears to suggest that the thermal process results in a mostly amorphous material with crystallites within. Further, the scattering intensity data was used to calculate a pair distribution function (PDF) to show more atomic structure. The PDF showed atom distances in the plasma ALD sample had structure up to 10 Å, while the thermal ALD sample showed the same structure below 10 Å. This structure that shows up below 10 Å matches the bond distances of HfO2 published in literature. The PDF for the thermal ALD sample also showed peaks up to 20 Å, suggesting repeating atomic spacing outside the HfO2 molecule in the sample. This appears to suggest that there is some crystalline structure within the thermal ALD sample.

  7. Raman study of localized recrystallization of amorphous silicon induced by laser beam

    KAUST Repository

    Tabet, Nouar A.

    2012-06-01

    The adoption of amorphous silicon based solar cells has been drastically hindered by the low efficiency of these devices, which is mainly due to a low hole mobility. It has been shown that using both crystallized and amorphous silicon layers in solar cells leads to an enhancement of the device performance. In this study the crystallization of a-Si prepared by PECVD under various growth conditions has been investigated. The growth stresses in the films are determined by measuring the curvature change of the silicon substrate before and after film deposition. Localized crystallization is induced by exposing a-Si films to focused 532 nm laser beam of power ranging from 0.08 to 8 mW. The crystallization process is monitored by recording the Raman spectra after various exposures. The results suggest that growth stresses in the films affect the minimum laser power (threshold power). In addition, a detailed analysis of the width and position of the Raman signal indicates that the silicon grains in the crystallized regions are of few nm diameter. © 2012 IEEE.

  8. Structural morphology of amorphous conducting carbon film

    Indian Academy of Sciences (India)

    P N Vishwakarma; V Prasad; S V Subramanyam; V Ganesan

    2005-10-01

    Amorphous conducting carbon films deposited over quartz substrates were analysed using X-ray diffraction and AFM technique. X-ray diffraction data reveal disorder and roughness in the plane of graphene sheet as compared to that of graphite. This roughness increases with decrease in preparation temperature. The AFM data shows surface roughness of carbon films depending on preparation temperatures. The surface roughness increases with decrease in preparation temperature. Also some nucleating islands were seen on the samples prepared at 900°C, which are not present on the films prepared at 700°C. Detailed analysis of these islands reveals distorted graphitic lattice arrangement. So we believe these islands to be nucleating graphitic. Power spectrum density (PSD) analysis of the carbon surface indicates a transition from the nonlinear growth mode to linear surface-diffusion dominated growth mode resulting in a relatively smoother surface as one moves from low preparation temperature to high preparation temperature. The amorphous carbon films deposited over a rough quartz substrate reveal nucleating diamond like structures. The density of these nucleating diamond like structures was found to be independent of substrate temperature (700–900°C).

  9. Threshold irradiation dose for amorphization of silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Snead, L.L.; Zinkle, S.J. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    The amorphization of silicon carbide due to ion and electron irradiation is reviewed with emphasis on the temperature-dependent critical dose for amorphization. The effect of ion mass and energy on the threshold dose for amorphization is summarized, showing only a weak dependence near room temperature. Results are presented for 0.56 MeV silicon ions implanted into single crystal 6H-SiC as a function of temperature and ion dose. From this, the critical dose for amorphization is found as a function of temperature at depths well separated from the implanted ion region. Results are compared with published data generated using electrons and xenon ions as the irradiating species. High resolution TEM analysis is presented for the Si ion series showing the evolution of elongated amorphous islands oriented such that their major axis is parallel to the free surface. This suggests that surface of strain effects may be influencing the apparent amorphization threshold. Finally, a model for the temperature threshold for amorphization is described using the Si ion irradiation flux and the fitted interstitial migration energy which was found to be {approximately}0.56 eV. This model successfully explains the difference in the temperature-dependent amorphization behavior of SiC irradiated with 0.56 MeV silicon ions at 1 x 10{sup {minus}3} dpa/s and with fission neutrons irradiated at 1 x 10{sup {minus}6} dpa/s irradiated to 15 dpa in the temperature range of {approximately}340 {+-} 10K.

  10. Nanocrystalline silicon films prepared by laser-induced crystallization

    Institute of Scientific and Technical Information of China (English)

    傅广生; 于威; 李社强; 侯海虹; 彭英才; 韩理

    2003-01-01

    The excimer laser-induced crystallization technique has been used to investigate the preparation of nanocrystalline silicon (nc-Si) from amorphous silicon (α-Si) thin films on silicon or glass substrates. The α-Si films without hydrogen grown by pulsed-laser deposition are chosen as precursor to avoid the problem of hydrogen effluence during annealing.Analyses have been performed by scanning electron microscopy, atomic force microscopy, Raman scattering spectroscopy and high-resolution transmission-electron microscopy. Experimental results show that silicon nanocrystals can be formed through laser annealing. The growth characters of nc-Si are strongly dependent on the laser energy density. It is shown that the volume of the molten silicon predominates essentially the grain size of nc-Si, and the surface tension of the crystallized silicon is responsible for the mechanism of nc-Si growth.

  11. Buckling instability in amorphous carbon films

    Science.gov (United States)

    Zhu, X. D.; Narumi, K.; Naramoto, H.

    2007-06-01

    In this paper, we report the buckling instability in amorphous carbon films on mirror-polished sapphire (0001) wafers deposited by ion beam assisted deposition at various growth temperatures. For the films deposited at 150 °C, many interesting stress relief patterns are found, which include networks, blisters, sinusoidal patterns with π-shape, and highly ordered sinusoidal waves on a large scale. Starting at irregular buckling in the centre, the latter propagate towards the outer buckling region. The maximum length of these ordered patterns reaches 396 µm with a height of ~500 nm and a wavelength of ~8.2 µm. However, the length decreases dramatically to 70 µm as the deposition temperature is increased to 550 °C. The delamination of the film appears instead of sinusoidal waves with a further increase of the deposition temperature. This experimental observation is correlated with the theoretic work of Crosby (1999 Phys. Rev. E 59 R2542).

  12. Silicon Thin-Film Solar Cells

    Directory of Open Access Journals (Sweden)

    Guy Beaucarne

    2007-01-01

    with plasma-enhanced chemical vapor deposition (PECVD. In spite of the fundamental limitation of this material due to its disorder and metastability, the technology is now gaining industrial momentum thanks to the entry of equipment manufacturers with experience with large-area PECVD. Microcrystalline Si (also called nanocrystalline Si is a material with crystallites in the nanometer range in an amorphous matrix, and which contains less defects than amorphous silicon. Its lower bandgap makes it particularly appropriate as active material for the bottom cell in tandem and triple junction devices. The combination of an amorphous silicon top cell and a microcrystalline bottom cell has yielded promising results, but much work is needed to implement it on large-area and to limit light-induced degradation. Finally thin-film polysilicon solar cells, with grain size in the micrometer range, has recently emerged as an alternative photovoltaic technology. The layers have a grain size ranging from 1 μm to several tens of microns, and are formed at a temperature ranging from 600 to more than 1000∘C. Solid Phase Crystallization has yielded the best results so far but there has recently been fast progress with seed layer approaches, particularly those using the aluminum-induced crystallization technique.

  13. Radial junction amorphous silicon solar cells on PECVD-grown silicon nanowires.

    Science.gov (United States)

    Yu, Linwei; O'Donnell, Benedict; Foldyna, Martin; Roca i Cabarrocas, Pere

    2012-05-17

    Constructing radial junction hydrogenated amorphous silicon (a-Si:H) solar cells on top of silicon nanowires (SiNWs) represents a promising approach towards high performance and cost-effective thin film photovoltaics. We here develop an all-in situ strategy to grow SiNWs, via a vapour-liquid-solid (VLS) mechanism on top of ZnO-coated glass substrate, in a plasma-enhanced chemical vapour deposition (PECVD) reactor. Controlling the distribution of indium catalyst drops allows us to tailor the as-grown SiNW arrays into suitable size and density, which in turn results in both a sufficient light trapping effect and a suitable arrangement allowing for conformal coverage of SiNWs by subsequent a-Si:H layers. We then demonstrate the fabrication of radial junction solar cells and carry on a parametric study designed to shed light on the absorption and quantum efficiency response, as functions of the intrinsic a-Si:H layer thickness and the density of SiNWs. These results lay a solid foundation for future structural optimization and performance ramp-up of the radial junction thin film a-Si:H photovoltaics.

  14. Comprehensive modeling of ion-implant amorphization in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Mok, K.R.C. [Departamento de E. y Electronica, Universidad de Valladolid, ETSIT Campus Miguel Delibes, 47011 Valladolid (Spain) and Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576 (Singapore)]. E-mail: g0202446@nus.edu.sg; Jaraiz, M. [Departamento de E. y Electronica, Universidad de Valladolid, ETSIT Campus Miguel Delibes, 47011 Valladolid (Spain); Martin-Bragado, I. [Departamento de E. y Electronica, Universidad de Valladolid, ETSIT Campus Miguel Delibes, 47011 Valladolid (Spain); Synopsys, Karl-Hammerschmidt Strasse 34, D-85609 Aschheim/Dornach (Germany); Rubio, J.E. [Departamento de E. y Electronica, Universidad de Valladolid, ETSIT Campus Miguel Delibes, 47011 Valladolid (Spain); Castrillo, P. [Departamento de E. y Electronica, Universidad de Valladolid, ETSIT Campus Miguel Delibes, 47011 Valladolid (Spain); Pinacho, R. [Departamento de E. y Electronica, Universidad de Valladolid, ETSIT Campus Miguel Delibes, 47011 Valladolid (Spain); Srinivasan, M.P. [Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576 (Singapore); Benistant, F. [Chartered Semiconductor Manufacturing. 60 Woodlands Industrial Park D, Street 2, Singapore 738406 (Singapore)

    2005-12-05

    A physically based model has been developed to simulate the ion-implant induced damage accumulation up to amorphization in silicon. Based on damage structures known as amorphous pockets (AP), which are three-dimensional, irregularly shaped agglomerates of interstitials (I) and vacancies (V) surrounded by crystalline silicon, the model is able to reproduce a wide range of experimental observations of damage accumulation and amorphization with interdependent implantation parameters. Instead of recrystallizing the I's and V's instantaneously, the recrystallization rate of an AP containing nI and mV is a function of its effective size, defined as min(n, m), irrespective of its internal spatial configuration. The parameters used in the model were calibrated using the experimental silicon amorphous-crystalline transition temperature as a function of dose rate for C, Si, and Ge. The model is able to show the superlinear damage build-up with dose, the extent of amorphous layer and the superadditivity effect of polyatomic ions.

  15. Ab initio modelling of boron related defects in amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Tiago A.; Torres, Vitor J.B. [Department of Physics, University of Aveiro, Campus Santiago, 3810-193 Aveiro (Portugal)

    2012-10-15

    We have modeled boron related point defects in amorphous silicon, using an ab initio method, the Density functional theory-pseudopotential code Aimpro. The boron atoms were embedded in 64 atom amorphous silicon cubic supercells. The calculations were performed using boron defects in 15 different supercells. These supercells were developed using a modified Wooten-Winer-Weaire bond switching mechanism. In average, the properties of the 15 supercells agree with the observed radial and bond angle distributions, as well the electronic and vibrational density of states and Raman spectra. In amorphous silicon it has been very hard to find real self-interstitials, since for almost all the tested configurations, the amorphous lattice relaxes overall. We found that substitutional boron prefers to be 4-fold coordinated. We find also an intrinsic hole-trap in the non-doped amorphous lattice, which may explain the low efficiency of boron doping. The local vibrational modes are, in average, higher than the correspondent crystalline values (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Supercontinuum generation in hydrogenated amorphous silicon waveguides at telecommunication wavelengths.

    Science.gov (United States)

    Safioui, Jassem; Leo, François; Kuyken, Bart; Gorza, Simon-Pierre; Selvaraja, Shankar Kumar; Baets, Roel; Emplit, Philippe; Roelkens, Gunther; Massar, Serge

    2014-02-10

    We report supercontinuum (SC) generation centered on the telecommunication C-band (1550 nm) in CMOS compatible hydrogenated amorphous silicon waveguides. A broadening of more than 550 nm is obtained in 1cm long waveguides of different widths using as pump picosecond pulses with on chip peak power as low as 4 W.

  17. First-principles study of hydrogenated amorphous silicon

    NARCIS (Netherlands)

    Jarolimek, K.; Groot, R.A. de; Wijs, G.A. de; Zeman, M.

    2009-01-01

    We use a molecular-dynamics simulation within density-functional theory to prepare realistic structures of hydrogenated amorphous silicon. The procedure consists of heating a crystalline structure of Si64H8 to 2370 K, creating a liquid and subsequently cooling it down to room temperature. The effect

  18. Effects of relaxation on the energy landscape of amorphous silicon

    Science.gov (United States)

    Kallel, Houssem; Mousseau, Normand; Schiettekatte, Francois

    2008-03-01

    Amorphous silicon is used in many devices around us, included as a thin-film transistor in most flat screens, it also serves as the reference for the study of disordered network systems. Recently, differential scanning calorimetry and nanocalorimetry measurements (DSC) ^1 have shown that the heat released as the temperature of the sample is raised following implantation, is temperature independent. To understand this behaviour, we characterize the energy landscape of model a-Si. Using the activation-relaxation technique (ART nouveau) with the modified Stillinger-Weber potential, we generate models at four levels of relaxation and identify the relaxation mechanisms by analysing 100 000 events for each model. We find that while the distribution of the activation barriers shifts to higher energy as the system is relaxed, the distribution of the relaxation energies is almost unchanged. The relation between these two phenomena is consistent with the DSC measurements. This work is supported, in part, by NSERC, FQRNT and the CRC Foundation. HK is grateful for a scholarship from the Tunisian Ministry of Higher Education, Scientific Research and Technology. ^1 R. Karmouch et al., Phys. Rev. B 75, 075304 (2007)

  19. Raman spectroscopy of PIN hydrogenated amorphous silicon solar cells

    Science.gov (United States)

    Keya, Kimitaka; Torigoe, Yoshihiro; Toko, Susumu; Yamashita, Daisuke; Seo, Hyunwoong; Itagaki, Naho; Koga, Kazunori; Shiratani, Masaharu

    2015-09-01

    Light-induced degradation of hydrogenated amorphous silicon (a-Si:H) is a key issue for enhancing competitiveness in solar cell market. A-Si:H films with a lower density of Si-H2 bonds shows higher stability. Here we identified Si-H2 bonds in PIN a-Si:H solar cells fabricated by plasma CVD using Raman spectroscopy. A-Si:H solar cell has a structure of B-doped μc-SiC:H (12.5 nm)/ non-doped a-Si:H (250nm)/ P-doped μc-Si:H (40 nm) on glass substrates (Asahi-VU). By irradiating HeNe laser light from N-layer, peaks correspond to Si-H2 bonds (2100 cm-1) and Si-H bonds (2000 cm-1) have been identified in Raman scattering spectra. The intensity ratio of Si-H2 and Si-H ISiH2/ISiH is found to correlate well to light induced degradation of the cells Therefore, Raman spectroscopy is a promising method for studying origin of light-induced degradation of PIN solar cells.

  20. Silicon nanoparticle optimization and integration into amorphous silicon via PECVD for use in photovoltaics

    Science.gov (United States)

    Klafehn, Grant W.

    An alternative approach to traditional growth methods of nanocrystalline material is co-deposition by injection of separately synthesized silicon nanoparticles into amorphous silicon. Current methods of co-deposition of silicon nanoparticles and amorphous silicon via plasma enhanced chemical vapor deposition allow the two reactors' pressures to affect each other, leading to either poor amorphous silicon quality or uncontrollable nanoparticle size and deposition rate. In this thesis, a technique for greater control of stand-alone silicon nanoparticle size and quality grown was achieved by using a slit nozzle. The nozzle was used to separate the nanoparticle and amorphous reactors, allowing for the ability to control nanoparticle size, crystallinity, and deposition rate during co-deposition, while still allowing for high quality amorphous silicon growth. Changing the width of the nozzle allowed for control of the size of the nanoparticles from 10 to 4.5 nm in diameter, and allowed for the precursor gas flow rate, and thus deposition rate, to be changed with only a 6 % change in size estimated from luminescence emission wavelength. Co-deposited samples were grown within a broad range of flow rates for the silicon nanoparticle precursor gas, resulting in each sample having a different crystal fraction. FTIR, PL, Raman, and XRD were used to analyze their composition. The silicon nanoparticle synthesis was separately optimized to control size and crystallinity, and the influence of the nanoparticle process gases on amorphous silicon growth was also explored. Finally, COMSOL simulations were performed to support and possibly predict Si-NP growth variables that pertain to Si-NP size.

  1. Novel Scheme of Amorphous/Crystalline Silicon Heterojunction Solar Cell

    Energy Technology Data Exchange (ETDEWEB)

    De Iuliis, S.; Geerligs, L.J. [ECN Solar Energy, Petten (Netherlands); Tucci, M.; Serenelli, L.; Salza, E. [ENEA Research Center Casaccia, Roma (Italy); De Cesare, G.; Caputo, D.; Ceccarelli, M. [University ' Sapienza' , Department of Electronic Engineering, Roma (Italy)

    2007-01-15

    In this paper we investigate in detail how the heterostructure concept can be implemented in an interdigitated back contact solar cell, in which both the emitters are formed on the back side of the c-Si wafer by amorphous/crystalline silicon heterostructure, and at the same time the grid-less front surface is passivated by a double layer of amorphous silicon and silicon nitride, which also provides an anti-reflection coating. The entire process, held at temperature below 300C, is photolithography-free, using a metallic self-aligned mask to create the interdigitated pattern, and we show that the alignment is feasible. An open-circuit voltage of 687 mV has been measured on a p-type monocrystalline silicon wafer. The mask-assisted deposition process does not influence the uniformity of the deposited amorphous silicon layers. Photocurrent limits factor has been investigated with the aid of one-dimensional modeling and quantum efficiency measurements. On the other hand several technological aspects that limit the fill factor and the short circuit current density still need improvements.

  2. Crystallization of amorphous silicon by self-propagation of nanoengineered thermites

    Science.gov (United States)

    Hossain, Maruf; Subramanian, Senthil; Bhattacharya, Shantanu; Gao, Yuanfang; Apperson, Steve; Shende, Rajesh; Guha, Suchi; Arif, Mohammad; Bai, Mengjun; Gangopadhyay, Keshab; Gangopadhyay, Shubhra

    2007-03-01

    Crystallization of amorphous silicon (a-Si) thin film occurred by the self-propagation of copper oxide/aluminum thermite nanocomposites. Amorphous Si films were prepared on glass at a temperature of 250°C by plasma enhanced chemical vapor deposition. The platinum heater was patterned on the edge of the substrate and the CuO /Al nanoengineered thermite was spin coated on the substrate that connects the heater and the a-Si film. A voltage source was used to ignite the thermites followed by a piranha solution (4:1 of H2SO4:H2O2) etch for the removal of residual products of thermite reaction. Raman spectroscopy was used to confirm the crystallization of a-Si.

  3. A study of ZnO:B films for thin film silicon solar cells

    Science.gov (United States)

    Yin, J.; Zhu, H.; Wang, Y.; Wang, Z.; Gao, J.; Mai, Y.; Ma, Y.; Wan, M.; Huang, Y.

    2012-10-01

    Boron doped zinc oxide (ZnO:B) films with different thicknesses were prepared with low pressure chemical vapor deposition (LPCVD) technique and implemented in thin film silicon solar cells as front and back electrodes. It is found that thick back ZnO:B film electrode in thin film silicon solar cells leads to a high fill factors (FF), which is attributed to an improvement of the electrical properties of the thick ZnO:B films, and in the meanwhile a slightly low short circuit currents (Jsc) due to a high light absorption in the thick back ZnO:B films. Differently, the thicker front ZnO:B film electrodes result in a high Jsc but a low FF of solar cells compared to the thinner ones. The low FF of the solar cells may be caused by the local shunt originated from the pinholes or by the cracks (zones of non-dense material) formed in particular in microcrystalline silicon materials deposited on rough front ZnO:B films. As to the high Jsc, it is expected to be due to a good light trapping effect inside solar cells grown on rough front ZnO:B films. Moreover, the application of high reflective polyvinyl butyral (PVB) foils effectively enhances the utilization of incident light in solar cells. By optimizing deposition process of the ZnO:B films, high efficiencies of 8.8% and 10% for single junction thin film amorphous silicon solar cells (a-Si:H, intrinsic layer thickness < 200 nm) and amorphous/microcrystalline silicon tandem solar cells (a-Si:H/μc-Si:H, intrinsic amorphous silicon layer thickness < 220 nm), respectively, are achieved.

  4. Solution growth of microcrystalline silicon on amorphous substrates

    Energy Technology Data Exchange (ETDEWEB)

    Heimburger, Robert

    2010-07-05

    This work deals with low-temperature solution growth of micro-crystalline silicon on glass. The task is motivated by the application in low-cost solar cells. As glass is an amorphous material, conventional epitaxy is not applicable. Therefore, growth is conducted in a two-step process. The first step aims at the spatial arrangement of silicon seed crystals on conductive coated glass substrates, which is realized by means of vapor-liquid-solid processing using indium as the solvent. Seed crystals are afterwards enlarged by applying a specially developed steady-state solution growth apparatus. This laboratory prototype mainly consists of a vertical stack of a silicon feeding source and the solvent (indium). The growth substrate can be dipped into the solution from the top. The system can be heated to a temperature below the softening point of the utilized glass substrate. A temperature gradient between feeding source and growth substrate promotes both, supersaturation and material transport by solvent convection. This setup offers advantages over conventional liquid phase epitaxy at low temperatures in terms of achievable layer thickness and required growth times. The need for convective solute transport to gain the desired thickness of at least 50 {mu}m is emphasized by equilibrium calculations in the binary system indium-silicon. Material transport and supersaturation conditions inside the utilized solution growth crucible are analyzed. It results that the solute can be transported from the lower feeding source to the growth substrate by applying an appropriate heating regime. These findings are interpreted by means of a hydrodynamic analysis of fluid flow and supporting FEM simulation. To ensure thermodynamic stability of all materials involved during steady-state solution growth, the ternary phase equilibrium between molybdenum, indium and silicon at 600 C was considered. Based on the obtained results, the use of molybdenum disilicide as conductive coating

  5. Amorphous silicon rich silicon nitride optical waveguides for high density integrated optics

    DEFF Research Database (Denmark)

    Philipp, Hugh T.; Andersen, Karin Nordström; Svendsen, Winnie Edith

    2004-01-01

    Amorphous silicon rich silicon nitride optical waveguides clad in silica are presented as a high-index contrast platform for high density integrated optics. Performance of different cross-sectional geometries have been measured and are presented with regards to bending loss and insertion loss...

  6. ENHANCING ADHESION OF TETRAHEDRAL AMORPHOUS CARBON FILMS

    Institute of Scientific and Technical Information of China (English)

    Zhao Yuqing; Lin Yi; Wang Xiaoyan; Wang Yanwu; Wei Xinyu

    2005-01-01

    Objective The high energy ion bombardment technique is applied to enhancing the adhesion of the tetrahedral amorphous carbon (TAC) films deposited by the filtered cathode vacuum arc (FCVA). Methods The abrasion method, scratch method, heating and shaking method as well as boiling salt solution method is used to test the adhesion of the TAC films on various material substrates. Results The test results show that the adhesion is increased as the ion bombardment energy increases. However, if the bombardment energy were over the corresponding optimum value, the adhesion would be enhanced very slowly for the harder material substrates and drops quickly, for the softer ones. Conclusion The optimum values of the ion bombardment energy are larger for the harder materials than that for the softer ones.

  7. Multi-band silicon quantum dots embedded in an amorphous matrix of silicon carbide

    Science.gov (United States)

    Chang, Geng-rong; Ma, Fei; Ma, Da-yan; Xu, Ke-wei

    2010-11-01

    Silicon quantum dots embedded in an amorphous matrix of silicon carbide were realized by a magnetron co-sputtering process and post-annealing. X-ray photoelectron spectroscopy, glancing x-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy were used to characterize the chemical composition and the microstructural properties. The results show that the sizes and size distribution of silicon quantum dots can be tuned by changing the annealing atmosphere and the atom ratio of silicon and carbon in the matrix. A physicochemical mechanism is proposed to demonstrate this formation process. Photoluminescence measurements indicate a multi-band configuration due to the quantum confinement effect of silicon quantum dots with different sizes. The PL spectra are further widened as a result of the existence of amorphous silicon quantum dots. This multi-band configuration would be extremely advantageous in improving the photoelectric conversion efficiency of photovoltaic solar cells.

  8. Thin metal layer as transparent electrode in n-i-p amorphous silicon solar cells

    Directory of Open Access Journals (Sweden)

    Theuring Martin

    2014-07-01

    Full Text Available In this paper, transparent electrodes, based on a thin silver film and a capping layer, are investigated. Low deposition temperature, flexibility and low material costs are the advantages of this type of electrode. Their applicability in structured n-i-p amorphous silicon solar cells is demonstrated in simulation and experiment. The influence of the individual layer thicknesses on the solar cell performance is discussed and approaches for further improvements are given. For the silver film/capping layer electrode, a higher solar cell efficiency could be achieved compared to a reference ZnO:Al front contact.

  9. Novel photochemical vapor deposition reactor for amorphous silicon solar cell deposition

    Science.gov (United States)

    Rocheleau, Richard E.; Hegedus, Steven S.; Buchanan, Wayne A.; Jackson, Scott C.

    1987-07-01

    A novel photochemical vapor deposition (photo-CVD) reactor having a flexible ultraviolet-transparent Teflon curtain and a secondary gas flow to eliminate deposition on the window has been used to deposit amorphous silicon films and p-i-n solar cells. The background levels of atmospheric contaminants (H2O, CO2, N2) depend strongly on the vacuum procedures but not on the presence of a Teflon curtain in the reactor. Intrinsic films with a midgap density of states of 3×1015 eV-1 cm-3 and all-photo-CVD pin solar cells with efficiencies of 8.5% have been deposited.

  10. Growth Induced Magnetic Anisotropy in Crystalline and Amorphous Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Hellman, Frances

    1998-10-03

    OAK B204 Growth Induced Magnetic Anisotropy in Crystalline and Amorphous Thin Films. The work in the past 6 months has involved three areas of magnetic thin films: (1) amorphous rare earth-transition metal alloys, (2) epitaxial Co-Pt and hTi-Pt alloy thin films, and (3) collaborative work on heat capacity measurements of magnetic thin films, including nanoparticles and CMR materials.

  11. Infrared transient grating measurements of the dynamics of hydrogen local mode vibrations in amorphous silicon-germanium

    NARCIS (Netherlands)

    Jobson, K.W.; Wells, J.P.R.; Schropp, R.E.I.; Vinh, N.Q.; Dijkhuis, J.I.

    2008-01-01

    We report on picosecond, time-resolved measurements of the vibrational relaxation and decay pathways of the Si–H and Ge–H stretching modes in hydrogenated amorphous silicon-germanium thin films (a-SiGe:H). It is demonstrated that the decay of both modes has a nonexponential shape, attributable to th

  12. Infrared transient grating measurements of the dynamics of hydrogen local mode vibrations in amorphous silicon-germanium

    NARCIS (Netherlands)

    Jobson, K. W.; Wells, J. P. R.; Schropp, R. E. I.; Vinh, N. Q.; Dijkhuis, J. I.

    2008-01-01

    We report on picosecond, time-resolved measurements of the vibrational relaxation and decay pathways of the Si-H and Ge-H stretching modes in hydrogenated amorphous silicon-germanium thin films (a-SiGe: H). It is demonstrated that the decay of both modes has a nonexponential shape, attributable to t

  13. Natively textured ZnO grown by PECVD as front electrode material for amorphous silicon pin solar cells

    NARCIS (Netherlands)

    Löffler, J.; Schropp, R.E.I.; Groenen, Ft.; Van De Sanden, M.C.M.; Linden, J.L.

    2000-01-01

    Natively textured ZnO layers for the application as front electrode material in amorphous silicon pin solar cells have been deposited by Expanding Thermal Plasma Chemical Vapor Deposition. Films deposited in the temperature regime from 150 to 350°C at a rate between 0.65 and 0.75 nm/s have been char

  14. Silicon nanocrystal inks, films, and methods

    Energy Technology Data Exchange (ETDEWEB)

    Wheeler, Lance Michael; Kortshagen, Uwe Richard

    2015-09-01

    Silicon nanocrystal inks and films, and methods of making and using silicon nanocrystal inks and films, are disclosed herein. In certain embodiments the nanocrystal inks and films include halide-terminated (e.g., chloride-terminated) and/or halide and hydrogen-terminated nanocrystals of silicon or alloys thereof. Silicon nanocrystal inks and films can be used, for example, to prepare semiconductor devices.

  15. Light-induced metastable structural changes in hydrogenated amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Fritzsche, H. [Univ. of Chicago, IL (United States)

    1996-09-01

    Light-induced defects (LID) in hydrogenated amorphous silicon (a-Si:H) and its alloys limit the ultimate efficiency of solar panels made with these materials. This paper reviews a variety of attempts to find the origin of and to eliminate the processes that give rise to LIDs. These attempts include novel deposition processes and the reduction of impurities. Material improvements achieved over the past decade are associated more with the material`s microstructure than with eliminating LIDs. We conclude that metastable LIDs are a natural by-product of structural changes which are generally associated with non-radiative electron-hole recombination in amorphous semiconductors.

  16. Compositional analysis of silicon oxide/silicon nitride thin films

    Directory of Open Access Journals (Sweden)

    Meziani Samir

    2016-06-01

    Full Text Available Hydrogen, amorphous silicon nitride (SiNx:H abbreviated SiNx films were grown on multicrystalline silicon (mc-Si substrate by plasma enhanced chemical vapour deposition (PECVD in parallel configuration using NH3/SiH4 gas mixtures. The mc-Si wafers were taken from the same column of Si cast ingot. After the deposition process, the layers were oxidized (thermal oxidation in dry oxygen ambient environment at 950 °C to get oxide/nitride (ON structure. Secondary ion mass spectroscopy (SIMS, Rutherford backscattering spectroscopy (RBS, Auger electron spectroscopy (AES and energy dispersive X-ray analysis (EDX were employed for analyzing quantitatively the chemical composition and stoichiometry in the oxide-nitride stacked films. The effect of annealing temperature on the chemical composition of ON structure has been investigated. Some species, O, N, Si were redistributed in this structure during the thermal oxidation of SiNx. Indeed, oxygen diffused to the nitride layer into Si2O2N during dry oxidation.

  17. In and Ga Codoped ZnO Film as a Front Electrode for Thin Film Silicon Solar Cells

    OpenAIRE

    Duy Phong Pham; Huu Truong Nguyen; Bach Thang Phan; Thi My Dung Cao; Van Dung Hoang; Vinh Ai Dao; Junsin Yi; Cao Vinh Tran

    2014-01-01

    Doped ZnO thin films have attracted much attention in the research community as front-contact transparent conducting electrodes in thin film silicon solar cells. The prerequisite in both low resistivity and high transmittance in visible and near-infrared region for hydrogenated microcrystalline or amorphous/microcrystalline tandem thin film silicon solar cells has promoted further improvements of this material. In this work, we propose the combination of major Ga and minor In impurities codop...

  18. Effect of Ion Bombardment on the Growth and Properties of Hydrogenated Amorphous Silicon-Germanium Alloys

    Science.gov (United States)

    Perrin, Jérôme; Takeda, Yoshihiko; Hirano, Naoto; Matsuura, Hideharu; Matsuda, Akihisa

    1989-01-01

    We report a systematic investigation of the effect of ion bombardment during the growth of amorphous silicon-germanium alloy films from silane and germane rf-glow discharge. Independent control of the plasma and the ion flux and energy is obtained by using a triode configuration. The ion contribution to the total deposition rate can reach 20% on negatively biased substrates. Although the Si and Ge composition of the film does not depend on the ion flux and energy, the optical, structural and electronic properties are drastically modified at low deposition temperatures when the maximum ion energy increases up to 50 eV, and remain constant above 50 eV. For a Ge atomic concentration of 37% and a temperature of 135°C, the optical gap decreases from 1.67 to 1.45 eV. This is correlated with a modification of hydrogen bonding configurations. Silicon dihydride sites disappear and preferential attachment of hydrogen to silicon is reduced in favour of germanium. Moreover the photoconductivity increases which shows that ion bombardment is a key parameter to optimize the quality of low band gap amorphous silicon-germanium alloys.

  19. The reliability and stability of multijunction amorphous silicon PV modules

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, D.E. [Solarex, Newtown, PA (United States)

    1995-11-01

    Solarex is developing a manufacturing process for the commercial production of 8 ft{sup 2} multijunction amorphous silicon (a-Si) PV modules starting in 1996. The device structure used in these multijunction modules is: glass/textured tin oxide/p-i-n/p-i-n/ZnO/Al/EVA/Tedlar where the back junction of the tandem structure contains an amorphous silicon germanium alloy. As an interim step, 4 ft{sup 2} multijunction modules have been fabricated in a pilot production mode over the last several months. The distribution of initial conversion efficiencies for an engineering run of 67 modules (4 ft{sup 2}) is shown. Measurements recently performed at NREL indicate that the actual efficiencies are about 5% higher than those shown, and thus exhibit an average initial conversion efficiency of about 9.5%. The data indicates that the process is relatively robust since there were no modules with initial efficiencies less than 7.5%.

  20. Electrochemical degradation of amorphous-silicon photovoltaic modules

    Science.gov (United States)

    Mon, G. R.; Ross, R. G., Jr.

    Techniques of module electrochemical corrosion research, developed during reliability studies of crystalline-silicon modules (C-Si), have been applied to this new investigation into amorphous-silicon (a-Si) module reliability. Amorphous-Si cells, encapsulated in the polymers polyvinyl butyral (PVB) and ethylene vinyl acetate (EVA), were exposed for more than 1200 hours in a controlled 85 C/85 percent RH environment, with a constant 500 volts applied between the cells and an aluminum frame. Plotting power output reduction versus charge transferred reveals that about 50 percent a-Si cell failures can be expected with the passage of 0.1 to 1.0 Coulomb/cm of cell-frame edge length; this threshold is somewhat less than that determined for C-Si modules.

  1. Infrared electroabsorption spectra in amorphous silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Lyou, J.H.; Schiff, E.A.; Hegedus, S.S.; Guha, S.; Yang, J.

    1999-07-01

    The authors report measurements of the infrared spectrum detected by modulating the reverse-bias voltage across amorphous silicon pin solar cells and Schottky barrier diodes. They find a band with a peak energy of 0.8 eV. The existence of this band has not, to their knowledge, been reported previously. The strength of the infrared band depends linearly upon applied bias, as opposed to the quadratic dependence for interband electroabsorption in amorphous silicon. The band's peak energy agrees fairly well with the known optical transition energies for dangling bond defects, but the linear dependence on bias and the magnitude of the signal are surprising if interpreted using an analogy to interband electroabsorption. A model based on absorption by defects near the n/i interface of the diodes accounts well for the infrared spectrum.

  2. Research and development of photovoltaic power system. Interface studies of amorphous silicon; Taiyoko hatsuden system no kenkyu kaihatsu. Amorphous silicon kaimen no kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Konagai, M. [Tokyo Institute of Technology, Tokyo (Japan). Faculty of Engineering

    1994-12-01

    This paper reports the result obtained during fiscal 1994 on research on interface of amorphous silicon for solar cells. In research on amorphous solar cells using ZnO for transparent electrically conductive films, considerations were given on a growth mechanism of a ZnO film using the MOCVD process. It was made clear that the ZnO film grows with Zn(OH)2 working as a film forming species. It was also shown that the larger the ZnO particle size is, the more the solar cell efficiency is improved. Furthermore, theoretical elucidation was made on effects of rear face of an interface on cell characteristics, and experimental discussions were given subsequently. In research on solar cells using hydrogen diluted `i` layers, delta-doped solar cells were fabricated based on basic data obtained in the previous fiscal year, and the hydrogen dilution effect was evaluated from the cell characteristics. When the hydrogen dilution ratio is increased from zero to one, the conversion efficiency has improved from 12.2% to 12.6%. In addition, experiments and discussions were given on solar cells fabricated by using SiH2Cl2. 9 figs.

  3. Evolution of the potential-energy surface of amorphous silicon

    OpenAIRE

    Kallel, Houssem; Mousseau, Normand; Schiettekatte, François

    2010-01-01

    The link between the energy surface of bulk systems and their dynamical properties is generally difficult to establish. Using the activation-relaxation technique (ART nouveau), we follow the change in the barrier distribution of a model of amorphous silicon as a function of the degree of relaxation. We find that while the barrier-height distribution, calculated from the initial minimum, is a unique function that depends only on the level of distribution, the reverse-barrier height distributio...

  4. Amorphous Silicon 16—bit Array Photodetector①

    Institute of Scientific and Technical Information of China (English)

    ZHANGShaoqiang; XUZhongyang; 等

    1997-01-01

    An amorphous silicon 16-bit array photodetector with the a-SiC/a-Si heterojunction diode is presented.The fabrication processes of the device were studied systematically.By the optimum of the diode structure and the preparation procedures,the diode with Id<10-12A/mm2 and photocurrentIp≥0.35A/W has been obtained at the wavelength of 632nm.

  5. The role of hydrogenated amorphous silicon oxide buffer layer on improving the performance of hydrogenated amorphous silicon germanium single-junction solar cells

    Science.gov (United States)

    Sritharathikhun, Jaran; Inthisang, Sorapong; Krajangsang, Taweewat; Krudtad, Patipan; Jaroensathainchok, Suttinan; Hongsingtong, Aswin; Limmanee, Amornrat; Sriprapha, Kobsak

    2016-12-01

    Hydrogenated amorphous silicon oxide (a-Si1-xOx:H) film was used as a buffer layer at the p-layer (μc-Si1-xOx:H)/i-layer (a-Si1-xGex:H) interface for a narrow band gap hydrogenated amorphous silicon germanium (a-Si1-xGex:H) single-junction solar cell. The a-Si1-xOx:H film was deposited by plasma enhanced chemical vapor deposition (PECVD) at 40 MHz in a same processing chamber as depositing the p-type layer. An optimization of the thickness of the a-Si1-xOx:H buffer layer and the CO2/SiH4 ratio was performed in the fabrication of the a-Si1-xGex:H single junction solar cells. By using the wide band gap a-Si1-xOx:H buffer layer with optimum thickness and CO2/SiH4 ratio, the solar cells showed an improvement in the open-circuit voltage (Voc), fill factor (FF), and short circuit current density (Jsc), compared with the solar cells fabricated using the conventional a-Si:H buffer layer. The experimental results indicated the excellent potential of the wide-gap a-Si1-xOx:H buffer layers for narrow band gap a-Si1-xGex:H single junction solar cells.

  6. Strong enhancement of spontaneous emission in amorphous-silicon-nitride photonic crystal based coupled-microcavity structures

    Energy Technology Data Exchange (ETDEWEB)

    Bayindir, M.; Tanriseven, S.; Aydinli, A.; Ozbay, E. [Bilkent Univ., Ankara (Turkey). Dept. of Physics

    2001-07-01

    We investigated photoluminescence (PL) from one-dimensional photonic band gap structures. The photonic crystals, a Fabry-Perot (FP) resonator and a coupled-microcavity (CMC) structure, were fabricated by using alternating hydrogenated amorphous-silicon-nitride and hydrogenated amorphous-silicon-oxide layers. It was observed that these structures strongly modify the PL spectra from optically active amorphous-silicon-nitride thin films. Narrow-band and wide-band PL spectra were achieved in the FP microcavity and the CMC structure, respectively. The angle dependence of PL peak of the FP resonator was also investigated. We also observed that the spontaneous emission increased drastically at the coupled-cavity band edge of the CMC structure due to extremely low group velocity and long photon lifetime. The measurements agree well with the transfer-matrix method results and the prediction of the tight-binding approximation. (orig.)

  7. Strong enhancement of spontaneous emission in amorphous-silicon-nitride photonic crystal based coupled-microcavity structures

    Science.gov (United States)

    Bayindir, M.; Tanriseven, S.; Aydinli, A.; Ozbay, E.

    We investigated photoluminescence (PL) from one-dimensional photonic band gap structures. The photonic crystals, a Fabry-Perot (FP) resonator and a coupled-microcavity (CMC) structure, were fabricated by using alternating hydrogenated amorphous-silicon-nitride and hydrogenated amorphous-silicon-oxide layers. It was observed that these structures strongly modify the PL spectra from optically active amorphous-silicon-nitride thin films. Narrow-band and wide-band PL spectra were achieved in the FP microcavity and the CMC structure, respectively. The angle dependence of PL peak of the FP resonator was also investigated. We also observed that the spontaneous emission increased drastically at the coupled-cavity band edge of the CMC structure due to extremely low group velocity and long photon lifetime. The measurements agree well with the transfer-matrix method results and the prediction of the tight-binding approximation.

  8. Two-phase electrochemical lithiation in amorphous silicon.

    Science.gov (United States)

    Wang, Jiang Wei; He, Yu; Fan, Feifei; Liu, Xiao Hua; Xia, Shuman; Liu, Yang; Harris, C Thomas; Li, Hong; Huang, Jian Yu; Mao, Scott X; Zhu, Ting

    2013-02-13

    Lithium-ion batteries have revolutionized portable electronics and will be a key to electrifying transport vehicles and delivering renewable electricity. Amorphous silicon (a-Si) is being intensively studied as a high-capacity anode material for next-generation lithium-ion batteries. Its lithiation has been widely thought to occur through a single-phase mechanism with gentle Li profiles, thus offering a significant potential for mitigating pulverization and capacity fade. Here, we discover a surprising two-phase process of electrochemical lithiation in a-Si by using in situ transmission electron microscopy. The lithiation occurs by the movement of a sharp phase boundary between the a-Si reactant and an amorphous Li(x)Si (a-Li(x)Si, x ~ 2.5) product. Such a striking amorphous-amorphous interface exists until the remaining a-Si is consumed. Then a second step of lithiation sets in without a visible interface, resulting in the final product of a-Li(x)Si (x ~ 3.75). We show that the two-phase lithiation can be the fundamental mechanism underpinning the anomalous morphological change of microfabricated a-Si electrodes, i.e., from a disk shape to a dome shape. Our results represent a significant step toward the understanding of the electrochemically driven reaction and degradation in amorphous materials, which is critical to the development of microstructurally stable electrodes for high-performance lithium-ion batteries.

  9. 10.5% efficient polymer and amorphous silicon hybrid tandem photovoltaic cell

    Science.gov (United States)

    Kim, Jeehwan; Hong, Ziruo; Li, Gang; Song, Tze-Bin; Chey, Jay; Lee, Yun Seog; You, Jingbi; Chen, Chun-Chao; Sadana, Devendra K.; Yang, Yang

    2015-03-01

    Thin-film solar cells made with amorphous silicon (a-Si:H) or organic semiconductors are considered as promising renewable energy sources due to their low manufacturing cost and light weight. However, the efficiency of single-junction a-Si:H or organic solar cells is typically photovoltaic cell by employing an a-Si:H film as a front sub-cell and a low band gap polymer:fullerene blend film as a back cell on planar glass substrates. Monolithic integration of 6.0% efficienct a-Si:H and 7.5% efficient polymer:fullerene blend solar cells results in a power conversion efficiency of 10.5%. Such high-efficiency thin-film tandem cells can be achieved by optical management and interface engineering of fully optimized high-performance front and back cells without sacrificing photovoltaic performance in both cells.

  10. 10.5% efficient polymer and amorphous silicon hybrid tandem photovoltaic cell.

    Science.gov (United States)

    Kim, Jeehwan; Hong, Ziruo; Li, Gang; Song, Tze-bin; Chey, Jay; Lee, Yun Seog; You, Jingbi; Chen, Chun-Chao; Sadana, Devendra K; Yang, Yang

    2015-03-04

    Thin-film solar cells made with amorphous silicon (a-Si:H) or organic semiconductors are considered as promising renewable energy sources due to their low manufacturing cost and light weight. However, the efficiency of single-junction a-Si:H or organic solar cells is typically photovoltaic cell by employing an a-Si:H film as a front sub-cell and a low band gap polymer:fullerene blend film as a back cell on planar glass substrates. Monolithic integration of 6.0% efficienct a-Si:H and 7.5% efficient polymer:fullerene blend solar cells results in a power conversion efficiency of 10.5%. Such high-efficiency thin-film tandem cells can be achieved by optical management and interface engineering of fully optimized high-performance front and back cells without sacrificing photovoltaic performance in both cells.

  11. Surface bioactivity of plasma implanted silicon and amorphous carbon

    Institute of Scientific and Technical Information of China (English)

    Paul K CHU

    2004-01-01

    Plasma immersion ion implantation and deposition (PⅢ&D) has been shown to be an effective technique to enhance the surface bioactivity of materials. In this paper, recent progress made in our laboratory on plasma surface modification single-crystal silicon and amorphous carbon is reviewed. Silicon is the most important material in the integrated circuit industry but its surface biocompatibility has not been investigated in details. We have recently performed hydrogen PⅢ into silicon and observed the biomimetic growth of apatite on its surface in simulated body fluid. Diamond-like carbon (DLC) is widely used in the industry due to its excellent mechanical properties and chemical inertness. The use of this material in biomedical engineering has also attracted much attention. It has been observed in our laboratory that doping DLC with nitrogen by means of PⅢ can improve the surface blood compatibility. The properties as well as in vitro biological test results will be discussed in this article.

  12. Growth model of lantern-like amorphous silicon oxide nanowires

    Science.gov (United States)

    Wu, Ping; Zou, Xingquan; Chi, Lingfei; Li, Qiang; Xiao, Tan

    2007-03-01

    Silicon oxide nanowire assemblies with lantern-like morphology were synthesized by thermal evaporation of the mixed powder of SnO2 and active carbon at 1000 °C and using the silicon wafer as substrate and source. The nano-lanterns were characterized by a scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), energy-dispersive spectroscope (EDS) and selective area electron diffraction (SAED). The results show that the nano-lantern has symmetrical morphology, with one end connecting with the silicon wafer and the other end being the tin ball. The diameter of the nano-lantern is about 1.5-3.0 µm. Arc silicon oxide nanowire assemblies between the two ends have diameters ranging from 70 to 150 nm. One single catalyst tin ball catalyzes more than one amorphous nanowires' growth. In addition, the growth mechanism of the nano-lantern is discussed and a growth model is proposed. The multi-nucleation sites round the Sn droplet's perimeter are responsible for the formation of many SiOx nanowires. The growing direction of the nanowires is not in the same direction of the movement of the catalyst tin ball, resulting in the bending of the nanowires and forming the lantern-like silicon oxide morphology. The controllable synthesis of the lantern-like silicon oxide nanostructure may have potential applications in the photoelectronic devices field.

  13. Growth model of lantern-like amorphous silicon oxide nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Wu Ping; Zou Xingquan; Chi Lingfei; Li Qiang; Xiao Tan [Department of Physics, Shantou University, Shantou 515063 (China)

    2007-03-28

    Silicon oxide nanowire assemblies with lantern-like morphology were synthesized by thermal evaporation of the mixed powder of SnO{sub 2} and active carbon at 1000 deg. C and using the silicon wafer as substrate and source. The nano-lanterns were characterized by a scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), energy-dispersive spectroscope (EDS) and selective area electron diffraction (SAED). The results show that the nano-lantern has symmetrical morphology, with one end connecting with the silicon wafer and the other end being the tin ball. The diameter of the nano-lantern is about 1.5-3.0 {mu}m. Arc silicon oxide nanowire assemblies between the two ends have diameters ranging from 70 to 150 nm. One single catalyst tin ball catalyzes more than one amorphous nanowires' growth. In addition, the growth mechanism of the nano-lantern is discussed and a growth model is proposed. The multi-nucleation sites round the Sn droplet's perimeter are responsible for the formation of many SiO{sub x} nanowires. The growing direction of the nanowires is not in the same direction of the movement of the catalyst tin ball, resulting in the bending of the nanowires and forming the lantern-like silicon oxide morphology. The controllable synthesis of the lantern-like silicon oxide nanostructure may have potential applications in the photoelectronic devices field.

  14. Thin-film amorphous silicon alloy research partnership. Phase 2, Annual technical progress report, 2 February 1996--1 February 1997

    Energy Technology Data Exchange (ETDEWEB)

    Guha, S [United Solar Systems Corp., Troy, MI (United States)

    1997-06-01

    This is Phase II of a 3-phase, 3-year program. It is intended to expand, enhance, and accelerate knowledge and capabilities for developing high-performance, two-terminal multijunction amorphous Si alloy modules. We discuss investigations on back reflectors to improve cell performance and investigate uniformity in performance over a 1-sq.-ft. area. We present results on component cell performance, both in the initial and in the light-degraded states, deposited over a 1-sq.-ft. area. The uniformity in deposited is investigated by studying the performance of subcells deposited over the entire area. We also present results on the performance of triple- junction cells and modules. The modules use grid-lines and encapsulants compatible with our production technology. We discuss the novel laser-processing technique that has bee developed at United Solar to improve energy-conversion efficiency and reduce manufacturing costs. We discuss in detail the optimization of the processing steps, and the performance of a laser-processed, triple- junction device of 12.6 cm{sup 2} area is presented. We also present experimental results on investigations of module reliability.

  15. Thin-film silicon for flexible metal-air batteries.

    Science.gov (United States)

    Garamoun, Ahmed; Schubert, Markus B; Werner, Jürgen H

    2014-12-01

    Due to its high energy density, theoretical studies propose silicon as a promising candidate material for metal-air batteries. Herein, for the first time, experimental results detail the use of n-type doped amorphous silicon and silicon carbide as fuel in Si-air batteries. Thin-film silicon is particularly interesting for flexible and rolled batteries with high specific energies. Our Si-air batteries exhibit a specific capacity of 269 Ah kg(-1) and an average cell voltage of 0.85 V at a discharge current density of 7.9 μA cm(-2) , corresponding to a specific energy of 229 Wh kg(-1) . Favorably in terms of safety, low concentrated alkaline solution serves as electrolyte. Discharging of the Si-air cells continues as long as there is silicon available for oxidation.

  16. Junction Transport in Epitaxial Film Silicon Heterojunction Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Young, D. L.; Li, J. V.; Teplin, C. W.; Stradins, P.; Branz, H. M.

    2011-07-01

    We report our progress toward low-temperature HWCVD epitaxial film silicon solar cells on inexpensive seed layers, with a focus on the junction transport physics exhibited by our devices. Heterojunctions of i/p hydrogenated amorphous Si (a-Si) on our n-type epitaxial crystal Si on n++ Si wafers show space-charge-region recombination, tunneling or diffusive transport depending on both epitaxial Si quality and the applied forward voltage.

  17. Growth induced magnetic anisotropy in crystalline and amorphous thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hellman, F.

    1998-07-20

    The work in the past 6 months has involved three areas of magnetic thin films: (1) amorphous rare earth-transition metal alloys, (2) epitaxial Co-Pt and Ni-Pt alloy thin films, and (3) collaborative work on heat capacity measurements of magnetic thin films, including nanoparticles and CMR materials. A brief summary of work done in each area is given.

  18. Silicon-based thin-film transistors with a high stability

    NARCIS (Netherlands)

    Stannowski, Bernd

    2002-01-01

    Thin-Film Transistors (TFTs) are widely applied as pixel-addressing devices in large-area electronics, such as active-matrix liquid-crystal displays (AMLCDs) or sensor arrays. Hydrogenated amorphous silicon (a-Si:H) and silicon nitride (a-SiNx:H) are generally used as the semiconductor and the insul

  19. Reversibility of silicidation of Ta filaments in HWCVD of thin film silicon

    NARCIS (Netherlands)

    van der Werf, C.H.M.; Li, H. B. T.; Verlaan, V.; Oliphant, C.J.; Bakker, R.; Houweling, Z.S.; Schropp, R.E.I.

    2009-01-01

    If tantalum filaments are used for the hot wire chemical vapour deposition (HWCVD) of thin film silicon, various types of tantalum silicides are formed, depending on the filament temperature. Under deposition conditions employed for device quality amorphous and microcrystalline silicon (Twire ≈ 1750

  20. Bandgap and Carrier Transport Engineering of Quantum Confined Mixed Phase Nanocrystalline/Amorphous Silicon

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Tianyuan; Klafehn, Grant; Kendrick, Chito; Theingi, San; Airuoyo, Idemudia; Lusk, Mark T.; Stradins, Paul; Taylor, Craig; Collins, Reuben T.

    2016-11-21

    Mixed phase nanocrystalline/amorphous-silicon (nc/a-Si:H) thin films with band-gap higher than bulk silicon are prepared by depositing silicon nanoparticles (SiNPs), prepared in a separate deposition zone, and hydrogenated amorphous silicon (a-Si:H), simultaneously. Since the two deposition phases are well decoupled, optimized parameters for each component can apply to the growth process. Photoluminescence spectroscopy (PL) shows that the embedded SiNPs are small enough to exhibit quantum confinement effects. The low temperature PL measurements on the mixed phase reveal a dominant emission feature, which is associated with SiNPs surrounded by a-Si:H. In addition, we compare time dependent low temperature PL measurements for both a-Si:H and mixed phase material under intensive laser exposure for various times up to two hours. The PL intensity of a-Si:H with embedded SiNPs degrades much less than that of pure a-Si:H. We propose this improvement of photostability occurs because carriers generated in the a-Si:H matrix quickly transfer into SiNPs and recombine there instead of recombining in a-Si:H and creating defect states (Staebler-Wronski Effect).

  1. Interference filter with amorphous silicon layer and direct laser recording on it

    Science.gov (United States)

    Kutanov, A.; Sydyk uluu, Nurbek; Snimshikov, I.; Kazakbaeva, Z.

    2016-08-01

    The interference spectral filters with amorphous silicon layer deposited by magnetron sputtering on the reflective metal layer on a glass substrate are developed. Interference filter select from white light source components corresponding to quasimonochromatic wavelength with a narrow bandwidth. The thickness of the amorphous silicon layer determines the center wavelength of the pass band of the filter. It proposed to use interference filter with amorphous silicon layer for direct laser recoding on it. Results on direct laser recording on amorphous silicon layer of the interference filter by single-mode Blu Ray laser (X = 405 nm) with high contrast reflected image are demonstrated.

  2. Stability of amorphous silicon alloy triple-junction solar cells and modules

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K.; Aiga, M.; Otsubo, M.

    1987-06-25

    Results on reliability test for amorphous silicon alloy triple-junction solar cells and modules are described. It has been found that, for a-SiGe:H pin cells, reduction of the stress in the film is of first importance for stability. Application of low-temperature-deposited microcrystalline p-layer for each sub cell and of thinner i-layers for the middle and the bottom cells improves stability of triple-junction cells, by enhancing the electric field in the i-layers.

  3. Grain boundary resistance to amorphization of nanocrystalline silicon carbide

    Science.gov (United States)

    Chen, Dong; Gao, Fei; Liu, Bo

    2015-11-01

    Under the C displacement condition, we have used molecular dynamics simulation to examine the effects of grain boundaries (GBs) on the amorphization of nanocrystalline silicon carbide (nc-SiC) by point defect accumulation. The results show that the interstitials are preferentially absorbed and accumulated at GBs that provide the sinks for defect annihilation at low doses, but also driving force to initiate amorphization in the nc-SiC at higher doses. The majority of surviving defects are C interstitials, as either C-Si or C-C dumbbells. The concentration of defect clusters increases with increasing dose, and their distributions are mainly observed along the GBs. Especially these small clusters can subsequently coalesce and form amorphous domains at the GBs during the accumulation of carbon defects. A comparison between displacement amorphized nc-SiC and melt-quenched single crystal SiC shows the similar topological features. At a dose of 0.55 displacements per atom (dpa), the pair correlation function lacks long range order, demonstrating that the nc-SiC is fully amorphilized.

  4. Amorphous silicon based p-i-i-n photodetectors for point-of-care testing

    Energy Technology Data Exchange (ETDEWEB)

    Furin, Dominik; Proll, Guenther; Gauglitz, Guenther [Universitaet Tuebingen, Institut fuer Physikalische und Theoretische Chemie, Auf der Morgenstelle 8, 72076 Tuebingen (Germany); Thielmann, Johannes; Harendt, Christine [Institut fuer Mikroelektronik Stuttgart, Allmandring 30a, 70569 Stuttgart (Germany); Pfaefflin, Albrecht; Schleicher, Erwin [Universitaetsklinikum und Medizinische Fakultaet, Universitaetsklinikum Tuebingen, Geissweg 3, 72076 Tuebingen (Germany); Schubert, Markus B. [Institut fuer Physikalische Elektronik, Universitaet Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart (Germany); Saemann, Marc

    2010-04-15

    Modern medical diagnostics demands point-of-care testing (POCT) systems for quick tests in clinical or out-patient environments. This investigation combines the Reflectometric Interference Spectroscopy (RIfS) with thin film technology for a highly sensitive, direct optical and label-free detection of proteins, e.g. inflammation or cardiovascular markers. Amorphous silicon (a-Si) based thin film photodetectors replace the so far needed spectrometer and permit downsizing of the POCT system. Photodetectors with p-i-i-n structure adjust their spectral sensitivity according to the applied read-out voltage. The use of amorphous silicon carbide in the p-type and the first intrinsic layer enhances the sensitivity through very low dark currents of the photodetectors and enables the adjustment of their absorption characteristics. Integrating the thin film photodetectors on the rear side of the RIfS substrate eliminates optical losses and distortions, as compared to the standard RIfS setup. An integrated Application Specific Integrated Circuit (ASIC) chip performs a current-frequency conversion to accurately detect the photocurrent of up to eight parallel photodetector channels. In addition to the optimization of the photo-detectors, this contribution presents first successful direct optical and label-free RIfS measurements of C-reactive protein (CRP) and D-dimer in buffer solution in physiological relevant concentrations. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Polycystalline silicon thin films for electronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Jaeger, Christian Claus

    2012-01-15

    For the thin polycrystalline Si films fabricated with the aluminium-induced-layer-exchange (ALILE) process a good structural quality up to a layer-thickness value of 10 nm was determined. For 5 nm thick layers however after the layer exchange no closes poly-silicon film was present. In this case the substrate was covered with spherically arranged semiconductor material. Furthermore amorphous contributions in the layer could be determined. The electrical characterization of the samples at room temperature proved a high hole concentration in the range 10{sup 18} cm{sup -3} up to 9.10{sup 19} cm{sup -3}, which is influenced by the process temperature and the layer thickness. Hereby higher hole concentrations at higher process temperatures and thinner films were observed. Furthermore above 150-200 K a thermically activated behaviour of the electrical conductivity was observed. At lower temperatures a deviation of the measured characteristic from the exponential Arrhenius behaviour was determined. For low temperatures (below 20 K) the conductivity follows the behaviour {sigma}{proportional_to}[-(T{sub 0}/T){sup 1/4}]. The hole mobility in the layers was lowered by a passivation step, which can be explained by defect states at the grain boundaries. The for these very thin layers present situation was simulated in the framework of the model of Seto, whereby both the defect states at the grain boundaries (with an area density Q{sub t}) and the defect states at the interfaces (with an area density Q{sub it}) were regarded. By this the values Q{sub t}{approx}(3-4).10{sup 12} cm{sup -2} and Q{sub it}{approx}(2-5).10{sup 12} cm{sup -2} could be determined for these thin ALILE layers on quartz substrates. Additionally th R-ALILE process was studied, which uses the reverse precursor-layer sequence substrate/amorphous silicon/oxide/aluminium. Hereby two steps in the crystallization process of the R-ALILE process were found. First a substrate/Al-Si mixture/poly-Si layer structure

  6. Laser annealing of thin film polycrystalline silicon solar cell

    Directory of Open Access Journals (Sweden)

    Chowdhury A.

    2013-11-01

    Full Text Available Performances of thin film polycrystalline silicon solar cell grown on glass substrate, using solid phase crystallization of amorphous silicon can be limited by low dopant activation and high density of defects. Here, we investigate line shaped laser induced thermal annealing to passivate some of these defects in the sub-melt regime. Effect of laser power and scan speed on the open circuit voltage of the polysilicon solar cells is reported. The processing temperature was measured by thermal imaging camera. Enhancement of the open circuit voltage as high as 210% is achieved using this method. The results are discussed.

  7. Effect of Hydrogen Dilution on Growth of Silicon Nanocrystals Embedded in Silicon Nitride Thin Film bv Plasma-Enhanced CVD

    Institute of Scientific and Technical Information of China (English)

    DING Wenge; ZHEN Lanfang; ZHANG Jiangyong; LI Yachao; YU Wei; FU Guangsheng

    2007-01-01

    An investigation was conducted into the effect of hydrogen dilution on the mi-crostructure and optical properties of silicon nanograins embedded in silicon nitride (Si/SiNx) thin film deposited by the helicon wave plasma-enhanced chemical vapour deposition technique. With Ar-diluted SiH4 and N2 as the reactant gas sources in the fabrication of thin film, the film was formed at a high deposition rate. There was a high density of defect at the amorphous silicon (a-Si)/SiNx interface and a relative low optical gap in the film. An addition of hydrogen into the reactant gas reduced the film deposition rate sharply. The silicon nanograins in the SiNx matrix were in a crystalline state, and the density of defects at the silicon nanocrystals (nc-Si)/SiNx interface decreased significantly and the optical gap of the films widened. These results suggested that hydrogen activated by the plasma could not only eliminate in the defects between the interface of silicon nanograins and SiNx matrix, but also helped the nanograins transform from the amorphous into crystalline state. By changing the hydrogen dilution ratio in the reactant gas sources, a tunable band gap from 1.87 eV to 3.32 eV was obtained in the Si/SiNx film.

  8. Comment on ``Electron drift mobility in doped amorphous silicon''

    Science.gov (United States)

    Overhof, H.; Silver, M.

    1989-05-01

    Experimental drift-mobility data obtained by different methods in doped amorphous silicon are compared. It is shown that the presence of a long-range random potential will lead to a modification of the drift mobility in one experiment while the corresponding values in other experiments are virtually unaffected. It is shown that this effect accounts for the apparent discrepancy between the results of these experiments rather than the shift of the mobility edge upon doping which was recently proposed by Street, Kakalios, and Hack [Phys. Rev. B 38, 5603 (1988)] in order to understand their data.

  9. Eigenmode Splitting in all Hydrogenated Amorphous Silicon Nitride Coupled Microcavity

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xian-Gao; HUANG Xin-Fan; CHEN Kun-Ji; QIAN Bo; CHEN San; DING Hong-Lin; LIU Sui; WANG Xiang; XU Jun; LI Wei

    2008-01-01

    Hydrogenated amorphous silicon nitride based coupled optical microcavity is investigated theoretically and experimentally. The theoretical calculation of the transmittance spectra of optical microcavity with one cavity and coupled microcavity with two-cavity is performed.The optical eigenmode splitting for coupled microcavity is found due to the interaction between the neighbouring localized cavities.Experimentally,the coupled cavity samples are prepared by plasma enhanced chemical vapour deposition and characterized by photoluminescence measurements.It is found that the photoluminescence peak wavelength agrees well with the cavity mode in the calculated transmittance spectra.This eigenmode splitting is analogous to the electron state energy splitting in diatom molecules.

  10. A study of ZnO:B films for thin film silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Yin, J.; Zhu, H.; Wang, Y.; Wang, Z.; Gao, J.; Mai, Y.; Ma, Y. [Baoding Tianwei Solarfilms Co., Ltd., 071051, Baoding (China); Wan, M. [Department of Chemistry and Material science, Hunan Institute of Humanities, Science and Technology, 417000, Loudi (China); Huang, Y., E-mail: y.huang@btw-solarfilms.com [Baoding Tianwei Solarfilms Co., Ltd., 071051, Baoding (China)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer ZnO:B films with different thicknesses were prepared with LPCVD technique. Black-Right-Pointing-Pointer The thicker ZnO:B back electrodes lead to higher FF but slightly lower J{sub sc.} Black-Right-Pointing-Pointer Back polyvinyl butyral (PVB) foils improves the utilization of incident light in solar cells. Black-Right-Pointing-Pointer The thicker ZnO:B front electrode films result in high J{sub sc} but lower FF. - Abstract: Boron doped zinc oxide (ZnO:B) films with different thicknesses were prepared with low pressure chemical vapor deposition (LPCVD) technique and implemented in thin film silicon solar cells as front and back electrodes. It is found that thick back ZnO:B film electrode in thin film silicon solar cells leads to a high fill factors (FF), which is attributed to an improvement of the electrical properties of the thick ZnO:B films, and in the meanwhile a slightly low short circuit currents (J{sub sc}) due to a high light absorption in the thick back ZnO:B films. Differently, the thicker front ZnO:B film electrodes result in a high J{sub sc} but a low FF of solar cells compared to the thinner ones. The low FF of the solar cells may be caused by the local shunt originated from the pinholes or by the cracks (zones of non-dense material) formed in particular in microcrystalline silicon materials deposited on rough front ZnO:B films. As to the high J{sub sc}, it is expected to be due to a good light trapping effect inside solar cells grown on rough front ZnO:B films. Moreover, the application of high reflective polyvinyl butyral (PVB) foils effectively enhances the utilization of incident light in solar cells. By optimizing deposition process of the ZnO:B films, high efficiencies of 8.8% and 10% for single junction thin film amorphous silicon solar cells (a-Si:H, intrinsic layer thickness < 200 nm) and amorphous/microcrystalline silicon tandem solar cells (a-Si:H/{mu}c-Si:H, intrinsic amorphous silicon layer

  11. Electrochromic study on amorphous tungsten oxide films by sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chuan, E-mail: cli10@yahoo.com [Department of Biomedical Engineering, National Yang Ming University, Taipei 11221, Taiwan (China); Department of Mechanical Engineering, National Central University, Jhongli, Taoyuan 32001, Taiwan (China); Hsieh, J.H. [Department of Materials Engineering, Ming Chi University of Technology, Taishan, Taipei 24301, Taiwan (China); Hung, Ming-Tsung [Department of Mechanical Engineering, National Central University, Jhongli, Taoyuan 32001, Taiwan (China); Huang, B.Q. [Department of Biomedical Engineering, National Yang Ming University, Taipei 11221, Taiwan (China)

    2015-07-31

    Tungsten oxide films under different oxygen flow rates are deposited by DC sputtering. The voltage change at target and analyses for the deposited films by X-ray diffraction, scanning electronic microscope, X-ray photoelectron spectroscopy and ultraviolet–visible-near infrared spectroscopy consistently indicate that low oxygen flow rate (5 sccm) only creates metal-rich tungsten oxide films, while higher oxygen flow rate (10–20 sccm) assures the deposition of amorphous WO{sub 3} films. To explore the electrochromic function of deposited WO{sub 3} films, we use electrochemical tests to perform the insertion of lithium ions and electrons into films. The WO{sub 3} films switch between color and bleach states effectively by both potentiostat and cyclic voltammetry. Quantitative evaluation on electrochemical tests indicates that WO{sub 3} film with composition close to its stoichiometry is an optimal choice for electrochromic function. - Highlights: • Amorphous WO{sub 3} films are deposited by DC sputtering under different O{sub 2} flow rates. • Higher oxygen flow rate (> 10 sccm) assures the deposition of amorphous WO{sub 3} films. • Both potentiostat and cyclic voltammetry make WO{sub 3} films switch its color. • An optimal electrochromic WO{sub 3} is to make films close to its stoichiometry.

  12. Molecular simulation of freestanding amorphous nickel thin films

    Energy Technology Data Exchange (ETDEWEB)

    Dong, T.Q. [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, UMR 8208 CNRS, 5 Boulevard Descartes, 77454 Marne-la-Vallée, Cedex 2 (France); Hoang, V.V., E-mail: vvhoang2002@yahoo.com [Department of Physics, Institute of Technology, National University of Ho Chi Minh City, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City (Viet Nam); Lauriat, G. [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, UMR 8208 CNRS, 5 Boulevard Descartes, 77454 Marne-la-Vallée, Cedex 2 (France)

    2013-10-31

    Size effects on glass formation in freestanding Ni thin films have been studied via molecular dynamics simulation with the n-body Gupta interatomic potential. Atomic mechanism of glass formation in the films is determined via analysis of the spatio-temporal arrangements of solid-like atoms occurred upon cooling from the melt. Solid-like atoms are detected via the Lindemann ratio. We find that solid-like atoms initiate and grow mainly in the interior of the film and grow outward. Their number increases with decreasing temperature and at a glass transition temperature they dominate in the system to form a relatively rigid glassy state of a thin film shape. We find the existence of a mobile surface layer in both liquid and glassy states which can play an important role in various surface properties of amorphous Ni thin films. We find that glass formation is size independent for models containing 4000 to 108,000 atoms. Moreover, structure of amorphous Ni thin films has been studied in details via coordination number, Honeycutt–Andersen analysis, and density profile which reveal that amorphous thin films exhibit two different parts: interior and surface layer. The former exhibits almost the same structure like that found for the bulk while the latter behaves a more porous structure containing a large amount of undercoordinated sites which are the origin of various surface behaviors of the amorphous Ni or Ni-based thin films found in practice. - Highlights: • Glass formation is analyzed via spatio-temporal arrangements of solid-like atoms. • Amorphous Ni thin film exhibits two different parts: surface and interior. • Mobile surface layer enhances various surface properties of the amorphous Ni thin films. • Undercoordinated sites play an important role in various surface activities.

  13. Amorphous Hydrogenated Carbon-Nitrogen Alloy Thin Films for Solar Cell Application

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zhi-Bin; DING Zheng-Ming; PANG Qian-Jun; CUI Rong-Qiang

    2001-01-01

    Amorphous hydrogenated carbon-nitrogen alloy (a-CNx :H) thin films have been deposited on silicon substratesby improved dc magnetron sputtering from a graphite target in nitrogen and hydrogen gas discharging. Thefilms are investigated by using Raman spectroscopy, x-ray photoelectron spectroscopy, spectral ellipsometer and electron spin resonance techniques. The optimized process condition for solar cell application is discussed. Thephotovoltaic property of a-CNx:H/silicon heterojunctions can be improved by the adjustment of the pressureratio of hydrogen to nitrogen and unbalanced magnetic field intensity. Open-circuit voltage and short-circuitcurrent reach 300mV and 5.52 Ma/cm2, respectively.

  14. Determining the Onset of Amorphization of Crystalline Silicon due to Hypervelocity Impact

    Science.gov (United States)

    Poletti, C. Shane; Bachlechner, Martina E.

    2009-03-01

    Atomistic simulations were performed to study a hypervelocity impactor striking a silicon/silicon nitride interface with varying silicon substrate thicknesses. Visualization indicates that the crystalline silicon amorphizes upon impact. The objective of the present study is to determine where the boundary between amorphous and crystalline silicon occurrs. In the analysis, the silicon substrate is separated into sixty layers and for each layer the average z displacement is determined. Our results show that the boundary between amorphous and crystalline silicon occurs between layers 20 and 22 for an impactor traveling at 5 km/s. This corresponds to a depth of approximately 32 Angstroms into the silicon. More detailed analyses reveals that the z displacement is noticeably larger for the layers that do not have a silicon atom bonded beneath them compared to the ones that do.

  15. Al-induced Lateral Crystallization of Amorphous Si Thin Films by Microwave Annealing

    Institute of Scientific and Technical Information of China (English)

    RAO Rui; XU Zhong-yang; ZENG Xiang-bing

    2002-01-01

    Al-induced lateral crystallization of amorphous silicon thin films by microwave annealing is investigated. The crystallized Si films are examined by optical microscopy , Raman spectroscopy, transmission electron microscopy and transmission electron diffraction micrography. After microwave annealing at 480 ℃ for 50 min,the amorphous Si is completely crystallized with large grains of main ( 111 ) orientation. The rate of lateral crystallization is 0.04μm/min. This process, labeled MILC-MA, not only lowers the temperature but also reduces the time of crystallization. The crystallization mechanism during microwave annealing and the electrical properties of polycrystalline Si thin films are analyzed. This MILC-MA process has potential applications in large area electronics.

  16. High-stability transparent amorphous oxide TFT with a silicon-doped back-channel layer

    Science.gov (United States)

    Lee, Hyoung-Rae; Park, Jea-Gun

    2014-10-01

    We significantly reduced various electrical instabilities of amorphous indium gallium zinc oxide thin-film transistors (TFTs) by using the co-deposition of silicon on an a-IGZO back channel. This process showed improved stability of the threshold voltage ( V th ) under high temperature and humidity and negative gate-bias illumination stress (NBIS) without any reduction of IDS. The enhanced stability was achieved with silicon, which has higher metal-oxide bonding strengths than gallium does. Additionally, SiO X distributed on the a-IGZO surface reduced the adsorption and the desorption of H2O and O2. This process is applicable to the TFT manufacturing process with a variable sputtering target.

  17. Spin transport, magnetoresistance, and electrically detected magnetic resonance in amorphous hydrogenated silicon nitride

    Science.gov (United States)

    Mutch, Michael J.; Lenahan, Patrick M.; King, Sean W.

    2016-08-01

    We report on a study of spin transport via electrically detected magnetic resonance (EDMR) and near-zero field magnetoresistance (MR) in silicon nitride films. Silicon nitrides have long been important materials in solid state electronics. Although electronic transport in these materials is not well understood, electron paramagnetic resonance studies have identified a single dominating paramagnetic defect and have also provided physical and chemical descriptions of the defects, called K centers. Our EDMR and MR measurements clearly link the near-zero field MR response to the K centers and also indicate that K center energy levels are approximately 3.1 eV above the a-SiN:H valence band edge. In addition, our results suggest an approach for the study of defect mediated spin-transport in inorganic amorphous insulators via variable electric field and variable frequency EDMR and MR which may be widely applicable.

  18. Vibrational Spectroscopy of Chemical Species in Silicon and Silicon-Rich Nitride Thin Films

    Directory of Open Access Journals (Sweden)

    Kirill O. Bugaev

    2012-01-01

    Full Text Available Vibrational properties of hydrogenated silicon-rich nitride (SiN:H of various stoichiometry (0.6≤≤1.3 and hydrogenated amorphous silicon (a-Si:H films were studied using Raman spectroscopy and Fourier transform infrared spectroscopy. Furnace annealing during 5 hours in Ar ambient at 1130∘C and pulse laser annealing were applied to modify the structure of films. Surprisingly, after annealing with such high-thermal budget, according to the FTIR data, the nearly stoichiometric silicon nitride film contains hydrogen in the form of Si–H bonds. From analysis of the FTIR data of the Si–N bond vibrations, one can conclude that silicon nitride is partly crystallized. According to the Raman data a-Si:H films with hydrogen concentration 15% and lower contain mainly Si–H chemical species, and films with hydrogen concentration 30–35% contain mainly Si–H2 chemical species. Nanosecond pulse laser treatments lead to crystallization of the films and its dehydrogenization.

  19. Experimental and Computer Modelling Studies of Metastability of Amorphous Silicon Based Solar Cells

    NARCIS (Netherlands)

    Munyeme, Geoffrey

    2003-01-01

    We present a combination of experimental and computer modelling studies of the light induced degradation in the performance of amorphous silicon based single junction solar cells. Of particular interest in this study is the degradation kinetics of different types of amorphous silicon single junction

  20. Solid state photochemistry. Subpanel A-2(b): Metastability in hydrogenated amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, D. [Solarex Corporation, Newton, PA (United States)

    1996-09-01

    All device quality amorphous silicon based materials exhibit degradation in electronic properties when exposed to sunlight. The photo-induced defects are associated with Si dangling bonds that are created by the recombination and/or trapping of photogenerated carriers. The defects are metastable and can be annealed out at temperatures of about 150 to 200 degrees Centigrade. The density of metastable defects is larger in films that are contaminated with > 10{sup 19} per cubic cm of impurities such as oxygen, carbon and nitrogen. However, recent experimental results indicate that some metastable defects are still present in films with very low impurity concentrations. The photo-induced defects typically saturate after 100 to 1000 hours of exposure to one sun illumination depending on the deposition conditions. There is also experimental evidence that photo-induced structural changes are occurring in the amorphous silicon based materials and that hydrogen may be playing an important role in both the photo-induced structural changes and in the creation of metastable defects.

  1. Amorphous silicon pixel layers with cesium iodide converters for medical radiography

    Energy Technology Data Exchange (ETDEWEB)

    Jing, T.; Cho, G. [Lawrence Berkeley Lab., CA (United States); Goodman, C.A. [Air Techniques, Inc., Hicksville, NY (United States)] [and others

    1993-11-01

    We describe the properties of evaporated layers of Cesium Iodide (Thallium activated) deposited on substrates that enable easy coupling to amorphous silicon pixel arrays. The CsI(Tl) layers range in thickness from 65 to 220{mu}m. We used the two-boat evaporator system to deposit CsI(Tl) layers. This system ensures the formation of the scintillator film with homogenous thallium concentration which is essential for optimizing the scintillation light emission efficiency. The Tl concentration was kept to 0.1--0.2 mole percent for the highest light output. Temperature annealing can affect the microstructure as well as light output of the CsI(Tl) film. 200--300C temperature annealing can increase the light output by a factor of two. The amorphous silicon pixel arrays are p-i-n diodes approximately l{mu}m thick with transparent electrodes to enable them to detect the scintillation light produced by X-rays incident on the CsI(Tl). Digital radiography requires a good spatial resolution. This is accomplished by making the detector pixel size less then 50{mu}m. The light emission from the CsI(Tl) is collimated by techniques involving the deposition process on pattered substrates. We have measured MTF of greater than 12 line pairs per mm at the 10% level.

  2. Flexible amorphous silicon solar cells and their application to PV systems

    Energy Technology Data Exchange (ETDEWEB)

    Ichikawa, Y.; Fujikake, S.; Yoshida, T.; Sakai, H.; Natsume, F. [Fuji Electric Co. Ltd., Yokosuka, Kanagawa (Japan). New Energy Lab.

    1996-12-31

    Hydrogenated amorphous silicon (a-Si:H) solar cells are regarded as the next generation product following crystalline silicon (c-Si) solar cells. The performance of the large area cells has been improved to a practical application level and the durability has been confirmed by a number of outdoor tests at demonstration sites under various climatic conditions. The mass production technology for realizing low cost a-Si photovoltaic (PV) modules, however, has not been developed very well and is still in an elementary stage. A flexible a-Si:H PV module has been developed, which is rolled up around a cylindrical core, has a width of about 1 m, and is able to be cut to any length. The amorphous solar cell fabricated on a heat resistant plastic film with a thickness of 50 {mu}m has a new monolithic series connected structure named SCAF (Series-Connection through Apertures formed on Film) to obtain a high output voltage required for practical use. The details of the structure and the technology of the fabrication process are described as well as some of its applications. (author). 11 figs., 3 refs.

  3. Angular magnetoresistance in semiconducting undoped amorphous carbon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sagar, Rizwan Ur Rehman; Saleemi, Awais Siddique; Zhang, Xiaozhong, E-mail: xzzhang@tsinghua.edu.cn [Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, People' s Republic of China and Beijing National Center for Electron Microscopy, Beijing 100084 (China)

    2015-05-07

    Thin films of undoped amorphous carbon thin film were fabricated by using Chemical Vapor Deposition and their structure was investigated by using High Resolution Transmission Electron Microscopy and Raman Spectroscopy. Angular magnetoresistance (MR) has been observed for the first time in these undoped amorphous carbon thin films in temperature range of 2 ∼ 40 K. The maximum magnitude of angular MR was in the range of 9.5% ∼ 1.5% in 2 ∼ 40 K. The origin of this angular MR was also discussed.

  4. Unusually High and Anisotropic Thermal Conductivity in Amorphous Silicon Nanostructures.

    Science.gov (United States)

    Kwon, Soonshin; Zheng, Jianlin; Wingert, Matthew C; Cui, Shuang; Chen, Renkun

    2017-02-02

    Amorphous Si (a-Si) nanostructures are ubiquitous in numerous electronic and optoelectronic devices. Amorphous materials are considered to possess the lower limit to the thermal conductivity (κ), which is ∼1 W·m(-1) K(-1) for a-Si. However, recent work suggested that κ of micrometer-thick a-Si films can be greater than 3 W·m(-1) K(-1), which is contributed to by propagating vibrational modes, referred to as "propagons". However, precise determination of κ in a-Si has been elusive. Here, we used structures of a-Si nanotubes and suspended a-Si films that enabled precise in-plane thermal conductivity (κ∥) measurement within a wide thickness range of 5 nm to 1.7 μm. We showed unexpectedly high κ∥ in a-Si nanostructures, reaching ∼3.0 and 5.3 W·m(-1) K(-1) at ∼100 nm and 1.7 μm, respectively. Furthermore, the measured κ∥ is significantly higher than the cross-plane κ on the same films. This unusually high and anisotropic thermal conductivity in the amorphous Si nanostructure manifests the surprisingly broad propagon mean free path distribution, which is found to range from 10 nm to 10 μm, in the disordered and atomically isotropic structure. This result provides an unambiguous answer to the century-old problem regarding mean free path distribution of propagons and also sheds light on the design and performance of numerous a-Si based electronic and optoelectronic devices.

  5. Amorphous Silicon Carbide Passivating Layers to Enable Higher Processing Temperature in Crystalline Silicon Heterojunction Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Boccard, Mathieu [Arizona State Univ., Mesa, AZ (United States); Holman, Zachary [Arizona State Univ., Mesa, AZ (United States)

    2015-04-06

    "Very efficient crystalline silicon (c-Si) solar cells have been demonstrated when thin layers of intrinsic and doped hydrogenated amorphous silicon (a-Si:H) are used for passivation and carrier selectivity in a heterojunction device. One limitation of this device structure is the (parasitic) absorption in the front passivation/collection a-Si:H layers; another is the degradation of the a-Si:H-based passivation upon temperature, limiting the post-processes to approximately 200°C thus restricting the contacting possibilities and potential tandem device fabrication. To alleviate these two limitations, we explore the potential of amorphous silicon carbide (a-SiC:H), a widely studied material in use in standard a-Si:H thin-film solar cells, which is known for its wider bandgap, increased hydrogen content and stronger hydrogen bonding compared to a-Si:H. We study the surface passivation of solar-grade textured n-type c-Si wafers for symmetrical stacks of 10-nm-thick intrinsic a-SiC:H with various carbon content followed by either p-doped or n-doped a-Si:H (referred to as i/p or i/n stacks). For both doping types, passivation (assessed through carrier lifetime measurements) is degraded by increasing the carbon content in the intrinsic a-SiC:H layer. Yet, this hierarchy is reversed after annealing at 350°C or more due to drastic passivation improvements upon annealing when an a-SiC:H layer is used. After annealing at 350°C, lifetimes of 0.4 ms and 2.0 ms are reported for i/p and i/n stacks, respectively, when using an intrinsic a-SiC:H layer with approximately 10% of carbon (initial lifetimes of 0.3 ms and 0.1 ms, respectively, corresponding to a 30% and 20-fold increase, respectively). For stacks of pure a-Si:H material the lifetimes degrade from 1.2 ms and 2.0 ms for i/p and i/n stacks, respectively, to less than 0.1 ms and 1.1 ms (12-fold and 2-fold decrease, respectively). For complete solar cells using pure a-Si:H i/p and i/n stacks, the open-circuit voltage (Voc

  6. Modelling structure and properties of amorphous silicon boron nitride ceramics

    Directory of Open Access Journals (Sweden)

    Johann Christian Schön

    2011-06-01

    Full Text Available Silicon boron nitride is the parent compound of a new class of high-temperature stable amorphous ceramics constituted of silicon, boron, nitrogen, and carbon, featuring a set of properties that is without precedent, and represents a prototypical random network based on chemical bonds of predominantly covalent character. In contrast to many other amorphous materials of technological interest, a-Si3B3N7 is not produced via glass formation, i.e. by quenching from a melt, the reason being that the binary components, BN and Si3N4, melt incongruently under standard conditions. Neither has it been possible to employ sintering of μm-size powders consisting of binary nitrides BN and Si3N4. Instead, one employs the so-called sol-gel route starting from single component precursors such as TADB ((SiCl3NH(BCl2. In order to determine the atomic structure of this material, it has proven necessary to simulate the actual synthesis route.Many of the exciting properties of these ceramics are closely connected to the details of their amorphous structure. To clarify this structure, it is necessary to employ not only experimental probes on many length scales (X-ray, neutron- and electron scattering; complex NMR experiments; IR- and Raman scattering, but also theoretical approaches. These address the actual synthesis route to a-Si3B3N7, the structural properties, the elastic and vibrational properties, aging and coarsening behaviour, thermal conductivity and the metastable phase diagram both for a-Si3B3N7 and possible silicon boron nitride phases with compositions different from Si3N4: BN = 1 : 3. Here, we present a short comprehensive overview over the insights gained using molecular dynamics and Monte Carlo simulations to explore the energy landscape of a-Si3B3N7, model the actual synthesis route and compute static and transport properties of a-Si3BN7.

  7. The nanoindentation applied to predict the interface delamination for the C/amorphous Si composite film

    Science.gov (United States)

    Han, Chang-Fu; Huang, Chao-Yu; Wu, Bo-Hsiung; Lin, Jen-Fin

    2009-10-01

    In the present study, the indentation depth corresponding to the pop-in arising in the loading process is found to be quite close to the C/amorphous Si composite film thickness, regardless of the C-film thickness. This load-depth behavior gives a clue that the occurrence of pop-in is perhaps related to the buckling of the composite film, which had already delaminated from the silicon substrate. This indentation depth of buckling predicted by the present model is quite close to the pop-in depth obtained from experimental results, regardless of the change in the C-film thickness. This characteristic reveals that the present model is developed successfully to predict the pop-in depth of a specimen, and the pop-in is indeed created due to the buckling of the composite film under a compression stress.

  8. Improving the performance of amorphous and crystalline silicon heterojunction solar cells by monitoring surface passivation

    Energy Technology Data Exchange (ETDEWEB)

    Schuettauf, J.W.A.; Van der Werf, C.H.M.; Kielen, I.M.; Van Sark, W.G.J.H.M.; Rath, J.K.; Schropp, R.E.I. [Utrecht University, Debye Institute for Nanomaterials Science, Nanophotonics, Physics of Devices, Princetonplein 5, 3584 CC Utrecht (Netherlands)

    2012-09-15

    The influence of thermal annealing on the crystalline silicon surface passivating properties of selected amorphous silicon containing layer stacks (including intrinsic and doped films), as well as the correlation with silicon heterojunction solar cell performance has been investigated. All samples have been isochronally annealed for 1 h in an N{sub 2} ambient at temperatures between 150C and 300C in incremental steps of 15C. For intrinsic films and intrinsic/n-type stacks, an improvement in passivation quality is observed up to 255C and 270C, respectively, and a deterioration at higher temperatures. For intrinsic/n-type a-Si:H layer stacks, a maximum minority carrier lifetime of 13.3 ms at an injection level of 10{sup 15} cm{sup -3} has been measured. In contrast, for intrinsic/p-type a-Si:H layer stacks, a deterioration in passivation is observed upon annealing over the whole temperature range. Comparing the lifetime values and trends for the different layer stacks to the performance of the corresponding cells, it is inferred that the intrinsic/p-layer stack is limiting device performance. Furthermore, thermal annealing of p-type layers should be avoided entirely. We therefore propose an adapted processing sequence, leading to a substantial improvement in efficiency to 16.7%, well above the efficiency of 15.8% obtained with the 'standard' processing sequence.

  9. Chemical vapor deposition of amorphous ruthenium-phosphorus alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Shin Jinhong [Texas Materials Institute, University of Texas at Austin, Austin, TX 78750 (United States); Waheed, Abdul [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Winkenwerder, Wyatt A. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Kim, Hyun-Woo [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Agapiou, Kyriacos [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Jones, Richard A. [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Hwang, Gyeong S. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Ekerdt, John G. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States)]. E-mail: ekerdt@che.utexas.edu

    2007-05-07

    Chemical vapor deposition growth of amorphous ruthenium-phosphorus films on SiO{sub 2} containing {approx} 15% phosphorus is reported. cis-Ruthenium(II)dihydridotetrakis-(trimethylphosphine), cis-RuH{sub 2}(PMe{sub 3}){sub 4} (Me = CH{sub 3}) was used at growth temperatures ranging from 525 to 575 K. Both Ru and P are zero-valent. The films are metastable, becoming increasingly more polycrystalline upon annealing to 775 and 975 K. Surface studies illustrate that demethylation is quite efficient near 560 K. Precursor adsorption at 135 K or 210 K and heating reveal the precursor undergoes a complex decomposition process in which the hydride and trimethylphosphine ligands are lost at temperatures as low at 280 K. Phosphorus and its manner of incorporation appear responsible for the amorphous-like character. Molecular dynamics simulations are presented to suggest the local structure in the films and the causes for phosphorus stabilizing the amorphous phase.

  10. Properties of interfaces in amorphous/crystalline silicon heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Olibet, Sara; Vallat-Sauvain, Evelyne; Fesquet, Luc; Damon-Lacoste, Jerome; De Wolf, Stefaan; Ballif, Christophe [Ecole Polytechnique Federale de Lausanne (EPFL), IMT, Photovoltaics and Thin Film Electronics Laboratory, Breguet 2, 2000 Neuchatel (Switzerland); Monachon, Christian; Hessler-Wyser, Aicha [Ecole Polytechnique Federale de Lausanne (EPFL), Interdisciplinary Centre for Electron Microscopy (CIME), 1015 Lausanne (Switzerland)

    2010-03-15

    To study recombination at the amorphous/crystalline Si (a-Si:H/c-Si) heterointerface, the amphoteric nature of silicon (Si) dangling bonds is taken into account. Modeling interface recombination measured on various test structures provides insight into the microscopic passivation mechanisms, yielding an excellent interface defect density reduction by intrinsic a-Si:H and tunable field-effect passivation by doped layers. The potential of this model's applicability to recombination at other Si heterointerfaces is demonstrated. Solar cell properties of a-Si:H/c-Si heterojunctions are in good accordance with the microscopic interface properties revealed by modeling, that are, e.g., slight asymmetries in the neutral capture cross-sections and band offsets. The importance of atomically abrupt interfaces and the difficulties to obtain them on pyramidally textured c-Si is studied in combination with transmission electron microscopy. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  11. Coaxial carbon plasma gun deposition of amorphous carbon films

    Science.gov (United States)

    Sater, D. M.; Gulino, D. A.; Rutledge, S. K.

    1984-01-01

    A unique plasma gun employing coaxial carbon electrodes was used in an attempt to deposit thin films of amorphous diamond-like carbon. A number of different structural, compositional, and electrical characterization techniques were used to characterize these films. These included scanning electron microscopy, scanning transmission electron microscopy, X ray diffraction and absorption, spectrographic analysis, energy dispersive spectroscopy, and selected area electron diffraction. Optical absorption and electrical resistivity measurements were also performed. The films were determined to be primarily amorphous, with poor adhesion to fused silica substrates. Many inclusions of particulates were found to be present as well. Analysis of these particulates revealed the presence of trace impurities, such as Fe and Cu, which were also found in the graphite electrode material. The electrodes were the source of these impurities. No evidence of diamond-like crystallite structure was found in any of the film samples. Details of the apparatus, experimental procedure, and film characteristics are presented.

  12. Optical and passivating properties of hydrogenated amorphous silicon nitride deposited by plasma enhanced chemical vapour deposition for application on silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wight, Daniel Nilsen

    2008-07-01

    Within this thesis, several important subjects related to the use of amorphous silicon nitride made by plasma enhanced chemical vapour deposition as an anti-reflective coating on silicon solar cells are presented. The first part of the thesis covers optical simulations to optimise single and double layer anti-reflective coatings with respect to optical performance when situated on a silicon solar cell. The second part investigates the relationship between important physical properties of silicon nitride films when deposited under different conditions. The optical simulations were either based on minimising the reflectance off a silicon nitride/silicon wafer stack or maximising the transmittance through the silicon nitride into the silicon wafer. The former method allowed consideration of the reflectance off the back surface of the wafer, which occurs typically at wavelengths above 1000 nm due to the transparency of silicon at these wavelengths. However, this method does not take into consideration the absorption occurring in the silicon nitride, which is negligible at low refractive indexes but quite significant when the refractive index increases above 2.1. For high-index silicon nitride films, the latter method is more accurate as it considers both reflectance and absorbance in the film to calculate the transmittance into the Si wafer. Both methods reach similar values for film thickness and refractive index for optimised single layer anti-reflective coatings, due to the negligible absorption occurring in these films. For double layer coatings, though, the reflectance based simulations overestimated the optimum refractive index for the bottom layer, which would have lead to excessive absorption if applied to real anti-reflective coatings. The experimental study on physical properties for silicon nitride films deposited under varying conditions concentrated on the estimation of properties important for its applications, such as optical properties, passivation

  13. Vibrational spectroscopy characterization of magnetron sputtered silicon oxide and silicon oxynitride films

    Energy Technology Data Exchange (ETDEWEB)

    Godinho, V., E-mail: godinho@icmse.csic.es [Instituto de Ciencia de Materiales de Sevilla-CSIC/US, Avda. Americo Vespucio no 49, 41092 Seville (Spain); Universite Libre de Bruxelles, Avenue F.D. Roosevelt 50, B 1050 Bruxelles (Belgium); Denisov, V.N.; Mavrin, B.N.; Novikova, N.N.; Vinogradov, E.A.; Yakovlev, V.A. [Institute for Spectroscopy - Russian Academy of Sciences, 142190, Troitsk, Moscow reg. (Russian Federation); Fernandez-Ramos, C. [Instituto de Ciencia de Materiales de Sevilla-CSIC/US, Avda. Americo Vespucio no 49, 41092 Seville (Spain); Institute for Prospective and Technological Studies-JRC European Commission, C/Inca Garcilaso s/n, 41092 Seville (Spain); Jimenez de Haro, M.C.; Fernandez, A. [Instituto de Ciencia de Materiales de Sevilla-CSIC/US, Avda. Americo Vespucio no 49, 41092 Seville (Spain)

    2009-10-15

    Vibrational (infrared and Raman) spectroscopy has been used to characterize SiO{sub x}N{sub y} and SiO{sub x} films prepared by magnetron sputtering on steel and silicon substrates. Interference bands in the infrared reflectivity measurements provided the film thickness and the dielectric function of the films. Vibrational modes bands were obtained both from infrared and Raman spectra providing useful information on the bonding structure and the microstructure (formation of nano-voids in some coatings) for these amorphous (or nanocrystalline) coatings. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis have also been carried out to determine the composition and texture of the films, and to correlate these data with the vibrational spectroscopy studies. The angular dependence of the reflectivity spectra provides the dispersion of vibrational and interference polaritons modes, what allows to separate these two types of bands especially in the frequency regions where overlaps/resonances occurred. Finally the attenuated total reflection Fourier transform infrared measurements have been also carried out demonstrating the feasibility and high sensitivity of the technique. Comparison of the spectra of the SiO{sub x}N{sub y} films prepared in various conditions demonstrates how films can be prepared from pure silicon oxide to silicon oxynitride with reduced oxygen content.

  14. Structure of silicon oxide films prepared by vacuum deposition

    Science.gov (United States)

    Saito, Yoshio; Kaito, Chihiro; Nishio, Kenzo; Naiki, Toshio

    1985-05-01

    The structure of thin silicon oxide films 5 nm in thickness, which were prepared by electron beam evaporation of SiO 2 glass onto a NaCl substrate, has been examined by high resolution electron microscopy and diffraction. Although the films which were prepared with substrate temperatures ranging from room up to 400°C gave rise to amorphous haloes, lattice fringes in areas 1-2 nm in extent were, however, seen in the micrographs. It is shown that the film is composed of α-quartz micro-crystallites. Crystals of α-cristobalite with sizes of several tens of nanometers appeared at a substrate temperature of 500°C. At a substrate temperature of 600°C, β-cristobalite crystals with sizes of several tens of nanometers appeared. The structural changes due to the substrate temperature were attributed to incorporation of sodium atoms from the substrate into the SiO 2 film.

  15. Nanocrystalline silicon and silicon quantum dots formation within amorphous silicon carbide by plasma enhanced chemical vapour deposition method controlling the Argon dilution of the process gases

    Energy Technology Data Exchange (ETDEWEB)

    Kole, Arindam; Chaudhuri, Partha, E-mail: erpc@iacs.res.in

    2012-11-01

    Structural and optical properties of the amorphous silicon carbide (a-SiC:H) thin films deposited by radio frequency plasma enhanced chemical vapour deposition method from a mixture of silane (SiH{sub 4}) and methane (CH{sub 4}) diluted in argon (Ar) have been studied with variation of Ar dilution from 94% to 98.4%. It is observed that nanocrystalline silicon starts to form within the a-SiC:H matrix by increasing the dilution to 96%. With further increase in Ar dilution to 98% formation of the silicon nanocrystals (nc-Si) with variable size is enhanced. The optical band gap (E{sub g}) of the a-SiC:H film decreases from 2.0 eV to 1.9 eV with increase in Ar dilution from 96% to 98% as the a-SiC:H films gradually become Si rich. On increasing the Ar dilution further to 98.4% leads to the appearance of crystalline silicon quantum dots (c-Si q-dots) of nearly uniform size of 3.5 nm. The quantum confinement effect is apparent from the sharp increase in the E{sub g} value to 2.6 eV. The phase transformation phenomenon from nc-Si within the a-SiC:H films to Si q-dot were further studied by high resolution transmission electron microscopy and the grazing angle X-ray diffraction spectra. A relaxation in the lattice strain has been observed with the formation of Si q-dots.

  16. Stability of thin films of microcrystalline silicon under light soaking

    Institute of Scientific and Technical Information of China (English)

    HAN Xiao-yan; Wang Yan; XUE Jun-ming; ZHAO Shu-wen; REN Hui-zhi; ZHAO Ying; LI Yang-xian; GENG Xin-hua

    2006-01-01

    Silicon thin films with different crystalline ratio(Xc) have been deposited by varying silane content(SC) of reactive gases in the RF-PECVD process.The effects of silane content on performance of the materials and the relationship between microstructure and opto-electronic properties were studied by means of Raman measurements,photoconductivity(σph),and dark conductivity(σd),followed by the measurements of light absorption coefficient(α),the product of quantum efficiency,mobility and lifetime (ημτ),before,during and after light soaking,respectively.The results indicate that the microcrystalline silicon near the transition region is suitable to prepare microcrystalline silicon of device grade,and that the amorphous region of the material is responsible to the light induced degradation.

  17. Amorphous SiC layers for electrically conductive Rugate filters in silicon based solar cells

    Science.gov (United States)

    Janz, S.; Peters, M.; Künle, M.; Gradmann, R.; Suwito, D.

    2010-05-01

    The subject of this work is the development of an electrically conductive Rugate filter for photovoltaic applications. We think that the optical as well as the electrical performance of the filter can be adapted especially to the requirements of crystalline Si thin-film and amorphous/crystalline silicon tandem solar cells. We have deposited amorphous hydrogenated Silicon Carbide layers (a-SixC1-x:H) with the precursor gases methane (CH4), silane (SiH4) and diborane (B2H6) applying Plasma Enhanced Chemical Vapour Deposition (PECVD). Through changing just the precursor flows a floating refractive index n from 1.9 to 3.5 (at 633 nm) could be achieved quite accurately. Different complex layer stacks (up to 200 layers) with a sinusoidal refractive index variation normal to the incident light were deposited in just 80 min on 100x100 mm2. Transmission measurements show good agreement between simulation and experiment which proofs our ability to control the deposition process, the good knowledge of the optical behaviour of the different SiC single layers and the advanced stage of our simulation model. The doped single layers show lateral conductivities which were extremely dependent on the Si/C ratio.

  18. Electrodeposition of amorphous gold alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Masaru; Senda, Kazutaka [Central Research Laboratory, Kanto Chemical Co., Inc., Saitama 340-0003 (Japan); Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Musha, Yuta [Department of Applied Chemistry, School of Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Sasano, Junji [Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, Tokyo 169-0051 (Japan); Okinaka, Yutaka [Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Osaka, Tetsuya [Department of Applied Chemistry, School of Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, Tokyo 169-0051 (Japan); Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan)], E-mail: osakatet@waseda.jp

    2007-11-20

    The process for electroplating amorphous gold-nickel-tungsten alloy that we developed previously based on the addition of a gold salt to a known amorphous Ni-W electroplating solution was investigated further using the X-ray diffraction (XRD) method for the purpose of quickly surveying the effects of various experimental variables on the microstructure of the alloy. In this system the gold concentration in the plating bath was found to be critical; i.e., when it is either very low or very high, the deposit becomes crystalline to XRD. The deposit composition varies linearly with the mole ratio of Au to Ni in solution, and the alloy deposit is amorphous to XRD when the atomic ratio of Au/Ni in the deposit is between 0.5 and 1.5. At suitable concentrations of the metal ions, the deposit contains essentially no tungsten. By extending the work on the Au-Ni-W system, an amorphous Au-Co alloy plating process was also developed.

  19. Improved conductivity of aluminum-doped ZnO: The effect of hydrogen diffusion from a hydrogenated amorphous silicon capping layer

    NARCIS (Netherlands)

    Ponomarev, M. V.; Sharma, K.; Verheijen, M. A.; M. C. M. van de Sanden,; Creatore, M.

    2012-01-01

    Plasma-deposited aluminum-doped ZnO (ZnO:Al) demonstrated a resistivity gradient as function of the film thickness, extending up to about 600 nm. This gradient decreased sharply when the ZnO:Al was capped by a hydrogenated amorphous silicon layer (a-Si:H) and subsequently treated according to the so

  20. Hydrogenated amorphous silicon p-i-n solar cells deposited under well controlled ion bombardment using pulse-shaped substrate biasing

    NARCIS (Netherlands)

    Wank, M. A.; van Swaaij, R.; R. van de Sanden,; Zeman, M.

    2012-01-01

    We applied pulse-shaped biasing (PSB) to the expanding thermal plasma deposition of intrinsic hydrogenated amorphous silicon layers at substrate temperatures of 200 degrees C and growth rates of about 1?nm/s. Fourier transform infrared spectroscopy of intrinsic films showed a densification with incr

  1. Growth and Physical Structure of Amorphous Boron Carbide Deposited by Magnetron Sputtering on a Silicon Substrate with a Titanium Interlayer

    Directory of Open Access Journals (Sweden)

    Roberto Caniello

    2013-01-01

    Full Text Available Multilayer amorphous boron carbide coatings were produced by radiofrequency magnetron sputtering on silicon substrates. To improve the adhesion, titanium interlayers with different thickness were interposed between the substrate and the coating. Above three hundreds nanometer, the enhanced roughness of the titanium led to the growth of an amorphous boron carbide with a dense and continuing columnar structure, and no delamination effect was observed. Correspondingly, the adhesion of the coating became three time stronger than in the case of a bare silicon substrate. Physical structure and microstructural proprieties of the coatings were investigated by means of a scan electron microscopy, atomic force microscopy and X-ray diffraction. The adhesion of the films was measured by a scratch tester.

  2. Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors

    Science.gov (United States)

    Nomura, Kenji; Ohta, Hiromichi; Takagi, Akihiro; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2004-11-01

    Transparent electronic devices formed on flexible substrates are expected to meet emerging technological demands where silicon-based electronics cannot provide a solution. Examples of active flexible applications include paper displays and wearable computers. So far, mainly flexible devices based on hydrogenated amorphous silicon (a-Si:H) and organic semiconductors have been investigated. However, the performance of these devices has been insufficient for use as transistors in practical computers and current-driven organic light-emitting diode displays. Fabricating high-performance devices is challenging, owing to a trade-off between processing temperature and device performance. Here, we propose to solve this problem by using a novel semiconducting material-namely, a transparent amorphous oxide semiconductor from the In-Ga-Zn-O system (a-IGZO)-for the active channel in transparent thin-film transistors (TTFTs). The a-IGZO is deposited on polyethylene terephthalate at room temperature and exhibits Hall effect mobilities exceeding 10cm2V-1s-1, which is an order of magnitude larger than for hydrogenated amorphous silicon. TTFTs fabricated on polyethylene terephthalate sheets exhibit saturation mobilities of 6-9cm2V-1s-1, and device characteristics are stable during repetitive bending of the TTFT sheet.

  3. Environmental life cycle assessment of roof-integrated flexible amorphous silicon/nanocrystalline silicon solar cell laminate

    NARCIS (Netherlands)

    N.J. Mohr; A. Meijer; M.A.J. Huijbregts; L. Reijnders

    2013-01-01

    This paper presents an environmental life cycle assessment of a roof-integrated flexible solar cell laminate with tandem solar cells composed of amorphous silicon/nanocrystalline silicon (a-Si/nc-Si). The a-Si/nc-Si cells are considered to have 10% conversion efficiency. Their expected service life

  4. A fax-machine amorphous silicon sensor for X-ray detection

    Energy Technology Data Exchange (ETDEWEB)

    Alberdi, J. [Association EURATOM/CIEMAT, Madrid (Spain); Barcala, J.M. [Association EURATOM/CIEMAT, Madrid (Spain); Chvatchkine, V. [Association EURATOM/CIEMAT, Madrid (Spain); Ioudine, I. [Association EURATOM/CIEMAT, Madrid (Spain); Molinero, A. [Association EURATOM/CIEMAT, Madrid (Spain); Navarrete, J.J. [Association EURATOM/CIEMAT, Madrid (Spain); Yuste, C. [Association EURATOM/CIEMAT, Madrid (Spain)

    1996-10-01

    Amorphous silicon detectors have been used, basically, as solar cells for energetics applications. As light detectors, linear sensors are used in fax and photocopier machines because they can be built with a large size, low price and have a high radiation hardness. Due to these performances, amorphous silicon detectors have been used as radiation detectors, and, presently, some groups are developing matrix amorphous silicon detectors with built-in electronics for medical X-ray applications. Our group has been working on the design and development of an X-ray image system based on a commercial fax linear amorphous silicon detector. The sensor scans the selected area and detects light produced by the X-ray in a scintillator placed on the sensor. Image-processing software produces a final image with better resolution and definition. (orig.).

  5. Transparent amorphous zinc oxide thin films for NLO applications

    Science.gov (United States)

    Zawadzka, A.; Płóciennik, P.; Strzelecki, J.; Sahraoui, B.

    2014-11-01

    This review focuses on the growth and optical properties of amorphous zinc oxide (ZnO) thin films. A high quality ZnO films fabricated by dip-coating (sol-gel) method were grown on quartz and glass substrates at temperature equal to 350 K. The amorphous nature of the films was verified by X-ray diffraction. Atomic Force Microscopy was used to evaluate the surface morphology of the films. The optical characteristics of amorphous thin films have been investigated in the spectral range 190-1100 nm. Measurement of the polarized optical properties was shows a high transmissivity (80-99%) and low absorptivity (<5%) in the visible and near infrared regions at different angles of incidence. Linear optical properties were investigated by classic and Time-Resolved Photoluminescence (TRPL) measurements. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. An innovative TRPL technique has enabled the measurement of the photoluminescence decay time as a function of temperature. TRPL measurements reveal a multiexponential decay behavior typical for amorphous thin films. Second and third harmonic generation measurements were performed by means of the rotational Maker fringe technique using Nd:YAG laser at 1064 nm in picosecond regime for investigations of the nonlinear optical properties. The obtained values of second and third order nonlinear susceptibilities were found to be high enough for the potential applications in the optical switching devices based on refractive index changes. Presented spectra confirm high structural and optical quality of the investigated zinc oxide thin films.

  6. High-Sensitivity X-ray Polarimetry with Amorphous Silicon Active-Matrix Pixel Proportional Counters

    Science.gov (United States)

    Black, J. K.; Deines-Jones, P.; Jahoda, K.; Ready, S. E.; Street, R. A.

    2003-01-01

    Photoelectric X-ray polarimeters based on pixel micropattern gas detectors (MPGDs) offer order-of-magnitude improvement in sensitivity over more traditional techniques based on X-ray scattering. This new technique places some of the most interesting astronomical observations within reach of even a small, dedicated mission. The most sensitive instrument would be a photoelectric polarimeter at the focus of 2 a very large mirror, such as the planned XEUS. Our efforts are focused on a smaller pathfinder mission, which would achieve its greatest sensitivity with large-area, low-background, collimated polarimeters. We have recently demonstrated a MPGD polarimeter using amorphous silicon thin-film transistor (TFT) readout suitable for the focal plane of an X-ray telescope. All the technologies used in the demonstration polarimeter are scalable to the areas required for a high-sensitivity collimated polarimeter. Leywords: X-ray polarimetry, particle tracking, proportional counter, GEM, pixel readout

  7. Image quality vs. radiation dose for a flat-panel amorphous silicon detector: a phantom study.

    Science.gov (United States)

    Geijer, H; Beckman, K W; Andersson, T; Persliden, J

    2001-01-01

    The aim of this study was to investigate the image quality for a flat-panel amorphous silicon detector at various radiation dose settings and to compare the results with storage phosphor plates and a screen-film system. A CDRAD 2.0 contrast-detail phantom was imaged with a flat-panel detector (Philips Medical Systems, Eindhoven, The Netherlands) at three different dose levels with settings for intravenous urography. The same phantom was imaged with storage phosphor plates at a simulated system speed of 200 and a screen-film system with a system speed of 160. Entrance surface doses were recorded for all images. At each setting, three images were read by four independent observers. The flat-panel detector had equal image quality at less than half the radiation dose compared with storage phosphor plates. The difference was even larger when compared with film with the flat-panel detector having equal image quality at approximately one-fifth the dose. The flat-panel detector has a very favourable combination of image quality vs radiation dose compared with storage phosphor plates and screen film.

  8. Image quality vs radiation dose for a flat-panel amorphous silicon detector: a phantom study

    Energy Technology Data Exchange (ETDEWEB)

    Geijer, H.; Andersson, T. [Dept. of Radiology, Oerebro Medical Centre Hospital (Sweden); Beckman, K.W.; Persliden, J. [Dept. of Medical Physics, Oerebro Medical Centre Hospital (Sweden)

    2001-09-01

    The aim of this study was to investigate the image quality for a flat-panel amorphous silicon detector at various radiation dose settings and to compare the results with storage phosphor plates and a screen-film system. A CDRAD 2.0 contrast-detail phantom was imaged with a flat-panel detector (Philips Medical Systems, Eindhoven, The Netherlands) at three different dose levels with settings for intravenous urography. The same phantom was imaged with storage phosphor plates at a simulated system speed of 200 and a screen-film system with a system speed of 160. Entrance surface doses were recorded for all images. At each setting, three images were read by four independent observers. The flat-panel detector had equal image quality at less than half the radiation dose compared with storage phosphor plates. The difference was even larger when compared with film with the flat-panel detector having equal image quality at approximately one-fifth the dose. The flat-panel detector has a very favourable combination of image quality vs radiation dose compared with storage phosphor plates and screen film. (orig.)

  9. Sputtering deposition and characterization of ultrathin amorphous carbon films

    Science.gov (United States)

    Lu, Wei

    1999-11-01

    This dissertation focuses on experimental investigations of ultrathin, ultrasmooth amorphous carbon (a-C) films deposited on Si(100) substrates by radio frequency (RF) sputtering and characterization of the nanomechanical and nanotribological properties and thermal stability of the films. Ultrathin a-C films of thickness 5--100 nm and typical root-mean-square roughness of 0.15--1 nm were deposited on ultrasmooth Si(100) substrates using pure argon as the sputtering gas. A low-pressure RF argon discharge model was used to analyze the plasma parameters in the film growth environment. These plasma parameters correlate the deposition conditions with the film growth processes. Atomic force microscopy (AFM) and surface force microscopy (SFM) were used to characterize the nanomechanical and nanotribological properties of the a-C films. X-ray photoelectron spectroscopy (XPS) was used to investigate the compositions and microstructures of the films. Sputter-etching measurements of the a-C films by energetic argon ion bombardment were used to study the surface binding energy of carbon atoms in a-C films deposited under different conditions. The dependence of film properties on deposition conditions was studied, and relations between nanomechanical and nanotribological properties were discussed in terms of a modified deformation index. The deformation and nanotribology mechanisms of the a-C films were compared with those of other films, such as TiC and Cr films (both 100 nm thick), and bulk Si(100). Reactive RF sputtering of nitrogenated amorphous carbon (a-CNx) films was investigated by introducing nitrogen into the a-C films during film growth by using an argon-nitrogen gas mixture as the sputtering gas. The alloying effect of nitrogen on the film growth and properties, such as hardness and surface energy, was studied and interpreted in terms of the changes in the plasma environment induced due to differences in the composition of the sputtering gas mixture. The thermal

  10. Research on fabrication technology for thin film solar cells for practical use. Research on low-cost fabrication technology for large-area modules (production technology for amorphous silicon solar cell modules); Usumaku taiyo denchi seizo gijutsu no jitsuyoka kenkyu. Daimenseki module no tei cost seizo gijutsu (amorphous taiyo denchi module seizo no gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    Tatsuta, M. [New Energy and Industrial Technology Development Organization, Tokyo (Japan)

    1994-12-01

    This paper reports the study results on the fabrication technology of amorphous Si solar cell modules in fiscal 1994. (1) On process technology for prototype film substrate solar cells, an advanced preprocessing equipment for film substrates, stepping roll type film forming technology, and prototype submodules were studied. A conversion efficiency of 7.2% was achieved by use of the submodule formed in an effective region of 40 {times} 40cm{sup 2}. (2) On efficiency improvement technology for film substrate solar cells, p/i and n/i interfaces, forming condition for Ag film electrodes, film thickness of transparent electrode ITO, and optimum transmissivity were studied. (3) On technology for advanced solar cells, high-quality a-SiGe: H film, ion control in plasma CVD, and a-Si film formation by plasma CVD using SiH2Cl2 were studied as production technology of narrow gap materials. (4) On advanced two-layer tandem solar cells, the defect density in optical degradation of a-Si cells by reverse bias dark current was evaluated, and outdoor exposure data were analyzed. 4 figs., 1 tab.

  11. Optimization of large amorphous silicon and silica structures for molecular dynamics simulations of energetic impacts

    Energy Technology Data Exchange (ETDEWEB)

    Samela, Juha, E-mail: juha.samela@helsinki.fi [Department of Physics and Helsinki Institute of Physics, University of Helsinki, P.O. Box 43, FI-00014 University of Helsinki (Finland); Norris, Scott A. [Southern Methodist University, Dallas, TX 75205 (United States); Nordlund, Kai [Department of Physics and Helsinki Institute of Physics, University of Helsinki, P.O. Box 43, FI-00014 University of Helsinki (Finland); Aziz, Michael J. [School of Engineering and Applied Sciences, Harvard University, 29 Oxford St., Cambridge, MA 02138 (United States)

    2011-07-15

    A practical method to create optimized amorphous silicon and silica structures for molecular dynamics simulations is developed and tested. The method is based on the Wooten, Winer, and Weaire algorithm and combination of small optimized blocks to larger structures. The method makes possible to perform simulations of either very large cluster hypervelocity impacts on amorphous targets or small displacements induced by low energy ion impacts in silicon.

  12. Spectroscopic Ellipsometry Studies of n-i-p Hydrogenated Amorphous Silicon Based Photovoltaic Devices

    Directory of Open Access Journals (Sweden)

    Laxmi Karki Gautam

    2016-02-01

    Full Text Available Optimization of thin film photovoltaics (PV relies on characterizing the optoelectronic and structural properties of each layer and correlating these properties with device performance. Growth evolution diagrams have been used to guide production of materials with good optoelectronic properties in the full hydrogenated amorphous silicon (a-Si:H PV device configuration. The nucleation and evolution of crystallites forming from the amorphous phase were studied using in situ near-infrared to ultraviolet spectroscopic ellipsometry during growth of films prepared as a function of hydrogen to reactive gas flow ratio R = [H2]/[SiH4]. In conjunction with higher photon energy measurements, the presence and relative absorption strength of silicon-hydrogen infrared modes were measured by infrared extended ellipsometry measurements to gain insight into chemical bonding. Structural and optical models have been developed for the back reflector (BR structure consisting of sputtered undoped zinc oxide (ZnO on top of silver (Ag coated glass substrates. Characterization of the free-carrier absorption properties in Ag and the ZnO + Ag interface as well as phonon modes in ZnO were also studied by spectroscopic ellipsometry. Measurements ranging from 0.04 to 5 eV were used to extract layer thicknesses, composition, and optical response in the form of complex dielectric function spectra (ε = ε1 + iε2 for Ag, ZnO, the ZnO + Ag interface, and undoped a-Si:H layer in a substrate n-i-p a-Si:H based PV device structure.

  13. Laser assisted patterning of hydrogenated amorphous silicon for interdigitated back contact silicon heterojunction solar cell

    Science.gov (United States)

    De Vecchi, S.; Desrues, T.; Souche, F.; Muñoz, D.; Lemiti, M.

    2012-10-01

    This work reports on the elaboration of a new industrial process based on laser selective ablation of dielectric layers for Interdigitated Back Contact Silicon Heterojunction (IBC Si-HJ) solar cells fabrication. Choice of the process is discussed and cells are processed to validate its performance. A pulsed green laser (515nm) with 10-20ns pulse duration is used for hydrogenated amorphous silicon (a-Si:H) layers patterning steps, whereas metallization is made by screen printed. High Open-Circuit Voltage (Voc=699mV) and Fill Factor (FF=78.5%) values are obtained simultaneously on IBC Si-HJ cells, indicating a high surface passivation level and reduced resistive losses. An efficiency of 19% on non textured 26 cm² solar cells has been reached with this new industrial process.

  14. Microcrystalline B-doped window layers prepared near amorphous to microcrystalline transition by HWCVD and its application in amorphous silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, P. [Department of Physics/Center of Optical Technologies and Laser Controlled Processes, University of Kaiserslautern, P.O. Box 3049, Kaiserslautern D-67653 (Germany)]. E-mail: kumarp@rhrk.uni-kl.de; Kupich, M. [Department of Physics/Center of Optical Technologies and Laser Controlled Processes, University of Kaiserslautern, P.O. Box 3049, Kaiserslautern D-67653 (Germany); Grunsky, D. [Department of Physics/Center of Optical Technologies and Laser Controlled Processes, University of Kaiserslautern, P.O. Box 3049, Kaiserslautern D-67653 (Germany); Schroeder, B. [Department of Physics/Center of Optical Technologies and Laser Controlled Processes, University of Kaiserslautern, P.O. Box 3049, Kaiserslautern D-67653 (Germany)

    2006-04-20

    The electronic and structural properties of p-type microcrystalline silicon films prepared near the microcrystalline to amorphous ({mu}c-amorphous) transition by hot-wire chemical vapor deposition are studied. Silane is used as a source gas while H{sub 2} as diluent and trimethylboron (TMB) and boron trifluoride (BF{sub 3}) as doping gases. Increasing TMB concentration from 0.01% to 5% favors the amorphous growth whereas for BF{sub 3} the crystalline fraction remains constant. The dark conductivity ({sigma} {sub d}) of {mu}c-Si:H p-layers remains approximately constant for TMB 1-5% at constant crystalline fraction X {sub c}. This dark conductivity behavior is attributed to the decrease in doping efficiency with increasing TMB concentration. The best initial efficiency obtained for a 400 nm amorphous pin solar cell with optimized {mu}c-Si:H p-layer is 7.7% (V {sub oc} = 874 mV, J {sub sc} = 12.91 mA/cm{sup 2}, FF = 68%)

  15. Electron beam recrystallization of amorphous semiconductor materials

    Science.gov (United States)

    Evans, J. C., Jr.

    1968-01-01

    Nucleation and growth of crystalline films of silicon, germanium, and cadmium sulfide on substrates of plastic and glass were investigated. Amorphous films of germanium, silicon, and cadmium sulfide on amorphous substrates of glass and plastic were converted to the crystalline condition by electron bombardment.

  16. Carrier transport in amorphous silicon utilizing picosecond photoconductivity

    Science.gov (United States)

    Johnson, A. M.

    1981-08-01

    The development of a high-speed electronic measurement capability permitted the direct observation of the transient photoresponse of amorphous silicon (a-Si) with a time resolution of approximately 10ps. This technique was used to measure the initial mobility of photogenerated (2.1eV) free carriers in three types of a-Si having widely different densities of structural defects (i.e., as prepared by: (1) RF glow discharge (a-Si:H); (2) chemical vapor deposition; and (3) evaporation in ultra-high vacuum). In all three types of a-Si, the same initial mobility of approximately 1 cu cm/Vs at room temperature was found. This result tends to confirm the often-made suggestion that the free carrier mobility is determined by the influence of shallow states associated with the disorder in the random atomic network, and is an intrinsic property of a-Si which is unaffected by the method of preparation. The rate of decay of the photocurrent correlates with the density of structural defects and varies from 4ps to 200ps for the three types of a-Si investigated. The initial mobility of a-Si:H was found to be thermally activated. The possible application of extended state transport controlled by multiple trapping and small polaron formation is discussed.

  17. Nanohole Structuring for Improved Performance of Hydrogenated Amorphous Silicon Photovoltaics.

    Science.gov (United States)

    Johlin, Eric; Al-Obeidi, Ahmed; Nogay, Gizem; Stuckelberger, Michael; Buonassisi, Tonio; Grossman, Jeffrey C

    2016-06-22

    While low hole mobilities limit the current collection and efficiency of hydrogenated amorphous silicon (a-Si:H) photovoltaic devices, attempts to improve mobility of the material directly have stagnated. Herein, we explore a method of utilizing nanostructuring of a-Si:H devices to allow for improved hole collection in thick absorber layers. This is achieved by etching an array of 150 nm diameter holes into intrinsic a-Si:H and then coating the structured material with p-type a-Si:H and a conformal zinc oxide transparent conducting layer. The inclusion of these nanoholes yields relative power conversion efficiency (PCE) increases of ∼45%, from 7.2 to 10.4% PCE for small area devices. Comparisons of optical properties, time-of-flight mobility measurements, and internal quantum efficiency spectra indicate this efficiency is indeed likely occurring from an improved collection pathway provided by the nanostructuring of the devices. Finally, we estimate that through modest optimizations of the design and fabrication, PCEs of beyond 13% should be obtainable for similar devices.

  18. Experiment and Simulation Study on the Amorphous Silicon Photovoltaic Walls

    Directory of Open Access Journals (Sweden)

    Wenjie Zhang

    2014-01-01

    Full Text Available Based on comparative study on two amorphous silicon photovoltaic walls (a-Si PV walls, the temperature distribution and the instant power were tested; and with EnergyPlus software, similar models of the walls were built to simulate annual power generation and air conditioning load. On typical sunshine day, the corresponding position temperature of nonventilated PV wall was generally 0.5~1.5°C higher than that of ventilated one, while the power generation was 0.2%~0.4% lower, which was consistent with the simulation results with a difference of 0.41% in annual energy output. As simulation results, in summer, comparing the PV walls with normal wall, the heat per unit area of these two photovoltaic walls was 5.25 kWh/m2 (nonventilated and 0.67 kWh/m2 (ventilated higher, respectively. But in winter the heat loss of nonventilated one was smaller, while ventilated PV wall was similar to normal wall. To annual energy consumption of heating and cooling, the building with ventilated PV wall and normal wall was also similar but slightly better than nonventilated one. Therefore, it is inferred that, at low latitudes, such as Zhuhai, China, air gap ventilation is suitable, while the length to thickness ratio of the air gap needs to be taken into account.

  19. Diffusion of Gold and Platinum in Amorphous Silicon

    CERN Multimedia

    Voss, T L

    2002-01-01

    By means of radiotracer experiments the diffusion of Au and Pt in radio-frequency-sputtered amorphous silicon (a-Si) was investigated. Specimens of a-Si with homogeneous doping concentrations of Au or Pt in the range 0$\\, - \\,$1,7~at.\\% were produced by co-sputtering of Si and Au or Pt, respectively. An additional tiny concentration of radioactive $^{195}$Au or $^{188}$Pt, about 10~at.ppm, was implanted at ISOLDE. The resulting Gaussian distribution of the implanted atoms served as a probe for measuring diffusion coefficients at various doping concentrations. It was found that for a given doping concentration the diffusion coefficients show Arrhenius-type temperature dependences, where the diffusion enthalpy and the pre-exponential factor depend on the doping concentration. From these results it was concluded that in a-Si Au and Pt undergo direct, interstitial-like diffusion that is retarded by temporary trapping of the radiotracer atoms at vacancy-type defects with different binding enthalpies. In the case o...

  20. Hot wire deposited hydrogenated amorphous silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Mahan, A.H.; Iwaniczko, E.; Nelson, B.P.; Reedy, R.C. Jr.; Crandall, R.S. [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    This paper details the results of a study in which low H content, high deposition rate hot wire (HW) deposited amorphous silicon (a-Si:H) has been incorporated into a substrate solar cell. The authors find that the treatment of the top surface of the HW i layer while it is being cooled from its high deposition temperature is crucial to device performance. They present data concerning these surface treatments, and correlate these treatments with Schottky device performance. The authors also present first generation HW n-i-p solar cell efficiency data, where a glow discharge (GD) {mu}c-Si(p) layer was added to complete the partial devices. No light trapping layer was used to increase the device Jsc. Their preliminary investigations have yielded efficiencies of up to 6.8% for a cell with a 4000 {Angstrom} thick HW i-layer, which degrade less than 10% after a 900 hour light soak. The authors suggest avenues for further improvement of their devices.

  1. Ultrafast carrier dynamics and the role of grain boundaries in polycrystalline silicon thin films grown by molecular beam epitaxy

    Science.gov (United States)

    Titova, Lyubov V.; Cocker, Tyler L.; Xu, Sijia; Baribeau, Jean-Marc; Wu, Xiaohua; Lockwood, David J.; Hegmann, Frank A.

    2016-10-01

    We have used time-resolved terahertz spectroscopy to study microscopic photoconductivity and ultrafast photoexcited carrier dynamics in thin, pure, non-hydrogenated silicon films grown by molecular beam epitaxy on quartz substrates at temperatures ranging from 335 °C to 572 °C. By controlling the growth temperature, thin silicon films ranging from completely amorphous to polycrystalline with minimal amorphous phase can be achieved. Film morphology, in turn, determines its photoconductive properties: in the amorphous phase, carriers are trapped in bandtail states on sub-picosecond time scales, while the carriers excited in crystalline grains remain free for tens of picoseconds. We also find that in polycrystalline silicon the photoexcited carrier mobility is carrier-density-dependent, with higher carrier densities mitigating the effects of grain boundaries on inter-grain transport. In a film grown at the highest temperature of 572 °C, the morphology changes along the growth direction from polycrystalline with needles of single crystals in the bulk of the film to small crystallites interspersed with amorphous silicon at the top of the film. Depth profiling using different excitation wavelengths shows corresponding differences in the photoconductivity: the photoexcited carrier lifetime and mobility are higher in the first 100-150 nm from the substrate, suggesting that thinner, low-temperature grown polycrystalline silicon films are preferable for photovoltaic applications.

  2. Amorphization and reduction of thermal conductivity in porous silicon by irradiation with swift heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Newby, Pascal J. [Institut des Nanotechnologies de Lyon, Universite de Lyon, INL-UMR5270, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Institut Interdisciplinaire d' Innovation Technologique (3IT), Universite de Sherbrooke, CNRS UMI-LN2, Sherbrooke, Quebec J1K0A5 (Canada); Canut, Bruno; Bluet, Jean-Marie; Lysenko, Vladimir [Institut des Nanotechnologies de Lyon, Universite de Lyon, INL-UMR5270, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Gomes, Severine [Centre de Thermique de Lyon, Universite de Lyon, CETHIL-UMR5008, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Isaiev, Mykola; Burbelo, Roman [Faculty of Physics, Taras Shevchenko National University of Kyiv, 64/13, Volodymyrs' ka St., Kyiv 01601 (Ukraine); Termentzidis, Konstantinos [Laboratoire LEMTA, Universite de Lorraine-CNRS UMR 7563, 54506 Vandoeuvre-les-Nancy cedex (France); Chantrenne, Patrice [Universite de Lyon, INSA de Lyon, MATEIS-UMR CNRS 5510, Villeurbanne 69621 (France); Frechette, Luc G. [Institut Interdisciplinaire d' Innovation Technologique (3IT), Universite de Sherbrooke, CNRS UMI-LN2, Sherbrooke, Quebec J1K0A5 (Canada)

    2013-07-07

    In this article, we demonstrate that the thermal conductivity of nanostructured porous silicon is reduced by amorphization and also that this amorphous phase in porous silicon can be created by swift (high-energy) heavy ion irradiation. Porous silicon samples with 41%-75% porosity are irradiated with 110 MeV uranium ions at six different fluences. Structural characterisation by micro-Raman spectroscopy and SEM imaging show that swift heavy ion irradiation causes the creation of an amorphous phase in porous Si but without suppressing its porous structure. We demonstrate that the amorphization of porous silicon is caused by electronic-regime interactions, which is the first time such an effect is obtained in crystalline silicon with single-ion species. Furthermore, the impact on the thermal conductivity of porous silicon is studied by micro-Raman spectroscopy and scanning thermal microscopy. The creation of an amorphous phase in porous silicon leads to a reduction of its thermal conductivity, up to a factor of 3 compared to the non-irradiated sample. Therefore, this technique could be used to enhance the thermal insulation properties of porous Si. Finally, we show that this treatment can be combined with pre-oxidation at 300 Degree-Sign C, which is known to lower the thermal conductivity of porous Si, in order to obtain an even greater reduction.

  3. Amorphous to nanocrystalline transition in HWCVD Si:H films by substrate temperature variation

    Energy Technology Data Exchange (ETDEWEB)

    Gogoi, Purabi; Jha, Himanshu S.; Agarwal, Pratima [Department of Physics, IIT Guwahati, Guwahati (India); Deva, Dinesh [Department of Chemical Engineering, IIT Kanpur, Kanpur (India)

    2010-04-15

    Thin films of hydrogenated silicon with band gap ranging from 2.0-2.34 eV are prepared at deposition rate 8-14A/sec in an indigenously fabricated HWCVD system keeping all parameters except substrate temperature fixed. The films grown at T{sub s}{<=}150 C are found to be pure amorphous, whereas the formation of nanocrystalline phase starts at T{sub s} {>=} 200 C. With increase in T{sub s}, crystalline fraction increases along with the increase in the band gap whereas the hydrogen content in the films and the deposition rate decreases. The variation of microstructure by varying substrate temperature without a significant decrease in deposition rate is useful for various device applications. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Studies of silicon carbide and silicon carbide nitride thin films

    Science.gov (United States)

    Alizadeh, Zhila

    Silicon carbide semiconductor technology is continuing to advance rapidly. The excellent physical and electronic properties of silicon carbide recently take itself to be the main focused power device material for high temperature, high power, and high frequency electronic devices because of its large band gap, high thermal conductivity, and high electron saturation drift velocity. SiC is more stable than Si because of its high melting point and mechanical strength. Also the understanding of the structure and properties of semiconducting thin film alloys is one of the fundamental steps toward their successful application in technologies requiring materials with tunable energy gaps, such as solar cells, flat panel displays, optical memories and anti-reflecting coatings. Silicon carbide and silicon nitrides are promising materials for novel semiconductor applications because of their band gaps. In addition, they are "hard" materials in the sense of having high elastic constants and large cohesive energies and are generally resistant to harsh environment, including radiation. In this research, thin films of silicon carbide and silicon carbide nitride were deposited in a r.f magnetron sputtering system using a SiC target. A detailed analysis of the surface chemistry of the deposited films was performed using x-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy whereas structure and morphology was studied atomic force microscopy (AFM), and nonoindentation.

  5. Preparation of fine silicon particles from amorphous silicon monoxide by the disproportionation reaction

    Science.gov (United States)

    Mamiya, Mikito; Takei, Humihiko; Kikuchi, Masae; Uyeda, Chiaki

    2001-07-01

    Fine Si particles have been prepared by the disproportionation reaction of silicon monoxide (SiO), that is: 2SiO→Si+SiO 2. Amorphous powders of SiO are heated between 900°C and 1400°C in a flow of Ar and the obtained specimens are analyzed by X-ray powder diffraction and high-resolution transmission electron microscopy. The treatments between 1000°C and 1300°C for more than 0.5 h result in origination of Si particles dispersed in amorphous oxide media. The particle size varies from 1-3 to 20-40 nm, depending on the heating temperature. Kinetic analyses of the reaction reveal that the activation energy is 1.1 eV (82.1 kJ mol -1). The specimens annealed above 1350°C changes into a mixture of Si and cristobalite, suggesting a solid state transformation in the surrounding oxides from the amorphous to crystalline states.

  6. Realistic inversion of diffraction data for an amorphous solid: The case of amorphous silicon

    Science.gov (United States)

    Pandey, Anup; Biswas, Parthapratim; Bhattarai, Bishal; Drabold, D. A.

    2016-12-01

    We apply a method called "force-enhanced atomic refinement" (FEAR) to create a computer model of amorphous silicon (a -Si) based upon the highly precise x-ray diffraction experiments of Laaziri et al. [Phys. Rev. Lett. 82, 3460 (1999), 10.1103/PhysRevLett.82.3460]. The logic underlying our calculation is to estimate the structure of a real sample a -Si using experimental data and chemical information included in a nonbiased way, starting from random coordinates. The model is in close agreement with experiment and also sits at a suitable energy minimum according to density-functional calculations. In agreement with experiments, we find a small concentration of coordination defects that we discuss, including their electronic consequences. The gap states in the FEAR model are delocalized compared to a continuous random network model. The method is more efficient and accurate, in the sense of fitting the diffraction data, than conventional melt-quench methods. We compute the vibrational density of states and the specific heat, and we find that both compare favorably to experiments.

  7. Amorphous hafnium-indium-zinc oxide semiconductor thin film transistors

    Science.gov (United States)

    Kim, Chang-Jung; Kim, Sangwook; Lee, Je-Hun; Park, Jin-Seong; Kim, Sunil; Park, Jaechul; Lee, Eunha; Lee, Jaechul; Park, Youngsoo; Kim, Joo Han; Shin, Sung Tae; Chung, U.-In

    2009-12-01

    We developed amorphous hafnium-indium-zinc oxide (HIZO) thin films as oxide semiconductors and investigated the films electrically and physically. Adding of hafnium (Hf) element can suppress growing the columnar structure and drastically decrease the carrier concentration and hall mobility in HIZO films. The thin film transistors (TFTs) with amorphous HIZO active channel exhibit good electrical properties with field effect mobility of around 10 cm2/Vs, S of 0.23 V/decade, and high Ion/off ratio of over 108, enough to operate the next electronic devices. In particular, under bias-temperature stress test, the HIZO TFTs with 0.3 mol % (Hf content) showed only 0.46 V shift in threshold voltage, compared with 3.25 V shift in HIZO TFT (0.1 mol %). The Hf ions may play a key role to improve the instability of TFTs due to high oxygen bonding ability. Therefore, the amorphous HIZO semiconductor will be a prominent candidate as an operation device for large area electronic applications.

  8. Preparation of microcrystalline single junction and amorphous-microcrystalline tandem silicon solar cells entirely by hot-wire CVD

    Energy Technology Data Exchange (ETDEWEB)

    Kupich, M.; Grunsky, D.; Kumar, P.; Schroeder, B. [University of Kaiserslautern (Germany). Department of Physics

    2004-01-25

    The hot-wire chemical vapour deposition (HWCVD) has been used to prepare highly conducting p- and n-doped microcrystalline silicon thin layers as well as highly photoconducting, low defect density intrinsic microcrystalline silicon films. These films were incorporated in all-HWCVD, all-microcrystalline nip and pin solar cells, achieving conversion efficiencies of {eta}=5.4% and 4.5%, respectively. At present, only the nip-structures are found to be stable against light-induced degradation. Furthermore, microcrystalline nip and pin structures have been successfully incorporated as bottom cells in all-hot-wire amorphous-microcrystalline nipnip- and pinpin-tandem solar cells for the first time. So far, the highest conversion efficiencies of the 'micromorph' tandem structures are {eta}=5.7% for pinpin-solar cells and 7.0% for nipnip solar cells. (author)

  9. Amorphous thin films for solar cell application. Final technical report, March 15, 1979-February 29, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Jonath, A D; Anderson, W W; Crowley, J L; MacMillan, H F; Junga, F A; Knudsen, J F; Monahan, K M; Thornton, J A

    1980-03-01

    Magnetron sputtering, a deposition method in which magnetic confinement of a plasma encourages high deposition rates at low working gas partial pressures, is under investigation in this program as a candidate production technology for large-scale manufacture of high-efficiency, thin-film amorphous silicon solar photovoltaic cells. The approach uses two dc magnetron geometries: (1) a low-cost planar magnetron (PM) system for exploratory and detailed examination of deposition parameter space; and (2) a cylindrical magnetron (CM) system, scalable to production sizes, for deposition of homogeneous films over large areas. Detailed descriptions of these two systems are included. During this first-year effort, amorphous silicon films and device structures were sputtered in both PM and CM systems under a wide range of deposition conditions (i.e., T/sub s/, P/sub Ar/, P/sub H/sub 2//) using both doped and undoped sputter targets. Measured electrical and optical film properties indicate that control over a wide range of conductivity, photoconductivity, conductivity activation energy, and optical and infrared absorption behavior is achievable. Multiple depositions to fabricate simple MIS device structures and simultaneously to deposit monitor samples of individual constituent layers have been successful. Other program highlights are: (1) deposition rates as great as 1500 A/min were achieved in high-power dc magnetron operation at practical substrate-target spacings; (2) p-type and n-type a-Si:H consistently deposited from p- and n-type targets, respectively; (3) demonstrated correlation of argon and hydrogen partial pressure variations with optical, electronic, and structural properties of magnetron-sputtered a-Si:H films; and (4) initial depositions have achieved properties comparable to those in films made by rf sputtering and glow-discharge methods.

  10. Amorphous carbon buffer layers for separating free gallium nitride films

    Science.gov (United States)

    Altakhov, A. S.; Gorbunov, R. I.; Kasharina, L. A.; Latyshev, F. E.; Tarala, V. A.; Shreter, Yu. G.

    2016-11-01

    The possibility of using amorphous diamond-like carbon (DLC) films for self-separation of gallium nitride (GaN) layers grown by hydride vapor-phase epitaxy has been analyzed. DLC films have been synthesized by plasma-enhanced chemical vapor deposition under low pressure on sapphire (Al2O3) substrates with a (0001) crystallographic orientation. The samples have been studied by the methods of Raman scattering and X-ray diffraction analysis. It is shown that thin DLC films affect only slightly the processes of nucleation and growth of gallium nitride films. Notably, the strength of the "GaN film-Al2O3" substrate interface decreases, which facilitates separation of the GaN layers.

  11. Raman spectra of amorphous carbon films deposited by SWP

    Science.gov (United States)

    Xu, Junqi; Liu, Weiguo; Hang, Lingxia; Su, Junhong; Fan, Huiqing

    2010-10-01

    Amorphous carbon film is one of the most important anti-reflection protective films coated on infrared optical components. In this paper, hydrogen-free amorphous carbon films were deposited by new type surface-wave-sustained plasma (SWP) source with a graphite target at various experiment parameters. The laser Raman spectroscopy at wavelength of 514 nm was used to investigate the structure and bonding of these carbon films. The results showed consanguineous correlations between the intensity ratio ID/IG and the experiment parameters such as microwave power, target voltage and gas pressure applied to the SWP source. Raman spectra proved the structure of these carbon films prepared by SWP technique is typical diamond-like carbon (DLC). The analysis on G peak position and intensity ratio ID/IG indicated that Raman shifts moves to low wavenumber and ID/IG decreases with the increasing of microwave power from 150 W to 330 W. These results means the formation of sp3 bond prefers higher microwave power. DLC films prepared at target voltage of -200 V have higher sp3 content than that of -350 V, moreover, an increase of gas pressure during experiments yields higher sp3 content at the microwave power below 270 W, whereas the change of sp3 content is slight with the various conditions when microwave power exceeds 270 W.

  12. Hydrogenated Amorphous Silicon Sensor Deposited on Integrated Circuit for Radiation Detection

    CERN Document Server

    Despeisse, M; Jarron, P; Kaplon, J; Moraes, D; Nardulli, A; Powolny, F; Wyrsch, N

    2008-01-01

    Radiation detectors based on the deposition of a 10 to 30 mum thick hydrogenated amorphous silicon (a-Si:H) sensor directly on top of integrated circuits have been developed. The performance of this detector technology has been assessed for the first time in the context of particle detectors. Three different circuits were designed in a quarter micron CMOS technology for these studies. The so-called TFA (Thin-Film on ASIC) detectors obtained after deposition of a-Si:H sensors on the developed circuits are presented. High internal electric fields (104 to 105 V/cm) can be built in the a-Si:H sensor and overcome the low mobility of electrons and holes in this amorphous material. However, the deposited sensor's leakage current at such fields turns out to be an important parameter which limits the performance of a TFA detector. Its detailed study is presented as well as the detector's pixel segmentation. Signal induction by generated free carrier motion in the a-Si:H sensor has been characterized using a 660 nm pul...

  13. Electronic properties of embedded graphene: doped amorphous silicon/CVD graphene heterostructures

    Science.gov (United States)

    Arezki, Hakim; Boutchich, Mohamed; Alamarguy, David; Madouri, Ali; Alvarez, José; Cabarrocas, Pere Roca i.; Kleider, Jean-Paul; Yao, Fei; Lee, Young Hee

    2016-10-01

    Large-area graphene film is of great interest for a wide spectrum of electronic applications, such as field effect devices, displays, and solar cells, among many others. Here, we fabricated heterostructures composed of graphene (Gr) grown by chemical vapor deposition (CVD) on copper substrate and transferred to SiO2/Si substrates, capped by n- or p-type doped amorphous silicon (a-Si:H) deposited by plasma-enhanced chemical vapor deposition. Using Raman scattering we show that despite the mechanical strain induced by the a-Si:H deposition, the structural integrity of the graphene is preserved. Moreover, Hall effect measurements directly on the embedded graphene show that the electronic properties of CVD graphene can be modulated according to the doping type of the a-Si:H as well as its phase i.e. amorphous or nanocrystalline. The sheet resistance varies from 360 Ω sq-1 to 1260 Ω sq-1 for the (p)-a-Si:H/Gr (n)-a-Si:H/Gr, respectively. We observed a temperature independent hole mobility of up to 1400 cm2 V-1 s-1 indicating that charge impurity is the principal mechanism limiting the transport in this heterostructure. We have demonstrated that embedding CVD graphene under a-Si:H is a viable route for large scale graphene based solar cells or display applications.

  14. Amorphous Hafnium-Indium-Zinc Oxide Semiconductor Thin Film Transistors

    Directory of Open Access Journals (Sweden)

    Sheng-Po Chang

    2012-01-01

    Full Text Available We reported on the performance and electrical properties of co-sputtering-processed amorphous hafnium-indium-zinc oxide (α-HfIZO thin film transistors (TFTs. Co-sputtering-processed α-HfIZO thin films have shown an amorphous phase in nature. We could modulate the In, Hf, and Zn components by changing the co-sputtering power. Additionally, the chemical composition of α-HfIZO had a significant effect on reliability, hysteresis, field-effect mobility (μFE, carrier concentration, and subthreshold swing (S of the device. Our results indicated that we could successfully and easily fabricate α-HfIZO TFTs with excellent performance by the co-sputtering process. Co-sputtering-processed α-HfIZO TFTs were fabricated with an on/off current ratio of ~106, higher mobility, and a subthreshold slope as steep as 0.55 V/dec.

  15. Elastic properties of amorphous thin films studied by Rayleigh waves

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, R.B.; Rubin, J.B.

    1993-08-01

    Physical vapor deposition in ultra-high vacuum was used to co-deposit nickel and zirconium onto quartz single crystals and grow amorphous Ni{sub 1-x}Zr{sub x} (0.1 < x < 0.87) thin film. A high-resolution surface acoustic wave technique was developed for in situ measurement of film shear moduli. The modulus has narrow maxima at x = 0. 17, 0.22, 0.43, 0.5, 0.63, and 0.72, reflecting short-range ordering and formation of aggregates in amorphous phase. It is proposed that the aggregates correspond to polytetrahedral atom arrangements limited in size by geometrical frustration.

  16. Crystallization of amorphous Co-Nb-Zr sputtered films

    Energy Technology Data Exchange (ETDEWEB)

    Battezzati, L.; Baricco, M.; Attina, P.

    1986-08-01

    Thermal analysis results obtained with some sputtered Co-Nb-Zr alloys are presented. Microstructural determinations at some stages of the crystallization process were made with transmission electron microscopy and the results given. Crystallization occurs over a wider temperature range than for binary Co/sub 90/Zr/sub 10/ ribbons. Binary Co-Nb films crystallize in the range 750-800K, some 10 degrees below ternary films. The presence of zirconium enhances the stability of the amorphous phase. An explanation of the results is given.

  17. Microcrystalline silicon films and solar cells investigatet by photoluminescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Merdzhanova, T.

    2005-07-01

    A systematic investigation on photoluminescence (PL) properties of microcrystalline silicon ({mu}c-Si:H) films with structural composition changing from highly crystalline to predominantly amorphous is presented. The samples were prepared by PECVD and HWCVD with different silane concentration in hydrogen (SC). By using photoluminescence in combination with Raman spectroscopy the relationship between electronic properties and the microstructure of the material is studied. The PL spectra of {mu}c-Si:H reveal a rather broad ({proportional_to}0.13 eV) featureless band at about 1 eV ('{mu}c'-Si-band). In mixed phase material of crystalline and amorphous regions, a band at about 1.3 eV with halfwidth of about 0.3 eV is found in addition to '{mu}c'-Si-band, which is attributed to the amorphous phase ('a'-Si-band). Similarly to amorphous silicon, the '{mu}c'-Si-band is assigned to recombination between electrons and holes in band tail states. An additional PL band centred at about 0.7 eV with halfwidth slightly broader than the '{mu}c'-Si-band is observed only for films prepared at high substrate temperature and it is preliminarily assigned to defect-related transitions as in polycrystalline silicon. With decreasing crystalline volume fraction, the '{mu}c'-Si-band shifts continuously to higher energies for all {mu}c-Si:H films but the linewidth of the PL spectra is almost unaffected. This is valid for all deposition conditions investigated. The results are interpreted, assuming decrease of the density of band tail states with decreasing crystalline volume fraction. A simple model is proposed to simulate PL spectra and V{sub oc} in {mu}c-Si:H solar cells as a function of temperature, based on carrier distributions in quasi-equilibrium conditions. In the model is assumed symmetric density of states distributions for electrons and holes in the conduction and the valence band tail states. The best agreement between

  18. PREPARATION AND CHARACTERIZATION OF POLY-CRYSTALLINE SILICON THIN FILM

    Institute of Scientific and Technical Information of China (English)

    Y.F. Hu; H. Shen; Z.Y. Liu; L.S. Wen

    2003-01-01

    Poly-crystalline silicon thin film has big potential of reducing the cost of solar cells.In this paper the preparation of thin film is introduced, and then the morphology of poly-crystalline thin film is discussed. On the film we developed poly-crystalline silicon thin film solar cells with efficiency up to 6. 05% without anti-reflection coating.

  19. Microstructural and Electrical Properties of ZrO2 Thin Films Prepared on silicon on Insulator with Thin Top silicon

    Institute of Scientific and Technical Information of China (English)

    章宁琳; 宋志棠; 沈勤我; 林成鲁

    2003-01-01

    Amorphous zirconia thin films were deposited directly on silicon-on-insulator (SOI) substrates with thin top silicon by ultra-high vacuum electron beam evaporation. Spreading resistance profile and scanning transmission-electron microscopy (TEM) were used to detect the interface quality and microstructure, revealing that the interface between the zirconium oxide films and top silicon was abrupt and clear. The films kept to be amorphous up to the rapid thermal temperature of 700°C for 300s, but arriving at 700°C an unknown interfacial product appeared,which was probably ZrSixOy. High frequency capacitance-voltage (C- V) characteristics at 1 MHz performed on metal-oxide-SOI structure revealed that this interfacial product exhibited good electrical properties of zirconia thin films. When the annealing temperature increased from 600°C to 700°C, flat voltage VFB changed from -2.451 to -1.741 eV, showing the improvement in the quality of the films. The cumulative region capacitance decreased from 3.058 × 10-11F to 3.012 × 10-11F, indicating increasing equivalent oxide thickness, which is in agreement with the result of high-resolution cross-sectional TEM.

  20. Thin-film crystalline silicon solar cells

    CERN Document Server

    Brendel, Rolf

    2011-01-01

    This introduction to the physics of silicon solar cells focuses on thin cells, while reviewing and discussing the current status of the important technology. An analysis of the spectral quantum efficiency of thin solar cells is given as well as a full set of analytical models. This is the first comprehensive treatment of light trapping techniques for the enhancement of the optical absorption in thin silicon films.

  1. Amorphous and microcrystalline silicon applied in very thin tandem solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Schicho, Sandra

    2011-07-28

    Thin-film solar cells are fabricated by low-cost production processes, and are therefore an alternative to conventionally used wafer solar cells based on crystalline silicon. Due to the different band gaps, tandem cells that consist of amorphous (a-Si:H) and microcrystalline ({mu}c-Si:H) single junction solar cells deposited on top of each other use the solar spectrum much more efficient than single junction solar cells. The silicon layers are usually deposited on TCO (Transparent Conductive Oxide)-coated glass and metal- or plastic foils. Compared to the CdTe and CIGS based thin-film technologies, silicon thin-film solar cells have the advantage that no limitation of raw material supply is expected and no toxic elements are used. Nevertheless, the production cost per Wattpeak is the decisive factor concerning competitiveness and can be reduced by, e.g., shorter deposition times or reduced material consumption. Both cost-reducing conceptions are simultaneously achieved by reducing the a-Si:H and {mu}c-Si:H absorber layer thicknesses in a tandem device. In the work on hand, the influence of an absorber layer thickness reduction up to 77% on the photovoltaic parameters of a-Si:H/{mu}c-Si:H tandem solar cells was investigated. An industry-oriented Radio Frequency Plasma-Enhanced Chemical Vapour Deposition (RF-PECVD) system was used to deposit the solar cells on glass substrates coated with randomly structured TCO layers. The thicknesses of top and bottom cell absorber layers were varied by adjusting the deposition time. Reduced layer thicknesses lead to lower absorption and, hence, to reduced short-circuit current densities which, however, are partially balanced by higher open-circuit voltages and fill factors. Furthermore, by using very thin amorphous top cells, the light-induced degradation decreases tremendously. Accordingly, a thickness reduction of 75% led to an efficiency loss of only 21 %. By adjusting the parameters for the deposition of a-Si:H top cells, a

  2. A study of the chemical, mechanical, and surface properties of thin films of hydrogenated amorphous carbon

    Energy Technology Data Exchange (ETDEWEB)

    Vandentop, G.J.

    1990-07-01

    Amorphous hydrogenated carbon (a-C:H) films were studied with the objective of elucidating the nucleation and growth mechanisms, and the origin of their unique physical properties. The films were deposited onto Si(100) substrates both on the powered (negatively self-biased) and on the grounded electrodes from methane in an rf plasma (13.56 MHz) at 65 mTorr and 300 to 370 K. The films produced at the powered electrode exhibited superior mechanical properties, such as high hardness. A mass spectrometer was used to identify neutral species and positive ions incident on the electrodes from the plasma, and also to measure ion energies. The effect of varying ion energy flux on the properties of a-C:H films was investigated using a novel pulsed biasing technique. It was demonstrated that ions were not the dominant deposition species as the total ion flux measured was insufficient to account for the observed deposition rate. The interface between thin films of a-C:H and silicon substrates was investigated using angle resolved x-ray photoelectron spectroscopy. A silicon carbide layer was detected at the interface of a hard a-C:H film formed at the powered electrode. At the grounded electrode, where the kinetic energy is low, no interfacial carbide layer was observed. Scanning tunneling microscopy and high energy electron energy loss spectroscopy was used to investigate the initial stages of growth of a-C:H films. On graphite substrates, films formed at the powered electrode were observed to nucleate in clusters approximately 50 {Angstrom} in diameter, while at the grounded electrode no cluster formation was observed. 58 figs.

  3. Photothermal deflection spectroscopy as characterisation method for thin film solar cells on the basis of amorphous silicon; Photothermische Deflexions-Spektroskopie als Charakterisierungsmethode fuer Duennschichtsolarzellen auf der Basis von amorphem Silizium

    Energy Technology Data Exchange (ETDEWEB)

    Hoehne, N.

    1997-09-01

    The potential of photothermal deflection spectroscopy (PDS) as a method to characterise solar cells based on amorphous silicon was studied in this thesis. It was demonstrated, how the proportions of the loss mechanisms of a solar cell under operating conditions can be obtained from PDS measurements as a function of the wavelength of the incident light. In addition, significant movement of heat sources in the layer system of the solar cell, such as the transition from absorption in the layers to absorption in the glass substrate can be detected using the phase of the PDS signal. However, detection of a change of the heat source distribution within the deposited layers of the solar cell was restricted by insufficient experimental resolution of the method. In particular, for the comparison with the experimental results, the dynamic heat transport within a layer system was simulated starting from a given heat source distribution and the expected amplitude and phase of the PDS signal was calculated. Experimental conditions were established to reach a high signal stability (1% in amplitude, 0.1 in phase) in order to resolve small phase shifts. Calibration experiments and theoretical calculations predict a phase shift of 0.35{+-}0.15 , if the heats source moves 0.4 {mu}m within the i-layer of a-Si:H PIN solar cell. However, phase shifts as a result of changes in the applied voltages, which are expected to be even smaller, could not be resolved experimentally. From PDS spectra at different voltages, the proportions of the loss mechanisms as a function of the wavelength were derived. 22 refs.

  4. 360-nm Photoluminescence from Silicon Oxide Films Embedded with Silicon Nanocrystals

    Institute of Scientific and Technical Information of China (English)

    YANG Lin-lin; GUO Heng-qun; ZENG You-hua; WANG Qi-ming

    2006-01-01

    Si-rich silicon oxide films were deposited by RF magnetron sputtering onto composite Si/SiO2 targets. After annealed at different temperature, the silicon oxide films embedded with silicon nanocrystals were obtained. The photoluminescence(PL) from the silicon oxide films embedded with silicon nanocrystals was observed at room temperature. The strong peak is at 360nm, its position is independent of the annealing temperature. The origin of the 360-nm PL in the silicon oxide films embedded with silicon nanocrystals was discussed.

  5. The optoelectronic properties of silicon films deposited by inductively coupled plasma CVD

    Energy Technology Data Exchange (ETDEWEB)

    Qin Yanli; Yan Hengqing; Li Fei; Qiao Li; Liu Qiming [Department of Physics, Lanzhou University, Lanzhou 730000 (China); He Deyan, E-mail: hedy@lzu.edu.cn [Department of Physics, Lanzhou University, Lanzhou 730000 (China)

    2010-11-15

    Hydrogenated amorphous and microcrystalline silicon films were deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD) at low substrate temperatures using H{sub 2}-diluted SiH{sub 4} as a source gas. High-density plasma generated by inductively coupled excitation facilitates the crystallization of silicon films at low temperatures, and microcrystalline silicon films were obtained at the substrate temperature as low as 180 deg. C. The columnar structure of the films becomes more and more compact with an increase of their crystallinity. The reduction of hydrogen content in the films causes a narrowing of the optical bandgap and an enhancement of the absorption with increasing the substrate temperature. The microcrystalline silicon films show two electronic transport mechanisms: one is related to the density of state distribution in the temperature region near room temperature and the other is the variable range hopping between localized electronic states close to the Fermi level below 170 K. A reasonable explanation is presented for the dependence of the optoelectronic properties on the microstructure of the silicon films. The films prepared at a substrate temperature of 300 deg. C have highly crystalline and compact columnar structure, high optical absorption coefficient and electrical conductivity, and a low hydrogen content of 3.8%.

  6. Core-shell amorphous silicon-carbon nanoparticles for high performance anodes in lithium ion batteries

    Science.gov (United States)

    Sourice, Julien; Bordes, Arnaud; Boulineau, Adrien; Alper, John P.; Franger, Sylvain; Quinsac, Axelle; Habert, Aurélie; Leconte, Yann; De Vito, Eric; Porcher, Willy; Reynaud, Cécile; Herlin-Boime, Nathalie; Haon, Cédric

    2016-10-01

    Core-shell silicon-carbon nanoparticles are attractive candidates as active material to increase the capacity of Li-ion batteries while mitigating the detrimental effects of volume expansion upon lithiation. However crystalline silicon suffers from amorphization upon the first charge/discharge cycle and improved stability is expected in starting with amorphous silicon. Here we report the synthesis, in a single-step process, of amorphous silicon nanoparticles coated with a carbon shell (a-Si@C), via a two-stage laser pyrolysis where decomposition of silane and ethylene are conducted in two successive reaction zones. Control of experimental conditions mitigates silicon core crystallization as well as formation of silicon carbide. Auger electron spectroscopy and scanning transmission electron microscopy show a carbon shell about 1 nm in thickness, which prevents detrimental oxidation of the a-Si cores. Cyclic voltammetry demonstrates that the core-shell composite reaches its maximal lithiation during the first sweep, thanks to its amorphous core. After 500 charge/discharge cycles, it retains a capacity of 1250 mAh.g-1 at a C/5 rate and 800 mAh.g-1 at 2C, with an outstanding coulombic efficiency of 99.95%. Moreover, post-mortem observations show an electrode volume expansion of less than 20% and preservation of the nanostructuration.

  7. The effect of substrate bias on titanium carbide/amorphous carbon nanocomposite films deposited by filtered cathodic vacuum arc

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xu, E-mail: zhangxu@bnu.edu.cn [Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University (China); Liang, Hong [Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University (China); Wu, Zhenglong [Analytical and Testing Center, Beijing Normal University (China); Wu, Xiangying; Zhang, Huixing [Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University (China)

    2013-07-15

    The titanium carbide/amorphous carbon nanocomposite films have been deposited on silicon substrate by filtered cathodic vacuum arc (FCVA) technology, the effects of substrate bias on composition, structures and mechanical properties of the films are studied by scanning electron spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy and nano-indentation. The results show that the Ti content, deposition rate and hardness at first increase and then decrease with increasing the substrate bias. Maximum hardness of the titanium carbide/amorphous carbon nanocomposite film is 51 Gpa prepared at −400 V. The hardness enhancement may be attributed to the compressive stress and the fraction of crystalline TiC phase due to ion bombardment.

  8. POROUS AMORPHOUS FLUOROPOLYMER FILMS WITH ULTRALOW DIELECTRIC CONSTANT

    Institute of Scientific and Technical Information of China (English)

    DING SHI-JIN; WANG PENG-FEI; ZHANG WEI; WANG JI-TAO; WEI WILLIAM LEE; ZHANG YE-WEN; KIA ZHONG-FU

    2000-01-01

    With the development of ultralarge scale integrated circuit, new interlayer dielectrics with low dielectric constant for multilevel interconnections are required, instead of conventional SiO2 films. For the sake of seeking perfect dielectrics, amorphous fluoropolymer (AF) thin film with a thickness of about 0.9μm has been prepared by spin-coating method, following the principle of phase separation. By capacitance-voltage (C-V) measurements the dielectric constant of the thin film is equal to 1.57 at 1 MHz, which is attributed to numerous pores contained in the film matrix. X-ray photoelectron spectroscopy (XPS) spectra show that after annealing, about 71% CFa groups in the AF film have decomposed into CF2, CF, etc. This leads to the increase of CF2 groups by three times and CF groups by 8% in the AF film. In a word, compared with the film without being annealed, about 25% carbon, 7% fluorine and 12% oxygen atoms will be lost after annealing at 400℃ for 30min.

  9. Crystallization and Transport Properties of Amorphous Cr-Si Thin Film Thermoelectrics

    Science.gov (United States)

    Novikov, S. V.; Burkov, A. T.; Schumann, J.

    2014-06-01

    We studied the thermoelectric properties, crystallization, and stability of amorphous and nanocrystalline states in Cr-Si composite films. Amorphous films, prepared by magnetron sputtering, were transformed into the nanocrystalline state by annealing with in situ thermopower and electrical resistivity measurements. We have found that the amorphous state is stable in these film composites to about 550 K. Prior to crystallization, the amorphous films undergo a structural relaxation, detected by peculiarities in the temperature dependences of the transport properties, but not visible in x-ray or electron diffraction. The magnitude and temperature dependences of electrical conductivity and thermopower indicate that electron transport in the amorphous films is through extended states. The amorphous films are crystallized at annealing temperatures above 550 K into a nanocrystalline composite with an average grain size of 10-20 nm.

  10. Low temperature deposition of polycrystalline silicon thin films on a flexible polymer substrate by hot wire chemical vapor deposition

    Science.gov (United States)

    Lee, Sang-hoon; Jung, Jae-soo; Lee, Sung-soo; Lee, Sung-bo; Hwang, Nong-moon

    2016-11-01

    For the applications such as flexible displays and solar cells, the direct deposition of crystalline silicon films on a flexible polymer substrate has been a great issue. Here, we investigated the direct deposition of polycrystalline silicon films on a polyimide film at the substrate temperature of 200 °C. The low temperature deposition of crystalline silicon on a flexible substrate has been successfully made based on two ideas. One is that the Si-Cl-H system has a retrograde solubility of silicon in the gas phase near the substrate temperature. The other is the new concept of non-classical crystallization, where films grow by the building block of nanoparticles formed in the gas phase during hot-wire chemical vapor deposition (HWCVD). The total amount of precipitation of silicon nanoparticles decreased with increasing HCl concentration. By adding HCl, the amount and the size of silicon nanoparticles were reduced remarkably, which is related with the low temperature deposition of silicon films of highly crystalline fraction with a very thin amorphous incubation layer. The dark conductivity of the intrinsic film prepared at the flow rate ratio of RHCl=[HCl]/[SiH4]=3.61 was 1.84×10-6 Scm-1 at room temperature. The Hall mobility of the n-type silicon film prepared at RHCl=3.61 was 5.72 cm2 V-1s-1. These electrical properties of silicon films are high enough and could be used in flexible electric devices.

  11. Effect of light trapping in an amorphous silicon solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Iftiquar, S.M., E-mail: iftiquar@skku.edu [College of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Jung, Juyeon; Park, Hyeongsik [College of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Cho, Jaehyun; Shin, Chonghoon [Department of Energy Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Jinjoo [College of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Jung, Junhee [Department of Energy Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Bong, Sungjae [College of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Sunbo [Department of Energy Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Yi, Junsin, E-mail: yi@yurim.skku.ac.kr [College of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Department of Energy Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2015-07-31

    Light trapping in amorphous silicon based solar cell has been investigated theoretically. The substrate for these cells can be textured, including pyramidally textured c-Si wafer, to improve capture of incident light. A thin silver layer, deposited on the substrate of an n–i–p cell, ultimately goes at the back of the cell structure and can act a back reflector to improve light trapping. The two physical solar cells we investigated had open circuit voltages (V{sub oc}) of 0.87, 0.90 V, short circuit current densities (J{sub sc}) of 14.2, 15.36 mA/cm{sup 2} respectively. The first cell was investigated for the effect on its performance while having and not having light trapping scheme (LT), when thickness of the active layer (d{sub i}) was changed in the range of 100 nm to 800 nm. In both the approaches, for having or not having LT, the short circuit current density increases with d{sub i} while the V{sub oc} and fill factor, decreases steadily. However, maximum cell efficiency can be obtained when d{sub i} = 400 nm, and hence it was considered optimized thickness of the active layer, that was used for further investigation. With the introduction of light trapping to the second cell, it shows a further enhancement in J{sub sc} and red response of the external quantum efficiency to 16.6 mA/cm{sup 2} and by 11.1% respectively. Considering multiple passages of light inside the cell, we obtained an improvement in cell efficiency from 9.7% to 10.6%. - Highlights: • A theoretical analysis of light trapping in p–i–n and n–i–p type solar cells • J{sub sc} increases and V{sub oc} decreases with the increase in i-layer thickness. • Observed optimized thickness of i-layer as 400 nm • J{sub sc} improved from 15.4 mA/cm{sup 2} to 16.6 mA/cm{sup 2} due to the light trapping. • Efficiency (η) improved from 9.7% to 10.6% due to better red response of the EQE.

  12. Structural properties of oxygenated amorphous cadmium telluride thin films

    Energy Technology Data Exchange (ETDEWEB)

    El Azhari, M.Y. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Azizan, M. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Bennouna, A. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Outzourhit, A. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Ameziane, E.L. [Laboratoire de Physique des Solides et des Couches Minces, Marakech (Morocco). Dept. de Physique; Brunel, M. [Laboratoire de Cristallographie, CNRS, Grenoble (France)

    1997-02-28

    Cadmium telluride (CdTe) thin films were prepared by diode radio-frequency sputtering from polycrystalline CdTe targets in an atmosphere of argon, nitrogen and oxygen. The layers prepared in the presence of nitrogen gas were amorphous and their oxygen contents increased with the partial pressure of nitrogen. The evolution of the composition of the layers as a function of the nitrogen partial pressure during deposition was followed by X-ray photoelectron spectroscopy. It is found that the oxygen is bound to both tellurium and cadmium atoms. The surface of the CdTe thin films was also studied as a function of their exposure time to a plasma containing a mixture of nitrogen and oxygen. It is found that the oxygen contents of the surface increases with increased exposure time. Also, this exposure resulted in an increase of the oxide thickness and a net decrease in the surface roughness of the films. (orig.)

  13. Quantum confinement in amorphous TiO(2) films studied via atomic layer deposition.

    Science.gov (United States)

    King, David M; Du, Xiaohua; Cavanagh, Andrew S; Weimer, Alan W

    2008-11-05

    Despite the significant recent increase in quantum-based optoelectronics device research, few deposition techniques can reliably create the required functional nanoscale systems. Atomic layer deposition (ALD) was used here to study the quantum effects attainable through the use of this ångström-level controlled growth process. Size-dependent quantum confinement has been demonstrated using TiO(2) layers of nanoscale thickness applied to the surfaces of silicon wafers. TiO(2) films were deposited at 100 °C using TiCl(4) and H(2)O(2) in a viscous flow ALD reactor, at a rate of 0.61 Å/cycle. The low-temperature process was utilized to guarantee the amorphous deposition of TiO(2) layers and post-deposition thermal annealing was employed to promote crystallite-size modification. Hydrogen peroxide significantly reduced the residual chlorine that remained from a typical TiCl(4)-H(2)O ALD process at this temperature, down to 1.6%. Spectroscopic ellipsometry was used to quantify the optical properties both below and above the bandgap energy. A central composite design was employed to map the surface response of the film thickness-dependent bandgap shift for the as-deposited case and up to a thermal annealing temperature of 550 °C. The Brus model was used to develop a correlation between the amorphous TiO(2) film thickness and the quantum length to promote equivalent bandgap shifts.

  14. Controlled fluoridation of amorphous carbon films deposited at reactive plasma conditions

    Directory of Open Access Journals (Sweden)

    Yoffe Alexander

    2015-09-01

    Full Text Available A study of the correlations between plasma parameters, gas ratios, and deposited amorphous carbon film properties is presented. The injection of a C4F8/Ar/N2 mixture of gases was successfully used in an inductively coupled plasma system for the preparation of amorphous carbon films with different fluoride doping at room-temperature, using silicon as a substrate. This coating was formed at low-pressure and low-energy using an inductively coupled plasma process. A strong dependence between the ratios of gases during deposition and the composition of the substrate compounds was shown. The values of ratios between Ar (or Ar+N2 and C4F8 - 1:1 and between N2 and Ar - 1:2 in the N2/Ar/C4F8 mixture were found as the best for low fluoridated coatings. In addition, an example of improving the etch-passivation in the Bosch procedure was described. Scanning electron microscopy with energy dispersive spectroscopy options, X-ray diffraction, and X-ray reflectivity were used for quantitative analysis of the deposited films.

  15. Stable, high-efficiency amorphous silicon solar cells with low hydrogen content

    Energy Technology Data Exchange (ETDEWEB)

    Fortmann, C.M.; Hegedus, S.S. (Institute of Energy Conversion, Newark, DE (United States))

    1992-12-01

    Results and conclusions obtained during a research program of the investigation of amorphous silicon and amorphous silicon based alloy materials and solar cells fabricated by photo-chemical vapor and glow discharge depositions are reported. Investigation of the effects of the hydrogen content in a-si:H i-layers in amorphous silicon solar cells show that cells with lowered hydrogen content i-layers are more stable. A classical thermodynamic formulation of the Staebler-Wronski effect has been developed for standard solar cell operating temperatures and illuminations. Methods have been developed to extract a lumped equivalent circuit from the current voltage characteristic of a single junction solar cell in order to predict its behavior in a multijunction device.

  16. Photoemission studies of amorphous silicon induced by P + ion implantation

    Science.gov (United States)

    Petö, G.; Kanski, J.

    1995-12-01

    An amorphous Si layer was formed on a Si (1 0 0) surface by P + implantation at 80 keV. This layer was investigated by means of photoelectron spectroscopy. The resulting spectra are different from earlier spectra on amorphous Si prepared by e-gun evaporation or cathode sputtering. The differences consist of a decreased intensity in the spectral region corresponding to p-states, and appearace of new states at higher binding energy. Qualitativity similar results have been reported for Sb implanted amorphous Ge and the modification seems to be due to the changed short range order.

  17. Thin film solar cells with Si nanocrystallites embedded in amorphous intrinsic layers by hot-wire chemical vapor deposition.

    Science.gov (United States)

    Park, Seungil; Parida, Bhaskar; Kim, Keunjoo

    2013-05-01

    We investigated the thin film growths of hydrogenated silicon by hot-wire chemical vapor deposition with different flow rates of SiH4 and H2 mixture ambient and fabricated thin film solar cells by implementing the intrinsic layers to SiC/Si heterojunction p-i-n structures. The film samples showed the different infrared absorption spectra of 2,000 and 2,100 cm(-1), which are corresponding to the chemical bonds of SiH and SiH2, respectively. The a-Si:H sample with the relatively high silane concentration provides the absorption peak of SiH bond, but the microc-Si:H sample with the relatively low silane concentration provides the absorption peak of SiH2 bond as well as SiH bond. Furthermore, the microc-Si:H sample showed the Raman spectral shift of 520 cm(-1) for crystalline phase Si bonds as well as the 480 cm(-1) for the amorphous phase Si bonds. These bonding structures are very consistent with the further analysis of the long-wavelength photoconduction tail and the formation of nanocrystalline Si structures. The microc-Si:H thin film solar cell has the photovoltaic behavior of open circuit voltage similar to crystalline silicon thin film solar cell, indicating that microc-Si:H thin film with the mixed phase of amorphous and nanocrystalline structures show the carrier transportation through the channel of nanocrystallites.

  18. A novel nondestructive testing method for amorphous Si-Sn-O films

    Science.gov (United States)

    Liu, Xianzhe; Cai, Wei; Chen, Jianqiu; Fang, Zhiqiang; Ning, Honglong; Hu, Shiben; Tao, Ruiqiang; Zeng, Yong; Zheng, Zeke; Yao, Rihui; Xu, Miao; Wang, Lei; Lan, Linfeng; Peng, Junbiao

    2016-12-01

    Traditional methods to evaluate the quality of amorphous silicon-substituted tin oxide (a-STO) semiconductor film are destructive and time-consuming. Here, a novel non-destructive, quick, and facile method named microwave photoconductivity decay (μ-PCD) is utilized to evaluate the quality of a-STO film for back channel etch (BCE) thin-film transistors (TFTs) by simply measuring the D value and peak reflectivity signal. Through the μ-PCD method, both optimum deposition procedure and optimal annealing temperature are attained to prepare a-STO film with superior quality. The a-STO TFTs are fabricated by the obtained optimum procedure that exhibits a mobility of 8.14 cm2 V-1 s-1, a I on/I off ratio of 6.07  ×  109, a V on of -1.2 V, a steep subthreshold swing of 0.21 V/decade, a low trap density (D t) of 1.68  ×  1012 eV-1 cm-2, and good stability under the positive/negative gate-bias stress. Moreover, the validity of the μ-PCD measurement for a-STO films is verified by x-ray photoelectron spectroscopy, Hall effect measurement, and the performance of STO TFTs measured by traditional methods. The non-destructive μ-PCD method sheds light on the fast optimization of the deposition procedure for amorphous oxide semiconductor films with excellent quality.

  19. In situ observation of shear-driven amorphization in silicon crystals

    Energy Technology Data Exchange (ETDEWEB)

    He, Yang; Zhong, Li; Fan, Feifei; Wang, Chongmin; Zhu, Ting; Mao, Scott X.

    2016-09-19

    Amorphous materials have attracted great interest in the scientific and technological fields. An amorphous solid usually forms under the externally driven conditions of melt-quenching, irradiation and severe mechanical deformation. However, its dynamic formation process remains elusive. Here we report the in situ atomic-scale observation of dynamic amorphization processes during mechanical straining of nanoscale silicon crystals by high resolution transmission electron microscopy (HRTEM). We observe the shear-driven amorphization (SDA) occurring in a dominant shear band. The SDA involves a sequence of processes starting with the shear-induced diamond-cubic to diamond-hexagonal phase transition that is followed by dislocation nucleation and accumulation in the newly formed phase, leading to the formation of amorphous silicon. The SDA formation through diamond-hexagonal phase is rationalized by its structural conformity with the order in the paracrystalline amorphous silicon, which maybe widely applied to diamond-cubic materials. Besides, the activation of SDA is orientation-dependent through the competition between full dislocation nucleation and partial gliding.

  20. Amorphization of silicon induced by nanodroplet impact: A molecular dynamics study

    Science.gov (United States)

    Saiz, Fernan; Gamero-Castaño, Manuel

    2012-09-01

    The hypervelocity impact of electrosprayed nanodroplets on crystalline silicon produces an amorphous layer with a thickness comparable to the droplet diameters. The phase transition is puzzling considering that amorphization has not been observed in macroscopic shock compression of silicon, the only apparent difference being the several orders of magnitude disparity between the sizes of the macroscopic and nanodroplet projectiles. This article investigates the physics of the amorphization by modeling the impact of a nanodrop on single-crystal silicon via molecular dynamics. The simulation shows that the amorphization results from the heating and subsequent melting of a thin layer of silicon surrounding the impact area, followed by an ultrafast quenching with cooling rates surpassing 1013 K/s. These conditions impede crystalline growth in the supercooled liquid phase, which finally undergoes a glass transition to render a disordered solid phase. The high temperature field near the impact interface is a localized effect. The significantly different temperatures and cooling rates near the surface and in the bulk explain why amorphization occurs in nanodroplet impact, while it is absent in macroscopic shock compression. Since these high temperatures and ultrafast quenching rates are likely to occur in other materials, nanodroplet impact may become a general amorphatization technique for treating the surfaces of most crystalline substrates.

  1. Light Entrapping, Modeling & Effect of Passivation on Amorphous Silicon Based PV Cell

    OpenAIRE

    Md Mostafizur Rahman; Md. Moidul Islam; Mission Kumar Debnath; Saifullah, S.M.; Samera Hossein; Nusrat Jahan Bristy

    2016-01-01

    This research paper present efforts to enhance the performance of amorphous silicon p-i-n type solar cell using sidewall passivation. For sidewall passivation, MEMS insulation material Al2O3 was used. The main objective of this paper is to observe the effect of sidewall passivation in amorphous silicon solar cell and increase the conversion efficiency of the solar cell. Passivation of Al2O3 is found effective to subdue reverse leakage. It increases the electric potential generated in the desi...

  2. Origin of the ESR signal with g=2.0055 in amorphous silicon

    OpenAIRE

    1990-01-01

    Defect-state wave functions for threefold- and fivefold-coordinated Si atoms in amorphous silicon clusters have been calculated with use of a first-principles linear combination of the atomic orbitals method in order to clarify the origin of the ESR signal with g=2.0055 in amorphous silicon. The wave function of the defect state originating from the threefold-coordinated Si atom is strongly localized on this atom. On the other hand, that for the fivefold-coordinated Si atom is extended on thi...

  3. Chromic mechanism in amorphous WO{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J G; Benson, D K; Tracy, C E; Deb, S K; Czanderna, A W [National Renewable Energy Lab., Golden, CO (United States); Bechinger, C [Universitaet Konstanz (Germany)

    1996-11-01

    The authors propose a new model for the chromic mechanism in amorphous tungsten oxide films (WO{sub 3{minus}y}{center_dot}nH{sub 2}O). This model not only explains a variety of seemingly conflicting experimental results reported in the literature that cannot be explained by existing models, it also has practical implications with respect to improving the coloring efficiency and durability of electrochromic devices. According to this model, a typical as-deposited tungsten oxide film has tungsten mainly in W{sup 6+} and W{sup 4+} states and can be represented as W{sub 1{minus}y}{sup 6+} W{sub y}{sup 4+}O{sub 3{minus}y}{center_dot}nH{sub 2}O. The proposed chromic mechanism is based on the small polaron transition between the charge-induced W{sup 5+} state and the original W{sup 4+} state instead of the W{sup 5+} and W{sup 6+} states as suggested in previous models. The correlation between the electrochromic and photochromic behavior in amorphous tungsten oxide films is also discussed.

  4. Elastic behavior of amorphous-crystalline silicon nanocomposite: An atomistic view

    Science.gov (United States)

    Das, Suvankar; Dutta, Amlan

    2017-01-01

    In the context of mechanical properties, nanocomposites with homogeneous chemical composition throughout the matrix and the dispersed phase are of particular interest. In this study, the elastic moduli of amorphous-crystalline silicon nanocomposite have been estimated using atomistic simulations. A comparison with the theoretical model reveals that the elastic behavior is significantly influenced by the crystal-amorphous interphase. On observing the effect of volume-fraction of the crystalline phase, an anomalous trend for the bulk modulus is obtained. This phenomenon is attributed to the relaxation displacements of the amorphous atoms.

  5. Irradiation of the amorphous carbon films by picosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Marcinauskas, L., E-mail: liutauras.marcinauskas@ktu.lt [Kaunas University of Technology, Studentu 50, LT-51368 Kaunas (Lithuania); Grigonis, A. [Kaunas University of Technology, Studentu 50, LT-51368 Kaunas (Lithuania); Račiukaitis, G.; Gedvilas, M. [Center for Physical Sciences and Technology, Savanoriu Ave. 231, LT-02300 Vilnius (Lithuania); Vinciūnaitė, V. [Kaunas University of Technology, Studentu 50, LT-51368 Kaunas (Lithuania)

    2015-10-30

    The effect of a picosecond laser irradiation on structure modification of diamond-like carbon (DLC) and graphite-like carbon (GLC) films was analyzed in this work. The DLC films were irradiated by Nd:YVO{sub 4} laser operating at the 532 nm wavelength with the picosecond (10 ps) pulse duration at the fluence in the range of (0.08–0.76) J/cm{sup 2}. The GLC films were irradiated only at the fluence of 0.76 J/cm{sup 2}. The different pulse number (1, 10, and 100) was used for irradiation the films. The micro-Raman spectroscopy measurements indicated that the laser irradiation led to rearrangement of the sp{sup 3} C–C bonds to the sp{sup 2} C=C bonds in the DLC films. The formation of silicon carbide (SiC) was found in the irradiated spot after 10 and 100 pulses. Modifications in the structure of the DLC film took place even in the areas with low intensity of the Gaussian beam wings (heat affected areas). The increase in the oxygen concentration up to ten times was detected in the heat affected areas after 100 pulses. Opposite to that, the laser irradiation decreased the oxygen concentration and smoothened the surface microrelief of the GLC films. The bonding type remained unchanged in the GLC films even after irradiation with 100 pulses per spot. - Highlights: • The picosecond laser irradiation led to the rearrangement of sp{sup 3} C-C to the sp{sup 2} C = C bonds in the diamond-like carbon film. • The ps-laser irradiation of the DLC films stipulates appearance of the aromatic carbon structures. • The bonding type of the graphite-like carbon films remained unchanged even after ps laser irradiation with 100 pulses.

  6. Silicon nitride film for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    El amrani, A.; Menous, I.; Mahiou, L.; Touati, A.; Lefgoum, A. [Silicon Technology Unit. 2, Boulevard Frantz Fanon, BP 140 Alger-7 Merveilles, 16200 Algiers (Algeria); Tadjine, R. [Advanced Technologies Development Centre, Cite 20 Aout 1656, Baba hassen, Algiers (Algeria)

    2008-10-15

    In this work, our aim was to determine the deposition parameters leading to optimal optical properties of Silicon nitride (SiN) film for photovoltaic application. The deposition was performed in an industrial pulsed direct-PECVD using a gas mixture of NH{sub 3}/SiH{sub 4}. After defining the optimum deposition parameters, we have chemically evaluated the film quality in BOE solution. Plasma removal of the optimized SiN films from multicrystalline 4-in solar cells allows highlighting and estimating the emitter passivation and ARC effects on the solar cell electrical performance. (author)

  7. Amorphous silicon oxide layers for surface passivation and contacting of heterostructure solar cells of amorphous and crystalline silicon; Amorphe Siliziumoxidschichten zur Oberflaechenpassivierung und Kontaktierung von Heterostruktur-Solarzellen aus amorphen und kristallinem Silizium

    Energy Technology Data Exchange (ETDEWEB)

    Einsele, Florian

    2010-02-05

    Atomic hydrogen plays a dominant role in the passivation of crystalline silicon surfaces by layers of amorphous silicon. In order to research into this role, this thesis presents the method of hydrogen effusion from thin amorphous films of silicon (a-Si:H) and silicon oxide (a-SiO{sub x}:H). The oxygen concentration of the sub-stoichiometric a-SiO{sub x}:H films ranges up to 10 at.-%. The effusion experiment yields information about the content and thermal stability of hydrogen and about the microstructure of the films. A mathematical description of the diffusion process of atomic hydrogen yields an analytical expression of the effusion rate R{sub E} depending on the linearly increasing temperature in the experiment. Fitting of the calculated effusion rates R{sub E} to measured effusion spectra yields the diffusion coefficient of atomic hydrogen in a-SiO{sub x}:H. With increasing oxygen concentration, the diffusion coefficient of hydrogen in the a-SiO{sub x}:H films decreases. This is attributed to an increasing Si-H bond energy due to back bonded oxygen, resulting in a higher stability of hydrogen in the films. This result is confirmed by an increasing thermal stability of the p-type c-Si passivation with a-SiO{sub x}:H of increasing oxygen concentrations up to 5 at.-%. The passivation reaches very low recombination velocities of S < 10 cm/s at the interface. However, for higher oxygen concentrations up to 10 at.-%, the passivation quality decreases significantly. Here, infrared spectroscopy of Si-H vibrational modes and hydrogen effusion show an increase of hydrogen-rich interconnected voids in the films. This microstructure results in a high amount of molecular hydrogen (H{sub 2}) in the layers, which is not suitable for the saturation of c-Si interface defects. Annealing of the films at temperatures around 400 C leads to a release of H{sub 2} from the voids, as a result of which Si-Si bonds in the material reconstruct. Subsequently, hydrogen migration in the

  8. Inprovement of Field Emission Properties of PBS Thin Films by Amorphous Carbon Coating

    Directory of Open Access Journals (Sweden)

    S. Jana

    2011-01-01

    Full Text Available Lead sulfide (PbS nanocrystalline thin films were synthesized at room temperature via chemical bath deposition on both silicon and glass substrates and coated with amorphous carbon of different thickness by varying deposition time in plasma enhanced chemical vapor deposition technique. The as prepared samples were characterized by X-ray diffraction (XRD, field emission scanning electron microscope (FESEM and atomic force microscope (AFM. XRD study reveals that coating of amorphous carbon does not change the crystal structure of PbS. From FESEM images it is seen that the average size of PbS nanoparticle does not exceed 100 nm, though sometomes small cubic particles agglomerated to form bigger particles. The coating of amorphous carbon can be clearly visible by the FESEM as well as from AFM micrographs. Field emission study show a significant betterment for the carbon coated sample as compared to the pure PbS. The effect of inter-electrode distance on the field emission characteristics of best field emitting sample has been studied for three different inter-electrode distances.

  9. Characterization of amorphous hydrogenated carbon films deposited by MFPUMST at different ratios of mixed gases

    Indian Academy of Sciences (India)

    Haiyang Dai; Changyong Zhan; Hui Jiang; Ningkang Huang

    2012-12-01

    Amorphous hydrogenated carbon films (-C:H) on -type (100) silicon wafers were prepared with a middle frequency pulsed unbalanced magnetron sputtering technique (MFPUMST) at different ratios of methane–argon gases. The band characteristics, mechanical properties as well as refractive index were measured by Raman spectra, X-ray photoelectron spectroscopy (XPS), nano-indentation tests and spectroscopic ellipsometry. It is found that the 3 fraction increases with increasing Ar concentration in the range of 17–50%, and then decreases when Ar concentration exceeds 50%. The nano-indentation tests reveal that nano-hardness and elastic modulus of the films increase with increasing Ar concentration in the range of 17–50%, while decreases with increasing Ar concentration from 50% to 86%. The variations in the nano-hardness and the elastic modulus could be interpreted due to different 3 fractions in the prepared -C:H films. The variation of refractive index with wavelength have the same tendency for the -C:H films prepared at different Ar concentrations, they decrease with increasing wavelength from 600 to 1700 nm. For certain wavelengths within 600–1700 nm, refractive index has the highest value at the Ar concentration of 50%, and it is smaller at the Ar concentration of 86% than at 17%. The results given above indicate that ratio of mixed gases has a strong influence on bonding configuration and properties of -C:H films during deposition. The related mechanism is discussed in this paper.

  10. The multilayered structure of ultrathin amorphous carbon films synthesized by filtered cathodic vacuum arc deposition

    KAUST Repository

    Wang, Na

    2013-08-01

    The structure of ultrathin amorphous carbon (a-C) films synthesized by filtered cathodic vacuum arc (FCVA) deposition was investigated by high-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoelectron spectroscopy. Results of the plasmon excitation energy shift and through-thickness elemental concentration show a multilayered a-C film structure comprising an interface layer consisting of C, Si, and, possibly, SiC, a buffer layer with continuously increasing sp 3 fraction, a relatively thicker layer (bulk film) of constant sp 3 content, and an ultrathin surface layer rich in sp 2 hybridization. A detailed study of the C K-edge spectrum indicates that the buffer layer between the interface layer and the bulk film is due to the partial backscattering of C+ ions interacting with the heavy atoms of the silicon substrate. The results of this study provide insight into the minimum thickness of a-C films deposited by FCVA under optimum substrate bias conditions. Copyright © 2013 Materials Research Society.

  11. Preparation and Characterisation of Amorphous-silicon Photovoltaic Devices Having Microcrystalline Emitters; Preparacion y Caracterizacion de Dispositivos Fotovoltaicos de Silicio Amorfo con Emisiones Microcristalinos

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, M. T.; Gandia, J. J.; Carabe, J. [CIEMAT. Madrid (Spain)

    1999-11-01

    The present work summarises the essential aspects of the research carried out so far at CIEMAT on amorphous-silicon solar cells. The experience accumulated on the preparation and characterisation of amorphous and microcrystalline silicon has allowed to start from intrinsic (absorbent) and p-and n-type (emitters) materials not only having excellent optoelectronic properties, but enjoying certain technological advantages with respect to those developed by other groups. Among these are absorbent-layer growth rates between 5 and 10 times as fast as conventional ones and microcrystalline emitters prepared without using hydrogen. The preparation of amorphous-silicon cells has required the solution of a number of problems, such as those related to pinholes, edge leak currents and diffusion of metals into the semiconductor. Once such constraints have been overcome, it has been demonstrated not only that the amorphous-silicon technology developed at CIEMAT is valid for making solar cells, but also that the quality of the semiconductor material is good for the application according to the partial results obtained. The development of thin-film laser-scribing technology is considered essential. Additionally it has been concluded that cross contamination, originated by the fact of using a single-chamber reactor, is the basic factor limiting the quality of the cells developed at CIEMAT. The present research activity is highly focused on the solution of this problem. (Author)

  12. Physics and technology of amorphous-crystalline heterostructure silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Sark, Wilfried G.J.H.M. van [Utrecht Univ. (Netherlands). Copernicus Institute, Science Technology and Society; Roca, Francesco [Unita Tecnologie Portici, Napoli (Italy). ENEA - Agenzia Nazionale per le Nuove Tecnologie, l' Energia e lo Sviluppo Economico Sostenibile; Korte, Lars [Helmholtz-Zentrum Berlin fuer Materialien und Energie (Germany). Inst. Silizium-Photovoltaik

    2012-07-01

    The challenge of developing photovoltaic (PV) technology to a cost-competitive alternative for established energy sources can be achieved using simple, high-throughput mass-production compatible processes. Issues to be addressed for large scale PV deployment in large power plants or in building integrated applications are enhancing the performance of solar energy systems by increasing solar cell efficiency, using low amounts of materials which are durable, stable, and abundant on earth, and reducing manufacturing and installation cost. Today's solar cell multi-GW market is dominated by crystalline silicon (c-Si) wafer technology, however new cell concepts are entering the market. One very promising solar cell design to answer these needs is the silicon hetero-junction solar cell, of which the emitter and back surface field are basically produced by a low temperature growth of ultra-thin layers of amorphous silicon. In this design, amorphous silicon (a-Si:H) constitutes both ''emitter'' and ''base-contact/back surface field'' on both sides of a thin crystalline silicon wafer-base (c-Si) where the photogenerated electrons and holes are generated; at the same time, a Si:H passivates the c-Si surface. Recently, cell efficiencies above 23% have been demonstrated for such solar cells. In this book, the editors present an overview of the state-of-the-art in physics and technology of amorphous-crystalline heterostructure silicon solar cells. (orig.)

  13. Amorphous silicon oxide layers for surface passivation and contacting of heterostructure solar cells of amorphous and crystalline silicon; Amorphe Siliziumoxidschichten zur Oberflaechenpassivierung und Kontaktierung von Heterostruktur-Solarzellen aus amorphen und kristallinem Silizium

    Energy Technology Data Exchange (ETDEWEB)

    Einsele, Florian

    2010-02-05

    Atomic hydrogen plays a dominant role in the passivation of crystalline silicon surfaces by layers of amorphous silicon. In order to research into this role, this thesis presents the method of hydrogen effusion from thin amorphous films of silicon (a-Si:H) and silicon oxide (a-SiO{sub x}:H). The oxygen concentration of the sub-stoichiometric a-SiO{sub x}:H films ranges up to 10 at.-%. The effusion experiment yields information about the content and thermal stability of hydrogen and about the microstructure of the films. A mathematical description of the diffusion process of atomic hydrogen yields an analytical expression of the effusion rate R{sub E} depending on the linearly increasing temperature in the experiment. Fitting of the calculated effusion rates R{sub E} to measured effusion spectra yields the diffusion coefficient of atomic hydrogen in a-SiO{sub x}:H. With increasing oxygen concentration, the diffusion coefficient of hydrogen in the a-SiO{sub x}:H films decreases. This is attributed to an increasing Si-H bond energy due to back bonded oxygen, resulting in a higher stability of hydrogen in the films. This result is confirmed by an increasing thermal stability of the p-type c-Si passivation with a-SiO{sub x}:H of increasing oxygen concentrations up to 5 at.-%. The passivation reaches very low recombination velocities of S < 10 cm/s at the interface. However, for higher oxygen concentrations up to 10 at.-%, the passivation quality decreases significantly. Here, infrared spectroscopy of Si-H vibrational modes and hydrogen effusion show an increase of hydrogen-rich interconnected voids in the films. This microstructure results in a high amount of molecular hydrogen (H{sub 2}) in the layers, which is not suitable for the saturation of c-Si interface defects. Annealing of the films at temperatures around 400 C leads to a release of H{sub 2} from the voids, as a result of which Si-Si bonds in the material reconstruct. Subsequently, hydrogen migration in the

  14. A Study on the Outdoor Degradation of Amorphous Silicon Thin-film Solar Cells%非晶硅薄膜太阳电池户外衰减效应的研究

    Institute of Scientific and Technical Information of China (English)

    杨娜娜

    2016-01-01

    One of the main problems in thin film silicon based modules is the degradation of their perform-ance upon exposure to light ,which can lead to inaccurate installation of photovoltaic system ,as it cannot accurately predict the power delivery .So this thesis investigates the annual degradation and seasonal fluc-tuation of the module ’ s IV parameters when the module is in the state of open circuit and short circuit . The dangling bonds mechanism and equivalent circuit are used to analyze the experiment phenomena .The results demonstrate that the power has degraded at a certain rate and seasonal oscillation , and that the degradation rate is increased when the external circuit is in open circuit compared to in short circuit .%非晶硅薄膜太阳电池最主要的问题之一就是会发生光致衰减,而这种衰减特性对电站的安装有很大的影响,导致安装容量无法准确地估量。本文对非晶硅薄膜太阳电池进行了户外衰减测试,得到电池 IV参数随着季节变化的衰减特征以及开路短路状态对衰减的影响,并用缺陷衰减机制和等效电路对户外的衰减结果进行分析。实验结果表明:非晶硅薄膜太阳电池的衰减随着季节呈周期性的动态变化,同时负载的变化对衰减产生很大的影响。

  15. Selective-resputtering-induced perpendicular magnetic anisotropy in amorphous TbFe films.

    Science.gov (United States)

    Harris, V G; Pokhil, T

    2001-08-06

    Perpendicular magnetic anisotropy energy in rf magnetron sputtered amorphous TbFe films is measured to increase exponentially with pair-order anisotropy induced by the selective resputtering of surface adatoms during film growth.

  16. Effect of Si additions on thermal stability and the phase transition sequence of sputtered amorphous alumina thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bolvardi, H.; Baben, M. to; Nahif, F.; Music, D., E-mail: music@mch.rwth-aachen.de; Schnabel, V.; Shaha, K. P.; Mráz, S.; Schneider, J. M. [Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, D-52074 Aachen (Germany); Bednarcik, J.; Michalikova, J. [Deutsches Elektronen Synchrotron DESY, FS-PE group, Notkestrasse 85, D-22607 Hamburg (Germany)

    2015-01-14

    Si-alloyed amorphous alumina coatings having a silicon concentration of 0 to 2.7 at. % were deposited by combinatorial reactive pulsed DC magnetron sputtering of Al and Al-Si (90-10 at. %) split segments in Ar/O{sub 2} atmosphere. The effect of Si alloying on thermal stability of the as-deposited amorphous alumina thin films and the phase formation sequence was evaluated by using differential scanning calorimetry and X-ray diffraction. The thermal stability window of the amorphous phase containing 2.7 at. % of Si was increased by more than 100 °C compared to that of the unalloyed phase. A similar retarding effect of Si alloying was also observed for the α-Al{sub 2}O{sub 3} formation temperature, which increased by more than 120 °C. While for the latter retardation, the evidence for the presence of SiO{sub 2} at the grain boundaries was presented previously, this obviously cannot explain the stability enhancement reported here for the amorphous phase. Based on density functional theory molecular dynamics simulations and synchrotron X-ray diffraction experiments for amorphous Al{sub 2}O{sub 3} with and without Si incorporation, we suggest that the experimentally identified enhanced thermal stability of amorphous alumina with addition of Si is due to the formation of shorter and stronger Si–O bonds as compared to Al–O bonds.

  17. Oxidation of fluorinated amorphous carbon (a-CF(x)) films.

    Science.gov (United States)

    Yun, Yang; Broitman, Esteban; Gellman, Andrew J

    2010-01-19

    Amorphous fluorinated carbon (a-CF(x)) films have a variety of potential technological applications. In most such applications these films are exposed to air and undergo partial surface oxidation. X-ray photoemission spectroscopy has been used to study the oxidation of fresh a-CF(x) films deposited by magnetron sputtering. The oxygen sticking coefficient measured by exposure to low pressures (<10(-3) Torr) of oxygen at room temperature is on the order of S approximately 10(-6), indicating that the surfaces of these films are relatively inert to oxidation when compared with most metals. The X-ray photoemission spectra indicate that the initial stages of oxygen exposure (<10(7) langmuirs) result in the preferential oxidation of the carbon atoms with zero or one fluorine atom, perhaps because these carbon atoms are more likely to be found in configurations with unsaturated double bonds and radicals than carbon atoms with two or three fluorine atoms. Exposure of the a-CF(x) film to atmospheric pressures of air (effective exposure of 10(12) langmuirs to O(2)) results in lower levels of oxygen uptake than the low pressure exposures (<10(7) langmuirs). It is suggested that this is the result of oxidative etching of the most reactive carbon atoms, leaving a relatively inert surface. Finally, low pressure exposures to air result in the adsorption of both nitrogen and oxygen onto the surface. Some of the nitrogen adsorbed on the surface at low pressures is in a reversibly adsorbed state in the sense that subsequent exposure to low pressures of O(2) results in the displacement of nitrogen by oxygen. Similarly, when an a-CF(x) film oxidized in pure O(2) is exposed to low pressures of air, some of the adsorbed oxygen is displaced by nitrogen. It is suggested that these forms of nitrogen and oxygen are bound to free radical sites in the film.

  18. Silicon Oxynitride Thin Film Barriers for PV Packaging (Poster)

    Energy Technology Data Exchange (ETDEWEB)

    del Cueto, J. A.; Glick, S. H.; Terwilliger, K. M.; Jorgensen, G. J.; Pankow, J. W.; Keyes, B. M.; Gedvilas, L. M.; Pern, F. J.

    2006-10-03

    Dielectric, adhesion-promoting, moisture barriers comprised of silicon oxynitride thin film materials (SiOxNy with various material stoichiometric compositions x,y) were applied to: 1) bare and pre-coated soda-lime silicate glass (coated with transparent conductive oxide SnO2:F and/or aluminum), and polymer substrates (polyethylene terephthalate, PET, or polyethylene napthalate, PEN); plus 2) pre- deposited photovoltaic (PV) cells and mini-modules consisting of amorphous silicon (a-Si) and copper indium gallium diselenide (CIGS) thin-film PV technologies. We used plasma enhanced chemical vapor deposition (PECVD) process with dilute silane, nitrogen, and nitrous oxide/oxygen gas mixtures in a low-power (< or = 10 milliW per cm2) RF discharge at ~ 0.2 Torr pressure, and low substrate temperatures < or = 100(degrees)C, over deposition areas ~ 1000 cm2. Barrier properties of the resulting PV cells and coated-glass packaging structures were studied with subsequent stressing in damp-heat exposure at 85(degrees)C/85% RH. Preliminary results on PV cells and coated glass indicate the palpable benefits of the barriers in mitigating moisture intrusion and degradation of the underlying structures using SiOxNy coatings with thicknesses in the range of 100-200 nm.

  19. Photoconduction in silicon rich oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Luna-Lopez, J A; Carrillo-Lopez, J; Flores-Gracia, F J; Garcia-Salgado, G [CIDS-ICUAP, Benemerita Universidad Autonoma de Puebla. Ed. 103 D and C, col. San Manuel, Puebla, Pue. Mexico 72570 (Mexico); Aceves-Mijares, M; Morales-Sanchez, A, E-mail: jluna@buap.siu.m, E-mail: jluna@inaoep.m [INAOE, Luis Enrique Erro No. 1, Apdo. 51, Tonantzintla, Puebla, Mexico 72000 (Mexico)

    2009-05-01

    Photoconduction of silicon rich oxide (SRO) thin films were studied by current-voltage (I-V) measurements, where ultraviolet (UV) and white (Vis) light illumination were applied. SRO thin films were deposited by low pressure chemical vapour deposition (LPCVD) technique, using SiH{sub 4} (silane) and N{sub 2}O (nitrous oxide) as reactive gases at 700 {sup 0}. The gas flow ratio, Ro = [N{sub 2}O]/[SiH{sub 4}] was used to control the silicon excess. The thickness and refractive index of the SRO films were 72.0 nm, 75.5 nm, 59.1 nm, 73.4 nm and 1.7, 1.5, 1.46, 1.45, corresponding to R{sub o} = 10, 20, 30 and 50, respectively. These results were obtained by null ellipsometry. Si nanoparticles (Si-nps) and defects within SRO films permit to obtain interesting photoelectric properties as a high photocurrent and photoconduction. These effects strongly depend on the silicon excess, thickness and structure type. Two different structures (Al/SRO/Si and Al/SRO/SRO/Si metal-oxide-semiconductor (MOS)-like structures) were fabricated and used as devices. The photocurrent in these structures is dominated by the generation of carriers due to the incident photon energies ({approx}3.0-1.6 eV and 5 eV). These structures showed large photoconductive response at room temperature. Therefore, these structures have potential applications in optoelectronics devices.

  20. Low contrast detectability and dose savings with an amorphous silicon detector designed for x-ray radiography

    Science.gov (United States)

    Xue, Ping; Schubert, Scott F.; Aufrichtig, Richard

    2000-04-01

    In an observer study we compare low contrast detectability and dose efficiency of an amorphous silicon x-ray detector versus a standard thoracic screen-film (Kodak InSight HC/InSight IT). Twelve images of a CDRAD contrast-detail phantom were acquired with the screen-film system using an entrance exposure corresponding to a conventional chest x-ray. Using the same x- ray system with an interchanged digital detector, we acquired four digital image sets (12 images each) at dose levels corresponding to 27%, 41%, 63% and 100% of the film dose. Prior to laser printing, the digital images were processed to match the film contrast and optical density level. A 4- alternative forced choice (4-AFC) paradigm with seven observers was used to measure the threshold contrasts of disk sizes from 0.5 to 4.0 mm. Further, we estimated the equivalent perceptual dose (EPD), which is the dose level of digital for which the same contrast detectability as film is obtained. Contrast detectability is significantly improved with the digital detector. On average, all disk shaped objects detected from the digital detector have lower threshold contrasts than those from film at the same dose level. The EPD value averaged over disk size is 44%, which corresponds to a 56% dose savings for the digital detector.

  1. Amorphization of silicon by bombardment with oxygen ions of energy below 5 keV

    Energy Technology Data Exchange (ETDEWEB)

    Zhukovskii, P.V.; Stel' makh, V.F.; Tkachev, V.D.

    1977-04-01

    Silicon was bombarded with /sup 16/O/sup +/ ions of 1.0 and 3.0 keV energies at room temperature. This bombardment created point defects which joined up to form amorphous layers about 100 A thick. (AIP)

  2. Thermal ideality factor of hydrogenated amorphous silicon p-i-n solar cells

    NARCIS (Netherlands)

    Kind, R.; Van Swaaij, R.A.C.M.M.; Rubinelli, F.A.; Solntsev, S.; Zeman, M.

    2011-01-01

    The performance of hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells is limited, as they contain a relatively high concentration of defects. The dark current voltage (JV) characteristics at low forward voltages of these devices are dominated by recombination processes. The recombination rate

  3. Light Entrapping, Modeling & Effect of Passivation on Amorphous Silicon Based PV Cell

    Directory of Open Access Journals (Sweden)

    Md. Mostafizur Rahman

    2016-07-01

    Full Text Available This research paper present efforts to enhance the performance of amorphous silicon p-i-n type solar cell using sidewall passivation. For sidewall passivation, MEMS insulation material Al2O3 was used. The main objective of this paper is to observe the effect of sidewall passivation in amorphous silicon solar cell and increase the conversion efficiency of the solar cell. Passivation of Al2O3 is found effective to subdue reverse leakage. It increases the electric potential generated in the designed solar cell. It also increases the current density generated in the solar cell by suppressing the leakage. Enhancement in J-V curve was observed after adding sidewall passivation. The short circuit current density (Jsc increased from 14.7 mA/cm2 to 18.5 mA/cm2, open circuit voltage (Voc improved from 0.87 V to 0.89 V, and the fill factor also slightly increased. Due to the sidewall of passivation of Al2O3, conversion efficiency of amorphous silicon solar cell increased by 29.07%. At the end, this research was a success to improve the efficiency of the amorphous silicon solar cell by adding sidewall passivation.

  4. Amorphous Silicon Position Detectors for the Link Alignment System of the CMS Detector: Users Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Calderon, A.; Gomez, G.; Gonzalez-Sanchez, F. J.; Martinez-Rivero, C.; Matorras, F.; Rodrigo, T.; Ruiz-Arbol, P.; Scodellaro, L.; Vila, I.; Virto, A. L.; Alberdi, J.; Arce, P.; Barcala, J.M.; Calvo, E.; Ferrando, A.; Josa, M. I.; Molinero, A.; Navarrete, J.; Oller, J. C.; Yuste, C.

    2007-07-01

    We present the general characteristics, calibration procedures and measured performance of the Amorphous Silicon Position Detectors installed in the Link Alignment System of the CMS Detector for laser beam detection and reconstruction and give the Data Base to be used as a Handbook during CMS operation. (Author) 10 refs.

  5. Photoselective Metal Deposition on Amorphous Silicon p-i-n Solar Cells

    NARCIS (Netherlands)

    Kooij, E.S.; Hamoumi, M.; Kelly, J.J.; Schropp, R.E.I.

    1997-01-01

    A novel method is described for the patternwise metallization of amorphous silicon solar cells, based on photocathodic deposition. The electric field of the p-i-n structure is used for the separation of photogenerated charge carriers. The electrons are driven to the interface of the n+-layer with th

  6. Results from multipoint alignment monitoring using the new generation of amorphous silicon position detectors

    Energy Technology Data Exchange (ETDEWEB)

    Alberdi, J.; Arce, P.; Barcala, J.M.; Calvo, E. [CIEMAT, 28040 Madrid (Spain); Ferrando, A. [CIEMAT, 28040 Madrid (Spain)], E-mail: antonio.ferrando@ciemat.es; Josa, M.I.; Molinero, A.; Navarrete, J.; Oller, J.C.; Yuste, C. [CIEMAT, 28040 Madrid (Spain); Calderon, A.; Gomez, G.; Gonzalez-Sanchez, F.J.; Martinez-Rivero, C.; Matorras, F.; Rodrigo, T.; Ruiz-Arbol, P.; Sobron, M.; Vila, I.; Virto, A.L. [Instituto de Fisica de Cantabria (IFCA), CSIC-University of Cantabria Santander (Spain)] (and others)

    2008-08-11

    We present the measured performance of a new generation of large sensitive area (28x28 mm{sup 2}) semitransparent amorphous silicon position detector sensors. More than 100 units have been characterized. They show a very high performance. To illustrate a multipoint application, we present results from the monitoring of five sensors placed in a 5.5-m-long light path.

  7. Multipoint alignment monitoring with amorphous silicon position detectors in a complex light path

    Energy Technology Data Exchange (ETDEWEB)

    Alberdi, J.; Arce, P.; Barcala, J.M.; Calvo, E. [CIEMAT, Madrid (Spain); Ferrando, A., E-mail: antonio.ferrando@ciemat.e [CIEMAT, Madrid (Spain); Josa, M.I.; Molinero, A.; Navarrete, J.; Oller, J.C.; Yuste, C. [CIEMAT, Madrid (Spain); Calderon, A.; Gomez, G.; Gonzalez-Sanchez, F.J.; Martinez-Rivero, C.; Matorras, F.; Rodrigo, T.; Ruiz-Arbol, P.; Sobron, M.; Vila, I.; Virto, A.L. [Instituto de Fisica de Cantabria. CSIC-University of Cantabria, Santander (Spain)

    2010-12-01

    This document presents an application of the new generation of amorphous silicon position detecting (ASPD) sensors to multipoint alignment. Twelve units are monitored along a 20 m long laser beam, where the light path is deflected by 90{sup o} using a pentaprism.

  8. Construction process and read-out electronics of amorphous silicon position detectors for multipoint alignment monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, C.; Schubert, M.B.; Lutz, B.; Werner, J.H. [Steinbeis-Transferzentrum fuer Angewandte Photovoltaik und Duennschichttechnik, Stuttgart (Germany); Alberdi, J.; Arce, P.; Barcala, J.M.; Calvo, E. [CIEMAT, Madrid (Spain); Ferrando, A. [CIEMAT, Madrid (Spain)], E-mail: antonio.ferrando@ciemat.es; Josa, M.I.; Molinero, A.; Navarrete, J.; Oller, J.C.; Yuste, C. [CIEMAT, Madrid (Spain); Calderon, A.; Fernandez, M.G.; Gomez, G.; Gonzalez-Sanchez, F.J.; Martinez-Rivero, C.; Matorras, F. [Instituto de Fisica de Cantabria IFCA/CSIC-University of Cantabria, Santander (Spain)] (and others)

    2009-09-01

    We describe the construction process of large-area high-performance transparent amorphous silicon position detecting sensors. Details about the characteristics of the associated local electronic board (LEB), specially designed for these sensors, are given. In addition we report on the performance of a multipoint alignment monitoring application of 12 sensors in a 13 m long light path.

  9. A comparison of degradation in three amorphous silicon PV module technologies

    Energy Technology Data Exchange (ETDEWEB)

    Radue, C.; van Dyk, E.E. [Physics Department, PO Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)

    2010-03-15

    Three commercial amorphous silicon modules manufactured by monolithic integration and consisting of three technology types were analysed in this study. These modules were deployed outdoors for 14 months and underwent degradation. All three modules experienced the typical light-induced degradation (LID) described by the Staebler-Wronski effect, and this was followed by further degradation. A 14 W single junction amorphous silicon module degraded by about 45% of the initial measured maximum power output (P{sub MAX}) at the end of the study. A maximum of 30% of this has been attributed to LID and the further 15% to cell mismatch and cell degradation. The other two modules, a 64 W triple junction amorphous silicon module, and a 68 W flexible triple junction amorphous silicon module, exhibited LID followed by seasonal variation in the degraded P{sub MAX}. The 64 W module showed a maximum degradation in P{sub MAX} of about 22%. This is approximately 4% more than the manufacturer allowed for the initial LID. However, the seasonal variation in P{sub MAX} seems to be centred around the manufacturer's rating ({+-}4%). The 68 W flexible module has shown a maximum decrease in P{sub MAX} of about 27%. This decrease is about 17% greater than the manufacturer allowed for the initial LID. (author)

  10. Amorphous silicon solar cells on natively textured ZnO grown by PECVD

    NARCIS (Netherlands)

    Löffler, J.; Groenen, R.; Linden, J.L.; Sanden, M.C.M. van de; Schropp, R.E.I.

    2001-01-01

    Natively textured ZnO layers deposited by the expanding thermal plasma CVD technique between 150 and 350°C at a deposition rate between 0.65 and 0.75 nm/s have been investigated with respect to their suitability as front electrode material for amorphous silicon pin solar cells in comparison to refer

  11. Effective interface state effects in hydrogenated amorphous-crystalline silicon heterostructures using ultraviolet laser photocarrier radiometry

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, A. [Center for Advanced Diffusion-Wave Technologies (CADIFT), Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8 (Canada); Mandelis, A. [Center for Advanced Diffusion-Wave Technologies (CADIFT), Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8 (Canada); Electrical and Computer Engineering, University of Toronto, Toronto, Ontario M5S 3G4 (Canada); Halliop, B.; Kherani, N. P. [Electrical and Computer Engineering, University of Toronto, Toronto, Ontario M5S 3G4 (Canada)

    2013-12-28

    Ultraviolet photocarrier radiometry (UV-PCR) was used for the characterization of thin-film (nanolayer) intrinsic hydrogenated amorphous silicon (i-a-Si:H) on c-Si. The small absorption depth (approximately 10 nm at 355 nm laser excitation) leads to strong influence of the nanolayer parameters on the propagation and recombination of the photocarrier density wave (CDW) within the layer and the substrate. A theoretical PCR model including the presence of effective interface carrier traps was developed and used to evaluate the transport parameters of the substrate c-Si as well as those of the i-a-Si:H nanolayer. Unlike conventional optoelectronic characterization methods such as photoconductance, photovoltage, and photoluminescence, UV-PCR can be applied to more complete quantitative characterization of a-Si:H/c-Si heterojunction solar cells, including transport properties and defect structures. The quantitative results elucidate the strong effect of a front-surface passivating nanolayer on the transport properties of the entire structure as the result of effective a-Si:H/c-Si interface trap neutralization through occupation. A further dramatic improvement of those properties with the addition of a back-surface passivating nanolayer is observed and interpreted as the result of the interaction of the increased excess bulk CDW with, and more complete occupation and neutralization of, effective front interface traps.

  12. Light trapping in amorphous silicon solar cells with periodic grating structures

    Energy Technology Data Exchange (ETDEWEB)

    Lia, Haihua; Wang, Qingkang; Chen, Jian [National Key Laboratory of Micro /Nano Fabrication Technology, Key Laboratory for Thin Film and Microfabrication Technology of Ministry of Education, Research Institute of Micro/Nano Science and Technology, Shanghai Jiao Tong University, Shanghai 200240 (China); Krc, J. [University of Ljubljana, Faculty of Electrical Engineering, Trzaska25, 1000 Ljubljana (Slovenia); Soppe, W.J. [Energy research Center of the Netherlands ECN, P. O. Box 1, 1755 ZG Pettern (Netherlands)

    2012-03-15

    We report on the design of amorphous silicon solar cells with the periodic grating structures. It is a combination of an anti-reflection structure and the metallic reflection grating. Optical coupling and light trapping in thin-film solar cells are studied numerically using the Rigorous Coupled Wave Analysis enhanced by the Modal Transmission Line theory. The impact of the structure parameters of the gratings is investigated. The results revealed that within the incident angles of - 40{sup 0} to + 40{sup 0} the reflectivity of the cell with a period of 0.5 {mu}m, a filling factor of 0.1 and a groove depth of 0.4 {mu}m is 4%-22.7% in the wavelength range of 0.3-0.6 {mu}m and 1%-20.8% in the wavelength range of 0.6-0.84 {mu}m, the absorption enhancement of the a-Si layer is 0.4%-10.8% and 20%-385%, respectively.

  13. Effective interface state effects in hydrogenated amorphous-crystalline silicon heterostructures using ultraviolet laser photocarrier radiometry

    Science.gov (United States)

    Melnikov, A.; Mandelis, A.; Halliop, B.; Kherani, N. P.

    2013-12-01

    Ultraviolet photocarrier radiometry (UV-PCR) was used for the characterization of thin-film (nanolayer) intrinsic hydrogenated amorphous silicon (i-a-Si:H) on c-Si. The small absorption depth (approximately 10 nm at 355 nm laser excitation) leads to strong influence of the nanolayer parameters on the propagation and recombination of the photocarrier density wave (CDW) within the layer and the substrate. A theoretical PCR model including the presence of effective interface carrier traps was developed and used to evaluate the transport parameters of the substrate c-Si as well as those of the i-a-Si:H nanolayer. Unlike conventional optoelectronic characterization methods such as photoconductance, photovoltage, and photoluminescence, UV-PCR can be applied to more complete quantitative characterization of a-Si:H/c-Si heterojunction solar cells, including transport properties and defect structures. The quantitative results elucidate the strong effect of a front-surface passivating nanolayer on the transport properties of the entire structure as the result of effective a-Si:H/c-Si interface trap neutralization through occupation. A further dramatic improvement of those properties with the addition of a back-surface passivating nanolayer is observed and interpreted as the result of the interaction of the increased excess bulk CDW with, and more complete occupation and neutralization of, effective front interface traps.

  14. Modelling the structure factors and pair distribution functions of amorphous germanium, silicon and carbon

    Energy Technology Data Exchange (ETDEWEB)

    Dalgic, Seyfettin; Gonzalez, Luis Enrique; Baer, Shalom; Silbert, Moises

    2002-12-01

    We present the results of calculations of the static structure factor S(k) and the pair distribution function g(r) of the tetrahedral amorphous semiconductors germanium, silicon and carbon using the structural diffusion model (SDM). The results obtained with the SDM for S(k) and g(r) are of comparable quality with those obtained by the unconstrained Reverse Monte Carlo simulations and existing ab initio molecular dynamics simulations for these systems. We have found that g(r) exhibits a small peak, or shoulder, a weak remnant of the prominent third neighbour peak present in the crystalline phase of these systems. This feature has been experimentally found to be present in recently reported high energy X-ray experiments of amorphous silicon (Phys. Rev. B 60 (1999) 13520), as well as in the previous X-ray diffraction of as-evaporated amorphous germanium (Phys. Rev. B 50 (1994) 539)

  15. Ferroelectric-Like Properties of Amorphous Metal Oxide Thin Films Prepared by Sol-Gel Technique.

    Science.gov (United States)

    Xu, Yuhuan

    1995-01-01

    Advances in the field of both optical and electrical integrated circuit devices require new thin film materials. Ferroelectric materials have attractive properties such as hysteresis behavior, pyroelectricity, piezoelectricity and nonlinear optical properties. Many ferroelectric thin films have been successfully prepared from metal organic compounds via sol-gel processing. Thus far, research has concentrated upon polycrystalline or epitaxial ferroelectric films. For amorphous ferroelectric thin films, preliminary experimental results in our laboratory indicated that these amorphous films possessed good ferroelectric -like properties. The purpose of this research is (1) to fabricate amorphous metal oxide thin films by the sol-gel technique, (2) to determine whether these amorphous metal oxide thin films have ferroelectric-like properties and (3) to propose a theoretical model ("ferrons model") to explain the ferroelectric-like properties of amorphous thin films, which deals with a structure of permanent dipoles of "partially ordered clusters" (ferrons) in the amorphous films. The theoretical model is based on our experimental results of thin films of two amorphous materials (barium titanite and lead zirconate titanate). This research may provide a new functional material which could be useful for producing integrated electronic and electrooptic devices.

  16. Effect of substrate temperature on the structure of amorphous oxygenated hydrocarbon films grown with a pulsed supersonic methane plasma flow

    Energy Technology Data Exchange (ETDEWEB)

    Fedoseeva, Yu. V., E-mail: fedoseeva@niic.nsc.ru [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Pozdnyakov, G.A. [Khristianovich Institute of Theoretical and Applied Mechanics, SB RAS, Novosibirsk 630090 (Russian Federation); Okotrub, A.V.; Kanygin, M.A. [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Nastaushev, Yu. V. [Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090 (Russian Federation); Vilkov, O.Y. [St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Bulusheva, L.G. [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation)

    2016-11-01

    Highlights: • A deposition of supersonic methane plasma flow on silicon substrate produces amorphous oxygenated hydrocarbon (CO{sub x}H{sub y}) film. • The thickness, composition, and wettability of the film depend on the substrate temperature. • A rise of the substrate temperature from 500 to 700 °C promotes the sp{sup 3}-hybridization carbon formation. - Abstract: Since amorphous oxygenated hydrocarbon (CO{sub x}H{sub y}) films are promising engineering materials a study of the structure and composition of the films depending on the conditions of synthesis is important for controlling of their physicochemical properties. Here, we used the methods of scanning and transmission electron microscopy, X-ray photoelectron, near-edge X-ray absorption fine structure, Fourier transform infrared and Raman spectroscopy to reveal changes in the chemical connectivity of CO{sub x}H{sub y} films grown on silicon substrates heated to 300, 500, and 700 °C using a supersonic flow of methane plasma. It was found that the CO{sub x}H{sub y} films, deposited at 300 and 500 °C, were mainly composed of the sp{sup 2}-hybridized carbon areas with various oxygen species. A rise of the substrate temperature caused an increase of the portion of tetrahedral carbon atoms as well as carboxyl and hydroxyl groups. With growth of the substrate temperature, the film thickness reduced monotonically from 400 to 180 nm, while the film adhesion improved substantially. The films, deposited at lower temperatures, showed high hydrophilicity due to porosity and presence of oxygenated groups both at the surface and in the bulk.

  17. Amorphous Si layers co-doped with B and Mn: Thin film growth and steering of magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Drera, G. [I-LAMP, Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia (Italy); Mozzati, M.C. [CNISM, Dipartimento di Fisica, Università di Pavia, Via Bassi 6, 27100 Pavia (Italy); Colombi, P. [CSMT Gestione s.c.a.r.l, Via Branze 45, 25123 Brescia (Italy); Salvinelli, G.; Pagliara, S.; Visentin, D. [I-LAMP, Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia (Italy); Sangaletti, L., E-mail: sangalet@dmf.unicatt.it [I-LAMP, Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia (Italy)

    2015-09-01

    Amorphous silicon thin films co-doped with manganese (5% at.) and boron (1.8% at.) have been prepared by RF sputtering on Al{sub 2}O{sub 3} substrates held at room temperature (RT). The films, with an average thickness of about 0.9 μm, were carefully characterized by micro-Raman and X-ray photoemission spectroscopies. A ferromagnetic (FM) behavior up to RT was observed. In order to discuss and possibly rule out extrinsic effects usually related to segregations of ferromagnetic impurities in the samples, magnetization measurements were carried out on the Al{sub 2}O{sub 3} substrates, as well as on Si:B and Si:Mn films grown with the same RF sputtering system. Only the Si:B:Mn films displayed a FM behavior up to RT. Since amorphous films doped with Mn alone did not display any signature of FM ordering, boron co-doping results to be crucial for the onset of the FM behavior. The conductivity of the samples is not affected by boron doping that, therefore, does not appear to significantly contribute to a possible carrier-mediated FM interaction between Mn ions by supplying extra charges to the system. On this basis, the capability of B to hinder the quenching of the Mn 3d magnetic moments has also to be regarded as a possible role of this co-dopant in the observed magnetization. - Highlights: • We successfully deposited amorphous silicon thin films co-doped with Mn and B. • Structural, electronic, and magnetic properties have been carefully characterized. • A ferromagnetic behavior up to room temperature was detected. • The extrinsic origin of magnetism is excluded. • Boron can play a relevant role to avoid quenching of magnetic moment in Mn ions.

  18. Crystalline-Amorphous Core−Shell Silicon Nanowires for High Capacity and High Current Battery Electrodes

    KAUST Repository

    Cui, Li-Feng

    2009-01-14

    Silicon is an attractive alloy-type anode material for lithium ion batteries because of its highest known capacity (4200 mAh/g). However silicon\\'s large volume change upon lithium insertion and extraction, which causes pulverization and capacity fading, has limited its applications. Designing nanoscale hierarchical structures is a novel approach to address the issues associated with the large volume changes. In this letter, we introduce a core-shell design of silicon nanowires for highpower and long-life lithium battery electrodes. Silicon crystalline- amorphous core-shell nanowires were grown directly on stainless steel current collectors by a simple one-step synthesis. Amorphous Si shells instead of crystalline Si cores can be selected to be electrochemically active due to the difference of their lithiation potentials. Therefore, crystalline Si cores function as a stable mechanical support and an efficient electrical conducting pathway while amorphous shells store Li ions. We demonstrate here that these core-shell nanowires have high charge storage capacity (̃1000 mAh/g, 3 times of carbon) with ̃90% capacity retention over 100 cycles. They also show excellent electrochemical performance at high rate charging and discharging (6.8 A/g, ̃20 times of carbon at 1 h rate). © 2009 American Chemical Society.

  19. AMORPHOUS SILICON ELECTRONIC STRUCTURE MODELING AND BASIC ELECTRO-PHYSICAL PARAMETERS CALCULATION

    Directory of Open Access Journals (Sweden)

    B. A. Golodenko

    2014-01-01

    Full Text Available Summary. The amorphous semiconductor has any unique processing characteristics and it is perspective material for electronic engineering. However, we have not authentic information about they atomic structure and it is essential knot for execution calculation they electronic states and electro physical properties. The author's methods give to us decision such problem. This method allowed to calculation the amorphous silicon modeling cluster atomics Cartesian coordinates, determined spectrum and density its electronic states and calculation the basics electro physical properties of the modeling cluster. At that determined numerical means of the energy gap, energy Fermi, electron concentration inside valence and conduction band for modeling cluster. The find results provides real ability for purposeful control to type and amorphous semiconductor charge carriers concentration and else provides relation between atomic construction and other amorphous substance physical properties, for example, heat capacity, magnetic susceptibility and other thermodynamic sizes.

  20. Effect of silane flow rate on structural, electrical and optical properties of silicon thin films grown by VHF PECVD technique

    Energy Technology Data Exchange (ETDEWEB)

    Gope, Jhuma [Physics of Energy Harvesting Division, CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Department of Physics, Banaras Hindu University, Varanasi 221005 (India); Kumar, Sushil, E-mail: skumar@nplindia.org [Physics of Energy Harvesting Division, CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Sudhakar, S.; Rauthan, C.M.S. [Physics of Energy Harvesting Division, CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Srivastava, P.C. [Department of Physics, Banaras Hindu University, Varanasi 221005 (India)

    2013-08-15

    Hydrogenated silicon thin films deposited by VHF PECVD process for various silane flow rates have been investigated. The silane flow rate was varied from 5 sccm to 30 sccm, maintaining all other parameters constant. The electrical, structural and optical properties of these films were systematically studied as a function of silane flow rate. These films were characterized by Raman spectroscopy, Scanning Electron Microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy and UV–visible (UV–Vis) spectroscopy. Different crystalline volume fraction (22%–60%) and band gap (∼1.58 eV–∼1.96 eV) were achieved for silicon thin films by varying the silane concentration. A transition from amorphous to nanocrystalline silicon has been confirmed by Raman and FTIR analysis. The film grown at this transition region shows the high conductivity in the order of 10{sup −4} Ω{sup −1} cm{sup −1}. - Highlights: • Silicon films grown using VHF PECVD at various F{sub silane} (silane flow rate). • Amorphous to nanocrystalline silicon transition at F{sub silane} ∼5 sccm–10 sccm. • Deposition rate increases with the increase of F{sub silane}. • Powder formation occurred beyond 20 sccm of F{sub silane}. • Film grown at 20 sccm shows max. crystalline fraction ∼60% with E{sub g} ∼1.58 eV.

  1. INFLUENCE OF THE SILICON INTERLAYER ON DIAMOND-LIKE CARBON FILMS DEPOSITED ON GLASS SUBSTRATES

    Directory of Open Access Journals (Sweden)

    Deiler Antonio Lima Oliveira

    2012-06-01

    Full Text Available Diamond-like carbon (DLC films as a hard protective coating have achieved great success in a diversity of technological applications. However, adhesion of DLC films to substrates can restrict their applications. The influence of a silicon interlayer in order to improve DLC adhesion on glass substrates was investigated. Amorphous silicon interlayer and DLC films were deposited using plasma enhanced chemical vapor deposition from silane and methane, respectively. The bonding structure, transmittance, refraction index, and adherence of the films were also evaluated regarding the thickness of the silicon interlayer. Raman scattering spectroscopy did not show any substantial difference in DLC structure due to the interlayer thickness of the silicon. Optical measurements showed a sharp decrease of transmittance in the ultra-violet region caused by the fundamental absorption of the light. In addition, the absorption edge of transmittance shifted toward longer wavelength side in the ultra-violet region as the thickness of the silicon interlayer increased. The tribological results showed an increase of DLC adherence as the silicon interlayer increased, which was characterized by less cracks around the grooves.

  2. Photoluminescence enhancement through silicon implantation on SRO-LPCVD films

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Sanchez, A., E-mail: amorales@inaoep.mx [INAOE, Electronics Department, Apartado 51, Puebla 72000 (Mexico); Leyva, K.M.; Aceves, M. [INAOE, Electronics Department, Apartado 51, Puebla 72000 (Mexico); Barreto, J.; Dominguez, C. [Instituto de Microelectronica de Barcelona, IMB-CNM (CSIC), Barcelona (Spain); Luna-Lopez, J.A.; Carrillo, J. [CIDS-BUAP, Apdo. 1651, Puebla 72000 (Mexico); Pedraza, J. [INAOE, Electronics Department, Apartado 51, Puebla 72000 (Mexico)

    2010-10-25

    Photoluminescence (PL) properties of thin and thick silicon-rich oxide (SRO) and silicon implanted SRO (SI-SRO) films with different silicon excess fabricated by low pressure chemical vapor deposition (LPCVD) were studied. The effects of the annealing temperature and silicon implantation on the PL were also studied. Maximum luminescence intensity was observed with an annealing temperature of 1150 and 1100 deg. C for thin and thick SRO films, respectively. The PL intensity is strongly enhanced when SRO films are implanted with silicon, especially for thin SRO films. Thin SI-SRO films emit up to six times more than non-implanted films, meanwhile the PL in thick SI-SRO films is only improved less than two times. Therefore, thin SI-SRO films are an interesting alternative for applications such as the fabrication of efficient Si-nps based LEDs.

  3. Selected area laser-crystallized polycrystalline silicon thin films by a pulsed Nd:YAG laser with 355 nm wavelength

    Institute of Scientific and Technical Information of China (English)

    Duan Chunyan; Liu Chao; Ai Bin; Lai Jianjun; Deng Youjun; Shen Hui

    2011-01-01

    Selected area laser-crystallized polycrystalline silicon(p-Si)thin films were prepared by the third harmonics(355 nm wavelength)generated by a solid-state pulsed Nd:YAG laser.Surface morphologies of 400 nm thick films after laser irradiation were analyzed.Raman spectra show that film crystallinity is improved with increase of laser energy.The optimum laser energy density is sensitive to the film thickness.The laser energy density for efficiently crystallizing amorphous silicon films is between 440-634 mJ/cm2 for 300 nm thick films and between 777-993 mJ/cm2 for 400 nm thick films.The optimized laser energy density is 634,975 and 1571 mJ/cm2 for 300,400 and 500 nm thick films,respectively.

  4. Nanomorph Silicon Thin Films Prepared by Using an HW-MWECR CVD System

    Institute of Scientific and Technical Information of China (English)

    HU Yue-Hui; MA Zhan-Jie; ZHOU Huai-En; ZHU Xiu-Hong; CHEN Guang-Hua; ZHOU Jian-Er; RONG Yan-Dong; LI Ying; SONG Xue-Mei; ZHANG Wen-Li; DING Yi; GAO Zhuo

    2005-01-01

    @@ We have prepared hydrogenated nano-amorph silicon (na-Si:H) films by using a hot-wire-assisted microwave electron-cyclotron-resonance (HW-MWECR) chemical vapour deposition (CVD) system. The films are deposited in two steps: in the first 9min, a hydrogenated amorphous silicon layer is deposited by using hydrogen-diluted silane with a concentration of SiH4/(SiH4+H2) = 20%, and then a nanocrystalline silicon (nc-Si) layer is deposited by using various highly hydrogen-diluted silane. The Raman TO-like mode peak of the films was found in the range 497-508 cm-1. When the silane concentration used for preparation of the nc-Si layer is 14.3%, the film has a large crystalline volume fraction of 65.4%, a wide optical band gap of 1.89eV and a low hydrogen content of 9.5at.%. Moreover, the na-Si:H films rather than nc-Si possess high photosensitivity of about 15.

  5. Boron Doped Nanocrystalline Film with Improved Work Function as a Buffer Layer in Thin Film Silicon Solar Cells.

    Science.gov (United States)

    Park, Jinjoo; Shin, Chonghoon; Park, Hyeongsik; Jung, Junhee; Lee, Youn-Jung; Bong, Sungjae; Dao, Vinh Ai; Balaji, Nagarajan; Yi, Junsin

    2015-03-01

    We investigated thin film silicon solar cells with boron doped hydrogenated nanocrystalline silicon/ hydrogenated amorphous silicon oxide [p-type nc-Si:H/a-SiOx:H] layer. First, we researched the bandgap engineering of diborane (B2H6) doped wide bandgap hydrogenated nanocryslline silicon (p-type nc-Si:H) films, which have excellent electrical properties of high dark conductivity, and low activation energy. The films prepared with lower doping ratio and higher hydrogen dilution ratio had higher optical gap (Eg), with higher dark conductivity (σ(d)), and lower activation energy (Ea). We controlled Eg from 2.10 eV to 1.75 eV, with σ(d) from 1.1 S/cm to 7.59 x 10(-3) S/cm, and Ea from 0.040 eV to 0.128 eV. Next, we focused on the fabrication of thin film silicon solar cells. By inserting p-type nc-Si:H film into the thin film silicon solar cells, we achieved a remarkable increase in the built-in potential from 0.803 eV to 0.901 eV. By forming p-type nc-Si:H film between SnO2:F/ZnO:Al (30 nm) and p-type a-SiOx:H layer, the solar cell properties of open circuit voltage (Voc), short circuit current density (Jsc), and efficiency (η) were improved by 3.7%, 9.2%, and 9.8%, respectively.

  6. Sub-amorphous thermal conductivity in ultrathin crystalline silicon nanotubes.

    Science.gov (United States)

    Wingert, Matthew C; Kwon, Soonshin; Hu, Ming; Poulikakos, Dimos; Xiang, Jie; Chen, Renkun

    2015-04-08

    Thermal transport behavior in nanostructures has become increasingly important for understanding and designing next generation electronic and energy devices. This has fueled vibrant research targeting both the causes and ability to induce extraordinary reductions of thermal conductivity in crystalline materials, which has predominantly been achieved by understanding that the phonon mean free path (MFP) is limited by the characteristic size of crystalline nanostructures, known as the boundary scattering or Casimir limit. Herein, by using a highly sensitive measurement system, we show that crystalline Si (c-Si) nanotubes (NTs) with shell thickness as thin as ∼5 nm exhibit a low thermal conductivity of ∼1.1 W m(-1) K(-1). Importantly, this value is lower than the apparent boundary scattering limit and is even about 30% lower than the measured value for amorphous Si (a-Si) NTs with similar geometries. This finding diverges from the prevailing general notion that amorphous materials represent the lower limit of thermal transport but can be explained by the strong elastic softening effect observed in the c-Si NTs, measured as a 6-fold reduction in Young's modulus compared to bulk Si and nearly half that of the a-Si NTs. These results illustrate the potent prospect of employing the elastic softening effect to engineer lower than amorphous, or subamorphous, thermal conductivity in ultrathin crystalline nanostructures.

  7. The role of oxide interlayers in back reflector configurations for amorphous silicon solar cells

    NARCIS (Netherlands)

    Demontis, V.; Sanna, C.; Melskens, J.; Santbergen, R.; Smets, A.H.M.; Damiano, A.; Zeman, M.

    2013-01-01

    Thin oxide interlayers are commonly added to the back reflector of thin-film silicon solar cells to increase their current. To gain more insight in the enhancement mechanism, we tested different back reflector designs consisting of aluminium-doped zinc oxide (ZnO:Al) and/or hydrogenated silicon oxid

  8. Reactive Infiltration of Silicon Melt Through Microporous Amorphous Carbon Preforms

    Science.gov (United States)

    Sangsuwan, P.; Tewari, S. N.; Gatica, J. E.; Singh, M.; Dickerson, R.

    1999-01-01

    The kinetics of unidirectional capillary infiltration of silicon melt into microporous carbon preforms have been investigated as a function of the pore morphology and melt temperature. The infiltrated specimens showed alternating bands of dark and bright regions, which corresponded to the unreacted free carbon and free silicon regions, respectively. The decrease in the infiltration front velocity for increasing infiltration distances, is in qualitative agreement with the closed-form solution of capillarity driven fluid flow through constant cross section cylindrical pores. However, drastic changes in the thermal response and infiltration front morphologies were observed for minute differences in the preforms microstructure. This suggests the need for a dynamic percolation model that would account for the exothermic nature of the silicon-carbon chemical reaction and the associated pore closing phenomenon.

  9. Amorphous grain boundary layers in the ferromagnetic nanograined ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Straumal, B.B., E-mail: straumal@mf.mpg.de [National University of Science and Technology ' Moscow Institute of Steel and Alloys, MISiS' , Leninsky prospect 4, 119991 Moscow (Russian Federation); Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow district, 142432 (Russian Federation); Karlsruher Institut fuer Technologie, Institut fuer Nanotechnologie, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Mazilkin, A.A.; Protasova, S.G. [Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow district, 142432 (Russian Federation); Max-Planck-Institut fuer Intelligente Systeme (former Institut fuer Metallforschung), Heisenbergstrasse 3, 70569 Stuttgart (Germany); Myatiev, A.A. [National University of Science and Technology ' Moscow Institute of Steel and Alloys, MISiS' , Leninsky prospect 4, 119991 Moscow (Russian Federation); Straumal, P.B. [National University of Science and Technology ' Moscow Institute of Steel and Alloys, MISiS' , Leninsky prospect 4, 119991 Moscow (Russian Federation); Institut fuer Materialphysik, Universitaet Muenster, Wilhelm-Klemm-Str. 10, D-48149 Muenster (Germany); Goering, E. [Max-Planck-Institut fuer Intelligente Systeme (former Institut fuer Metallforschung), Heisenbergstrasse 3, 70569 Stuttgart (Germany); and others

    2011-12-01

    Pure ZnO thin films were obtained by the wet chemistry ('liquid ceramics') method from the butanoate precursors. Films consist of dense equiaxial nanograins and reveal ferromagnetic behaviour. The structure of the ZnO films was studied by the high-resolution transmission electron microscopy. The intergranular regions in the nanograined ZnO films obtained by the 'liquid ceramics' method are amorphous. It looks like fine areas of the second amorphous phase which wets (covers) some of the ZnO/ZnO grain boundaries. Most probably these amorphous intergranular regions contain the defects which are responsible for the ferromagnetic behaviour.

  10. Amorphous and microcrystalline silicon applied in very thin tandem solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Schicho, Sandra

    2011-07-28

    Thin-film solar cells are fabricated by low-cost production processes, and are therefore an alternative to conventionally used wafer solar cells based on crystalline silicon. Due to the different band gaps, tandem cells that consist of amorphous (a-Si:H) and microcrystalline ({mu}c-Si:H) single junction solar cells deposited on top of each other use the solar spectrum much more efficient than single junction solar cells. The silicon layers are usually deposited on TCO (Transparent Conductive Oxide)-coated glass and metal- or plastic foils. Compared to the CdTe and CIGS based thin-film technologies, silicon thin-film solar cells have the advantage that no limitation of raw material supply is expected and no toxic elements are used. Nevertheless, the production cost per Wattpeak is the decisive factor concerning competitiveness and can be reduced by, e.g., shorter deposition times or reduced material consumption. Both cost-reducing conceptions are simultaneously achieved by reducing the a-Si:H and {mu}c-Si:H absorber layer thicknesses in a tandem device. In the work on hand, the influence of an absorber layer thickness reduction up to 77% on the photovoltaic parameters of a-Si:H/{mu}c-Si:H tandem solar cells was investigated. An industry-oriented Radio Frequency Plasma-Enhanced Chemical Vapour Deposition (RF-PECVD) system was used to deposit the solar cells on glass substrates coated with randomly structured TCO layers. The thicknesses of top and bottom cell absorber layers were varied by adjusting the deposition time. Reduced layer thicknesses lead to lower absorption and, hence, to reduced short-circuit current densities which, however, are partially balanced by higher open-circuit voltages and fill factors. Furthermore, by using very thin amorphous top cells, the light-induced degradation decreases tremendously. Accordingly, a thickness reduction of 75% led to an efficiency loss of only 21 %. By adjusting the parameters for the deposition of a-Si:H top cells, a

  11. Delafossite-CuAlO{sub 2} films prepared by annealing of amorphous Cu-Al-O films at high temperature under controlled atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hong-Ying, E-mail: hychen@cc.kuas.edu.tw; Tsai, Ming-Wei

    2011-07-01

    In this study, amorphous Cu-Al-O films were deposited onto a (100) p-type silicon substrate by a magnetron sputtering system. The films were then annealed at 700 deg. C and 800 deg. C for 2 h in N{sub 2}, air and O{sub 2}. X-ray diffraction patterns showed that the as-deposited films were amorphous. When the films were annealed at 700 deg. C, the monoclinic-CuO and spinel-CuAl{sub 2}O{sub 4} phases were detected in all atmospheres. As the annealing temperature increased to 800 deg. C, delafossite-CuAlO{sub 2} (R3-bar m and P6{sub 3}/mmc phases) appeared in N{sub 2} whereas monoclinic-CuO and spinel-CuAl{sub 2}O{sub 4} phases were detected in air and O{sub 2}. Thermodynamic calculations can explain the formation of delafossite-CuAlO{sub 2} films. The optical bandgap and conductivity of delafossite-CuAlO{sub 2} films were 3.30 eV and 6.8 x 10{sup -3} S/cm, respectively, which are compatible with other data in the literature. The p-type characteristic in delafossite-CuAlO{sub 2} films was verified by a hot-probe method.

  12. Mechanical properties of bismuth implanted amorphous Ge film

    Energy Technology Data Exchange (ETDEWEB)

    Juhasz, A.; Szommer, P.; Lendvai, J.; Vertesy, Z.; Peto, G. E-mail: peto@mfa.kfki.hu

    1999-01-02

    Mechanical properties of Bi ion implanted a-Ge film were studied by dynamic microhardness tests and compared to those of unimplanted a-Ge film. 400 nm thick films were evaporated in units of 30 nm thick layers and bombarded with Bi ions at 60 keV energy and 2 {mu}A/cm{sup 2} current. Cyclic load-unload indentation tests and indentation creep tests were performed to determine the hardness and ductility of the ion implanted and unimplanted specimens, respectively. The brittleness of the materials was characterised by scanning electron microscopic observation of crack formation around the Vickers indentations. The dynamic hardness was much larger, the ductility lower, the crack formation was significantly larger in the case of the unimplanted than in the ion bombarded specimens. The observed differences in the mechanical properties indicate structural differences between the two types of a-Ge are in agreement with the earlier reported formation of a new amorphous phase of Ge induced by ion implantation (G. Peto, J. Kanski, U. Sodervall, Phys. Lett. 124 (1987) 510)

  13. Mechanical properties of bismuth implanted amorphous Ge film

    Science.gov (United States)

    Juhász, A.; Szommer, P.; Lendvai, J.; Vértesy, Z.; Pető, G.

    1999-01-01

    Mechanical properties of Bi ion implanted a-Ge film were studied by dynamic microhardness tests and compared to those of unimplanted a-Ge film. 400 nm thick films were evaporated in units of 30 nm thick layers and bombarded with Bi ions at 60 keV energy and 2 μA/cm 2 current. Cyclic load-unload indentation tests and indentation creep tests were performed to determine the hardness and ductility of the ion implanted and unimplanted specimens, respectively. The brittleness of the materials was characterised by scanning electron microscopic observation of crack formation around the Vickers indentations. The dynamic hardness was much larger, the ductility lower, the crack formation was significantly larger in the case of the unimplanted than in the ion bombarded specimens. The observed differences in the mechanical properties indicate structural differences between the two types of a-Ge are in agreement with the earlier reported formation of a new amorphous phase of Ge induced by ion implantation (G. Pető, J. Kanski, U. Sodervall, Phys. Lett. 124 (1987) 510 [6]).

  14. An overview of uncooled infrared sensors technology based on amorphous silicon and silicon germanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, Roberto; Mireles, Jose Jr. [Technology and Engineering Institute, Ciudad Juarez University UACJ, Av. Del Charro 450N, 32310 Chihuahua (Mexico); Moreno, Mario; Torres, Alfonso; Kosarev, Andrey [National Institute for Astrophysics Optics and Electronics INAOE, Luis E. Erro 1, PO Box 51 and 216, 7200 Puebla (Mexico); Heredia, Aurelio [Universidad Popular Autonoma del Estado de Puebla, 21 sur 1103 Col. Santiago, 72160 Puebla (Mexico)

    2010-04-15

    At the present time there are commercially available large un-cooled micro-bolometer arrays (as large as 1024 x 768 pixels) for a variety of thermal imaging applications. Different thermo-sensing materials have been employed as thermo sensing elements as Vanadium Oxide (VO{sub x}), metals, and amorphous and polycrystalline semiconductors. Those materials present good characteristics but also have some disadvantages. As a consequence none of the commercially available arrays contain optimum pixels with an optimum thermo-sensing material. This paper reviews the development of the un-cooled bolometer technology and the research achievements on this area, with special attention on the key factors that would lead to improve the pixels performance characteristics. The work considers the R and D of microbolometer arrays and the integration with MEMS and IC technologies. A comparative study with the state of the art and data reported in literature is presented. Finally, further directions of uncooled bolometer based in thin films materials are also discussed in this paper. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Transport properties of low-dimensional amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, Somnath [Nano-Electronics Centre, Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey (United Kingdom)]. E-mail: s.bhattacharyya@surrey.ac.uk; Silva, S.R.P. [Nano-Electronics Centre, Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey (United Kingdom)

    2005-06-22

    Research on amorphous carbon (a-C) to date has focused on the distinction between the sp{sup 2} and sp{sup 3} phases and understanding the properties on the basis of the sp{sup 2}-C bonded component. Recently, sufficient information on the sp{sup 2}-bonded clusters and nanoforms of carbon has helped to identify the importance of sp{sup 2}-C over sp{sup 3}-C, especially in transport properties and encouraged many groups to exploit this knowledge for device design. However, at present, few studies dedicated purely to understanding the transport properties and electronic structure of the family of a-C films as a whole is available. In this paper, we try to identify the key issues in using a-C as an unconventional semiconducting material and try to elaborate on how to overcome these hurdles in order to utilize this extremely versatile material for active device fabrication.

  16. Amorphous IZO-based transparent thin film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Paine, David C. [Division of Engineering, Brown University, Providence, RI 02912 (United States)], E-mail: David_Paine@Brown.edu; Yaglioglu, Burag; Beiley, Zach; Lee, Sunghwan [Division of Engineering, Brown University, Providence, RI 02912 (United States)

    2008-07-01

    Active electronics implemented on cheap flexible polymer substrates offer the promise of novel display technologies, wearable electronics, large area memory, and a multitude of other, as-yet-unthought-of applications that require low cost and high volume manufacturing. Thin film transistors (TFT's) fabricated on temperature-sensitive plastic substrates at low temperatures are the key to this technology. TFT's that use metal (In, Zn, Sn, Ga) oxide channels offer both high mobility (relative to amorphous Si) and the advantage of optical transparency in the visible regime. We report on the fabrication and performance of amorphous oxide transparent thin film transistors that use dc-magnetron sputter techniques to deposit IZO (In{sub 2}O{sub 3} - 10 wt.% ZnO) at low oxygen potential (0 vol.% O{sub 2}) for the source, drain, and gate-contact metallization and, at higher oxygen partial pressures (10 vol.% O{sub 2}), for the semi-conducting channel. The devices in this study were processed at room temperature except for a single 280 {sup o}C PECVD deposition step to deposit a 230 nm-thick SiO{sub x} gate dielectric. The devices are optically transparent and operate in depletion mode with a threshold voltage of - 5 V, mobility of 15 cm{sup 2}/V s, an on-off ratio of > 10{sup 6} and, a sub-threshold slope of 1.2 V/decade. In addition, we report persistent photo-conductivity in the channel region of these devices when exposed to UV illumination.

  17. Preparation and Properties of Amorphous NiFe/Cu/NiFe Thin Films

    Institute of Scientific and Technical Information of China (English)

    YE Yun; JIANG Ya-dong; HU Wen-cheng; ZENG Hong-juan

    2004-01-01

    The amorphous of Permalloy on the copper subtract was studied using composite electroplating method. A portion of hydrogen brings the counteraction on the surface of cathode leading nickel-iron alloys to be anomalous in the process of co-depositing. The results of X-ray diffraction (XRD) show that the Ni-Fe alloys layer is amorphous. The Giant Magneto -Impedance (GMI) effect of Ni-Fe alloys was obtained under the optimal conditions, dependence on the soft magnetic property of Ni-Fe amorphous thin film. As a result, the ratios△ Z/Z of NiFe/Cu/NiFe amorphous thin film are 30% at 40 kHz which is in low frequency. Furthermore, the GMI value of NiFe/Cu/NiFe amorphous thin film with a sandwich structure is higher than that of single-layer ferromagnetic films of the same thickness.

  18. Variation in the structure and optical properties of polymorphous silicon thin films using dichlorosilane as silicon precursor

    Energy Technology Data Exchange (ETDEWEB)

    Remolina, A.; Hamui, L.; Monroy, B.M.; Garcia-Sanchez, M.F.; Santana, G. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, AP 70-360, Cd. Universitaria, Coyoacan, C. P. 04510, Mexico D. F. (Mexico); Ponce, A. [Centro de Investigacion en Quimica Aplicada, Blvd. Enrique Reyna Hermosillo 140, C. P. 25290, Saltillo, Coahuila (Mexico); Picquart, M. [Departamento de Fisica, Universidad Autonoma Metropolitana, AP 55-534, Av. Sn Rafael Atlixco 186, Col. Vicentina, Iztapalapa, C.P. 09340, Mexico D. F. (Mexico)

    2011-03-15

    Polymorphous silicon thin films were obtained by plasma enhanced chemical vapor deposition using dichlorosilane as silicon precursor. The RF power and the dichlorosilane to hydrogen flow rate ratio were varied to obtain different crystalline fractions and average sizes of silicon nanocrystals embedded in the amorphous silicon matrix. Microscopy images confirmed the existence of nanocrystallites with averages sizes between 2 and 6 nm. Broader size distributions were obtained with increasing RF power. Raman results confirmed that different nanocrystalline fractions (from 12% to 54%) can be achieved in these films by regulating the selected growth parameters. The optical band gap calculated by the Tauc model from UV-visible transmittance measurements varies between 1.8 to 2.3 eV. The relationship between the optical properties is discussed in terms of the different nanostructures of the samples. Depending on their absorption properties and effective band gap, these materials can be suitable for application in thin film solar cell devices (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Effect of amorphous C films deposited by RF magnetron sputtering on smoothing K9 glass substrate

    Science.gov (United States)

    Deng, Songwen; Qi, Hongji; Wei, Chaoyang; Yi, Kui; Fan, Zhengxiu; Shao, Jianda

    2009-12-01

    Soft X-ray multilayer reflectors must be deposited on super-smooth surface such as super-polished silicon wafers or glasses, which are complicate, time-consuming and expensive to produce. To overcome this shortage, C films deposited by RF magnetron sputtering were considered to smooth the K9 glass substrates' surface in the present paper. The structure of C films was systematically studied by XRD and Raman spectrum. The surface morphology and rms-roughness were obtained by AFM. Then, we calculated the impact of the C layers on the reflectivity curve of Mo/Si soft X-ray multilayer reflector around 13.5 nm. The C films exhibit typical amorphous state. With the increasing of power and thickness, the content of sp3 hybrid bonding decreases while the amount or size of well-organized graphite clusters increases. The surface rms-roughness decreases from 2.4 nm to 0.62 nm after smoothed by an 80 nm thick C layer deposited in 500 W, which is the smoothest C layer surface we have obtained. The calculation results show that the theoretical normal incidence reflectivity of Mo/Si multilayer at 13.5 nm increases from 7% to 63%.

  20. Effect of varying nitrogen flow rates on the optical properties of amorphous-SiCN thin films

    Science.gov (United States)

    Rahman, Mohd Azam Abdul; Tong, Goh Boon; Mahmood, Mohamad Rusop; Siong, Chiu Wee; Yian, Haw Choon; Rahman, Saadah Abdul

    2016-11-01

    Series of amorphous silicon carbon nitride (a-SiCN) films are synthesized using RF-PECVD technique on glass and silicon substrates from precursor gas of silane, methane and nitrogen. In this work, the change in nitrogen flow rate from 0 sccm to 50 sccm is a mean used to vary the elemental composition and bonding properties which lead to change in optical properties. The films thickness varies between 327 nm to 944 nm. The changes for the stated properties are discussed against the change in the stated nitrogen flow rate. The optical properties are investigated by means of UV-VIS spectroscopy in the wavelength range of 190 nm to 2500 nm. The transmittance of the films at ultra-violet wavelength is found to increases with increase in nitrogen flow rate. The index of refraction, n obtained for SiCN films from transmittance and reflectance measurements is lower compared to SiC films. The films optical band gap increases from 1.74 eV to 2.08 eV before it decreases to 1.89 eV as nitrogen flow rate increases from 0 to 50 sccm. The optical dispersion parameters were determined according to Wemple and Didomenico method.

  1. Plasma-initiated rehydrogenation of amorphous silicon to increase the temperature processing window of silicon heterojunction solar cells

    Science.gov (United States)

    Shi, Jianwei; Boccard, Mathieu; Holman, Zachary

    2016-07-01

    The dehydrogenation of intrinsic hydrogenated amorphous silicon (a-Si:H) at temperatures above approximately 300 °C degrades its ability to passivate silicon wafer surfaces. This limits the temperature of post-passivation processing steps during the fabrication of advanced silicon heterojunction or silicon-based tandem solar cells. We demonstrate that a hydrogen plasma can rehydrogenate intrinsic a-Si:H passivation layers that have been dehydrogenated by annealing. The hydrogen plasma treatment fully restores the effective carrier lifetime to several milliseconds in textured crystalline silicon wafers coated with 8-nm-thick intrinsic a-Si:H layers after annealing at temperatures of up to 450 °C. Plasma-initiated rehydrogenation also translates to complete solar cells: A silicon heterojunction solar cell subjected to annealing at 450 °C (following intrinsic a-Si:H deposition) had an open-circuit voltage of less than 600 mV, but an identical cell that received hydrogen plasma treatment reached a voltage of over 710 mV and an efficiency of over 19%.

  2. Kinetics of the laser-induced solid phase crystallization of amorphous silicon-Time-resolved Raman spectroscopy and computer simulations

    Science.gov (United States)

    Očenášek, J.; Novák, P.; Prušáková, L.

    2017-01-01

    This study demonstrates that a laser-induced crystallization instrumented with Raman spectroscopy is, in general, an effective tool to study the thermally activated crystallization kinetics. It is shown, for the solid phase crystallization of an amorphous silicon thin film, that the integral intensity of Raman spectra corresponding to the crystalline phase grows linearly in the time-logarithmic scale. A mathematical model, which assumes random nucleation and crystal growth, was designed to simulate the crystallization process in the non-uniform temperature field induced by laser. The model is based on solving the Eikonal equation and the Arhenius temperature dependence of the crystal nucleation and the growth rate. These computer simulations successfully approximate the crystallization process kinetics and suggest that laser-induced crystallization is primarily thermally activated.

  3. Low temperature NbSi thin film thermometers on Silicon Nitride membranes for bolometer applications

    Energy Technology Data Exchange (ETDEWEB)

    Camus, Ph. E-mail: camus@csnsm.in2p3.fr; Berge, L.; Dumoulin, L.; Marnieros, S.; Torre, J.P

    2000-04-07

    We report the design of amorphous NbSi thin film bolometer thermometers on Silicon Nitride membranes. Due to the low-thermal conductivity of Si{sub 3}N{sub 4}, this material has several applications in millimeter wavelength bolometers and microcalorimetry. Compared to NTD-Ge thermometers, similar sensitivities are obtained with a 50 times lesser volume. The smallest realized films have a rectangular surface (100x400 {mu}m{sup 2}) and are 100 nm thick. Optimization of the thermometer shape, NbSi composition and electrical material contact is discussed. The goal of this development is to manufacture a complete array of bolometers by photolithography techniques.

  4. Annealing Temperature dependence of Photoluminescence from Silicon-rich silica Films

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The silicon-rich silica films were prepared by a dual-ion-beam co-sputtering method from a composite Target in an argon atmosphere. The structure of the films studied by the aid of TEM and XRD is amorphous. The photoluminescence (PL) spectra were found to have a 4luminescent band peak at 320 nm, 410 nm, 560 nm, and 630 nm, respectively, at room temperature.The intensity and the wavelength position of PL are dependent on annealing temperature (Ta),and the luminescent mechanism is analyzed.

  5. Electroless plating of thin gold films directly onto silicon nitride thin films and into micropores.

    Science.gov (United States)

    Whelan, Julie C; Karawdeniya, Buddini Iroshika; Bandara, Y M Nuwan D Y; Velleco, Brian D; Masterson, Caitlin M; Dwyer, Jason R

    2014-07-23

    A method to directly electrolessly plate silicon-rich silicon nitride with thin gold films was developed and characterized. Films with thicknesses plating free-standing ultrathin silicon nitride membranes, and we successfully plated the interior walls of micropore arrays in 200 nm thick silicon nitride membranes. The method is thus amenable to coating planar, curved, and line-of-sight-obscured silicon nitride surfaces.

  6. 4.0-nm-thick amorphous Nb–Ni film as a conducting diffusion barrier layer for integrating ferroelectric capacitor on Si

    Energy Technology Data Exchange (ETDEWEB)

    Dai, X.H. [Hebei Key Lab of Optic-electronic Information and Materials, College of Physics Science & Technology, Hebei University, Hebei 071002 (China); College of Electronic and Information Engineering, Hebei University of Technology, Tianjin 300401 (China); Guo, J.X.; Zhang, L.; Jia, D.M.; Qi, C.G.; Zhou, Y.; Li, X.H.; Shi, J.B.; Fu, Y.J.; Wang, Y.L.; Lou, J.Z. [Hebei Key Lab of Optic-electronic Information and Materials, College of Physics Science & Technology, Hebei University, Hebei 071002 (China); Ma, L.X. [Department of Physics, Blinn College, Bryan, TX 77805 (United States); Zhao, H.D. [College of Electronic and Information Engineering, Hebei University of Technology, Tianjin 300401 (China); Liu, B.T., E-mail: btliu@hbu.cn [Hebei Key Lab of Optic-electronic Information and Materials, College of Physics Science & Technology, Hebei University, Hebei 071002 (China)

    2015-10-05

    Highlights: • 4-nm-thick amorphous Nb–Ni film is first used as the conducting barrier layer. • No obvious interdiffusion/reaction can be found from the LSCO/PZT/LSCO/Nb–Ni/Si. • The LSCO/PZT/LSCO capacitor, measured at 5 V, possesses very good properties. • Ultrathin amorphous Nb–Ni film is ideal to fabricate silicon-based FRAM. - Abstract: We have successfully integrated La{sub 0.5}Sr{sub 0.5}CoO{sub 3}/PbZr{sub 0.4}Ti{sub 0.6}O{sub 3}/La{sub 0.5}Sr{sub 0.5}CoO{sub 3} (LSCO/PZT/LSCO) capacitors on silicon substrate using a ∼4.0-nm-thick amorphous Nb–Ni film as the conducting diffusion barrier layer. Transmission electron microscopy technique confirms that the Nb–Ni film is still amorphous after fabrication of the capacitors, and the interfaces related to Nb–Ni are clean and sharp without any findable interdiffusion/reaction. The LSCO/PZT/LSCO capacitor, measured at 5 V, possesses very good properties, such as large remanent polarization of ∼22.1 μC/cm{sup 2}, small coercive voltage of ∼1.27 V, good fatigue-resistance, and small pulse width dependence, implying that ultrathin amorphous Nb–Ni film is ideal as the conducting diffusion barrier layer to fabricate high-density silicon-based ferroelectric random access memories.

  7. Picosecond all-optical switching in hydrogenated amorphous silicon microring resonators

    CERN Document Server

    Pelc, Jason S; Vo, Sonny; Santori, Charles; Fattal, David A; Beausoleil, Raymond G

    2014-01-01

    We utilize cross-phase modulation to observe all-optical switching in microring resonators fabricated with hydrogenated amorphous silicon (a-Si:H). Using 2.7-ps pulses from a mode-locked fiber laser in the telecom C-band, we observe optical switching of a cw telecom-band probe with full-width at half-maximum switching times of 14.8 ps, using approximately 720 fJ of energy deposited in the microring. In comparison with telecom-band optical switching in crystalline silicon microrings, a-Si:H exhibits substantially higher switching speeds due to reduced impact of free-carrier processes.

  8. Property change during nanosecond pulse laser annealing of amorphous NiTi thin film

    Indian Academy of Sciences (India)

    S K Sadrnezhaad; Noushin Yasavol; Mansoureh Ganjali; Sohrab Sanjabi

    2012-06-01

    Nanosecond lasers of different intensities were pulsed into sputter-deposited amorphous thin films of near equiatomic Ni/Ti composition to produce partially crystallized highly sensitive -phase spots surrounded by amorphous regions. Scanning electron microscopy having secondary and back-scattered electrons, field emission scanning electron microscopy, optical microscopy and X-ray diffraction patterns were used to characterize the laser treated spots. Effect of nanosecond pulse lasering on microstructure, morphology, thermal diffusion and inclusion formation was investigated. Increasing beam intensity and laser pulse-number promoted amorphous to -phase transition. Lowering duration of the pulse incidence reduced local film oxidation and film/substrate interference.

  9. Microstructure of ternary Zn1-xCdxO films on silicon substrate

    Institute of Scientific and Technical Information of China (English)

    LU Huan-ming; YE Zhi-zhen; MA De-wei; HUANG Jing-yun; ZHU Li-ping; ZHAO Bing-hui

    2005-01-01

    Ternary Zn1-xCdx O alloying films were deposited on silicon substrates by a reactive magnetron sputtering method.The structures of the films were characterized by transmission electron microscopy(TEM) and X-ray diffraction (XRD) analysis, respectively. The XRD measurement shows that the wurtzite-type structure of Zn1-xCdxO can be stabilized up to Cd content of x=0.53 without a cubic CdO phase separation.The TEM measurement shows that the films have a columnar structure and the grains are highly c-axis oriented perpendicularly on silicon substrate although some grain boundaries are slightly tilted.High resolution TEM observation indicates that a native layer of amorphous SiO2 exists at the ZnCdO/Si interface and that ZnCdO grains with c-axis preferred orientation nucleate directly on substrate surface.

  10. An alternative system for mycotoxin detection based on amorphous silicon sensors

    Science.gov (United States)

    Caputo, D.; de Cesare, G.; De Rossi, P.; Fanelli, C.; Nascetti, A.; Ricelli, A.; Scipinotti, R.

    2007-05-01

    In this work we investigate, for the first time, the performances of a system based on hydrogenated amorphous silicon photosensors for the detection of Ochratoxin A. The sensor is a n-type/intrinsic/p-type amorphous silicon stacked structure deposited on a glass substrate. The mycotoxin is deposited on a thin layer chromatographic plate and aligned with the sensor. An ultraviolet radiation excites the ochratoxin A, whose fluorescence produces a photocurrent in the sensor. The photocurrent value is proportional to the deposited mycotoxin quantity. An excellent linearity of the detector response over more than two orders of magnitude of ochratoxin A amount is observed. The minimum detected mycotoxin quantity is equal to 0.1ng, suggesting that the presented detection system could be a good candidate to perform rapid and analytical ochratoxin A analysis in different kind of samples.

  11. Development of laser-fired contacts for amorphous silicon layers obtained by Hot-Wire CVD

    Energy Technology Data Exchange (ETDEWEB)

    Munoz, D. [XaRMAE-Universitat de Barcelona, Departament de Fisica Aplicada i Optica, Diagonal 647, Barcelona 08028 (Spain)], E-mail: delfina@eel.upc.edu; Voz, C.; Blanque, S. [Universitat Politecnica de Catalunya, Grup de Recerca en Micro i Nanotecnologies, Jordi Girona 1-3, Barcelona 08034 (Spain); Ibarz, D.; Bertomeu, J. [XaRMAE-Universitat de Barcelona, Departament de Fisica Aplicada i Optica, Diagonal 647, Barcelona 08028 (Spain); Alcubilla, R. [Universitat Politecnica de Catalunya, Grup de Recerca en Micro i Nanotecnologies, Jordi Girona 1-3, Barcelona 08034 (Spain)

    2009-03-15

    In this work we study aluminium laser-fired contacts for intrinsic amorphous silicon layers deposited by Hot-Wire CVD. This structure could be used as an alternative low temperature back contact for rear passivated heterojunction solar cells. An infrared Nd:YAG laser (1064 nm) has been used to locally fire the aluminium through the thin amorphous silicon layers. Under optimized laser firing parameters, very low specific contact resistances ({rho}{sub c} {approx} 10 m{omega} cm{sup 2}) have been obtained on 2.8 {omega} cm p-type c-Si wafers. This investigation focuses on maintaining the passivation quality of the interface without an excessive increase in the series resistance of the device.

  12. Arrays of ZnO nanocolumns for 3-dimensional very thin amorphous and microcrystalline silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Neykova, Neda, E-mail: neykova@fzu.cz [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 16253 Prague 6 (Czech Republic); Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering Trojanova 13, 120 00 Prague 2 (Czech Republic); Hruska, Karel; Holovsky, Jakub; Remes, Zdenek; Vanecek, Milan [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 16253 Prague 6 (Czech Republic)

    2013-09-30

    We report on the hydrothermal growth of high quality arrays of single crystalline zinc oxide (ZnO) nanocolumns, oriented perpendicularly to the transparent conductive oxide substrate. In order to obtain precisely defined spacing and arrangement of ZnO nanocolumns over an area up to 0.5 cm{sup 2}, we used electron beam lithography. Vertically aligned ZnO (multicrystalline or single crystals) nanocolumns were grown in an aqueous solution of zinc nitrate hexahydrate and hexamethylenetetramine at 95 °C, with a growth rate 0.5 ÷ 1 μm/h. The morphology of the nanostructures was visualized by scanning electron microscopy. Such nanostructured ZnO films were used as a substrate for the recently developed 3-dimensional thin film silicon (amorphous, microcrystalline) solar cell, with a high efficiency potential. The photoelectrical and optical properties of the ZnO nanocolumns and the silicon absorber layers of these type nanostructured solar cells were investigated in details. - Highlights: • Vertically-oriented ZnO nanocolumns were grown by hydrothermal method. • The ZnO nanocolumns were grown over an area of 0.5 cm{sup 2}. • For precise arrangement of the ZnO nanocolumns electron beam lithography was used. • We report on 3-D design of nanostructured solar cell. • Optical thickness of nanostructured cell was three times higher compared to flat cell.

  13. Full breast digital mammography with an amorphous silicon-based flat panel detector: Physical characteristics of a clinical prototype

    OpenAIRE

    2000-01-01

    The physical characteristics of a clinical prototype amorphous silicon-based flat panel imager for full-breast digital mammography have been investigated. The imager employs a thin thallium doped CsI scintillator on an amorphous silicon matrix of detector elements with a pixel pitch of 100 μm. Objective criteria such as modulation transfer function (MTF), noise power spectrum, detective quantum efficiency (DQE), and noise equivalent quanta were employed for this evaluation. The presampling MT...

  14. Transparent Conductive Oxides for Thin-Film Silicon Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Loeffler, J.

    2005-04-25

    This thesis describes research on thin-film silicon solar cells with focus on the transparent conductive oxide (TCO) for such devices. In addition to the formation of a transparent and electrically conductive front electrode for the solar cell allowing photocurrent collection with low ohmic losses, the front TCO plays an important role for the light enhancement of thin-film silicon pin type solar cells. If the TCO is rough, light scattering at rough interfaces in the solar cell in combination with a highly reflective back contact leads to an increase in optical path length of the light. Multiple (total) internal reflectance leads to virtual 'trapping' of the light in the solar cell structure, allowing a further decrease in absorber thickness and thus thin-film silicon solar cell devices with higher and more stable efficiency. Here, the optical mechanisms involved in the light trapping in thin-film silicon solar cells have been studied, and two types of front TCO materials have been investigated with respect to their suitability as front TCO in thin-film silicon pin type solar cells. Undoped and aluminum doped zinc oxide layers have been fabricated for the first time by the expanding thermal plasma chemical vapour deposition (ETP CVD) technique at substrate temperatures between 150C and 350C, and successfully implemented as a front electrode material for amorphous silicon pin superstrate type solar cells. Solar cells with efficiencies comparable to cells on Asahi U-type reference TCO have been reproducibly obtained. A higher haze is needed for the ZnO samples studied here than for Asahi U-type TCO in order to achieve comparable long wavelength response of the solar cells. This is attributed to the different angular distribution of the scattered light, showing higher scattering intensities at large angles for the Asahi U-type TCO. A barrier at the TCO/p interface and minor collection problems may explain the slightly lower fill factors obtained for the

  15. Transparent conductive oxides for thin-film silicon solar cells

    Science.gov (United States)

    Löffler, J.

    2005-04-01

    This thesis describes research on thin-film silicon solar cells with focus on the transparent conductive oxide (TCO) for such devices. In addition to the formation of a transparent and electrically conductive front electrode for the solar cell allowing photocurrent collection with low ohmic losses, the front TCO plays an important role for the light enhancement of thin-film silicon pin type solar cells. If the TCO is rough, light scattering at rough interfaces in the solar cell in combination with a highly reflective back contact leads to an increase in optical path length of the light. Multiple (total) internal reflectance leads to virtual 'trapping' of the light in the solar cell structure, allowing a further decrease in absorber thickness and thus thin-film silicon solar cell devices with higher and more stable efficiency. Here, the optical mechanisms involved in the light trapping in thin-film silicon solar cells have been studied, and two types of front TCO materials have been investigated with respect to their suitability as front TCO in thin-film silicon pin type solar cells. Undoped and aluminum doped zinc oxide layers have been fabricated for the first time by the expanding thermal plasma chemical vapour deposition (ETP CVD) technique at substrate temperatures between 150 º C and 350 º C, and successfully implemented as a front electrode material for amorphous silicon pin superstrate type solar cells. Solar cells with efficiencies comparable to cells on Asahi U-type reference TCO have been reproducibly obtained. A higher haze is needed for the ZnO samples studied here than for Asahi U-type TCO in order to achieve comparable long wavelength response of the solar cells. This is attributed to the different angular distribution of the scattered light, showing higher scattering intensities at large angles for the Asahi U-type TCO. A barrier at the TCO/p interface and minor collection problems may explain the slightly lower fill factors obtained for the cells

  16. Silicon Light: a European FP7 project aiming at high efficiency thin film silicon solar cells on foil. Monolithic series interconnection of flexible thin-film PV devices

    Energy Technology Data Exchange (ETDEWEB)

    Soppe, W. [ECN Solar Energy, P.O. Box 1, 1755 ZG Petten (Netherlands); Haug, F.J. [Ecole Polytechnique Federale de Lausanne EPFL, Photovoltaics and Thin Film Electronics Laboratory, Rue A.-L. Breguet 2, 2000 Neuchatel (Switzerland); Couty, P. [VHFTechnologies SA, Rue Edouard-Verdan 2, CH-1400 Yverdon-les-Bains (Switzerland); Duchamp, M. [Technical University of Denmark, Center for Electron Nanoscopy, DK-2800 Kongens Lyngby (Denmark); Schipper, W. [Nanoptics GmbH, Innungstr.5, 21244 Buchholz (Germany); Krc, J. [University of Ljubljana, Faculty of Electrical Engineering, Trzaska 25, SI-1000 Ljubljana (Slovenia); Sanchez, G. [Universidad Politecnica de Valencia, I.U.I. Centro de Tecnologia Nanofotonica, 46022 Valencia (Spain); Leitner, K. [Umicore Thin Film Products AG, Balzers (Liechtenstein); Wang, Q. [Shanghai Jiaotong University, Research Institute of Micro/Nanometer Science and Technology, 800 Dongchuan Road, Min Hang, 200240 Shanghai (China)

    2011-09-15

    Silicon-Light is a European FP7 project, which started January 1st, 2010 and aims at development of low cost, high-efficiency thin film silicon solar cells on foil. Three main routes are explored to achieve these goals: (a) advanced light trapping by implementing nanotexturization through UV Nano Imprinting Lithography (UV-NIL); (b) growth of crack-free silicon absorber layers on highly textured substrates; (c) development of new TCOs which should combine the best properties of presently available materials like ITO and AZO. The paper presents the midterm status of the project results, showing model calculations of ideal nanotextures for light trapping in thin film silicon solar cells; the fabrication of masters and the replication and roll-to-roll fabrication of these nanotextures. Further, results on ITO variants with improved work function are presented. Finally, the status of cell fabrication on foils with nanotexture is shown. Microcrystalline and amorphous silicon single junction cells with stable efficiencies with more than 8% have been made, paving the way towards a-Si/{mu}c-Si tandem cells with more than 11% efficiency.

  17. Results on photon and neutron irradiation of semitransparent amorphous-silicon sensors

    CERN Document Server

    Carabe, J; Ferrando, A; Fuentes, J; Gandia, J J; Josa-Mutuberria, I; Molinero, A; Oller, J C; Arce, P; Calvo, E; Figueroa, C F; García, N; Matorras, F; Rodrigo, T; Vila, I; Virto, A L; Fenyvesi, A; Molnár, J; Sohler, D

    2000-01-01

    Semitransparent amorphous-silicon sensors are basic elements for laser 2D position reconstruction in the CMS multipoint alignment link system. Some of the sensors have to work in a very hard radiation environment. Two different sensor types have been irradiated with /sup 60/Co photons (up to 100 kGy) and fast neutrons (up to 10/sup 15 / cm/sup -2/), and the subsequent change in their performance has been measured. (13 refs).

  18. First Measurements of the Performance of New Semitransparent Amorphous Silicon Sensor Prototypes

    Energy Technology Data Exchange (ETDEWEB)

    Calderon, A.; Calvo, E.; Martinez-Rivero, C.; Matorras, F.; Rodrigo, T.; Sobron, M.; Vila, I.; Virto, A. L.; Alberdi, J.; Arce, P.; Barcala, J. M.; Ferrando, A.; Josa, M. I.; Luque, J. M.; Molinero, A.; Navarrete, J.; Oller, J. C.; Yuste, C.

    2004-07-01

    We present first results on the performance of a new generation of semitransparent amorphous silicon position detectors having good properties such as an intrinsic position resolution better than 5{mu}m, an spatial point reconstruction precision better than 10 {mu}m, deflection angles smaller than 10{mu}rad and transmission in the visible and NIR higher than 70%. In addition the sensitive area is very large: 30x30 cm''3. (Author) 10 refs.

  19. Tandem solar cells made from amorphous silicon and polymer bulk heterojunction sub-cells.

    Science.gov (United States)

    Park, Sung Heum; Shin, Insoo; Kim, Kwang Ho; Street, Robert; Roy, Anshuman; Heeger, Alan J

    2015-01-14

    A tandem solar cell based on a combination of an amorphous silicon (a-Si) and polymer solar cell (PSC) is demonstrated. As these tandem devices can be readily fabricated by low-cost methods, they require only a minor increase in the total manufacturing cost. Therefore, a combination of a-Si and PSC provides a compelling solution to reduce the cost of electricity produced by photovoltaics.

  20. Magneto-optical switch with amorphous silicon waveguides on magneto-optical garnet

    Science.gov (United States)

    Ishida, Eiichi; Miura, Kengo; Shoji, Yuya; Mizumoto, Tetsuya; Nishiyama, Nobuhiko; Arai, Shigehisa

    2016-08-01

    We fabricated a magneto-optical (MO) switch with a hydrogenated amorphous silicon waveguide on an MO garnet. The switch is composed of a 2 × 2 Mach-Zehnder interferometer (MZI). The switch state is controlled by an MO phase shift through a magnetic field generated by a current flowing in an electrode located on the MZI. The switching operation was successfully demonstrated with an extinction ratio of 11.7 dB at a wavelength of 1550 nm.

  1. 2H-SiC Dendritic Nanocrystals In Situ Formation from Amorphous Silicon Carbide under Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Under electron beam irradiation, the in-situ formation of 2H-SiC dentritic nanocrystals from amorphous silicon carbide at room temperature was observed. The homogenous transition mainly occurs at the thin edge and on the surface of specimen where the energy obtained from electron beam irradiation is high enough to cause the amorphous crystallizing into 2H-SiC.

  2. High spatial resolution radiation detectors based on hydrogenated amorphous silicon and scintillator

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Tao [Univ. of California, Berkeley, CA (United States). Dept. of Engineering-Nuclear Engineering

    1995-05-01

    Hydrogenated amorphous silicon (a-Si:H) as a large-area thin film semiconductor with ease of doping and low-cost fabrication capability has given a new impetus to the field of imaging sensors; its high radiation resistance also makes it a good material for radiation detectors. In addition, large-area microelectronics based on a-Si:H or polysilicon can be made with full integration of peripheral circuits, including readout switches and shift registers on the same substrate. Thin a-Si:H p-i-n photodiodes coupled to suitable scintillators are shown to be suitable for detecting charged particles, electrons, and X-rays. The response speed of CsI/a-Si:H diode combinations to individual particulate radiation is limited by the scintillation light decay since the charge collection time of the diode is very short (< 10ns). The reverse current of the detector is analyzed in term of contact injection, thermal generation, field enhanced emission (Poole-Frenkel effect), and edge leakage. A good collection efficiency for a diode is obtained by optimizing the p layer of the diode thickness and composition. The CsI(Tl) scintillator coupled to an a-Si:H photodiode detector shows a capability for detecting minimum ionizing particles with S/N ~20. In such an arrangement a p-i-n diode is operated in a photovoltaic mode (reverse bias). In addition, a p-i-n diode can also work as a photoconductor under forward bias and produces a gain yield of 3--8 for shaping times of 1 {micro}s. The mechanism of the formation of structured CsI scintillator layers is analyzed. Initial nucleation in the deposited layer is sensitive to the type of substrate medium, with imperfections generally catalyzing nucleation. Therefore, the microgeometry of a patterned substrate has a significant effect on the structure of the CsI growth.

  3. Efficient nanorod-based amorphous silicon solar cells with advanced light trapping

    Energy Technology Data Exchange (ETDEWEB)

    Kuang, Y. [Physics of Devices, Debye Institute for Nanomaterials Science, Utrecht University, High Tech Campus, Building 21, 5656 AE Eindhoven (Netherlands); Department of Applied Physics, Plasma & Materials Processing, Eindhoven University of Technology (TUE), P.O. Box 513, 5600 MB Eindhoven (Netherlands); Lare, M. C. van; Polman, A. [Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam (Netherlands); Veldhuizen, L. W.; Schropp, R. E. I., E-mail: r.e.i.schropp@tue.nl [Department of Applied Physics, Plasma & Materials Processing, Eindhoven University of Technology (TUE), P.O. Box 513, 5600 MB Eindhoven (Netherlands); Rath, J. K. [Physics of Devices, Debye Institute for Nanomaterials Science, Utrecht University, High Tech Campus, Building 21, 5656 AE Eindhoven (Netherlands)

    2015-11-14

    We present a simple, low-cost, and scalable approach for the fabrication of efficient nanorod-based solar cells. Templates with arrays of self-assembled ZnO nanorods with tunable morphology are synthesized by chemical bath deposition using a low process temperature at 80 °C. The nanorod templates are conformally coated with hydrogenated amorphous silicon light absorber layers of 100 nm and 200 nm thickness. An initial efficiency of up to 9.0% is achieved for the optimized design. External quantum efficiency measurements on the nanorod cells show a substantial photocurrent enhancement both in the red and the blue parts of the solar spectrum. Key insights in the light trapping mechanisms in these arrays are obtained via a combination of three-dimensional finite-difference time-domain simulations, optical absorption, and external quantum efficiency measurements. Front surface patterns enhance the light incoupling in the blue, while rear side patterns lead to enhanced light trapping in the red. The red response in the nanorod cells is limited by absorption in the patterned Ag back contact. With these findings, we develop and experimentally realize a further advanced design with patterned front and back sides while keeping the Ag reflector flat, showing significantly enhanced scattering from the back reflector with reduced parasitic absorption in the Ag and thus higher photocurrent generation. Many of the findings in this work can serve to provide insights for further optimization of nanostructures for thin-film solar cells in a broad range of materials.

  4. The structure and physical properties of paracrystalline atomistic models of amorphous silicon.

    Energy Technology Data Exchange (ETDEWEB)

    Voyles, P. M.; Zotov, N.; Nakhmanson, S. M.; Drabold, D. A.; Gibson, J. M.; Treacy, M. M. J.; Keblinski, P.; Materials Science Division; Univ. of Illinois; Univ. Bayreuth; Ohio Univ.; NEC Research Inst.; Rensselaer Polytechnic Inst.

    2001-11-01

    We have examined the structure and physical properties of paracrystalline molecular dynamics models of amorphous silicon. Simulations from these models show qualitative agreement with the results of recent mesoscale fluctuation electron microscopy experiments on amorphous silicon and germanium. Such agreement is not found in simulations from continuous random network models. The paracrystalline models consist of topologically crystalline grains which are strongly strained and a disordered matrix between them. We present extensive structural and topological characterization of the medium range order present in the paracrystalline models and examine their physical properties, such as the vibrational density of states, Raman spectra, and electron density of states. We show by direct simulation that the ratio of the transverse acoustic mode to transverse optical mode intensities I{sub TA}/I{sub TO} in the vibrational density of states and the Raman spectrum can provide a measure of medium range order. In general, we conclude that the current paracrystalline models are a good qualitative representation of the paracrystalline structures observed in the experiment and thus provide guidelines toward understanding structure and properties of medium-range-ordered structures of amorphous semiconductors as well as other amorphous materials.

  5. Intense Yellow Photoluminescence from Silicon Oxynitride Films Prepared by Dual Ion Beam Sputtering

    Institute of Scientific and Technical Information of China (English)

    成珏飞; 吴雪梅; 诸葛兰剑

    2004-01-01

    In this work, results on the study of the structure and photoluminescence (PL)properties of SiOxNy thin films are presented. The films were deposited at room temperature using a dual-ion-beam co-sputtering system. The XRD and TEM results show that the deposited films have an amorphous structure. In the XPS result, we find N 1s spectra consist of one symmetric single peak at 397.8 eV, indicating that the nitrogen atoms are mainly bonded to silicon. It is in agreement to the result of FTIR. In SiOxNy films, an intense single PL peak at 590 nm is observed. Furthermore, with the increase of the N content in the SiOxNy films, the intensity of the PL peak at 590 nm increases a lot. The PL peak of 590 nm is suggested to originate from N-related defects.

  6. Exchange bias and bistable magneto-resistance states in amorphous TbFeCo thin films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaopu, E-mail: xl6ba@virginia.edu; Ma, Chung T.; Poon, S. Joseph, E-mail: sjp9x@virginia.edu [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Lu, Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Devaraj, Arun [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Spurgeon, Steven R.; Comes, Ryan B. [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)

    2016-01-04

    Amorphous TbFeCo thin films sputter deposited at room temperature on thermally oxidized Si substrate are found to exhibit strong perpendicular magnetic anisotropy. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb atomic percentages distributed within the amorphous film. Exchange bias accompanied by bistable magneto-resistance states has been uncovered near room temperature by magnetization and magneto-transport measurements. The exchange anisotropy originates from the exchange interaction between the ferrimagnetic and ferromagnetic components corresponding to the two amorphous phases. This study provides a platform for exchange bias and magneto-resistance switching using single-layer amorphous ferrimagnetic thin films that require no epitaxial growth.

  7. Exchange bias and bistable magneto-resistance states in amorphous TbFeCo thin films

    Science.gov (United States)

    Li, Xiaopu; Ma, Chung T.; Lu, Jiwei; Devaraj, Arun; Spurgeon, Steven R.; Comes, Ryan B.; Poon, S. Joseph

    2016-01-01

    Amorphous TbFeCo thin films sputter deposited at room temperature on thermally oxidized Si substrate are found to exhibit strong perpendicular magnetic anisotropy. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb atomic percentages distributed within the amorphous film. Exchange bias accompanied by bistable magneto-resistance states has been uncovered near room temperature by magnetization and magneto-transport measurements. The exchange anisotropy originates from the exchange interaction between the ferrimagnetic and ferromagnetic components corresponding to the two amorphous phases. This study provides a platform for exchange bias and magneto-resistance switching using single-layer amorphous ferrimagnetic thin films that require no epitaxial growth.

  8. Epitaxial growth of amorphous Ge films deposited on single-crystal Ge

    OpenAIRE

    M. G. Grimaldi; Mäenpää, M. (Markus); Paine, B. M.; Nicolet, M-A.; Lau, S. S.; Tseng, W. F.

    1981-01-01

    The epitaxial growth of amorphous Ge films deposited onto 110 Ge substrate is demonstrated. Substrate cleaning prior to deposition involves only conventional chemical procedures. The growth appears to be a strong function of the interface cleanliness. Two different growth mechanisms are observed: (a) a direct transition from amorphous to single-crystalline layer and (b) the growth involving the transition of amorphous to polycrystals to single crystal.

  9. Silicon carbide and other films and method of deposition

    Science.gov (United States)

    Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy (Inventor)

    2011-01-01

    A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

  10. High-performance back-channel-etched thin-film transistors with amorphous Si-incorporated SnO2 active layer

    Science.gov (United States)

    Liu, Xianzhe; Ning, Honglong; Chen, Jianqiu; Cai, Wei; Hu, Shiben; Tao, Ruiqiang; Zeng, Yong; Zheng, Zeke; Yao, Rihui; Xu, Miao; Wang, Lei; Lan, Linfeng; Peng, Junbiao

    2016-03-01

    In this report, back-channel-etched (BCE) thin-film transistors (TFTs) were achieved by using Si-incorporated SnO2 (silicon tin oxide (STO)) film as active layer. It was found that the STO film was acid-resistant and in amorphous state. The BCE-TFT with STO active layer exhibited a mobility of 5.91 cm2/V s, a threshold voltage of 0.4 V, an on/off ratio of 107, and a steep subthreshold swing of 0.68 V/decade. Moreover, the device had a good stability under the positive/negative gate-bias stress.

  11. Hardness and stress of amorphous carbon film deposited by glow discharge and ion beam assisting deposition

    CERN Document Server

    Marques, F C

    2000-01-01

    The hardness and stress of amorphous carbon films prepared by glow discharge and by ion beam assisting deposition are investigated. Relatively hard and almost stress free amorphous carbon films were deposited by the glow discharge technique. On the other hand, by using the ion beam assisting deposition, hard films were also obtained with a stress of the same order of those found in tetrahedral amorphous carbon films. A structural analysis indicates that all films are composed of a sp sup 2 -rich network. These results contradict the currently accepted concept that both stress and hardness are only related to the concentration of sp sup 3 sites. Furthermore, the same results also indicate that the sp sup 2 sites may also contribute to the hardness of the films.

  12. Polycrystalline Si films with unique microstructures formed from amorphous Si films by non-thermal equilibrium flash lamp annealing

    Energy Technology Data Exchange (ETDEWEB)

    Ohdaira, Keisuke; Nishikawa, Takuya; Shiba, Kazuhiro; Takemoto, Hiroyuki; Matsumura, Hideki [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), Ishikawa (Japan)

    2010-04-15

    Flash lamp annealing (FLA), with millisecond-order duration, can crystallize amorphous silicon (a-Si) films a few {mu}m thick on glass substrates, resulting in formation of polycrystalline Si (poly-Si) films with unprecedented periodic microstructures. The characteristic microstructure, formed spontaneously during crystallization, consists of large-grain regions, containing relatively large grains more than 100 nm in size, and fine-grain regions, including only 10-nm-sized fine grains. The microstructures results from explosive crystallization (EC), driven by heat generation corresponding to the difference of the enthalpies of meta-stable a-Si and stable crystalline Si(c-Si) states, which realizes lateral crystallization velocity on the order of m/s. The lateral crystallization may stop when the temperature of a-Si in the vicinity of c-Si, which is decided by both homogeneous heating from flash irradiation and thermal diffusion from c-Si, falls below a crystallization temperature. This idea is supported by the experimental fact that a lateral crystallization length decreases with decreasing pulse duration. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Gettering of interstitial iron in silicon by plasma-enhanced chemical vapour deposited silicon nitride films

    Science.gov (United States)

    Liu, A. Y.; Sun, C.; Markevich, V. P.; Peaker, A. R.; Murphy, J. D.; Macdonald, D.

    2016-11-01

    It is known that the interstitial iron concentration in silicon is reduced after annealing silicon wafers coated with plasma-enhanced chemical vapour deposited (PECVD) silicon nitride films. The underlying mechanism for the significant iron reduction has remained unclear and is investigated in this work. Secondary ion mass spectrometry (SIMS) depth profiling of iron is performed on annealed iron-contaminated single-crystalline silicon wafers passivated with PECVD silicon nitride films. SIMS measurements reveal a high concentration of iron uniformly distributed in the annealed silicon nitride films. This accumulation of iron in the silicon nitride film matches the interstitial iron loss in the silicon bulk. This finding conclusively shows that the interstitial iron is gettered by the silicon nitride films during annealing over a wide temperature range from 250 °C to 900 °C, via a segregation gettering effect. Further experimental evidence is presented to support this finding. Deep-level transient spectroscopy analysis shows that no new electrically active defects are formed in the silicon bulk after annealing iron-containing silicon with silicon nitride films, confirming that the interstitial iron loss is not due to a change in the chemical structure of iron related defects in the silicon bulk. In addition, once the annealed silicon nitride films are removed, subsequent high temperature processes do not result in any reappearance of iron. Finally, the experimentally measured iron decay kinetics are shown to agree with a model of iron diffusion to the surface gettering sites, indicating a diffusion-limited iron gettering process for temperatures below 700 °C. The gettering process is found to become reaction-limited at higher temperatures.

  14. Hydrogen pumping in amorphous deutered carbon films irradiated by swift heavy ions

    Science.gov (United States)

    Pawlak, F.; Balanzat, E.; Dufour, Ch.; Laurent, A.; Paumier, E.; Perriere, J.; Stoquert, J. P.; Toulemonde, M.

    1997-02-01

    Deutered amorphous carbon films have been irradiated at GANIL using 5 to 10 MeV/u sulfur beam with an electronic stopping power from 1 to 1.4 keV/nm. Such films have been deposited on silicon substrates by decomposition of CD 4 gas containing 10% of CH 4 in a dc multipolar plasma. After irradiation, they were analyzed firstly using absorption infrared spectroscopy to determine the number of CD and CH bonds. Secondly, deuterium, hydroge and carbon areal density were determined by ERDA and RBS. The results analysis shows a decrease of the atomic ratio ( {D}/{C}) as well as CD bonds down to a minimum value versus the fluence without a threshold fluence and in the same time an increase of the atomic ratio ( {H}/{C}) as well as CH bonds to a maximum value. So we may conclude that the hydrogen pumped after the irradiation is stabilized on broken (or unpaired) bonds.

  15. Nitrogen-doped amorphous carbon-silicon core-shell structures for high-power supercapacitor electrodes

    Science.gov (United States)

    Tali, S. A. Safiabadi; Soleimani-Amiri, S.; Sanaee, Z.; Mohajerzadeh, S.

    2017-02-01

    We report successful deposition of nitrogen-doped amorphous carbon films to realize high-power core-shell supercapacitor electrodes. A catalyst-free method is proposed to deposit large-area stable, highly conformal and highly conductive nitrogen-doped amorphous carbon (a-C:N) films by means of a direct-current plasma enhanced chemical vapor deposition technique (DC-PECVD). This approach exploits C2H2 and N2 gases as the sources of carbon and nitrogen constituents and can be applied to various micro and nanostructures. Although as-deposited a-C:N films have a porous surface, their porosity can be significantly improved through a modification process consisting of Ni-assisted annealing and etching steps. The electrochemical analyses demonstrated the superior performance of the modified a-C:N as a supercapacitor active material, where specific capacitance densities as high as 42 F/g and 8.5 mF/cm2 (45 F/cm3) on silicon microrod arrays were achieved. Furthermore, this supercapacitor electrode showed less than 6% degradation of capacitance over 5000 cycles of a galvanostatic charge-discharge test. It also exhibited a relatively high energy density of 2.3 × 103 Wh/m3 (8.3 × 106 J/m3) and ultra-high power density of 2.6 × 108 W/m3 which is among the highest reported values.

  16. Accelerated growth from amorphous clusters to metallic nanoparticles observed in electrochemical deposition of platinum within nanopores of porous silicon

    NARCIS (Netherlands)

    Munoz-Noval, Alvaro; Fukami, Kazuhiro; Koyama, Akira; Gallach, Dario; Hermida-Merino, Daniel; Portale, Giuseppe; Kitada, Atsushi; Murase, Kuniaki; Abe, Takeshi; Hayakawa, Shinjiro; Sakka, Tetsuo

    2016-01-01

    This study examined the formation of amorphous platinum (Pt) clusters in nanopores of porous silicon at an initial stage of pore filling. The time dependency of the chemical state and local structure of Pt in the nanoporous silicon were characterized by X-ray absorption fine structure spectroscopy (

  17. A Study of The Evolution of The Silicon Nanocrystallites in The Amorphous Silicon Carbide Under Argon Dilution of the Source Gases

    Directory of Open Access Journals (Sweden)

    A. Kole

    2011-01-01

    Full Text Available Structural evolution of the hydrogenated amorphous silicon carbide (a-SiC:H films deposited by rf-PECVD from a mixture of SiH4 and CH4 diluted in Ar shows that a smooth transition from amorphous to nanocrystalline phase occurs in the material by increasing the Ar dilution. The optical band gap (Eg decreases from 1.99 eV to 1.91 eV and the H-content (CH decreases from 14.32 at% to 5.29 at% by increasing the dilution from 94 % to 98 %. at 98 % Ar dilution, the material contains irregular shape Si nanocrystallites with sizes over 10 nm. Increasing the Ar dilution further to 98.4 % leads to a reduction of the size of the Si nanocrystals to regular shape Si quantum dots of size about 5 nm. The quantum confinement effect is apparent from the increase in the Eg value to 2.6 eV at 98.4 % Ar dilution. Formation of Si quantum dots may be explained by the etching of the nanocrystallites of Si by the energetic ion bombardment from the plasma.

  18. Study of low resistivity and high work function ITO films prepared by oxygen flow rates and N2O plasma treatment for amorphous/crystalline silicon heterojunction solar cells.

    Science.gov (United States)

    Hussain, Shahzada Qamar; Oh, Woong-Kyo; Kim, Sunbo; Ahn, Shihyun; Le, Anh Huy Tuan; Park, Hyeongsik; Lee, Youngseok; Dao, Vinh Ai; Velumani, S; Yi, Junsin

    2014-12-01

    Pulsed DC magnetron sputtered indium tin oxide (ITO) films deposited on glass substrates with lowest resistivity of 2.62 x 10(-4) Ω x cm and high transmittance of about 89% in the visible wavelength region. We report the enhancement of ITO work function (Φ(ITO)) by the variation of oxygen (O2) flow rate and N2O surface plasma treatment. The Φ(ITO) increased from 4.43 to 4.56 eV with the increase in O2 flow rate from 0 to 4 sccm while surface treatment of N2O plasma further enhanced the ITO work function to 4.65 eV. The crystallinity of the ITO films improved with increasing O2 flow rate, as revealed by XRD analysis. The ITO work function was increased by the interfacial dipole resulting from the surface rich in O- ions and by the dipole moment formed at the ITO surface during N2O plasma treatment. The ITO films with high work functions can be used to modify the front barrier height in heterojunction with intrinsic thin layer (HIT) solar cells.

  19. Effect of substrate temperature on the structure of amorphous oxygenated hydrocarbon films grown with a pulsed supersonic methane plasma flow

    Science.gov (United States)

    Fedoseeva, Yu. V.; Pozdnyakov, G. A.; Okotrub, A. V.; Kanygin, M. A.; Nastaushev, Yu. V.; Vilkov, O. Y.; Bulusheva, L. G.

    2016-11-01

    Since amorphous oxygenated hydrocarbon (COxHy) films are promising engineering materials a study of the structure and composition of the films depending on the conditions of synthesis is important for controlling of their physicochemical properties. Here, we used the methods of scanning and transmission electron microscopy, X-ray photoelectron, near-edge X-ray absorption fine structure, Fourier transform infrared and Raman spectroscopy to reveal changes in the chemical connectivity of COxHy films grown on silicon substrates heated to 300, 500, and 700 °C using a supersonic flow of methane plasma. It was found that the COxHy films, deposited at 300 and 500 °C, were mainly composed of the sp2-hybridized carbon areas with various oxygen species. A rise of the substrate temperature caused an increase of the portion of tetrahedral carbon atoms as well as carboxyl and hydroxyl groups. With growth of the substrate temperature, the film thickness reduced monotonically from 400 to 180 nm, while the film adhesion improved substantially. The films, deposited at lower temperatures, showed high hydrophilicity due to porosity and presence of oxygenated groups both at the surface and in the bulk.

  20. Effect of crystalline/amorphous interfaces on thermal transport across confined thin films and superlattices

    Science.gov (United States)

    Giri, Ashutosh; Braun, Jeffrey L.; Hopkins, Patrick E.

    2016-06-01

    We report on the thermal boundary resistances across crystalline and amorphous confined thin films and the thermal conductivities of amorphous/crystalline superlattices for Si/Ge systems as determined via non-equilibrium molecular dynamics simulations. Thermal resistances across disordered Si or Ge thin films increase with increasing length of the interfacial thin films and in general demonstrate higher thermal boundary resistances in comparison to ordered films. However, for films ≲3 nm, the resistances are highly dependent on the spectral overlap of the density of states between the film and leads. Furthermore, the resistances at a single amorphous/crystalline interface in these structures are much lower than those at interfaces between the corresponding crystalline materials, suggesting that diffusive scattering at an interface could result in higher energy transmissions in these systems. We use these findings, together with the fact that high mass ratios between amorphous and crystalline materials can lead to higher thermal resistances across thin films, to design amorphous/crystalline superlattices with very low thermal conductivities. In this regard, we study the thermal conductivities of amorphous/crystalline superlattices and show that the thermal conductivities decrease monotonically with increasing interface densities above 0.1 nm-1. These thermal conductivities are lower than that of the homogeneous amorphous counterparts, which alludes to the fact that interfaces non-negligibly contribute to thermal resistance in these superlattices. Our results suggest that the thermal conductivity of superlattices can be reduced below the amorphous limit of its material constituent even when one of the materials remains crystalline.

  1. Induced growth of high quality ZnO thin films by crystallized amorphous ZnO

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Jun; Song Li-Jun; Li Shou-Chun; Lu You-Ming; Tian Yun-Xia; Liu Jia-Yi; Wang Lian-Yuan

    2006-01-01

    This paper reports the induced growth of high quality ZnO thin film by crystallized amorphous ZnO. Firstly amorphous ZnO was prepared by solid-state pyrolytic reaction, then by taking crystallized amorphous ZnO as seeds (buffer layer), ZnO thin films have been grown in diethyene glycol solution of zinc acetate at 80℃. X-ray Diffraction curve indicates that the films were preferentially oriented [001] out-of-plane direction of the ZnO. Atomic force microscopy and scanning electron microscopy were used to evaluate the surface morphology of the ZnO thin film. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. The results indicate that high quality ZnO thin film was obtained.

  2. Leakage current mechanisms and their dependence on composition in silicon carbonitride thin films

    Science.gov (United States)

    Vijayakumar, Vishnuvardhanan; Varadarajan, Bhadri

    2015-04-01

    Electrical conduction in amorphous silicon carbonitride (a-SiCN:H) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) is investigated for varying carbon to nitrogen ratios at room temperature. Films deposited with a lower carbon/nitrogen ratio showed two modes of electrical conduction; namely, Schottky emission mode below 2.3 MV cm-1 electric field and Poole-Frenkel mode from 2.3 MV cm-1 up to the breakdown field. Films with higher carbon/nitrogen ratios showed only Poole-Frenkel mode of conduction throughout the entire range of operation up to the breakdown field. The carbon rich films exhibited higher leakage currents attributed to its shallow defect energy levels leading to its higher Poole-Frenkel conductivity.

  3. Programmable SERS active substrates for chemical and biosensing applications using amorphous/crystalline hybrid silicon nanomaterial

    Science.gov (United States)

    Powell, Jeffery Alexander; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-01

    We present the creation of a unique nanostructured amorphous/crystalline hybrid silicon material that exhibits surface enhanced Raman scattering (SERS) activity. This nanomaterial is an interconnected network of amorphous/crystalline nanospheroids which form a nanoweb structure; to our knowledge this material has not been previously observed nor has it been applied for use as a SERS sensing material. This material is formed using a femtosecond synthesis technique which facilitates a laser plume ion condensation formation mechanism. By fine-tuning the laser plume temperature and ion interaction mechanisms within the plume, we are able to precisely program the relative proportion of crystalline Si to amorphous Si content in the nanospheroids as well as the size distribution of individual nanospheroids and the size of Raman hotspot nanogaps. With the use of Rhodamine 6G (R6G) and Crystal Violet (CV) chemical dyes, we have been able to observe a maximum enhancement factor of 5.38 × 106 and 3.72 × 106 respectively, for the hybrid nanomaterial compared to a bulk Si wafer substrate. With the creation of a silicon-based nanomaterial capable of SERS detection of analytes, this work demonstrates a redefinition of the role of nanostructured Si from an inactive to SERS active role in nano-Raman sensing applications.

  4. Low-mobility solar cells: a device physics primer with application to amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Schiff, E.A. [Syracuse University, New York (United States). Department of Physics

    2003-07-01

    The properties of pin solar cells based on photogeneration of charge carriers into low-mobility materials were calculated for two models. Ideal p- and n-type electrode layers were assumed in both cases. The first, elementary case involves only band mobilities and direct electron-hole recombination. An analytical approximation indicates that the power in thick cells rises as the 1/4 power of the lower band mobility, which reflects the buildup of space-charge under illumination. The approximation agrees well with computer simulation. The second model includes exponential bandtail trapping, which is commonly invoked to account for very low hole drift mobilities in amorphous silicon and other amorphous semiconductors. The two models have similar qualitative behavior. Predictions for the solar conversion efficiency of amorphous silicon-based cells that are limited by valence bandtail trapping are presented. The predictions account adequately for the efficiencies of present a-Si : H cells in their 'as-prepared' state (without light-soaking), and indicate the improvement that may be expected if hole drift mobilities (and valence bandtail widths) can be improved. (author)

  5. Non-classical crystallization of silicon thin films during hot wire chemical vapor deposition

    Science.gov (United States)

    Jung, Jae-Soo; Lee, Sang-Hoon; Kim, Da-Seul; Kim, Kun-Su; Park, Soon-Won; Hwang, Nong-Moon

    2017-01-01

    The deposition behavior of silicon films by hot wire chemical vapor deposition (HWCVD) was approached by non-classical crystallization, where the building block of deposition is a nanoparticle generated in the gas phase of the reactor. The puzzling phenomenon of the formation of an amorphous incubation layer on glass could be explained by the liquid-like property of small charged nanoparticles (CNPs), which are generated in the initial stage of the HWCVD process. Using the liquid-like property of small CNPs, homo-epitaxial growth as thick as 150 nm could be successfully grown on a silicon wafer at 600 °C under the processing condition where CNPs as small as possible could be supplied steadily by a cyclic process which periodically resets the process. The size of CNPs turned out to be an important parameter in the microstructure evolution of thin films.

  6. Fabrication of hexagonal gallium nitride films on silicon (111) substrates

    Institute of Scientific and Technical Information of China (English)

    YANG Li; XUE Chengshan; WANG Cuimei; LI Huaixiang; REN Yuwen

    2003-01-01

    Hexagonal gallium nitride films were successfully fabricated through ammoniating Ga2O3 films deposited on silicon (111 ) substrates by electrophoresis. The structure, composition, and surface morphology of the formed films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM),and transmission electron microscopy (TEM). The measurement results reveal that the polycrystalline GaN films with hexagonal wurtzite structure were successfully grown on the silicon (111) substrates. Preliminary results suggest that varying the ammoniating temperature has obvious effect on the quality of the GaN films formed with this method.

  7. Amorphous Indium Selenide Thin Films Prepared by RF Sputtering: Thickness-Induced Characteristics.

    Science.gov (United States)

    Han, Myoung Yoo; Park, Yong Seob; Kim, Nam-Hoon

    2016-05-01

    The influence of indium composition, controlled by changing the film thickness, on the optical and electrical properties of amorphous indium selenide thin films was studied for the application of these materials as Cd-free buffer layers in CI(G)S solar cells. Indium selenide thin films were prepared using RF magnetron sputtering method. The indium composition of the amorphous indium selenide thin films was varied from 94.56 to 49.72 at% by increasing the film thickness from 30 to 70 nm. With a decrease in film thickness, the optical transmittance increased from 87.63% to 96.03% and Eg decreased from 3.048 to 2.875 eV. Carrier concentration and resistivity showed excellent values of ≥1015 cm(-3) and ≤ 10(4) Ω x cm, respectively. The conductivity type of the amorphous indium selenide thin films could be controlled by changing the film-thickness-induced amount of In. These results indicate the possibility of tuning the properties of amorphous indium selenide thin films by changing their composition for use as an alternate buffer layer material in CI(G)S solar cells.

  8. Band offsets at the crystalline / hydrogenated amorphous silicon interface from first-principles

    Science.gov (United States)

    Hazrati, Ebrahim; Jarolimek, Karol; de Wijs, Gilles A.; InstituteMolecules; Materials Team

    2015-03-01

    The heterojunction formed between crystalline silicon (c-Si) and hydrogenated amorphous silicon (a-Si:H) is a key component of a new type of high-efficiency silicon solar cell. Since a-Si:H has a larger band gap than c-Si, band offsets are formed at the interface. A band offset at the minority carrier band will mitigate recombination and lead to an increased efficiency. Experimental values of band offsets scatter in a broad range. However, a recent meta-analysis of the results (W. van Sark et al.pp. 405, Springer 2012) gives a larger valence offset (0.40 eV) than the conduction offset (0.15 eV). In light of the conflicting reports our goal is to calculate the band offsets at the c-Si/a-Si:H interface from first-principles. We have prepared several atomistic models of the interface. The crystalline part is terminated with (111) surfaces on both sides. The amorphous structure is generated by simulating an annealing process at 1100 K, with DFT molecular dynamics. Once the atomistic is ready it can be used to calculate the electronic structure of the interface. Our preliminary results show that the valence offset is larger than the conduction band offset.

  9. Oxide film assisted dopant diffusion in silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Tin, Chin-Che, E-mail: cctin@physics.auburn.ed [Department of Physics, Auburn University, Alabama 36849 (United States); Mendis, Suwan [Department of Physics, Auburn University, Alabama 36849 (United States); Chew, Kerlit [Department of Electrical and Electronic Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kuala Lumpur (Malaysia); Atabaev, Ilkham; Saliev, Tojiddin; Bakhranov, Erkin [Physical Technical Institute, Uzbek Academy of Sciences, 700084 Tashkent (Uzbekistan); Atabaev, Bakhtiyar [Institute of Electronics, Uzbek Academy of Sciences, 700125 Tashkent (Uzbekistan); Adedeji, Victor [Department of Chemistry, Geology and Physics, Elizabeth City State University, North Carolina 27909 (United States); Rusli [School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore)

    2010-10-01

    A process is described to enhance the diffusion rate of impurities in silicon carbide so that doping by thermal diffusion can be done at lower temperatures. This process involves depositing a thin film consisting of an oxide of the impurity followed by annealing in an oxidizing ambient. The process uses the lower formation energy of silicon dioxide relative to that of the impurity-oxide to create vacancies in silicon carbide and to promote dissociation of the impurity-oxide. The impurity atoms then diffuse from the thin film into the near-surface region of silicon carbide.

  10. Transformation from amorphous to nano-crystalline SiC thin films prepared by HWCVD technique without hydrogen dilution

    Indian Academy of Sciences (India)

    F Shariatmadar Tehrani

    2015-09-01

    Silicon carbide (SiC) thin films were deposited on Si(111) by the hot wire chemical vapour deposition (HWCVD) technique using silane (SiH4) and methane (CH4) gases without hydrogen dilution. The effects of SiH4 to CH4 gas flow ratio (R) on the structural properties, chemical composition and photoluminescence (PL) properties of the films deposited at the different gas flow ratios were investigated and compared. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra revealed a structural transition from amorphous SiC to cubic nano-crystalline SiC films with the increase in the gas flow ratio. Raman scattering confirmed the multi-phased nature of the films. Auger electron spectroscopy showed that the carbon incorporation in the film structure was strongly dependent on the gas flow ratio. A similar broad visible room-temperature PL with two peaks was observed for all SiC films. The main PL emission was correlated to the band to band transition in uniform a-SiC phase and the other lower energy emission was related to the confined a-Si : H clusters in a-SiC matrix. SiC nano-crystallites exhibit no significant contribution to the radiative recombination.

  11. Thermal oxidation of Zr–Cu–Al–Ni amorphous metal thin films

    Energy Technology Data Exchange (ETDEWEB)

    Oleksak, R.P.; Hostetler, E.B.; Flynn, B.T. [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331 (United States); McGlone, J.M.; Landau, N.P.; Wager, J.F. [School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, OR 97331 (United States); Stickle, W.F. [Hewlett-Packard Company, Corvallis, OR 97333 (United States); Herman, G.S., E-mail: greg.herman@oregonstate.edu [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331 (United States)

    2015-11-30

    The initial stages of thermal oxidation for Zr–Cu–Al–Ni amorphous metal thin films were investigated using X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The as-deposited films had oxygen incorporated during sputter deposition, which helped to stabilize the amorphous phase. After annealing in air at 300 °C for short times (5 min) this oxygen was found to segregate to the surface or buried interface. Annealing at 300 °C for longer times leads to significant composition variation in both vertical and lateral directions, and formation of a surface oxide layer that consists primarily of Zr and Al oxides. Surface oxide formation was initially limited by back-diffusion of Cu and Ni (< 30 min), and then by outward diffusion of Zr (> 30 min). The oxidation properties are largely consistent with previous observations of Zr–Cu–Al–Ni metallic glasses, however some discrepancies were observed which could be explained by the unique sample geometry of the amorphous metal thin films. - Highlights: • Thermal oxidation of amorphous Zr–Cu–Al–Ni thin films was investigated. • Significant short-range inhomogeneities were observed in the amorphous films. • An accumulation of Cu and Ni occurs at the oxide/metal interface. • Diffusion of Zr was found to limit oxide film growth.

  12. Nano-structural Modification of Amorphous Carbon Thin Films by Low-energy Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    EijiIwamura; MasanoriYamaguchi

    2004-01-01

    A new approach using a low-energy electron beam radiation system was investigated to synthesize carbon hybrid structures in amorphous carbon thin films. Two types of amorphous carbon films, which were 15at% iron containing film and with column/inter-column structures, were deposited onto Si substrates by a sputtering technique and subsequently exposed to an electron shower of which the energy and dose rate were much smaller compared to an intense electron beam used in a transmission electron microscopy. As a result of the low-energy and low-dose electron irradiation process, graphitic structures formed in amorphous matrix at a relatively low temperature up to 450 K. Hybrid carbon thin films containing onion-like structures in an amorphous carbon matrix were synthesized by dynamic structural modification of iron containing amorphous carbon thin films. It was found that the graphitization progressed more in the electron irradiation than in annealing at 773K, and it was attributed to thermal and catalytic effects which are strongly related to grain growth of metal clusters. On the other hand, a reversal of TEM image contrast was observed in a-C films with column/inter-column structures. It is presumed that preferable graphitization occurred in the inter-column regions induced by electron irradiation.

  13. Nano-structural Modification of Amorphous Carbon Thin Films by Low-energy Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    Eiji Iwamura; Masanori Yamaguchi

    2004-01-01

    A new approach using a low-energy electron beam radiation system was investigated to synthesize carbon hybrid structures in amorphous carbon thin films. Two types of amorphous carbon films, which were 15at% iron containing film and with column/inter-column structures, were deposited onto Si substrates by a sputtering technique and subsequently exposed to an electron shower of which the energy and dose rate were much smaller compared to an intense electron beam used in a transmission electron microscopy. As a result of the low-energy and low-dose electron irradiation process,graphitic structures formed in amorphous matrix at a relatively low temperature up to 450 K. Hybrid carbon thin films containing onion-like structures in an amorphous carbon matrix were synthesized by dynamic structural modification of iron containing amorphous carbon thin films. It was found that the graphitization progressed more in the electron irradiation than in annealing at 773K, and it was attributed to thermal and catalytic effects which are strongly related to grain growth of metal clusters. On the other hand, a reversal of TEM image contrast was observed in a-C films with column/inter-column structures. It is presumed that preferable graphitization occurred in the inter-column regions induced by electron irradiation.

  14. Near-field optical study of 3rd order nonlinear properties of amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yun Jin; Park, J.H.; Kim, M.R.; Jhe, Won Ho [Seoul National University, Seoul (Korea, Republic of); Rhee, B.K. [Sogang University, Seoul (Korea, Republic of)

    1999-07-01

    The 3rd order nonlinear properties show optical bleaching (Saturation) and Reverse saturation in absorption aspect, whereas self-focusing and self-defocusing in refraction aspect. Optical bleaching and self-focusing phenomena of those properties in particular can be useful to make the optical beam spot size smaller for application on the higher optical storage density. In this experiment, amorphous silicon layer is used to investigate the effect of 3rd order nonlinear material(1) on the spot size. The amorphous silicon (A-Si) layer is deposited by the method of PECVD on the corning 1737 fusion glass and its thickness is 300 nm. Two experiments are carried out in this work. One is the far-field Z-Scan and the other is the near-field Z-scan where the laser beam spot is scanned by NSOM in the near field region of the material. The former is for investigating the general 3rd order nonlinear properties of amorphous silicon and the latter is for measuring the change of the beam spot size directly. The far-field Z-scan shows Reverse saturation (Im{chi}{sup (3)} {approx} 8 X 10{sup -3} esu) and self-focusing (Re{chi}{sup (3)} {approx} 2 X 10{sup -2} esu) properties for the A-Si layer. In the second experiment, we present the change the beam spot size as a function of the input beam intensity for the A-Si layer. As a result, we find that the stronger the input beam intensity is, the smaller a beam spot size is obtained for A-Si layer. (author)

  15. Low-energy electron irradiation induced top-surface nanocrystallization of amorphous carbon film

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Cheng [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Fan, Xue, E-mail: fanx@szu.edu.cn [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China); Diao, Dongfeng, E-mail: dfdiao@szu.edu.cn [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China)

    2016-10-30

    Graphical abstract: Low-energy electron irradiation was proposed to nanocrystallize the top-surface of the as-deposited amorphous carbon film, and sp{sup 2} nanocrystallites formed in the film top-surface within 4 nm thickness. Display Omitted - Abstract: We report a low-energy electron irradiation method to nanocrystallize the top-surface of amorphous carbon film in electron cyclotron resonance plasma system. The nanostructure evolution of the carbon film as a function of electron irradiation density and time was examined by transmission electron microscope (TEM) and Raman spectroscopy. The results showed that the electron irradiation gave rise to the formation of sp{sup 2} nanocrystallites in the film top-surface within 4 nm thickness. The formation of sp{sup 2} nanocrystallite was ascribed to the inelastic electron scattering in the top-surface of carbon film. The frictional property of low-energy electron irradiated film was measured by a pin-on-disk tribometer. The sp{sup 2} nanocrystallized top-surface induced a lower friction coefficient than that of the original pure amorphous film. This method enables a convenient nanocrystallization of amorphous surface.

  16. Low-temperature, vapor-liquid-solid, laterally grown silicon films using alloyed catalysts

    Science.gov (United States)

    LeBoeuf, Jerome L.; Brodusch, Nicolas; Gauvin, Raynald; Quitoriano, Nathaniel J.

    2014-12-01

    Using amorphous oxide templates known as micro-crucibles which confine a vapor-liquid-solid catalyst to a specific geometry, two-dimensional silicon thin-films of a single orientation have been grown laterally over an amorphous substrate and defects within crystals have been necked out. The vapor-liquid-solid catalysts consisted nominally of 99% gold with 1% titanium, chromium, or aluminum, and each alloy affected the processing of micro-crucibles and growth within them significantly. It was found that chromium additions inhibited the catalytic effect of the gold catalysts, titanium changed the morphology of the catalyst during processing and aluminum stabilized a potential third phase in the gold-silicon system upon cooling. Two mechanisms for growing undesired nanowires were identified both of which hindered the VLS film growth, fast silane cracking rates and poor gold etching, which left gold nanoparticles near the gold-vapor interface. To reduce the silane cracking rates, growth was done at a lower temperature while an engineered heat and deposition profile helped to reduce NWs caused by the second mechanism. Through experimenting with catalyst compositions, the fundamental mechanisms which produce concentration gradients across the gold-silicon alloy within a given micro-crucible have been proposed. Using the postulated mechanisms, micro-crucibles were designed which promote high-quality, single crystal growth of semiconductors.

  17. Present status of amorphous In–Ga–Zn–O thin-film transistors

    Directory of Open Access Journals (Sweden)

    Toshio Kamiya, Kenji Nomura and Hideo Hosono

    2010-01-01

    Full Text Available The present status and recent research results on amorphous oxide semiconductors (AOSs and their thin-film transistors (TFTs are reviewed. AOSs represented by amorphous In–Ga–Zn–O (a-IGZO are expected to be the channel material of TFTs in next-generation flat-panel displays because a-IGZO TFTs satisfy almost all the requirements for organic light-emitting-diode displays, large and fast liquid crystal and three-dimensional (3D displays, which cannot be satisfied using conventional silicon and organic TFTs. The major insights of this review are summarized as follows. (i Most device issues, such as uniformity, long-term stability against bias stress and TFT performance, are solved for a-IGZO TFTs. (ii A sixth-generation (6G process is demonstrated for 32'' and 37'' displays. (iii An 8G sputtering apparatus and a sputtering target have been developed. (iv The important effect of deep subgap states on illumination instability is revealed. (v Illumination instability under negative bias has been intensively studied, and some mechanisms are proposed. (vi Degradation mechanisms are classified into back-channel effects, the creation of traps at an interface and in the gate insulator, and the creation of donor states in annealed a-IGZO TFTs by the Joule heating; the creation of bulk defects should also be considered in the case of unannealed a-IGZO TFTs. (vii Dense passivation layers improve the stability and photoresponse and are necessary for practical applications. (viii Sufficient knowledge of electronic structures and electron transport in a-IGZO has been accumulated to construct device simulation models.

  18. Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Junghwan, E-mail: JH.KIM@lucid.msl.titech.ac.jp; Miyokawa, Norihiko; Ide, Keisuke [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Toda, Yoshitake [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan)

    2016-01-15

    We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors.

  19. Structural and optical studies on hot wire chemical vapour deposited hydrogenated silicon films at low substrate temperature

    Energy Technology Data Exchange (ETDEWEB)

    Gogoi, Purabi; Agarwal, Pratima [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam (India)

    2009-02-15

    Thin films of hydrogenated silicon are deposited by hot wire chemical vapour deposition technique, as an alternative of plasma enhanced chemical vapour deposition technique. By varying the hydrogen and silane flow rate, we deposited the films ranging from pure amorphous to nanocrystallite-embedded amorphous in nature. In this paper we report extensively studied structural and optical properties of these films. It is observed that the rms bond angle deviation decreases with increase in hydrogen flow rate, which is an indication of improved order in the films. We discuss this under the light of breaking of weak Si-Si bonds and subsequent formation of strong Si-Si bonds and coverage of the growing surface by atomic hydrogen. (author)

  20. Amorphous Silicon Solar cells with a Core-Shell Nanograting Structure

    CERN Document Server

    Yang, L; Okuno, Y; He, S

    2011-01-01

    We systematically investigate the optical behaviors of an amorphous silicon solar cell based on a core-shell nanograting structure. The horizontally propagating Bloch waves and Surface Plasmon Polariton (SPP) waves lead to significant absorption enhancements and consequently short-circuit current enhancements of this structure, compared with the conventional planar one. The perpendicular carrier collection makes this structure optically thick and electronically thin. An optimal design is achieved through full-field numerical simulation, and physical explanation is given. Our numerical results show that this configuration has ultrabroadband, omnidirectional and polarization-insensitive responses, and has a great potential in photovoltaics.

  1. Review of amorphous silicon based particle detectors: the quest for single particle detection

    Science.gov (United States)

    Wyrsch, N.; Ballif, C.

    2016-10-01

    Hydrogenated amorphous silicon (a-Si:H) is attractive for radiation detectors because of its radiation resistance and processability over large areas with mature Si microfabrication techniques. While the use of a-Si:H for medical imaging has been very successful, the development of detectors for particle tracking and minimum-ionizing-particle detection has lagged, with almost no practical implementation. This paper reviews the development of various types of a-Si:H-based detectors and discusses their respective achievements and limitations. It also presents more recent developments of detectors that could potentially achieve single particle detection and be integrated in a monolithic fashion into a variety of applications.

  2. Large-size high-performance transparent amorphous silicon sensors for laser beam position detection

    Energy Technology Data Exchange (ETDEWEB)

    Calderon, A. [Instituto de Fisica de Cantabria. CSIC-University of Cantabria, Santander (Spain); Martinez-Rivero, C. [Instituto de Fisica de Cantabria. CSIC-University of Cantabria, Santander (Spain); Matorras, F. [Instituto de Fisica de Cantabria. CSIC-University of Cantabria, Santander (Spain); Rodrigo, T. [Instituto de Fisica de Cantabria. CSIC-University of Cantabria, Santander (Spain); Sobron, M. [Instituto de Fisica de Cantabria. CSIC-University of Cantabria, Santander (Spain); Vila, I. [Instituto de Fisica de Cantabria. CSIC-University of Cantabria, Santander (Spain); Virto, A.L. [Instituto de Fisica de Cantabria. CSIC-University of Cantabria, Santander (Spain); Alberdi, J. [CIEMAT, Madrid (Spain); Arce, P. [CIEMAT, Madrid (Spain); Barcala, J.M. [CIEMAT, Madrid (Spain); Calvo, E. [CIEMAT, Madrid (Spain); Ferrando, A. [CIEMAT, Madrid (Spain)]. E-mail: antonio.ferrando@ciemat.es; Josa, M.I. [CIEMAT, Madrid (Spain); Luque, J.M. [CIEMAT, Madrid (Spain); Molinero, A. [CIEMAT, Madrid (Spain); Navarrete, J. [CIEMAT, Madrid (Spain); Oller, J.C. [CIEMAT, Madrid (Spain); Yuste, C. [CIEMAT, Madrid (Spain); Koehler, C. [Steinbeis-Transferzentrum fuer Angewandte Photovoltaik und Duennschichttechnik, Stuttgart (Germany); Lutz, B. [Steinbeis-Transferzentrum fuer Angewandte Photovoltaik und Duennschichttechnik, Stuttgart (Germany); Schubert, M.B. [Steinbeis-Transferzentrum fuer Angewandte Photovoltaik und Duennschichttechnik, Stuttgart (Germany); Werner, J.H. [Steinbeis-Transferzentrum fuer Angewandte Photovoltaik und Duennschichttechnik, Stuttgart (Germany)

    2006-09-15

    We present the measured performance of a new generation of semitransparent amorphous silicon position detectors. They have a large sensitive area (30x30mm{sup 2}) and show good properties such as a high response (about 20mA/W), an intrinsic position resolution better than 3{mu}m, a spatial-point reconstruction precision better than 10{mu}m, deflection angles smaller than 10{mu}rad and a transmission power in the visible and NIR higher than 70%.

  3. Large Size High Performance Transparent Amorphous Silicon Sensors for Laser Beam Position Detection and Monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Calderon, A.; Martinez Rivero, C.; Matorras, F.; Rodrigo, T.; Sobron, M.; Vila, I.; Virto; Alberdi, J.; Arce, P.; Barcala, J. M.; Calvo, E.; Ferrando, A.; Josa, M. I.; Luque, J. M.; Molinero, A.; Navarrete, J.; Oller, J. C.; Kohler, C.; Lutz, B.; Schubert, M. B.

    2006-09-04

    We present the measured performance of a new generation of semitransparente amorphous silicon position detectors. They have a large sensitive area (30 x 30 mm2) and show good properties such as a high response (about 20 mA/W), an intinsic position resolution better than 3 m, a spatial point reconstruction precision better than 10 m, deflection angles smaller than 10 rad and a transmission power in the visible and NIR higher than 70%. In addition, multipoint alignment monitoring, using up to five sensors lined along a light path of about 5 meters, can be achieved with a resolution better than 20m. (Author)

  4. Defects left after regrowth of amorphous silicon on crystalline Si : C (V) and DLTS studies

    OpenAIRE

    Castaing, J.; Cass, T.

    1985-01-01

    n and p-type silicon have been self-ion implanted at 77 K with multi-energetic beams. This process was used to amorphize a 0.4 μm layer with a minimum amount of damage in the underlying crystal. After regrowth by a 550 °C anneal, the remaining defects were assessed by capacitance-voltage (C(V )) measurements and deep level transient spectroscopy (DLTS). In n-type Si, a buried layer of deep donors in large concentration was found, whereas in p-type Si, their concentration was small. These trap...

  5. Self-lubricated Array Film of Amorphous Carbon Nanorods on an Aluminum Substrate

    Institute of Scientific and Technical Information of China (English)

    JIANGChun-xi; TUJiang-ping; GUOShao-yi; FUMing-fu; ZHAOXin-bing

    2004-01-01

    A self-lubricated array film of amorphous carbon nanorods was prepared by chemical catalytic pyrolysis of acetylene on the anodic aluminum oxide membrane fabricated by two-step anodization of aluminum. The tribological properties of the array film of amorphous carbon nanorods in ambient air were investigated using a ball-on-disk tester at applied loads range from 245 mN to 1960 mN at a sliding velocity of 0.2 m/s. The self-lubricated array film exhibited a small value of the friction coefficient as well as good wear resistance. The friction coefficient of array film of amorphous carbon nanorods decreased gradually with increasing the applied load. The approach proposed demonstrated a new efficient route towards enhanced the friction and wear performances of aluminum.

  6. The effect of amorphous silicon surface hydrogenation on morphology, wettability and its implication on the adsorption of proteins

    Science.gov (United States)

    Filali, Larbi; Brahmi, Yamina; Sib, Jamal Dine; Bouhekka, Ahmed; Benlakehal, Djamel; Bouizem, Yahya; Kebab, Aissa; Chahed, Larbi

    2016-10-01

    We study the effect of amorphous silicon (a-Si) surface hydrogenation on Bovine Serum Albumin (BSA) adsorption. A set of (a-Si) films was prepared by radio frequency magnetron sputtering (RFMS) and after deposition; they were treated in molecular hydrogen ambient at different pressures (1-3 Pa). Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy and spectroscopic ellipsometry (SE) were used to study the hydrogenation effect and BSA adsorption. Atomic force microscopy (AFM) was used to evaluate morphological changes caused by hydrogenation. The wettability of the films was measured using contact angle measurement, and in the case of the hydrogenated surfaces, it was found to be driven by surface roughness. FTIR-ATR spectroscopy and SE measurements show that proteins had the strongest affinity toward the surfaces with the highest hydrogen content and their secondary structure was affected by a significant decrease of the α-helix component (-27%) compared with the proteins adsorbed on the un-treated surface, which had a predominantly α-helix (45%) structure. The adsorbed protein layer was found to be densely packed with a large thickness (30.9 nm) on the hydrogen-rich surfaces. The most important result is that the surface hydrogen content was the dominant factor, compared to wettability and morphology, for protein adsorption.

  7. Study of the amorphization of surface silicon layers implanted by low-energy helium ions

    Science.gov (United States)

    Lomov, A. A.; Myakon'kikh, A. V.; Oreshko, A. P.; Shemukhin, A. A.

    2016-03-01

    The structural changes in surface layers of Si(001) substrates subjected to plasma-immersion implantation by (2-5)-keV helium ions to a dose of D = 6 × 1015-5 × 1017 cm-2 have been studied by highresolution X-ray diffraction, Rutherford backscattering, and spectral ellipsometry. It is found that the joint application of these methods makes it possible to determine the density depth distribution ρ( z) in an implanted layer, its phase state, and elemental composition. Treatment of silicon substrates in helium plasma to doses of 6 × 1016 cm-2 leads to the formation of a 20- to 30-nm-thick amorphized surface layer with a density close to the silicon density. An increase in the helium dose causes the formation of an internal porous layer.

  8. Hydex Glass and Amorphous Silicon for Integrated Nonlinear Optical Signal Processing

    CERN Document Server

    Morandotti, Roberto

    2015-01-01

    Photonic integrated circuits that exploit nonlinear optics in order to generate and process signals all-optically have achieved performance far superior to that possible electronically - particularly with respect to speed. Although silicon-on-insulator has been the leading platform for nonlinear optics for some time, its high two-photon absorption at telecommunications wavelengths poses a fundamental limitation. We review the recent achievements based in new CMOS-compatible platforms that are better suited than SOI for nonlinear optics, focusing on amorphous silicon and Hydex glass. We highlight their potential as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement.

  9. Two-dimensional modeling of the back amorphous-crystalline silicon heterojunction (BACH) photovoltaic device

    Science.gov (United States)

    Chowdhury, Zahidur R.; Chutinan, Alongkarn; Gougam, Adel B.; Kherani, Nazir P.; Zukotynski, Stefan

    2010-06-01

    Back Amorphous-Crystalline Silicon Heterojunction (BACH)1 solar cell can be fabricated using low temperature processes while integrating high efficiency features of heterojunction silicon solar cells and back-contact homojunction solar cells. This article presents a two-dimensional modeling study of the BACH cell concept. A parametric study of the BACH cell has been carried out using Sentaurus after benchmarking the software. A detailed model describing the optical generation is defined. Solar cell efficiency of 24.4% is obtained for AM 1.5 global spectrum with VOC of greater than 720 mV and JSC exceeding 40 mA/cm2, considering realistic surface passivation quality and other dominant recombination processes.

  10. Structural and optical characterization of ZrO2 thin films grown on silicon and quartz substrates

    Science.gov (United States)

    Hojabri, Alireza

    2016-09-01

    Zirconium oxide thin films were grown successfully by thermal annealing of zirconium thin films deposited on quartz and silicon substrates by direct current magnetron sputtering technique. The structural and optical properties in relation to thermal annealing times were investigated. The X-ray diffraction patterns revealed that structure of films changes from amorphous to crystalline by increase of annealing times in range 60-240 min. The composition of films was determined by Rutherford back scattering spectroscopy. Atomic force microscopy results exhibited that surface morphology and roughness of films depend on the annealing time. The refractive index of the films was calculated using Swanepoel's method. The optical band gap energy of annealed films decreased from 5.50 to 5.34 eV with increasing thermal annealing time.

  11. Spectro-ellipsometric studies of sputtered amorphous Titanium dioxide thin films: simultaneous determination of refractive index, extinction coefficient, and void distribution

    CERN Document Server

    Lee, S I; Oh, S G

    1999-01-01

    Amorphous titanium dioxide thin films were deposited onto silicon substrates by using RF magnetron sputtering, and the index of refraction, the extinction coefficient, and the void distribution of these films were simultaneously determined from the analyses of there ellipsometric spectra. In particular, our novel strategy, which combines the merits of multi-sample fitting, the dual dispersion function, and grid search, was proven successful in determining optical constants over a wide energy range, including the energy region where the extinction coefficient was large. Moreover, we found that the void distribution was dependent on the deposition conditions, such as the sputtering power, the substrate temperature, and the substrate surface.

  12. Reciprocal space analysis of the microstructure of luminescent and nonluminescent porous silicon films

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.R.; Barbour, J.C.; Medernach, J.W.; Stevenson, J.O.; Custer, J.S.

    1994-12-31

    The microstructure of anodically prepared porous silicon films was determined using a novel X-ray diffraction technique. This technique uses double-crystal diffractometry combined with position-sensitive X- ray detection to efficiently and quantitatively image the reciprocal space structure of crystalline materials. Reciprocal space analysis of newly prepared, as well as aged, p{sup {minus}} porous silicon films showed that these films exhibit a very broad range of crystallinity. This material appears to range in structure from a strained, single-crystal, sponge-like material exhibiting long-range coherency to isolated, dilated nanocrystals embedded in an amorphous matrix. Reciprocal space analysis of n{sup +} and p{sup +} porous silicon showed these materials are strained single-crystals with a spatially-correlated array of vertical pores. The vertical pores in these crystals may be surrounded by nanoporous or nanocrystalline domains as small as a few nm in size which produce diffuse diffraction indicating their presence. The photoluminescence of these films was examined using 488 nm Ar laser excitation in order to search for possible correlations between photoluminescent intensity and crystalline microstructure.

  13. Tailored Voltage Waveform Deposition of Microcrystalline Silicon Thin Films from Hydrogen-Diluted Silane and Silicon Tetrafluoride: Optoelectronic Properties of Films

    Science.gov (United States)

    Johnson, Erik V.; Pouliquen, Sylvain; Delattre, Pierre-Alexandre; Booth, Jean-Paul

    2012-08-01

    The use of tailored voltage waveforms (TVW's) to excite a plasma for the deposition of thin films of hydrogenated microcrystalline silicon (µc-Si:H) has been shown to be an effective technique to decouple mean ion bombardment energy (IBE) from injected power. In this work, we examine the changes in material properties controlled by this technique through Raman scattering and spectroscopic ellipsometry for films deposited from H2-diluted SiH4, and we examine the electrical properties of such films using temperature dependent conductivity. As the laboratory-scale deposition system used had neither a load lock nor an oxygen filter in the H2 line, accidental O-doping was observed for the µc-Si:H films. We investigated suppression of this doping by adding varying amounts of SiF4, and using an SiF4/Ar pre-etch step to clean the reactor. This technique is shown to be effective in decreasing the accidental doping of the films, and intrinsic µc-Si:H films are produced with an activation energy of up to 0.55 eV. As well, an important difference in the amorphous-to-microcrystalline transition is observed once SiF4 is included in the gas mixture.

  14. Characterization and Electrochemical Properties of Oxygenated Amorphous Carbon (a-C) Films

    OpenAIRE

    Palomäki, Tommi; Wester, Niklas; Johansson, Leena-Sisko; Laitinen, Mikko; Jiang, Hua; Arstila, Kai; Sajavaara, Timo; Han, Jeon G.; Koskinen, Jari; Laurila, Tomi

    2016-01-01

    Amorphous carbon (a-C) films with varying oxygen content were deposited by closed-field unbalanced magnetron sputtering with the aim to understand the effect of oxygen on the structural and physical properties of the films and subsequently correlate these changes with electrochemical properties. The a-C films were characterized by transmission electron microscopy, helium-ion microscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and time-of-flight elastic re...

  15. Fourier transform infrared analysis of ceramic powders: Quantitative determination of alpha, beta, and amorphous phases of silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Trout, T.K.; Bellama, J.M.; Brinckman, F.E.; Faltynek, R.A.

    1989-03-01

    Fourier transform infrared spectroscopy (FT-IR) forms the basis for determining the morphological composition of mixtures containing alpha, beta, and amorphous phases of silicon nitride. The analytical technique, involving multiple linear regression treatment of Kubelka-Munk absorbance values from diffuse reflectance measurements, yields specific percent composition data for the amorphous phase as well as the crystalline phases in ternary mixtures of 0--1% by weight Si/sub 3/N/sub 4/ in potassium bromide.

  16. Light management in thin-film silicon solar cells

    NARCIS (Netherlands)

    Isabella, O.

    2013-01-01

    Solar energy can fulfil mankind’s energy needs and secure a more balanced distribution of primary sources of energy. Wafer-based and thin-film silicon solar cells dominate todays’ photovoltaic market because silicon is a non-toxic and abundant material and high conversion efficiencies are achieved

  17. Characterization of doped hydrogenated nanocrystalline silicon films prepared by plasma enhanced chemical vapour deposition

    Institute of Scientific and Technical Information of China (English)

    Wang Jin-Liang; Wu Er-Xing

    2007-01-01

    The B-and P-doped hydrogenated nanocrystalline silicon films (nc-Si:H) are prepared by plasma-enhanced chemical vapour deposition (PECVD) .The microstructures of doped nc-Si:H films are carefully and systematically char acterized by using high resolution electron microscopy (HREM) ,Raman scattering,x-ray diffraction (XRD) ,Auger electron spectroscopy (AES) ,and resonant nucleus reaction (RNR) .The results show that as the doping concentration of PH3 increases,the average grain size (d) tends to decrease and the crystalline volume percentage (Xc) increases simultaneously.For the B-doped samples,as the doping concentration of B2H6 increases,no obvious change in the value of d is observed,but the value of Xc is found to decrease.This is especially apparent in the case of heavy B2H6 doped samples,where the films change from nanocrystalline to amorphous.

  18. Amorphous silicon crystallization by laser. Report of the experiments at Frascati (Project Foto); Cristallizzazione di silicio amorfo via laser. Rapporto degli esperimenti a frascati (Progetto Foto)

    Energy Technology Data Exchange (ETDEWEB)

    Bollanti, S.; Di Lazzaro, P.; Murra, D. [ENEA, Centro Ricerche Frascati, Frascati, RM (Italy). Div. Fisica Applicata; Imparato, A.; Privato, C. [ENEA, Centro Ricerche Portici, Naples (Italy). Div. Fonti Rinnovabili; Carluccio, R.; Fortunato, G.; Mariucci, L.; Pecora, A. [CNR Istituto di Elettronica dello Stato Solido, Rome (Italy)

    2000-07-01

    The final goal of the Project FOTO is the construction of a laboratory in a clean room for the production of active matrix which can be used to obtain Active Matrix Liquid Crystal Displays (AMLCD). The AMLCD are based on Thin Film Transistors (TFT), which can be obtained by poly-silicon (poly-Si) thin films, achieved, e.g., by irradiating films of amorphous silicon (a-Si) by ultraviolet laser radiation. In this report, are presented the results of the a-Si irradiation by using the laser-facility Hercules (excimer XeCl, l=0,308 mm) done at the ENEA Frascati Centre. The transformation of a-Si into poly-Si is commented upon the variation of the space-time characteristics of the laser pulses, of the irradiation conditions and of the characteristics of the irradiated a-Si films. [Italian] Il macro-obiettivo del Progetto FOTO e' la realizzazione di un laboratorio in camera pulita per lo sviluppo di processi atti a fabbricare matrici attive utilizzabili per ottenere schermi piatti a cristalli liquidi (AMLCD, Active Matrix Liquid Crystal Display). Uno dei primi passi del processo consiste nel creare transistori a film sottile (TFT, Thin Film Transistor). A tal fine, e' necessario ottenere strati sottili di Silicio policristallino irragiando films di silicio amorfo con luce laser ultravioletta. In questo rapporto, sono presentati i risultati degli irraggiamenti di film sottili di silicio amorfo tramite la laser-facility Hercules (eccimero XeCl, l=0,308 mm) effettuati presso il C.R. ENEA di Frascati. La trasformazione di silicio amorfo in silicio policristallino cosi' ottenuta e' commentata al variare delle caratteristiche spazio-temporali dell'impulso laser, delle condizioni di irraggiamento e delle caratteristiche del film di silicio amorfo irraggiato.

  19. Achieving thermography with a thermal security camera using uncooled amorphous silicon microbolometer image sensors

    Science.gov (United States)

    Wang, Yu-Wei; Tesdahl, Curtis; Owens, Jim; Dorn, David

    2012-06-01

    Advancements in uncooled microbolometer technology over the last several years have opened up many commercial applications which had been previously cost prohibitive. Thermal technology is no longer limited to the military and government market segments. One type of thermal sensor with low NETD which is available in the commercial market segment is the uncooled amorphous silicon (α-Si) microbolometer image sensor. Typical thermal security cameras focus on providing the best image quality by auto tonemaping (contrast enhancing) the image, which provides the best contrast depending on the temperature range of the scene. While this may provide enough information to detect objects and activities, there are further benefits of being able to estimate the actual object temperatures in a scene. This thermographic ability can provide functionality beyond typical security cameras by being able to monitor processes. Example applications of thermography[2] with thermal camera include: monitoring electrical circuits, industrial machinery, building thermal leaks, oil/gas pipelines, power substations, etc...[3][5] This paper discusses the methodology of estimating object temperatures by characterizing/calibrating different components inside a thermal camera utilizing an uncooled amorphous silicon microbolometer image sensor. Plots of system performance across camera operating temperatures will be shown.

  20. Fabrication and characterization of monolithically integrated microchannel plates based on amorphous silicon.

    Science.gov (United States)

    Franco, Andrea; Geissbühler, Jonas; Wyrsch, Nicolas; Ballif, Christophe

    2014-04-04

    Microchannel plates are vacuum-based electron multipliers for particle--in particular, photon--detection, with applications ranging from image intensifiers to single-photon detectors. Their key strengths are large signal amplification, large active area, micrometric spatial resolution and picosecond temporal resolution. Here, we present the first microchannel plate made of hydrogenated amorphous silicon (a-Si:H) instead of lead glass. The breakthrough lies in the possibility of realizing amorphous silicon-based microchannel plates (AMCPs) on any kind of substrate. This achievement is based on mastering the deposition of an ultra-thick (80-120 μm) stress-controlled a-Si:H layer from the gas phase at temperatures of about 200 °C and micromachining the channels by dry etching. We fabricated AMCPs that are vertically integrated on metallic anodes of test structures, proving the feasibility of monolithic integration of, for instance, AMCPs on application-specific integrated circuits for signal processing. We show an electron multiplication factor exceeding 30 for an aspect ratio, namely channel length over aperture, of 12.5:1. This result was achieved for input photoelectron currents up to 100 pA, in the continuous illumination regime, which provides a first evidence of the a-Si:H effectiveness in replenishing the electrons dispensed in the multiplication process.

  1. Silica nanoparticles on front glass for efficiency enhancement in superstrate-type amorphous silicon solar cells

    Science.gov (United States)

    Das, Sonali; Banerjee, Chandan; Kundu, Avra; Dey, Prasenjit; Saha, Hiranmay; Datta, Swapan K.

    2013-10-01

    Antireflective coating on front glass of superstrate-type single junction amorphous silicon solar cells (SCs) has been applied using highly monodispersed and stable silica nanoparticles (NPs). The silica NPs having 300 nm diameter were synthesized by Stober technique where the size of the NPs was controlled by varying the alcohol medium. The synthesized silica NPs were analysed by dynamic light scattering technique and Fourier transform infrared spectroscopy. The NPs were spin coated on glass side of fluorinated tin oxide (SnO2: F) coated glass superstrate and optimization of the concentration of the colloidal solution, spin speed and number of coated layers was done to achieve minimum reflection characteristics. An estimation of the distribution of the NPs for different optimization parameters has been done using field-emission scanning electron microscopy. Subsequently, the transparent conducting oxide coated glass with the layer having the minimum reflectance is used for fabrication of amorphous silicon SC. Electrical analysis of the fabricated cell indicates an improvement of 6.5% in short-circuit current density from a reference of 12.40 mA cm-2 while the open circuit voltage and the fill factor remains unaltered. A realistic optical model has also been proposed to gain an insight into the system.

  2. Three hydrogenated amorphous silicon photodiodes stacked for an above integrated circuit colour sensor

    Energy Technology Data Exchange (ETDEWEB)

    Gidon, Pierre; Giffard, Benoit; Moussy, Norbert; Parrein, Pascale; Poupinet, Ludovic [CEA-LETI, MINATEC, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2010-03-15

    We present theoretical simulation and experimental results of a new colour pixel structure. This pixel catches the light in three stacked amorphous silicon photodiodes encompassed between transparent electrodes. The optical structure has been simulated for signal optimisation. The thickness of each stacked layer is chosen in order to absorb the maximum of light and the three signals allow to linearly calculate the CIE colour coordinates 1 with minimum error and noise. The whole process is compatible with an above integrated circuit (IC) approach. Each photodiode is an n-i-p structure. For optical reason, the upper diode must be controlled down to 25 nm thickness. The first test pixel structure allows a good recovering of colour coordinates. The measured absorption spectrum of each photodiode is in good agreement with our simulations. This specific stack with three photodiodes per pixel totalises two times more signal than an above IC pixel under a standard Bayer pattern 2,3. In each square of this GretagMacbeth chart is the reference colour on the right and the experimentally measured colour on the left with three amorphous silicon photodiodes per pixel. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  3. Non-negligible Contributions to Thermal Conductivity From Localized Modes in Amorphous Silicon Dioxide

    Science.gov (United States)

    Lv, Wei; Henry, Asegun

    2016-10-01

    Thermal conductivity is important for almost all applications involving heat transfer. The theory and modeling of crystalline materials is in some sense a solved problem, where one can now calculate their thermal conductivity from first principles using expressions based on the phonon gas model (PGM). However, modeling of amorphous materials still has many open questions, because the PGM itself becomes questionable when one cannot rigorously define the phonon velocities. In this report, we used our recently developed Green-Kubo modal analysis (GKMA) method to study amorphous silicon dioxide (a-SiO2). The predicted thermal conductivities exhibit excellent agreement with experiments and anharmonic effects are included in the thermal conductivity calculation for all the modes in a-SiO2 for the first time. Previously, localized modes (locons) have been thought to have a negligible contribution to thermal conductivity, due to their highly localized nature. However, in a-SiO2 our results indicate that locons contribute more than 10% to the total thermal conductivity from 400 K to 800 K and they are largely responsible for the increase in thermal conductivity of a-SiO2 above room temperature. This is an effect that cannot be explained by previous methods and therefore offers new insight into the nature of phonon transport in amorphous/glassy materials.

  4. Non-negligible Contributions to Thermal Conductivity From Localized Modes in Amorphous Silicon Dioxide.

    Science.gov (United States)

    Lv, Wei; Henry, Asegun

    2016-10-21

    Thermal conductivity is important for almost all applications involving heat transfer. The theory and modeling of crystalline materials is in some sense a solved problem, where one can now calculate their thermal conductivity from first principles using expressions based on the phonon gas model (PGM). However, modeling of amorphous materials still has many open questions, because the PGM itself becomes questionable when one cannot rigorously define the phonon velocities. In this report, we used our recently developed Green-Kubo modal analysis (GKMA) method to study amorphous silicon dioxide (a-SiO2). The predicted thermal conductivities exhibit excellent agreement with experiments and anharmonic effects are included in the thermal conductivity calculation for all the modes in a-SiO2 for the first time. Previously, localized modes (locons) have been thought to have a negligible contribution to thermal conductivity, due to their highly localized nature. However, in a-SiO2 our results indicate that locons contribute more than 10% to the total thermal conductivity from 400 K to 800 K and they are largely responsible for the increase in thermal conductivity of a-SiO2 above room temperature. This is an effect that cannot be explained by previous methods and therefore offers new insight into the nature of phonon transport in amorphous/glassy materials.

  5. Grazing incidence X-ray absorption characterization of amorphous Zn-Sn-O thin film

    Science.gov (United States)

    Moffitt, S. L.; Ma, Q.; Buchholz, D. B.; Chang, R. P. H.; Bedzyk, M. J.; Mason, T. O.

    2016-05-01

    We report a surface structure study of an amorphous Zn-Sn-O (a-ZTO) transparent conducting film using the grazing incidence X-ray absorption spectroscopy technique. By setting the measuring angles far below the critical angle at which the total external reflection occurs, the details of the surface structure of a film or bulk can be successfully accessed. The results show that unlike in the film where Zn is severely under coordinated (N coordinated (N = 4) near the surface while the coordination number around Sn is slightly smaller near the surface than in the film. Despite a 30% Zn doping, the local structure in the film is rutile-like.

  6. Size Control of Nanoscale Silicon Particles Formed in Thermally Annealed A- Si: H Films and Its Photoluminescence

    Institute of Scientific and Technical Information of China (English)

    XUE Qing

    2005-01-01

    A method to control the size of nanoscale silicon grown in thermally annealed hydrogenated amorphous silicon (a-Si : H) films is reported. Using the characterizing techniques of micro-Raman scattering,X-ray diffraction and computer simulation, it is found that the sizes of the formed silicon particles change with the temperature rising rate in thermally annealing the a-Si : H films. When the a-Si: H films have been annealed with high rising rate( ~ 100 C/s), the sizes of nanoscale silicon particles are in the range of 1.6~ 15nm. On the other hand, if the a-Si: H films have been annealed with low temperature rising rate(~1 C/s),the sizes of nanoscale silicon particles are in the range of 23~46 nm. Based on the theory of crystal nucleation and growth, the effect of temperature rising rate on the sizes of the formed silicon particles is discussed. Under high power laser irradiation, in situ nanocrystallization and subsequent nc-Si clusters are small enough for visible light emission, authors have not detected any visible photoluminescence(PL) from these nc-Si clusters before surface passivation. After electrochemical oxidization in hydrofluoric acid, however, intense red PL has been detected. Cyclic hydrofluoric oxidization and air exposure can cause subsequent blue shift in the red emission. The importance of surface passivation and quantum confinement in the visible emissions has been discussed.

  7. High-Efficiency Amorphous Silicon Alloy Based Solar Cells and Modules; Final Technical Progress Report, 30 May 2002--31 May 2005

    Energy Technology Data Exchange (ETDEWEB)

    Guha, S.; Yang, J.

    2005-10-01

    The principal objective of this R&D program is to expand, enhance, and accelerate knowledge and capabilities for development of high-efficiency hydrogenated amorphous silicon (a-Si:H) and amorphous silicon-germanium alloy (a-SiGe:H) related thin-film multijunction solar cells and modules with low manufacturing cost and high reliability. Our strategy has been to use the spectrum-splitting triple-junction structure, a-Si:H/a-SiGe:H/a-SiGe:H, to improve solar cell and module efficiency, stability, and throughput of production. The methodology used to achieve the objectives included: (1) explore the highest stable efficiency using the triple-junction structure deposited using RF glow discharge at a low rate, (2) fabricate the devices at a high deposition rate for high throughput and low cost, and (3) develop an optimized recipe using the R&D batch large-area reactor to help the design and optimization of the roll-to-roll production machines. For short-term goals, we have worked on the improvement of a-Si:H and a-SiGe:H alloy solar cells. a-Si:H and a-SiGe:H are the foundation of current a-Si:H based thin-film photovoltaic technology. Any improvement in cell efficiency, throughput, and cost reduction will immediately improve operation efficiency of our manufacturing plant, allowing us to further expand our production capacity.

  8. Carbon-Incorporated Amorphous Indium Zinc Oxide Thin-Film Transistors

    Science.gov (United States)

    Parthiban, S.; Park, K.; Kim, H.-J.; Yang, S.; Kwon, J.-Y.

    2014-11-01

    We propose the use of amorphous-carbon indium zinc oxide (a-CIZO) as a channel material for thin-film transistor (TFT) fabrication. This study chose a carbon dopant as a carrier suppressor and strong oxygen binder in amorphous-indium zinc oxide (a-IZO) channel material. a-CIZO thin films were deposited using radiofrequency (RF) sputtering and postannealed at 150°C. X-ray diffraction and transmission electron microscopy analysis revealed that the film remained amorphous even after postannealing. The a-CIZO TFT postannealed at 150°C exhibited saturation field-effect mobility of 16.5 cm2 V-1 s-1 and on-off current ratio of ˜4.3 × 107.

  9. Materials and Electrical Characterization of Physical Vapor Deposited LaxLu1-xO3 Thin Films on 300 mm Silicon

    Energy Technology Data Exchange (ETDEWEB)

    L Edge; T Vo; V Paruchuri; R Iijima; J Bruley; J Jordan-Sweet; B Linder; A Kellock; T Tsunoda; S Shinde

    2011-12-31

    La{sub x}Lu{sub 1-x}O{sub 3} thin films were deposited on 300 mm silicon wafers by physical vapor deposition and fabricated into field-effect transistors using a gate-first process flow. The films were characterized using transmission electron microscopy, Rutherford backscattering spectrometry, and synchrotron x-ray diffraction. The results show the films remain amorphous even at temperatures of 1000 C. The dielectric properties of La{sub x}Lu{sub 1-x}O{sub 3} (0.125 {<=} x {<=} 0.875) thin films were evaluated as a function of film composition. The amorphous La{sub x}Lu{sub 1-x}O{sub 3} thin films have a dielectric constant (K) of 23 across the composition range. The inversion thickness (T{sub inv}) of the La{sub x}Lu{sub 1-x}O{sub 3} thin films was scaled to <1.0 nm.

  10. Structure and magnetic properties of amorphous and polycrystalline Fe3O4 thin films

    Institute of Scientific and Technical Information of China (English)

    TANG Xiao-li; ZHANG Huai-wu; SU Hua; ZHONG Zhi-yong; JING Yu-lan

    2006-01-01

    Half-metallic Fe3O4 films prepared by DC magnetron reactive sputtering with a tantalum(Ta) buffer layer was investigated. Primary emphasis is placed on the structural impact on its magnetic properties. The experimental results show that the amorphous Fe3O4 films exhibit a superparamagnetic response at a large-scale from 20 nm to 150 nm,and the magnetoresistance (MR) isn't detected. By contrast,the polycrystalline Fe3O4 films possess large saturation magnetization Ms of 420 A/(kg-cm) and a clear magnetoresistance with a field of 40 kA/m. The unusual properties for the amorphous Fe3O4 film are attributed to the existing large density of the similar structure as anti-phase boundaries in the film.

  11. Development of Doped Microcrystalline Silicon Oxide and its Application to Thin‑Film Silicon Solar Cells

    NARCIS (Netherlands)

    Lambertz, A.

    2015-01-01

    The aim of the present study is the development of doped microcrystalline silicon oxide (µc‑SiOx:H) alloys and its application in thin‑film silicon solar cells. The doped µc‑SiOx:H material was prepared from carbon dioxide (CO2), silane (SiH4), hydrogen (H2) gas mixtures using plasma enhanced chemic

  12. Magnetic and microwave properties of amorphous FeCoNbBCu thin films

    Science.gov (United States)

    Bi, Mei; Wang, Xin; Lu, Haipeng; Deng, Longjiang; Sunday, Katie Jo; Taheri, Mitra L.; Harris, Vincent G.

    2016-01-01

    The soft magnetic and microwave properties of amorphous FeCoNbBCu thin films with thicknesses varying from 70 nm to 450 nm have been systematically investigated. Due to the amorphous structure, the coercivity is 1.5 Oe in thicker films. The thickness-dependent microwave characteristics of the films were measured over the range 0.5-6 GHz and analyzed using the Landau-Lifshitz-Gilbert equation. Without applying magnetic field during deposition and measurement, an in-plane uniaxial anisotropy in amorphous thin films was obtained, ranging from 21 to 45 Oe. The interface interaction between substrate and film is confirmed to be the origin of the induced anisotropy, whereas the volume anisotropy contribution is more pronounced with increasing film thickness. For films possessing an in-plane uniaxial anisotropy, the shift of resonance frequency with thickness is observed and verified by the Kittel equation. The demonstration of a controllable and tunable anisotropy suggests that the FeCoNbBCu thin films have potential application as magnetic materials for Spintronics-based microwave devices.

  13. The physics and applications of amorphous semiconductors

    CERN Document Server

    Madan, Arun

    1988-01-01

    This comprehensive, detailed treatise on the physics and applications of the new emerging technology of amorphous semiconductors focuses on specific device research problems such as the optimization of device performance. The first part of the book presents hydrogenated amorphous silicon type alloys, whose applications include inexpensive solar cells, thin film transistors, image scanners, electrophotography, optical recording and gas sensors. The second part of the book discusses amorphous chalcogenides, whose applications include electrophotography, switching, and memory elements. This boo

  14. Far IR Transmission Characteristics of Silicon Nitride Films using Fourier Transform Spectroscopy

    Science.gov (United States)

    Ferrusca, D.; Castillo-Domínguez, E.; Velázquez, M.; Hughes, D.; Serrano, A.; Torres-Jácome, A.

    2009-12-01

    We are fabricating amorphous Silicon (a-Si) bolometers doped with boron with a measured NEP˜1.5×10-16 W/Hz1/2 suitable for use in millimeter and sub-millimeter astronomy. In this paper we present the preliminary results of the absorber optimization for the a-Si bolometers. A film of Silicon Nitride (SiN), deposited by LPCVD (Low Pressure Chemical Vapor Deposition) process at INAOE, with or without metallic coating is used as a weak thermal link to the heat sink as well as an absorber. We have measured the transmission spectrum of thin films of SiN in the range of 200 to 1000 GHz using Fourier Transform Spectroscopy (FTS) and a bolometric system with a NEP˜1.26×10-13. The transmission of thin films of SiN with a thickness of 0.4 μn has been measured at temperatures of 290 K and 4 K. The uncoated SiN films have a transmission of 80% and we expect a 50% transmission for the metallic (e.g. Titanium) coated films.

  15. Electrochemical Intercalation of Sodium into Silicon Thin Film

    Institute of Scientific and Technical Information of China (English)

    Dong-Yeon Kim; Hyo-Jun Ahn; Gyu-Bong Cho; Jong-Seon Kim; Ho-Suk Ryu; Ki-Won Kim; Jou-Hyeon Ahn; Won-Cheol Shin

    2008-01-01

    In order to investigate the possibility of Si thin film as an anode for Na battery, we studied the electrochemical intercalation of sodium into the Si film. Amorphous Si thin film electrode was prepared using DC magnetron sputtering. Sodium ion could intercalate into Si thin film upto Na0.52Si, i.e. 530mAh · g-1-Si. The first discharge capacity was 80mAh.·g-1-Si, which meant reversible amount of sodium intercalation. The discharge capacity slightly decreased to 70mAh · g-1-Si after 10 cycles.

  16. Characterization of an amorphous silicon flat panel for controlling the positioning accuracy of sheet; Caracterizacion de un panel plano de silicio amorfo para control de la exactitud en el posicionamiento de laminas

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, J.; Gonzalez, V.; Gimeno, J.; Dolores, V. de los; Pastor, V.; Crispin, V.; Guardino, C.

    2011-07-01

    It has established a method for measuring the position of the blades in a multi leaf collimator (MLC) used to measure dose portal imaging device (EPID) of amorphous silicon, and verified its accuracy using radiochromic films and measures water with diode Cuba, techniques perfectly well validated in our institution. This dose profiles are studied for each sheet and determine their position at the point which has 50% of the dose in the open field.

  17. Charge storage characteristics and tunneling mechanism of amorphous Ge-doped HfOx films

    Science.gov (United States)

    Qiu, X. Y.; Zhang, S. Y.; Zhang, T.; Wang, R. X.; Li, L. T.; Zhang, Y.; Dai, J. Y.

    2016-09-01

    Amorphous Ge-doped HfOx films have been deposited on p-Si(100) substrates by means of RF magnetron sputtering. Microstructural investigations reveal the partial oxidation of doped Ge atoms in the amorphous HfOx matrix and the existence of HfSiOx interfacial layer. Capacitance-voltage hysteresis of the Ag-/Ge-doped HfOx/Si/Ag memory capacitor exhibits a memory window of 3.15 V which can maintain for >5 × 104 cycles. Current-voltage characteristics reveal that Poole-Frenkel tunneling is responsible for electron transport in the Ge-doped HfOx film.

  18. Laser process for extended silicon thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Hessmann, M.T., E-mail: hessmann@zae.uni-erlangen.de [Bavarian Center for Applied Energy Research, Am Weichselgarten 7, 91058 Erlangen (Germany); Kunz, T.; Burkert, I.; Gawehns, N. [Bavarian Center for Applied Energy Research, Am Weichselgarten 7, 91058 Erlangen (Germany); Schaefer, L.; Frick, T.; Schmidt, M. [Bayerisches Laserzentrum, Konrad-Zuse-Str 2-6, 91052 Erlangen (Germany); Meidel, B. [Schott Solar AG, Carl-Zeiss-Strasse 4, 63755 Alzenau (Germany); Auer, R. [Bavarian Center for Applied Energy Research, Am Weichselgarten 7, 91058 Erlangen (Germany); Brabec, C.J. [Bavarian Center for Applied Energy Research, Am Weichselgarten 7, 91058 Erlangen (Germany); Chair VI - Materials for Electronics and Energy Technology, University of Erlangen-Nuremberg, Martensstrasse 7, 91058 Erlangen (Germany)

    2011-10-31

    We present a large area thin film base substrate for the epitaxy of crystalline silicon. The concept of epitaxial growth of silicon on large area thin film substrates overcomes the area restrictions of an ingot based monocrystalline silicon process. Further it opens the possibility for a roll to roll process for crystalline silicon production. This concept suggests a technical pathway to overcome the limitations of silicon ingot production in terms of costs, throughput and completely prevents any sawing losses. The core idea behind these thin film substrates is a laser welding process of individual, thin silicon wafers. In this manuscript we investigate the properties of laser welded monocrystalline silicon foils (100) by micro-Raman mapping and spectroscopy. It is shown that the laser beam changes the crystalline structure of float zone grown silicon along the welding seam. This is illustrated by Raman mapping which visualizes compressive stress as well as tensile stress in a range of - 147.5 to 32.5 MPa along the welding area.

  19. Analysis of the silicon market: Will thin films profit?

    Energy Technology Data Exchange (ETDEWEB)

    Sark, W.G.J.H.M. van; Brandsen, G.W. [Copernicus Institute for Sustainable Development and Innovation, Utrecht University, Utrecht (Netherlands). Department of Science, Technology and Society; Fleuster, M. [Solland Solar Energy, Heerlen (Netherlands); Hekkert, M.P. [Copernicus Institute for Sustainable Development and Innovation, Utrecht University, Utrecht (Netherlands). Department of Innovation Studies

    2007-06-15

    The photovoltaic industry has been growing with astonishing rates over the past years. The supply of silicon to the wafer-based industry has recently become a problem. This paper presents a thorough analysis of the PV industry and quantifies the silicon shortage. It is expected that this leads to a decrease in production in 2006 rather than the usual increase. Due to a mismatch in expansion plans of silicon feedstock manufacturers and solar cell manufacturers, a large cell overcapacity will persist up to 2010. The thin-film PV market is expected to profit from the silicon shortage problem; its market share may substantially increase to about 25% in 2010. (author)

  20. Spectroscopic ellipsometry characterization of thin-film silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Jellison, G.E. Jr.; Modine, F.A. [Oak Ridge National Lab., TN (United States); Doshi, P.; Rohatgi, A. [Georiga Inst. of Technology, Atlanta, GA (United States)

    1997-05-01

    We have measured and analyzed the optical characteristics of a series of silicon nitride thin films prepared by plasma-enhanced chemical vapor deposition on silicon substrates for photovoltaic applications. Spectroscopic ellipsometry measurements were made by using a two-channel spectroscopic polarization modulator ellipsometer that measures N, S, and C data simultaneously. The data were fit to a model consisting of air / roughness / SiN / crystalline silicon. The roughness was modeled using the Bruggeman effective medium approximation, assuming 50% SiN, 50% voids. The optical functions of the SiN film were parameterized using a model by Jellison and Modine. All the {Chi}{sup 2} are near 1, demonstrating that this model works extremely well for all SiN films. The measured dielectric functions were used to make optimized SiN antireflection coatings for crystalline silicon solar cells.

  1. Effect of the initial structure on the electrical property of crystalline silicon films deposited on glass by hot-wire chemical vapor deposition.

    Science.gov (United States)

    Chung, Yung-Bin; Lee, Sang-Hoon; Bae, Sung-Hwan; Park, Hyung-Ki; Jung, Jae-Soo; Hwang, Nong-Moon

    2012-07-01

    Crystalline silicon films on an inexpensive glass substrate are currently prepared by depositing an amorphous silicon film and then crystallizing it by excimer laser annealing, rapid thermal annealing, or metal-induced crystallization because crystalline silicon films cannot be directly deposited on glass at a low temperature. It was recently shown that by adding HCI gas in the hot-wire chemical vapor deposition (HWCVD) process, the crystalline silicon film can be directly deposited on a glass substrate without additional annealing. The electrical properties of silicon films prepared using a gas mixture of SiH4 and HCl in the HWCVD process could be further improved by controlling the initial structure, which was achieved by adjusting the delay time in deposition. The size of the silicon particles in the initial structure increased with increasing delay time, which increased the mobility and decreased the resistivity of the deposited films. The 0 and 5 min delay times produced the silicon particle sizes of approximately 10 and approximately 28 nm, respectively, in the initial microstructure, which produced the final films, after deposition for 300 sec, of resistivities of 0.32 and 0.13 Omega-cm, mobilities of 1.06 and 1.48 cm2 V(-1) S(-1), and relative densities of 0.87 and 0.92, respectively.

  2. Structural and mechanical properties of amorphous carbon films deposited by the dual plasma technique

    Institute of Scientific and Technical Information of China (English)

    Yaohui Wang; Xu Zhang; Xianying Wu; Huixing Zhang; Xiaoji Zhang

    2008-01-01

    Direct current metal filtered cathodic vacuum are (FCVA) and acetylene gas (C2H2) were wielded to synthesize Ti-containing amorphous carbon films on Si (100). The influence of substrate bias voltage and acetylene gas on the microstructure and mechanical properties of the films were investigated. The results show that the phase of TiC in the (111) preferential crystallo-graphic orientation exists in the film, and rite main existing pattern of carbon is sp2. With increasing the acetylene flow rate, the con-tents of Ti and TiC phase of the film gradually reduce; however, the thickness of the film increases. When the substrate bias voltage reaches -600 V, the internal stress of the film reaches 1.6 GPa. The micro-hardness and elastic modulus of the film can reach 33.9 and 237.6 GPa, respectively, and the friction coefficient of the film is 0.25.

  3. Integration of field emitter array and thin-film transistor using polycrystalline silicon process technology

    CERN Document Server

    Song, Y H; Kang, S Y; Park Jeong Man; Cho, K I

    1998-01-01

    We present the monolithic integration of a gated polycrystalline silicon field emitter array (poly-Si FEA) and a thin-film transistor(TFT) on an insulating substrate for active-matrix field emission displays (AMFEDs). The TFT was designed to have low off-state currents even at a high drain voltage. Amorphous silicon has been used as a starting material of the poly-Si FEA for improving surface smoothness and uniformity of the tips, and the gate holes have been formed by using an etch-back process. The integrated poly-Si TFT controlled electron emissions of the poly-Si FEA actively, resulting in great improvement in the emission reliability along with a low-voltage control, below 15 V, of field emission, The developed technology has potential applications in AMFEDs on glass substrates.

  4. Absorption coefficient modeling of microcrystalline silicon thin film using Maxwell-Garnett effective medium theory.

    Science.gov (United States)

    Chen, Sheng-Hui; Wang, Hsuan-Wen; Chang, Ting-Wei

    2012-03-12

    Considering the Mott-Davis density of state model and Rayleigh scattering effect, we present an approach to model the absorption profile of microcrystalline silicon thin films in this paper. Maxwell-Garnett effective medium theory was applied to analyze the absorption curves. To validate the model, several experimental profiles have been established and compared with those results from the model. With the assistance of the genetic algorithm, our results show that the absorption curves from the model are in good agreement with the experiments. Our findings also indicate that, as the crystal volume fraction increases, not only do the defects in amorphous silicon reduce, but the bulk scattering effect is gradually enhanced as well.

  5. Research on fabrication technology for thin film solar cells for practical use. Technological development for qualitative improvement (improvement of conversion efficiency of amorphous silicon solar cells after degradation); Usumaku taiyo denchi seizo gijutsu no jitsuyoka kenkyu. Kohinshitsuka gijutsu (amorphous taiyo denchi no shoki rekkago koritsu kojo no gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    Tatsuta, M. [New Energy and Industrial Technology Development Organization, Tokyo (Japan)

    1994-12-01

    This paper reports the study results on technological development for qualitative improvement of a-Si solar cells after initial degradation in fiscal 1994. On the fabrication technology of light-stable a-Si films, the film formation method possible to control combined hydrogen by repetitive formation/treatment was developed. The obtained high-quality light-stable a-Si film was featured by low defect density in a wide optical band gap range, and defect density of nearly 3 {times} 10{sup 16}/cm{sup -3} after light irradiation. The light degradation rate of the cell where the a-Si film was applied to i layer was relatively stable by 10% or less. The a-Si/a-Si double-layer tandem cell fabricated by this technology produced a high conversion efficiency of 10.5%. By applying {mu}c-Si material to photoactive layer as narrow band gap material, the cell with optical sensitivity even in long wavelength ranges more than 1000nm was obtained. The a-Si/{mu}c-Si double-layer tandem cell produced an initial efficiency of 8.0% and an efficiency after degradation of 7.5%. 12 figs., 3 tabs.

  6. Nanostructuring of GeTiO amorphous films by pulsed laser irradiation

    Directory of Open Access Journals (Sweden)

    Valentin S. Teodorescu

    2015-04-01

    Full Text Available Laser pulse processing of surfaces and thin films is a useful tool for amorphous thin films crystallization, surface nanostructuring, phase transformation and modification of physical properties of thin films. Here we show the effects of nanostructuring produced at the surface and under the surface of amorphous GeTiO films through laser pulses using fluences of 10–30 mJ/cm2. The GeTiO films were obtained by RF magnetron sputtering with 50:50 initial atomic ratio of Ge:TiO2. Laser irradiation was performed by using the fourth harmonic (266 nm of a Nd:YAG laser. The laser-induced nanostructuring results in two effects, the first one is the appearance of a wave-like topography at the film surface, with a periodicity of 200 nm and the second one is the structure modification of a layer under the film surface, at a depth that is related to the absorption length of the laser radiation. The periodicity of the wave-like relief is smaller than the laser wavelength. In the modified layer, the Ge atoms are segregated in spherical amorphous nanoparticles as a result of the fast diffusion of Ge atoms in the amorphous GeTiO matrix. The temperature estimation of the film surface during the laser pulses shows a maximum of about 500 °C, which is much lower than the melting temperature of the GeTiO matrix. GeO gas is formed at laser fluences higher than 20 mJ/cm2 and produces nanovoids in the laser-modified layer at the film surface. A glass transition at low temperatures could happen in the amorphous GeTiO film, which explains the formation of the wave-like topography. The very high Ge diffusivity during the laser pulse action, which is characteristic for liquids, cannot be reached in a viscous matrix. Our experiments show that the diffusivity of atomic and molecular species such as Ge and GeO is very much enhanced in the presence of the laser pulse field. Consequently, the fast diffusion drives the formation of amorphous Ge nanoparticles through the

  7. Intense Red Catho- and Photoluminescence from 200 nm Thick Samarium Doped Amorphous AlN Thin Films

    Directory of Open Access Journals (Sweden)

    Ali Tariq

    2009-01-01

    Full Text Available Abstract Samarium (Sm doped aluminum nitride (AlN thin films are deposited on silicon (100 substrates at 77 K by rf magnetron sputtering method. Thick films of 200 nm are grown at 100–200 watts RF power and 5–8 m Torr nitrogen, using a metal target of Al with Sm. X-ray diffraction results show that films are amorphous. Cathodoluminescence (CL studies are performed and four peaks are observed in Sm at 564, 600, 648, and 707 nm as a result of4G5/2 → 6H5/2,4G5/2 → 6H7/2,4G5/2 → 6H9/2, and4G5/2 → 6H11/2transitions. Photoluminescence (PL provides dominant peaks at 600 and 707 nm while CL gives the intense peaks at 600 nm and 648 nm, respectively. Films are thermally activated at 1,200 K for half an hour in a nitrogen atmosphere. Thermal activation enhances the intensity of luminescence.

  8. Flexible amorphous oxide thin-film transistors on polyimide substrate for AMOLED

    Science.gov (United States)

    Xu, Zhiping; Li, Min; Xu, Miao; Zou, Jianhua; Gao, Zhuo; Pang, Jiawei; Guo, Ying; Zhou, Lei; Wang, Chunfu; Fu, Dong; Peng, Junbiao; Wang, Lei; Cao, Yong

    2014-10-01

    We report a flexible amorphous Lanthanide doped In-Zn-O (IZO) thin-film transistor (TFT) backplane on polyimide (PI) substrate. In order to de-bond the PI film from the glass carrier easily after the flexible AMOLED process, a special inorganic film is deposited on the glass before the PI film is coated. The TFT exhibited a field-effect mobility of 6.97 cm2V-1 s-1, a subthreshold swing of 0.248 V dec-1, and an Ion/Ioff ratio of 5.19×107, which is sufficient to drive the OLEDs.

  9. Photoluminescence of amorphous carbon films fabricated by layer-by-layer hydrogen plasma chemical annealing method

    Institute of Scientific and Technical Information of China (English)

    徐骏; 黄晓辉; 李伟; 王立; 陈坤基

    2002-01-01

    A method in which nanometre-thick film deposition was alternated with hydrogen plasma annealing (layer-by-layermethod) was applied to fabricate hydrogenated amorphous carbon films in a conventional plasma-enhanced chemicalvapour deposition system. It was found that the hydrogen plasma treatment could decrease the hydrogen concentrationin the films and change the sp2/sp3 ratio to some extent by chemical etching. Blue photoluminescence was observed atroom temperature, as a result of the reduction of sp2 clusters in the films.

  10. Charge deep-level transient spectroscopy study of high-energy-electron-beam-irradiated hydrogenated amorphous silicon

    NARCIS (Netherlands)

    Klaver, A.; Nádaždy, V.; Zeman, M.; Swaaiij, R.A.C.M.M.

    2006-01-01

    We present a study of changes in the defect density of states in hydrogenated amorphous silicon (a-Si:H) due to high-energy electron irradiation using charged deep-level transient spectroscopy. It was found that defect states near the conduction band were removed, while in other band gap regions the

  11. Investigation of crystallization and amorphization dynamics of phase-change thin films by subnanosecond laser pulses.

    Science.gov (United States)

    Kieu, Khanh; Narumi, Kenji; Mansuripur, Masud

    2006-10-20

    We report experimental results on amorphization and crystallization dynamics of reversible phase-change (PC) thin-film samples, GeSbTe and GeBiTe, for optical disk data storage. The investigation was conducted with subnanosecond laser pulses using a pump-and-probe configuration. Amorphization of the crystalline films could be achieved with a single subnanosecond laser pulse; the amorphization dynamics follow closely the temperature kinetics induced in the irradiated spot. As for crystallization of the samples initially in the amorphous state, a single subnanosecond pulse was found to be insufficient to fully crystallize the irradiated spot, but we could crystallize the PC film (in the area under the focused spot) by applying multiple short pulses. Our multipulse studies reveal that the GeSbTe crystallization is dominated by the growth of nuclei whose initial formation is slow but, once formed, their subsequent growth (under a sequence of subnanosecond pulses) happens quickly. In the case of GeBiTe samples, the crystalline nuclei appear to be present in the material initially, as they grow immediately upon illumination with laser pulses. Whereas our amorphous GeSbTe samples required approximately 200 pulses for full crystallization, for the GeBiTe samples approximately 15 pulses sufficed.

  12. STEM-EELS analysis reveals stable high-density He in nanopores of amorphous silicon coatings deposited by magnetron sputtering.

    Science.gov (United States)

    Schierholz, Roland; Lacroix, Bertrand; Godinho, Vanda; Caballero-Hernández, Jaime; Duchamp, Martial; Fernández, Asunción

    2015-02-20

    A broad interest has been showed recently on the study of nanostructuring of thin films and surfaces obtained by low-energy He plasma treatments and He incorporation via magnetron sputtering. In this paper spatially resolved electron energy-loss spectroscopy in a scanning transmission electron microscope is used to locate and characterize the He state in nanoporous amorphous silicon coatings deposited by magnetron sputtering. A dedicated MATLAB program was developed to quantify the helium density inside individual pores based on the energy position shift or peak intensity of the He K-edge. A good agreement was observed between the high density (∼35-60 at nm(-3)) and pressure (0.3-1.0 GPa) values obtained in nanoscale analysis and the values derived from macroscopic measurements (the composition obtained by proton backscattering spectroscopy coupled to the macroscopic porosity estimated from ellipsometry). This work provides new insights into these novel porous coatings, providing evidence of high-density He located inside the pores and validating the methodology applied here to characterize the formation of pores filled with the helium process gas during deposition. A similar stabilization of condensed He bubbles has been previously demonstrated by high-energy He ion implantation in metals and is newly demonstrated here using a widely employed methodology, magnetron sputtering, for achieving coatings with a high density of homogeneously distributed pores and He storage capacities as high as 21 at%.

  13. Coulomb blockade effects in silicon nanoparticles embedded in thin silicon-rich oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Sanchez, A; Barreto, J; Dominguez, C [IMB-CNM (CSIC), Campus UAB, Bellaterra 08193, Barcelona (Spain); Aceves, M; Yu, Z [INAOE, Electronics Department, Apartado 51, Puebla, 72000 (Mexico); Luna-Lopez, J A [CCMC, UNAM, Optics Department, Ensenada, BC, 22800 (Mexico)], E-mail: alfredo.morales@cnm.es

    2008-04-23

    Silicon nanoparticles (Si-nps) embedded in silicon oxide matrix were created using silicon-rich oxide (SRO) films deposited by low pressure chemical vapour deposition (LPCVD) followed by a thermal annealing at 1100 deg. C. The electrical properties were studied using metal-oxide-semiconductor (MOS) structures with the SRO films as the active layers. Capacitance versus voltage (C-V) exhibited downward and upward peaks in the accumulation region related to charge trapping and de-trapping effects of Si-nps, respectively. Current versus voltage (I-V) measurements showed fluctuations in the form of spike-like peaks and a clear staircase at room temperature. These effects have been related to the Coulomb blockade (CB) effect in the silicon nanoparticles embedded in SRO films. The observed quantum effects are due to 1 nm nanoparticles.

  14. Electron emission degradation of nano-structured sp2-bonded amorphous carbon films

    Institute of Scientific and Technical Information of China (English)

    Lu Zhan-Ling; Wang Chang-Qing; Jia Yu; Zhang Bing-Lin; Yao Ning

    2007-01-01

    The initial field electron emission degradation behaviour of original nano-structured sp2-bonded amorphous carbon films has been observed.which can be attributed to the increase of the work function of the film in the field emission process analysed using a Fowler-Nordheim plot.The possible re.on for the change of work function is suggested to be the desorption of hydrogen from the original hydrogen termination