WorldWideScience

Sample records for amorphous silicon alloys

  1. 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

  2. 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.

  3. 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.

  4. Highly ordered amorphous silicon-carbon alloys obtained by RF PECVD

    CERN Document Server

    Pereyra, I; Carreno, M N P; Prado, R J; Fantini, M C A

    2000-01-01

    We have shown that close to stoichiometry RF PECVD amorphous silicon carbon alloys deposited under silane starving plasma conditions exhibit a tendency towards c-Si C chemical order. Motivated by this trend, we further explore the effect of increasing RF power and H sub 2 dilution of the gaseous mixtures, aiming to obtain the amorphous counterpart of c-Si C by the RF-PECVD technique. Doping experiments were also performed on ordered material using phosphorus and nitrogen as donor impurities and boron and aluminum as acceptor ones. For nitrogen a doping efficiency close to device quality a-Si:H was obtained, the lower activation energy being 0,12 eV with room temperature dark conductivity of 2.10 sup - sup 3 (OMEGA.cm). Nitrogen doping efficiency was higher than phosphorous for all studied samples. For p-type doping, results indicate that, even though the attained conductivity values are not device levels, aluminum doping conducted to a promising shift in the Fermi level. Also, aluminum resulted a more efficie...

  5. 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.

  6. 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.)

  7. Energy loss process analysis for radiation degradation and immediate recovery of amorphous silicon alloy solar cells

    Science.gov (United States)

    Sato, Shin-ichiro; Beernink, Kevin; Ohshima, Takeshi

    2015-06-01

    Performance degradation of a-Si/a-SiGe/a-SiGe triple-junction solar cells due to irradiation of silicon ions, electrons, and protons are investigated using an in-situ current-voltage measurement system. The performance recovery immediately after irradiation is also investigated. Significant recovery is always observed independent of radiation species and temperature. It is shown that the characteristic time, which is obtained by analyzing the short-circuit current annealing behavior, is an important parameter for practical applications in space. In addition, the radiation degradation mechanism is discussed by analyzing the energy loss process of incident particles (ionizing energy loss: IEL, and non-ionizing energy loss: NIEL) and their relative damage factors. It is determined that ionizing dose is the primarily parameter for electron degradation whereas displacement damage dose is the primarily parameter for proton degradation. This is because the ratio of NIEL to IEL in the case of electrons is small enough to be ignored the damage due to NIEL although the defect creation ratio of NIEL is much larger than that of IEL in the cases of both protons and electrons. The impact of “radiation quality effect” has to be considered to understand the degradation due to Si ion irradiation.

  8. 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.

  9. 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.

  10. Bulk amorphous Mg-based alloys

    DEFF Research Database (Denmark)

    Pryds, Nini

    2004-01-01

    The present paper describes the preparation and properties of bulk amorphous quarternary Mg-based alloys and the influence of additional elements on the ability of the alloy to form bulk amorphous. The main goal is to find a Mg-based alloy system which shows both high strength to weight ratio and...

  11. 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.

  12. 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.

  13. Development of amorphous silicon-germanium-alloys for stacked solar cells; Entwicklung von amorphen Silizium-Germanium-Legierungen fuer den Einsatz in Stapelsolarzellen

    Energy Technology Data Exchange (ETDEWEB)

    Lundszien, D.

    2001-01-01

    To obtain high efficiency silicon based thin film solar cells, the concept of stacked solar cells is routinely used. The use of component cells with different optical bandgaps provides a better utilization of the solar spectrum. In a stacked cell structure, a high quality narrow bandgap material is needed for the active layer of the bottom cell. Amorphous silicon-germanium-alloys (a-SiGe:H) have been successfully employed because of their tunable optical bandgap E{sub G} between 1.8 eV (a-Si:H) and 1.1 eV (a-Ge:H). Considerable effort has been put into the development of a-SiGe:H. Still, with increasing Ge content, the material shows a characteristic deterioration of its electronic properties, like an exponential increase of the defect density, thus counteracting the gain in absorption obtained for higher Ge contents. It is the defect density which has the dominant influence on carrier transport and cell efficiency by affecting the mobility lifetime product and the electric field in the devices. The performance of a-SiGe:H pin solar cells with a wide range of Ge contents i.e. a wide range of optical band gaps (E{sub G}=1.3 to 1.6 eV) are compared. It is demonstrated how the deterioration of the material properties can be overcome by careful adjustment of the device design and the use of highly reflective ZnO/Ag back contacts. (orig.)

  14. Iron-based amorphous alloys and methods of synthesizing iron-based amorphous alloys

    Science.gov (United States)

    Saw, Cheng Kiong; Bauer, William A.; Choi, Jor-Shan; Day, Dan; Farmer, Joseph C.

    2016-05-03

    A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. Several amorphous iron-based metal alloys are also presented, including corrosion-resistant amorphous iron-based metal alloys and radiation-shielding amorphous iron-based metal alloys.

  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. Transformers with amorphous alloy nucleus in distribution system; Transformadores com nucleo de liga amorfa em sistemas de distribuicao

    Energy Technology Data Exchange (ETDEWEB)

    Luciano, Benedito Antonio; Freire, Raimundo Carlos Silverio [Universidade Federal de Campina Grande (UFCG), PB (Brazil); Bezerra, Reno Barroso [Industria de Transformadores Itaipu, Campinas, SP (Brazil); Inacio, Renato Cucatu [Companhia de Energia Eletrica do Estado do Tocantins (CELTINS), TO (Brazil)

    2010-01-15

    This paper compares the performance of amorphous alloy nucleus with oriented grain silicon steel alloy, related to losses, energy efficiency and energy quality. Besides, are highlighted the process obtention of the amorphous alloys and the electric, magnetic and mechanicals, magneto thermal treatment, effect of oxidation properties, and etc. (author)

  17. 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)

  18. 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.

  19. 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.

  20. 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%.

  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. 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

  3. 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

  4. Production, Properties and Applications of Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    Tao Zhang; Akihisa Inoue

    2000-01-01

    A review is given of recent work concerned with the production method, the characteristic properties(1) Bulk amorphous system; (2) Mechanical and magnetic properties of bulkamorphous alloys; (3)application of bulk amorphous alloys.

  5. 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.

  6. 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.

  7. Amorphous Alloy and Magnetic Stabilization Bed

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Sponsored by NSFC,a research team led by Prof.Enze Min (CAS Member) from Research Institute of Petroleum Processing,through 20 years' effort,settled the puzzled grave issue that amorphous alloy material has small specific surface area and low thermal stability.

  8. 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.

  9. 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.

  10. 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.

  11. Metal induced crystallization of silicon germanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gjukic, M.

    2007-05-15

    In the framework of this thesis the applicability of the aluminium-induced layer exchange on binary silicon germanium alloys was studied. It is here for the first time shown that polycrstalline silicon-germanium layers can be fabricated over the whole composition range by the aluminium-induced layer exchange. The experimental results prove thet the resulting material exhibits a polycrystalline character with typocal grain sizes of 10-100 {mu}m. Raman measurements confirm that the structural properties of the resulting layers are because of the large crystallites more comparable with monocrystalline than with nano- or microcrystalline silicon-germanium. The alloy ratio of the polycrystalline layer correspondes to the chemical composition of the amorphous starting layer. The polycrystalline silicon-germanium layers possess in the range of the interband transitions a reflection spectrum, as it is otherwise only known from monocrystalline reference layers. The improvement of the absorption in the photovoltaically relevant spectral range aimed by the application of silicon-germanium could be also proved by absorption measurments. Strongly correlated with the structural properties of the polycrystalline layers and the electronic band structure resulting from this are beside the optical properties also the electrical properties of the material, especially the charge-carrier mobility and the doping concentration. For binary silicon-germanium layers the hole concentration of about 2 x 10{sup 18} cm{sup -3} for pure silicon increrases to about 5 x 10{sup 20} cm{sub -3} for pure germanium. Temperature-resolved measurements were applied in order to detect doping levels respectively semiconductor-metal transitions. In the last part of the thesis the hydrogen passivation of polycrystalline thin silicon-germanium layers, which were fabricated by means of aluminium-induced layer exchange, is treated.

  12. Standard Specification for Copper-Aluminum-Silicon-Cobalt Alloy, Copper-Nickel-Silicon-Magnesium Alloy, Copper-Nickel-Silicon Alloy, Copper-Nickel-Aluminum-Magnesium Alloy, and Copper-Nickel-Tin Alloy Sheet and Strip

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Copper-Aluminum-Silicon-Cobalt Alloy, Copper-Nickel-Silicon-Magnesium Alloy, Copper-Nickel-Silicon Alloy, Copper-Nickel-Aluminum-Magnesium Alloy, and Copper-Nickel-Tin Alloy Sheet and Strip

  13. 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...

  14. Excessively High Vapor Pressure of Al-based Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Jae Im Jeong

    2015-10-01

    Full Text Available Aluminum-based amorphous alloys exhibited an abnormally high vapor pressure at their approximate glass transition temperatures. The vapor pressure was confirmed by the formation of Al nanocrystallites from condensation, which was attributed to weight loss of the amorphous alloys. The amount of weight loss varied with the amorphous alloy compositions and was inversely proportional to their glass-forming ability. The vapor pressure of the amorphous alloys around 573 K was close to the vapor pressure of crystalline Al near its melting temperature, 873 K. Our results strongly suggest the possibility of fabricating nanocrystallites or thin films by evaporation at low temperatures.

  15. 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.

  16. Composition Range of Amorphous Mg-Ni-Y Alloys

    Institute of Scientific and Technical Information of China (English)

    陈红梅; 钟夏平; 欧阳义芳

    2003-01-01

    Based on the thermodynamic point of view, a method for predication of the composition range of amorphous ternary alloys was proposed. The composition range of amorphous ternary alloys is determined by the comparison of the excess free energy of the amorphous alloy and the free energy of competing crystalline states. The free energy is extrapolated from the data of three binary alloys by using Toop′s model. The method was applied to predict the composition range of amorphous Mg-Ni-Y alloys. The theoretical results are in good agreement with the available experimental results. It indicates that the present method can be used to predict the composition range for amorphous ternary alloys.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Parametrized dielectric functions of amorphous GeSn alloys

    Science.gov (United States)

    D'Costa, Vijay Richard; Wang, Wei; Schmidt, Daniel; Yeo, Yee-Chia

    2015-09-01

    We obtained the complex dielectric function of amorphous Ge1-xSnx (0 ≤ x ≤ 0.07) alloys using spectroscopic ellipsometry from 0.4 to 4.5 eV. Amorphous GeSn films were formed by room-temperature implantation of phosphorus into crystalline GeSn alloys grown by molecular beam epitaxy. The optical response of amorphous GeSn alloys is similar to amorphous Ge and can be parametrized using a Kramers-Kronig consistent Cody-Lorentz dispersion model. The parametric model was extended to account for the dielectric functions of amorphous Ge0.75Sn0.25 and Ge0.50Sn0.50 alloys from literature. The compositional dependence of band gap energy Eg and parameters associated with the Lorentzian oscillator have been determined. The behavior of these parameters with varying x can be understood in terms of the alloying effect of Sn on Ge.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Devitrification of rapidly quenched Al–Cu–Ti amorphous alloys

    Indian Academy of Sciences (India)

    D K Misra; R S Tiwari; O N Srivastava

    2003-08-01

    X-ray diffraction, transmission electron microscopy and differential scanning calorimetry were carried out to study the transformation from amorphous to icosahedral/crystalline phases in the rapidly quenched Al50Cu45Ti5 and Al45Cu45Ti10 alloys. In the present investigation, we have studied the formation and stability of amorphous phase in Al50Cu45Ti5 and Al45Cu45Ti10 rapidly quenched alloys. The DSC curve shows a broad complex type of exothermic overlapping peaks (288–550°C) for Al50Cu45Ti5 and a well defined peak around 373°C for Al45Cu45Ti10 alloy. In the case of Al50Cu45Ti5 alloy amorphous to icosahedral phase transformation has been observed after annealing at 280°C for 73 h. Large dendritic growth of icosahedral phase along with -Al phase has been found. Annealing of Al50Cu45Ti5 alloy at 400°C for 8 h results in formation of Al3Ti type phase. Al45Cu45Ti10 amorphous alloy is more stable in comparison to Al50Cu45Ti5 alloy and after annealing at 400°C for 8 h it also transforms to Al3Ti type phase. However, this alloy does not show amorphous to icosahedral phase transformation.

  12. Powder Processing of Amorphous Tungsten-bearing Alloys and Composites

    Science.gov (United States)

    2015-03-01

    8725 John J. Kingman Road, MS-6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-14-73 Powder Processing of Amorphous Tungsten ...Technology, Boise State University, Army Research Laboratory Project Title: Powder Processing of Amorphous Tungsten -bearing Alloys and Composites...strength, we made them better suited to study the mechanical alloying of tungsten -transition metal couples in which interdiffusion during mechanical

  13. Creep of FINEMET alloy at amorphous to nanocrystalline transition

    NARCIS (Netherlands)

    Csach, K.; Miškuf, J.; Juríková, A.; Ocelík, V.

    2009-01-01

    The application of FINEMET-type materials with specific magnetic properties prepared by the crystallization of amorphous alloys is often limited by their brittleness. The structure of these materials consists of nanosized Fe-based grains surrounded with amorphous phase. Then the final macroscopic me

  14. Preparation of Ti-based amorphous brazing alloy

    Institute of Scientific and Technical Information of China (English)

    ZOU Jia-sheng; JIANG Zhi-guo; XU Zhi-rong; CHEN Guang

    2006-01-01

    A new kind of amorphous active brazing alloy foil with the composition of Ti40Zr25Ni15Cu20 was successfully synthesized using melt spinning in roll forging machine in argon atmosphere. The amorphous structure and composition were examined by X-ray diffraction, differential thermal analysis and energy dispersive X-ray detector. The results show that the Ti40Zr25Ni15Cu20 amorphous alloy foil has excellent wettability on Si3N4 ceramic and demonstrate a strong glass forming ability. The reduced glass transition temperature (Trg) and the temperature interval of supercooled liquid region before crystallization are 0.76 and 78 K, respectively.

  15. 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.

  16. 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.

  17. Parametrized dielectric functions of amorphous GeSn alloys

    Energy Technology Data Exchange (ETDEWEB)

    D' Costa, Vijay Richard, E-mail: elevrd@nus.edu.sg; Wang, Wei; Yeo, Yee-Chia, E-mail: eleyeoyc@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583 (Singapore); Schmidt, Daniel [Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603 (Singapore)

    2015-09-28

    We obtained the complex dielectric function of amorphous Ge{sub 1−x}Sn{sub x} (0 ≤ x ≤ 0.07) alloys using spectroscopic ellipsometry from 0.4 to 4.5 eV. Amorphous GeSn films were formed by room-temperature implantation of phosphorus into crystalline GeSn alloys grown by molecular beam epitaxy. The optical response of amorphous GeSn alloys is similar to amorphous Ge and can be parametrized using a Kramers-Kronig consistent Cody-Lorentz dispersion model. The parametric model was extended to account for the dielectric functions of amorphous Ge{sub 0.75}Sn{sub 0.25} and Ge{sub 0.50}Sn{sub 0.50} alloys from literature. The compositional dependence of band gap energy E{sub g} and parameters associated with the Lorentzian oscillator have been determined. The behavior of these parameters with varying x can be understood in terms of the alloying effect of Sn on Ge.

  18. Properties of electrodeposited amorphous Fe-Ni-W alloy deposits

    Institute of Scientific and Technical Information of China (English)

    HE Feng-jiao; WANG Miao; LU Xin

    2006-01-01

    A new technique of electroplating amorphous Fe-Ni-W alloy deposits was proposed. The structure and morphology of Fe-Ni-W alloy deposit were detected by XRD and SEM. The friction and wear behavior of Fe-Ni-W alloy deposit were studied and compared with that of chromium deposit. The corrosion properties against 5% sodium chloride, 5% sulfuric acid and 5% sodium hydroxide were also discussed. The experimental results indicate that Fe-Ni-W alloy deposits have superior properties against wear than hard chromium deposits under dry sliding condition. Under oil sliding condition, except their better wear resistance, the deposits can protect their counterparts against wear. The deposits plated on brass and AISI 1045 steel show good behavior against corrosion of 5% sodium chloride, 5% sulfuric acid and 5% sodium hydroxide. The bath of electroplating amorphous Fe-Ni-W alloy deposits is environmentally friendly and would find widely use in industry.

  19. Amorphous Alloy Membranes for High Temperature Hydrogen Separation

    Energy Technology Data Exchange (ETDEWEB)

    Coulter, K

    2013-09-30

    At the beginning of this project, thin film amorphous alloy membranes were considered a nascent but promising new technology for industrial-scale hydrogen gas separations from coal- derived syngas. This project used a combination of theoretical modeling, advanced physical vapor deposition fabricating, and laboratory and gasifier testing to develop amorphous alloy membranes that had the potential to meet Department of Energy (DOE) targets in the testing strategies outlined in the NETL Membrane Test Protocol. The project is complete with Southwest Research Institute® (SwRI®), Georgia Institute of Technology (GT), and Western Research Institute (WRI) having all operated independently and concurrently. GT studied the hydrogen transport properties of several amorphous alloys and found that ZrCu and ZrCuTi were the most promising candidates. GT also evaluated the hydrogen transport properties of V, Nb and Ta membranes coated with different transition-metal carbides (TMCs) (TM = Ti, Hf, Zr) catalytic layers by employing first-principles calculations together with statistical mechanics methods and determined that TiC was the most promising material to provide catalytic hydrogen dissociation. SwRI developed magnetron coating techniques to deposit a range of amorphous alloys onto both porous discs and tubular substrates. Unfortunately none of the amorphous alloys could be deposited without pinhole defects that undermined the selectivity of the membranes. WRI tested the thermal properties of the ZrCu and ZrNi alloys and found that under reducing environments the upper temperature limit of operation without recrystallization is ~250 °C. There were four publications generated from this project with two additional manuscripts in progress and six presentations were made at national and international technical conferences. The combination of the pinhole defects and the lack of high temperature stability make the theoretically identified most promising candidate amorphous alloys

  20. 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.

  1. 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.

  2. 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.)

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. Electroplating process of amorphous Fe-Ni-Cr alloy

    Institute of Scientific and Technical Information of China (English)

    何湘柱; 夏畅斌; 王红军; 龚竹清; 蒋汉瀛

    2001-01-01

    A novel process of electroplating amorphous Fe-Cr-Ni alloy in chloride aqueous solution with Fe( Ⅱ ), Ni ( lⅡ ) and Cr( Ⅲ ) was reported. Couple plasma atomic emission spectrometry (ICP-AES), X-ray diffractometry(XRD),scanning electronic microscopy(SEM), microhardness test and rapid heating-cooling method were adopted to detect the properties of the amorphous Fe-Ni-Cr deposit, such as composition, crystalline structure, micrograph, hardness, and adherence between deposit and substrate. The effects of the operating parameters on the electrodeposit of the amorphous FeNi-Cr alloy were discussed in detail. The results show that a 8.7 μm thick mirror-like amorphous Fe-Ni-Cr alloy deposit,with Vicker's hardness of 530 and composition of 45%~55% Fe, 33%~37% Ni, 9%~23% Cr was obtained by electroplating for 20 min at room temperature( 10 30 C ), cathode current 10~16 A/dm2, pH = 1.0~3.0. The XRD pat terns show that there only appears a broad hump around 2θ of 41 °~47 °for the amorphous Fe-Ni-Cr alloy deposit, while the SEM micrographs show that the deposit contains only a few fine cracks but no pinholes.

  9. XAFS Study on Solid State Amorphization of Alloys by Mechanical Alloying

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Structural evolution of alloys by ball-milling during solid stateamorphization were studied by means of XAFS technique. The first one is amorphization process of Fe and B powder mixtures by mechanical alloying (MA), and the second one is amorphization process of ordered B2 CoZr intermetallic compound by mechanical milling (MM). The mixing process of Fe and B and disintegration process of ordered B2 CoZr intermetallic compound crystal were observed clearly in atomic level by XAFS method. The micro-mechanism of amorphization process of alloy by ball-milling was discussed.

  10. 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.

  11. 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.

  12. 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

  13. 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...

  14. Structural transformations and wear resistance of abrasive-affected amorphous Fe- and Co-based alloys

    Science.gov (United States)

    Korshunov, L. G.; Chernenko, N. L.

    2008-12-01

    The abrasive wear resistance of the Fe64Co30Si3B3, Fe82.6Nb5Cu3Si8B1.4, Co86.5Cr4Si7B2.5, and Fe81Si4B13C2 amorphous alloys (ribbon 30 μm thick) has been investigated upon sliding over fixed abrasives (corundum and silicon carbide). The character of fracture of the surface and structural transformations initiated in these materials by the abrasive action have been studied by the metallographic, X-ray diffraction, and electron-microscopic methods. It has been shown that the abrasive wear resistance of the amorphous alloys is smaller by a factor of 1.6-2.9 than that of the Kh12M and U8 tool steels possessing approximately the same level of hardness. A pronounced softening of the surface layer of the amorphous alloys in the process of wear, which is characterized by a decrease in their microhardness reaching 12.5%, has been found. It has been shown that in the surface layer of these amorphous alloys upon wear there arises a small amount (on the order of several volume percent) of the nanocrystalline structure, which does not exert a marked effect on the microhardness and wear resistance of the alloys. In the alloys under study, the main factor that is responsible for their comparatively low abrasive wear resistance is their local softening in the process of wear caused by specific features of deformation processes occurring heterogeneously under the action of high shear contact stresses.

  15. 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.

  16. 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.

  17. SOME PECULIARITIES OF DUCTILE SHEAR FAILURE OF AMORPHOUS ALLOY RIBBONS

    NARCIS (Netherlands)

    BENGUS, VZ; TABACHNIKOVA, ED; SHUMILIN, SE; GOLOVIN, YI; MAKAROV, MV; SHIBKOV, AA; MISKUF, J; CSACH, K; Ocelik, Vaclav

    1993-01-01

    The kinetics of a shear crack propagation under ductile shear failure of amorphous alloys ribbons is studied experimentally. Some phenomena that accompany this failure are also studied: repeated alternation of the shear crack orientation, plastic corrugation of a ribbon, extreme local heating at the

  18. 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.

  19. 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.

  20. 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.

  1. 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...

  2. 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.

  3. Simulation study for atomic size and alloying effects during forming processes of amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    ZHENG Caixing; LIU Rangsu; PENG Ping; ZHOU Qunyi

    2004-01-01

    A molecular dynamics (MD) simulation study has been performed for the solidification processes of two binary liquid alloys Ag6Cu4 and CuNi by adopting the quantum Sutton-Chen many-body potentials. By analyzing bond-types, it is demonstrated that at the cooling rate of 2×1012K/s, the CuNi forms fcc crystal structures, while the Ag6Cu4 forms amorphous structures. The original reason is that the atomic radius ratio (1.13) of the CuAg is bigger than that (1.025) of the CuNi. This shows that the atomic size difference is indeed the main factor for forming amorphous alloys. Moreover, for Ag60Cu40,corresponding to the deep eutectic point in the phase diagram, it forms amorphous structure easily. This confirms that as to the forming tendency and stability of amorphous alloys, the alloying effect plays a key role. In addition, having analyzed the transformation of microstructures by using the bond-type index and cluster-type index methods, not only the key role of the icosahedral configuration to the formation and stability of amorphous alloys can be explained, but also the solidification processes of liquid metals and the characteristics of amorphous structures can be further understood.

  4. 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.

  5. 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.

  6. 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.

  7. Surface magnetic anisotropy in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tejedor, M.; Rubio, H.; Elbaile, L.; Iglesias, R. (Univ. de Oviedo (Spain). Dept. de Fisica)

    1993-11-01

    The total in-plane magnetic anisotropy and the in-plane surface magnetic anisotropy constants have been measured in nearly-zero magnetostrictive amorphous ribbons in as-quenched state. The magnetostatic energy of a two-dimensional square-lattice of parallelepipeds or ellipsoids, whose dimensions are determined by the parameters characterizing the roughness, is evaluated. From the results obtained, they can conclude that the in-plane surface anisotropy can be magnetostatic in origin but it has little influence on the total in-plane magnetic anisotropy of the ribbon.

  8. 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.

  9. 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.

  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. Amorphization in Gd-Co alloys and multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, J.A. [Departamento de Fisica Teorica, Universidad de Valladolid, Valladolid (Spain); Hojvat de Tendler, R. [Instituto de Estudios Nucleares, Centro Atomico Ezeiza, CNEA, Buenos Aires (Argentina); Barbiric, D.A. [Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Universidad de Buenos Aires, Buenos Aires (Argentina); Riveiro, J.M. [Departamento de Fisica Aplicada, Universidad de Castilla-La Mancha, Ciudad Real (Spain)

    2002-10-07

    A semiempirical model is used to analyse the results of published experiments reporting on the solid-state amorphization reactions in bilayers and multilayers formed by Gd and Co. The role of the interfacial effects in raising the free energy of the initial arrangement in a multilayered configuration, and in promoting the amorphization reaction, is studied in detail. The model explains the observation of amorphous alloys over a broad composition range in the bilayer experiments. The preferred composition obtained in the multilayer experiments is discussed critically and the model prediction of a preferred composition Gd{sub 0.46}Co{sub 0.54} is in good agreement with the compositions observed in recent experiments. (author)

  12. 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.

  13. 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.

  14. Corrosion resistance of Fe-based amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Botta, W.J., E-mail: wjbotta@ufscar.br [LEPMI, UMR5279 CNRS, Grenoble INP, Université de Savoie, Université Joseph Fourier, 1130, Rue de la piscine, BP 75, 38402 Saint Martin d’Hères (France); Departamento de Engenharia de Materiais, Universidade Federal de São Carlos, Rod. Washington Luiz, Km 235, 13565-905 São Carlos, SP (Brazil); Berger, J.E.; Kiminami, C.S. [Departamento de Engenharia de Materiais, Universidade Federal de São Carlos, Rod. Washington Luiz, Km 235, 13565-905 São Carlos, SP (Brazil); Roche, V.; Nogueira, R.P. [LEPMI, UMR5279 CNRS, Grenoble INP, Université de Savoie, Université Joseph Fourier, 1130, Rue de la piscine, BP 75, 38402 Saint Martin d’Hères (France); Bolfarini, C. [Departamento de Engenharia de Materiais, Universidade Federal de São Carlos, Rod. Washington Luiz, Km 235, 13565-905 São Carlos, SP (Brazil)

    2014-02-15

    Highlights: ► We report corrosion properties of Fe-based amorphous alloys in different media. ► The Cr-containing alloys had corrosion resistance close to that of Pt in all media. ► The wide range of electrochemical stability is relevant in many industrial domains. -- Abstract: Fe-based amorphous alloys can be designed to present an attractive combination of properties with high corrosion resistance and high mechanical strength. Such properties are clearly adequate for their technological use as coatings, for example, in steel pipes. In this work, we studied the corrosion properties of amorphous ribbons of the following Fe-based compositions: Fe{sub 66}B{sub 30}Nb{sub 4}, [(Fe{sub 0.6}Co{sub 0.4}){sub 0.75}B{sub 0.2}Si{sub 0.05}]{sub 96}Nb{sub 4}, [(Fe{sub 0.7}Co{sub 0.3}){sub 0.75}B{sub 0.2}Si{sub 0.05}]{sub 96}Nb{sub 4}, Fe{sub 56}Cr{sub 23}Ni{sub 5.7}B{sub 16}, Fe{sub 53}Cr{sub 22}Ni{sub 5.6}B{sub 19} and Fe{sub 50}Cr{sub 22}Ni{sub 5.4}B{sub 23}. The ribbons were obtained by rapid solidification using the melt-spinning process, and were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and optical (OM) and scanning electron microscopy (SEM). The corrosion properties were evaluated by corrosion potential survey and potentiodynamic polarization. The Cr containing alloys, that is the FeCrNiB type of alloys, showed the best corrosion resistance properties with the formation of a stable passive film that ensured a very large passivation plateau.

  15. 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.

  16. 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.

  17. 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.

  18. 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)

  19. Design of multi materials combining crystalline and amorphous metallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Volland, A.; Ragani, J.; Liu, Y.; Gravier, S.; Suery, M. [Grenoble University/CNRS, SIMAP Laboratory, Grenoble INP/UJF, 38402 Saint-Martin d' Heres (France); Blandin, J.J., E-mail: jean-jacques.blandin@simap.grenoble-inp.fr [Grenoble University/CNRS, SIMAP Laboratory, Grenoble INP/UJF, 38402 Saint-Martin d' Heres (France)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Elaboration of multi materials associating metallic glasses and conventional crystalline alloys by co-deformation performed at temperatures close to the glass transition temperature of the metallic glasses. Black-Right-Pointing-Pointer Elaboration of filamentary metal matrix composites with a core in metallic glass by co extrusion. Black-Right-Pointing-Pointer Sandwich structures produced by co-pressing. Black-Right-Pointing-Pointer Detection of atomic diffusion from the glass to the crystalline alloys during the processes. Black-Right-Pointing-Pointer Good interfaces between the metallic glasses and the crystalline alloys, as confirmed by mechanical characterisation. - Abstract: Multi materials, associating zirconium based bulk metallic glasses and crystalline metallic alloys like magnesium alloys or copper are elaborated by co-deformation processing performed in the supercooled liquid regions (SLR) of the bulk metallic glasses. Two processes are investigated: co-extrusion and co-pressing. In the first case, filamentary composites with various designs can be produced whereas in the second case sandwich structures are obtained. The experimental window (temperature, time) in which processing can be carried out is directly related to the crystallisation resistance of the glass which requires getting information about the crystallisation conditions in the selected metallic glasses. Thermoforming windows are identified for the studied BMGs by thermal analysis and compression tests in their SLR. The mechanical properties of the produced multi materials are investigated thanks to specifically developed mechanical devices and the interfaces between the amorphous and the crystalline alloys are characterised.

  20. 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.

  1. Bulk amorphous metallic alloys: Synthesis by fluxing techniques and properties

    Energy Technology Data Exchange (ETDEWEB)

    He, Yi; Shen, Tongde; Schwarz, R.B.

    1997-05-01

    Bulk amorphous alloys having dimensions of at least 1 cm diameter have been prepared in the Pd-Ni-P, Pd-Cu-P, Pd-Cu-Ni-P, and Pd-Ni-Fe-P systems using a fluxing and water quenching technique. The compositions for bulk glass formation have been determined in these systems. For these bulk metallic glasses, the difference between the crystallization temperature T{sub x}, and the glass transition temperature T{sub g}, {Delta}T = T{sub x} - T{sub g}, ranges from 60 to 1 10 K. These large values of {Delta}T open the possibility for the fabrication of amorphous near net-shape components using techniques such as injection molding. The thermal, elastic, and magnetic properties of these alloys have been studied, and we have found that bulk amorphous Pd{sub 40}Ni{sub 22.5}Fe{sub 17.5}P{sub 20} has spin glass behavior for temperatures below 30 K. 65 refs., 14 figs., 3 tabs.

  2. 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

  3. Preparation and characterization of electroplated amorphous gold-nickel alloy film for electrical contact applications

    Energy Technology Data Exchange (ETDEWEB)

    Togasaki, Norihiro [Department of Applied Chemistry, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Okinaka, Yutaka [Advanced Research Institute for Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Homma, Takayuki [Department of Applied Chemistry, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Advanced Research Institute for Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Osaka, Tetsuya [Department of Applied Chemistry, Waseda University, Okubo, Shinjuku, Tokyo 169-8555, Japan and Advanced Research Institute for Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan)]. E-mail: osakatet@waseda.jp

    2005-11-10

    A process for electroplating amorphous gold-nickel alloy with the atomic ratio of unity was developed. The plating bath was prepared by adding potassium cyanoaurate(I) into a known plating bath which produces amorphous nickel-tungsten alloy. At a sufficiently high gold concentration, the alloy deposit did not contain any tungsten. The amorphous nature of the Au-Ni alloy produced in the new bath was confirmed by using TEM and THEED. Hardness, resistivity, and contact resistance of this new alloy were determined, and the results are discussed for applications as an electrical contact material.

  4. Structural and thermal properties of Cu-Hf-Ti bulk amorphous alloys

    Science.gov (United States)

    Rontó, V.; Nagy, E.; Svéda, M.; Roósz, A.; Tranta, F.

    2009-01-01

    Cu-Hf-Ti amorphous alloys are high strength and wear resistant materials. Master alloys of Cu57.5Hf27.5Ti15 and Cu57.5Hf25Ti17.5 ternary alloys have been prepared by arc melting, and wedge and rod shaped samples have been cast by centrifugal casting. Liquidus and solidus temperatures of the alloys were determined by DTA. The fully amorphous size was determined by X-ray diffraction. Thermodynamic properties of the amorphous alloys were studied by DSC measurements and Kissinger analyses were performed.

  5. Blistering and flaking of amorphous alloys bombarded with He ions

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The blistering and flaking behavior of many kinds of amorphous al loys under helium ion bombardment at room temperature was investigated. Helium ions with energies of 40keV and 60keV were implanted within the fluence range (1.0~4.0)×1018ions/cm2. The surface topography of samples after irradiation was observed by using a scanning electron microscope. The diameter of blister and the thickness of exfoliated blister lids were measured. The results showed that many kinds of surface topography characteristics appeared for different fluences, energies and amorphous alloys, such as flaking, blistering, exfoliation, blister rupture, secondgeneration blistering and porous structure. The dependdence of surface damage modesand the critical fluence for the onset of blistering and flaking on the sort of materials and ion energy was discussed.

  6. Deformation-driven catalysis of nanocrystallization in amorphous Al alloys

    Directory of Open Access Journals (Sweden)

    Rainer J. Hebert

    2016-10-01

    Full Text Available Nanocrystals develop in amorphous alloys usually during annealing treatments with growth- or nucleation-controlled mechanisms. An alternative processing route is intense deformation and nanocrystals have been shown to develop in shear bands during the deformation process. Some controversy surrounded the idea of adiabatic heating in shear bands during their genesis, but specific experiments have revealed that the formation of nanocrystals in shear bands has to be related to localized deformation rather than thermal effects. A much less debated issue has been the spatial distribution of deformation in the amorphous alloys during intense deformation. The current work examines the hypothesis that intense deformation affects the regions outside shear bands and even promotes nanocrystal formation in those regions upon annealing. Melt-spun amorphous Al88Y7Fe5 alloy was intensely cold rolled. Microcalorimeter measurements at 60 °C indicated a slight but observable growth of nanocrystals in shear bands over the annealing time of 10 days. When the cold-rolled samples were annealed at 210 °C for one hour, transmission electron images did not show any nanocrystals for as-spun ribbons, but nanocrystals developed outside shear bands for the cold rolled samples. X-ray analysis indicated an increase in intensity of the Al peaks following the 210 °C annealing while the as-spun sample remained “X-ray amorphous”. These experimental observations strongly suggest that cold rolling affects regions (i.e., spatial heterogeneities outside shear bands and stimulates the formation of nanocrystals during annealing treatments at temperatures well below the crystallization temperature of undeformed ribbons.

  7. 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.

  8. Properties and Applications of Nanocrystalline Alloys from Amorphous Precursors

    CERN Document Server

    Idzikowski, Bogdan; Miglierini, Marcel

    2005-01-01

    Metallic (magnetic and non-magnetic) nanocrystalline materials have been known for over ten years but only recent developments in the research into those complex alloys and their metastable amorphous precursors have created a need to summarize the most important accomplishments in the field. This book is a collection of articles on various aspects of metallic nanocrystalline materials, and an attempt to address this above need. The main focus of the papers is put on the new issues that emerge in the studies of nanocrystalline materials, and, in particular, on (i) new compositions of the alloys, (ii) properties of conventional nanocrystalline materials, (iii) modeling and simulations, (iv) preparation methods, (v) experimental techniques of measurements, and (vi) different modern applications. Interesting phenomena of the physics of nanocrystalline materials are a consequence of the effects induced by the nanocrystalline structure. They include interface physics, the influence of the grain boundaries, the aver...

  9. 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.

  10. Electrical transport in transverse direction through silicon carbon alloy multilayers containing regular size silicon quantum dots

    Science.gov (United States)

    Mandal, Aparajita; Kole, Arindam; Dasgupta, Arup; Chaudhuri, Partha

    2016-11-01

    Electrical transport in the transverse direction has been studied through a series of hydrogenated silicon carbon alloy multilayers (SiC-MLs) deposited by plasma enhanced chemical vapor deposition method. Each SiC-ML consists of 30 cycles of the alternating layers of a nearly amorphous silicon carbide (a-SiC:H) and a microcrystalline silicon carbide (μc-SiC:H) that contains high density of silicon quantum dots (Si-QDs). A detailed investigation by cross sectional TEM reveals preferential growth of densely packed Si-QDs of regular sizes ∼4.8 nm in diameter in a vertically aligned columnar structure within the SiC-ML. More than six orders of magnitude increase in transverse current through the SiC-ML structure were observed for decrease in the a-SiC:H layer thickness from 13 nm to 2 nm. The electrical transport mechanism was established to be a combination of grain boundary or band tail hopping and Frenkel-Poole (F-P) type conduction depending on the temperature and externally applied voltage ranges. Evaluation of trap concentration within the multilayer structures from the fitted room temperature current voltage characteristics by F-P function shows reduction up-to two orders of magnitude indicating an improvement in the short range order in the a-SiC:H matrix for decrease in the thickness of a-SiC:H layer.

  11. 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.)

  12. 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.

  13. 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, ...

  14. Influence Intensive Plastic Deformation on Phase Formation Process in Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    V.I. Lysov

    2016-06-01

    Full Text Available The influence of intensive plastic deformation on structure and properties of amorphous alloys were investigated experimentally. Using highly sensitive dilatometer techniques shown that intensive plastic deformation of amorphous alloys leads to increased of thermal stability interval that can be explained by a shift of the phase equilibria in heterogeneous system: amorphous matrix - frozen crystallization centers. Thus there is a dissolution frozen crystallization centers present in the original sample that confirmed by electron researches.

  15. Stable, high-efficiency amorphous silicon solar cells with low hydrogen content. Annual subcontract report, 1 March 1991--31 January 1992

    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. 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.

  17. 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

  18. 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

  19. 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}.

  20. 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.

  1. 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

  2. Short range ordering and microstructure property relationship in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shariq, A.

    2006-07-01

    A novel algorithm, ''Next Neighbourhood Evaluation (NNE)'', is enunciated during the course of this work, to elucidate the next neighbourhood atomic vicinity from the data, analysed using tomographic atom probe (TAP) that allows specifying atom positions and chemical identities of the next neighbouring atoms for multicomponent amorphous materials in real space. The NNE of the Pd{sub 55}Cu{sub 23}P{sub 22} bulk amorphous alloy reveals that the Pd atoms have the highest probability to be the next neighbours to each other. Moreover, P-P correlation corroborates earlier investigations with scattering techniques that P is not a direct next neighbour to another P atom. Analogous investigations on the Fe{sub 40}Ni{sub 40}B{sub 20} metallic glass ribbons, in the as quenched state and for a state heat treated at 350 C for 1 hour insinuate a pronounced elemental inhomogeneity for the annealed state, though, it also depicts glimpse of a slight inhomogeneity for B distribution even for the as quenched sample. Moreover, a comprehensive microstructural investigation has been carried out on the Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy system. TEM and TAP investigations evince that the as cast bulk samples constitutes a composite structure of an amorphous phase and crystalline phase(s). The crystallization is essentially triggered at the mould walls due to heterogeneous nucleation. The three dimensional atomic reconstruction maps of the volume analysed by TAP reveal a complex stereological interconnected network of two phases. The phase that is rich in Zr and Al concentration is depleted in Co concentration while the phase that is rich in Co concentration is depleted both in Zr and Al. Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy splat samples exhibit a single exothermic crystallization peak contrary to the as cast bulk sample with a different T{sub g} temperature. A single homogeneous amorphous phase revealed by TEM investigations depicts that the faster cooling

  3. 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)

  4. Calculating formation range of binary amorphous alloys fabricated by electroless plating

    Science.gov (United States)

    Zhang, Bangwei; Liao, Shuzhi; Shu, Xiaolin; Xie, Haowen

    2016-06-01

    A lot of amorphous alloy deposits in the binary (Ni, Co, Cu)-(P, B) alloy systems fabricated by electroless plating (EP) have been reported up to date. But no one reported their theoretical modeling of the amorphous formation and calculated their concentration range of amorphous formation (RAF). Using Miedema model and subregular model scheme, the RAFs for the six EP (Ni, Co, Cu)-(P, B) alloys and three Ni-Cu, Ni-Co and Co-Cu alloys have been calculated systematically for the first time. The calculated results are in agreement with experimental observations. Experiments and calculations for the RAFs in the latter three alloy systems reveal that not any RAF formed except crystalline states. The huge difference between the six metal-metalloid alloys and three metal-metal alloys in RAF has been discussed in detail in the paper.

  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. 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.

  7. 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

  8. 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

  9. Magnetic properties of Fe80-xCoxZr7Si13 (x = 0 - 30) amorphous alloys

    Science.gov (United States)

    Kopcewicz, M.; Grabias, A.; Latuch, J.

    2011-11-01

    Amorphous Fe80-xCoxZr7Si13 (x = 0 - 30) alloys, in which boron was completely replaced by silicon as a glass forming element, have been prepared by melt quenching. Partial substitution of iron by cobalt causes the increase of the hyperfine fields from about 19 to 27 T for x = 0 and 30, respectively, as revealed by conventional Mössbauer spectroscopy. The specialized rf-Mössbauer technique permitted us to estimate the soft magnetic properties of the alloys. The rf-collapse effect, which is very sensitive to the local anisotropy field, is observed for all amorphous FeCoZrSi alloys revealing that they are magnetically very soft. The rf-sidebands intensities, which are related to the magnetostriction, increase with the increase of Co content in the alloys. In Fe60Co20Zr7Si13 and Fe50Co30Zr7Si13 samples the rf field exposure induced partial crystallization that was attributed to mechanical deformations related to high frequency magnetostrictive vibrations forced by the rf field. The magnetostrictive origin of this effect was supported by the measurements of magnetostriction constants of the studied alloys. Measurements of the hysteresis loops revealed that coercivity increases for higher Co content.

  10. Formation and crystallization of bulk Pd82Si18 amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    蒲建; 王敬丰; 肖建中; 崔昆

    2003-01-01

    Bulk amorphous Pd82Si18 alloy with the largest diameter of 8 mm was prepared by water quenching the molten alloy with flux medium in a quartz tube. The calculation result indicates that the bulk Pd82Si18 amorphous alloys have a low critical cooling rate (Rc) of 4.589 K/s or less. The experimental results show that purifying melt may improve glass forming ability(GFA) of undercooled melt, while liquid phase separation (LPS) of undercooled melt will decrease its GFA. There are some differences in crystallization experiments between bulk metallic glass and amorphous ribbons of Pd82Si18 alloys. These include the numbers of exothermic peak, glass transition temperature Tg, crystallization temperature Tx, region of undercooling liquid (ΔT=Tx-Tg) respectively. The links of cooling rates of melt and crystallization of Pd82Si18 amorphous alloys are explored.

  11. 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%.

  12. 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.).

  13. Crystallization behaviour of Al-Sm amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Battezzati, L. (Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali, Universita di Torino, Via P. Giuria 9, 10125 Torino (Italy)); Baricco, M. (Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali, Universita di Torino, Via P. Giuria 9, 10125 Torino (Italy)); Schumacher, P. (Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)); Shih, W.C.; Greer, A.L.

    1994-05-01

    Various Al[sub 100-x]Sm[sub x] alloys (10[<=]qslantx[<=]qslant14) have been rapidly solidified by single-roller melt spinning with careful control of the atmosphere in the quenching device. The structural state and subsequent devitrification behaviour of the melt-spun ribbons are found to be particularly sensitive to the quenching conditions. Except for the thinnest ribbons, there are inhomogeneities both through the ribbon thickness and along the length. Both fully and partially amorphous ribbons have been obtained. The crystallization processes of the amorphous phases have been followed by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry (DSC). Al[sub 92]Sm[sub 8] shows primary crystallization of Al, followed by the formation of metastable phases; Al[sub 90]Sm[sub 10] transforms polymorphically to a metastable intermetallic; Al[sub 88]Sm[sub 12] and Al[sub 86]Sm[sub 14] display eutectic crystallization into Al and a metastable mixture of compounds. For Al[sub 90]Sm[sub 10], the DSC traces involve several overlapping peaks. This may be the result of transformations occurring in distinct parts of the ribbon with different mechanisms. A kinetic analysis of the crystallization processes has been performed by means of isothermal and non-isothermal DSC experiments. A discussion of the kinetic parameters derived from Kissinger and Avrami analyses is provided. ((orig.))

  14. 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.

  15. 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.

  16. 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.

  17. Fabrication of nanoporous silver by de-alloying Cu-Zr-Ag amorphous alloys

    Science.gov (United States)

    Wang, Hui; Xiao, Shang-gang; Zhang, Tao

    2016-07-01

    Nanoporous silver (NPS) with a ligament size ranging from 15 to 40 nm was fabricated by de-alloying (Cu50Zr50)100- x Ag x ( x = 10at%, 20at%, 30at%, and 40at%) amorphous ribbons in a mixed aqueous solution of hydrofluoric (HF) acid and nitric acid under free corrosion conditions. Nanoporous silver ligaments and pore sizes were able to be fine-tuned through tailoring the chemical composition, corrosion conditions, and de-alloying time. The ligament size increases with an increase in Ag content and de-alloying time, but decreases with an increase in HF concentration. This phenomenon may be attributed to the dissolution of Zr/Cu and the diffusion, aggregation, nucleation, and recrystallization of Ag, leading to an oriented attachment of adjacent nanocrystals as revealed by TEM analysis.

  18. Fabrication of nanoporous silver by de-alloying CuZrAg amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    Hui Wang; Shang-gang Xiao; Tao Zhang

    2016-01-01

    Nanoporous silver (NPS) with a ligament size ranging from 15 to 40 nm was fabricated by de-alloying (Cu50Zr50)100-xAgx (x = 10at%, 20at%, 30at%, and 40at%) amorphous ribbons in a mixed aqueous solution of hydrofluoric (HF) acid and nitric acid under free cor-rosion conditions. Nanoporous silver ligaments and pore sizes were able to be fine-tuned through tailoring the chemical composition, corro-sion conditions, and de-alloying time. The ligament size increases with an increase in Ag content and de-alloying time, but decreases with an increase in HF concentration. This phenomenon may be attributed to the dissolution of Zr/Cu and the diffusion, aggregation, nucleation, and recrystallization of Ag, leading to an oriented attachment of adjacent nanocrystals as revealed by TEM analysis.

  19. Medium-Range Order Structure and Fragility of Superheated Melts of Amorphous CuHf Alloys

    Institute of Scientific and Technical Information of China (English)

    BIAN Xiu-Fang; SUN Bao-An; HU Li-Na

    2006-01-01

    @@ The structural factors of amorphous CuHf alloys at different temperatures are determined by using a high temperature x-ray diffractometer. It is found that not only the short-range order structure but also the medium-range order structure exists in amorphous CuHf alloys. The dynamic viscosities of CuHf alloy melts are measured by a torsional oscillation viscometer. The fragility of superheated melts of CuHf alloys is calculated based on the viscosity data. The experimental results show that the glass-forming ability of the CuHf alloys is closely related to the fragility of their superheated melt. The relationship between the medium-range order structures and the fragility of superheated melts has also been established in amorphous CuHf alloys. In contrast to the fragility of supercooled liquids, the fragility of superheated liquids promises a better approach to reflecting the dynamics of glass forming liquids.

  20. 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.

  1. 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.

  2. 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)

  3. 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.

  4. 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...

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. STUDY ON MAXIMUM HYDROGEN CAPACITY FOR Zr-Ni AMORPHOUS ALLOY

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    To design the amorphous hydrogen storage alloy efficiently, the maximum hydrogen capacities for Zr-Ni amorphous alloy were calculated. Based on the Rhomb Unit Structure Model(RUSM) for amorphous alloy and the experimental result that hydrogen atoms exist in 3Zr1Ni and 4Zr tetrahedron interstices in Zr-Ni amorphous alloy, the numbers of 3Zr-1Ni and 4Zr tetrahedron interstices in a RUSM were calculated which correspond to the hydrogen capacity. The two extremum Zr distribution states were calculated, such as highly heterogeneous Zr distribution and homogeneous Zr distribution. The calculated curves of hydrogen capacity with different Zr contents at two states indicate that the hydrogen capacity increases with increasing Zr content and reaches its maximum when Zr is 75%. The theoretical maximum hydrogen capacity for Zr-Ni amorphous alloy is 2.0(H/M). Meanwhile, the hydrogen capacity of heterogeneous Zr distribution alloy is higher than that of homogenous one at the same Zr content. The experimental results prove the calculated results reasonable, and accordingly, the experimental results that the distribution of Zr atom in amorphous alloy occur heterogeneous after a few hydrogen absorption-desorption cycles can be explained.

  10. 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.

  11. 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.

  12. Anisotropic Magnetoresistance Effect in Amorphous and Nanocrystalline Fe(Cu,Nb)-Si-B Alloys

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The magnetoresistance effect and magnetic properties in amorphous and nanocrystalline Fe(Cu, Nb)-Si-B ribbons have been investigated. It was observed that the anisotropic magnetoresistance (AMR) of nanocrystalline alloy is much smaller than that of amorphous alloy, indicating that the anisotropy of nanocrystalline alloy becomes smaller after crystallizing, and the smallest AMR is coincident with the excellent soft magnetic characteristics. It is believed that the smaller magnetic crystalline anisotropy is the origin of the excellent soft magnetic characteristics of nanocrystalline alloy.

  13. Spectroscopic and mechanical studies on the Fe-based amorphous alloy 2605SA1

    Energy Technology Data Exchange (ETDEWEB)

    Cabral P, A.; Garcia S, I. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Contreras V, J. A.; Garcia S, F. [Universidad Autonoma del Estado de Mexico, Facultad de Ciencias, El Cerrillo Piedras Blancas, Toluca, Estado de Mexico (Mexico); Nava, N., E-mail: agustin.cabral@inin.gob.m [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, 07730 Mexico D. F. (Mexico)

    2010-07-01

    The Vickers micro-hardness of this alloy was unusually dependent on the heat treatment from 300 to 634 K, inferring important micro-structural changes and the presence of amorphous grains before its phase transition. Once the alloy is crystallized, the micro-hardness is characteristic of a brittle alloy, the main problem of these alloys. Within the amorphous state, other properties like free-volume, magnetic states and Fe-Fe distances were followed by Positron annihilation lifetime spectroscopy and Moessbauer spectroscopy, respectively, to analyze those micro-structural changes, thermally induced, which are of paramount interest to understand their brittleness problem. (Author)

  14. Curie Temperature of the Intergranular Amorphous Phase in Nanocrystalline Fe89Zr7B4 Alloy

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The FeZrB amorphous alloys for simulating the intergranular amorphous phase in the nanocrystalline Fe89Zr7B4 soft magnetic materials were obtained by mechanical alloying of a mixture of elemental Fe, Zr and B powdersfor 25 h. It is shown that the Curie temperature of the simulated intergranular phase alloy is much lower than thatof the intergranular phase with the same chemical composition in the nanocrystalline Fe89Zr7B4 alloy. The possiblemechanism is mainly due to the strong ferromagnetic exchange force among the nanocrystalline α-Fe grains.

  15. Pressure effects on Al89La6Ni5 amorphous alloy crystallization

    DEFF Research Database (Denmark)

    Zhuang, Yanxin; Jiang, Jianzhong; Zhou, T. J.;

    2000-01-01

    The pressure effect on the crystallization of the Al89La6Ni5 amorphous alloy has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction using synchrotron radiation. The amorphous alloy crystallizes in two steps in the pressure range studied (0-4 GPa). The first...... process, corresponding to simultaneous precipitation of fcc-Al crystals and the metastable bcc-(AlNi)(11)La-3-like phase, is governed by a eutectic reaction. The second process corresponds to the transformation of a residual amorphous alloy into fcc-Al, Al11La3, Al3Ni, and as yet unidentified phase......(s). The applied pressure strongly affects the crystallization processes of the amorphous alloy. Both temperatures first decrease with pressure in the pressure range of 0-1 GPa and then increase with pressure up to 4 GPa. The results are discussed with reference to competing processes between the thermodynamic...

  16. Research on fabricating Fe base amorphous alloy by bar plasma spraying

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Since amorphous alloys have wider application, they can not be fabricated using the conventional cooling velocity. The bar material plasma spraying is adopted to fabricate Fe base amorphous alloy in this investigation. The crystallization degree, microstructure, micro-hardness, composition, crystallization temperature of the amorphous alloy and the flying rules of the atomized particles in the process of the plasma spray are tested. The results show that the alloy prepared has the high amorphous degree and homogeneous microstructure, micro-hardness and the crystallization temperature can reach 1187HV and 531℃ respectively. The atomization is very well during the process of plasma spraying; and there is high thermal gradient, the cooling velocity reaches 6.07×107K/s.

  17. The use of amorphous boron powder enhances mechanical alloying in soft magnetic FeNbB alloy: A magnetic study

    Energy Technology Data Exchange (ETDEWEB)

    Ipus, J. J.; Blazquez, J. S.; Franco, V.; Conde, A. [Dpto. Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain)

    2013-05-07

    Saturation magnetization and magnetic anisotropy have been studied during mechanical alloying of Fe{sub 75}Nb{sub 10}B{sub 15} alloys prepared using crystalline and commercial amorphous boron. The evolution of saturation magnetization indicates a more efficient dissolution of boron into the matrix using amorphous boron, particularly for short milling times. The magnetization of the crystalline phase increases as boron is incorporated into this phase. Two milling time regimes can be used to describe the evolution of magnetic anisotropy: a first regime governed by microstrains and a second one mainly governed by crystal size and amorphous fraction.

  18. NEW METHOD OF PRODUCTION OF ALUNINUM SILICON ALLOYS

    Directory of Open Access Journals (Sweden)

    V. K. Afanasiev

    2015-01-01

    Full Text Available A new approach to the preparation of aluminum-silicon alloys, based on the concept of the leading role of hydrogen in determining the structure and properties of alloys consists in using as charge materials of silicon dioxide (silica and hydrogen instead of crystalline silicon was described. Practical ways to implement the new method were proposed on the example of industrial alloys prepared on charge synthetic alloy. It is shown that the application of the proposed method allows to improve the mechanical properties and reduce the coefficient of thermal expansion alloys, Al-Si. The effect of heat treatment on mechanical properties, density and thermal expansion of synthetic alloys was researched.

  19. Calorimetric studies of non-isothermal crystallization in amorphous CuTi100– alloys

    Indian Academy of Sciences (India)

    N Mehta; K Singh; N S Saxena

    2011-12-01

    The present paper reports the composition dependence of pre-exponential factor and activation energy of non-isothermal crystallization in amorphous alloys of CuTi100– system using differential scanning calorimeter (DSC) technique. The applicability of Meyer–Neldel relation between the pre-exponential factor and activation energy of non-isothermal crystallization for amorphous alloys of Cu–Ti system was verified.

  20. Development of Amorphous Filler Alloys for the Joining of Nuclear Materials

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jai Young; Kim, Dong Myong; Kang, Yoon Sun; Jung, Jae Han; Yu, Ji Sang; Kim, Hae Yeol; Lee, Ho [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1997-08-01

    In the case of advanced CANDU fuel being useful in future, the fabrication processes for soundness insurance of a improved nuclear fuel bundle must be developed at the same time because it have three times combustibility as existing fuel. In particular, as the improved nuclear fuel bundle in which a coated layer thickness is thinner than existing that, firmity of a joint part is very important. Therefore, we need to develop a joint technique using new solder which can settle a potential problem in current joining method. As the Zr-Be alloy system is composed with the elements having high neutron permeability, they are suitable for joint of nuclear fuel pack. The various compositions Zr-Be binary metallic glass alloys were applicable to the joining the nuclear fuel bundles. The thickness of joint layer using the Zr{sub 1}-{sub x}Be{sub x} amorphous ribbon as a solder is thinner than that using physical vapor deposited Be. Among the Zr{sub 1}-{sub x}Be{sub x} amorphous binary alloys, Zr{sub 0}.7Be-0.3 binary alloy is the most appropriate for joint of nuclear fuel bundle because its joint layer is smooth and thin due to low degree of Be diffusion. In the case of the Zr{sub (}0.7-y)Ti{sub y}Be{sub 0}.3 and Zr{sub (}0.7-y)Nb{sub y}Be{sub 0}3 ternary amorphous alloys, the crystallization temperature(T{sub x}) and activation energy(E{sub x}) increase as the contents of Nb and Ti increase respectively. In the aspect of thermal stability, the ternary amorphous alloys are superior than Zr-Be binary amorphous alloys and Zr-Ti-Be amorphous alloy is superior than Zr-Nb-Be amorphous alloy. 12 refs., 5 tabs., 25 figs. (author)

  1. Formation of nanophases by crystallization of amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Baricco, M. [Turin Univ. (Italy). Dipt. di Chimica Inorganica; Tiberto, P. [Istituto Elettrotecnico Nazionale, Turin (Italy); Battezzati, L. [Turin Univ. (Italy). Dipt. di Chimica Inorganica

    1995-12-31

    A comparison is made of crystallization mechanisms in Fe-based amorphous alloys (Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9}, Fe{sub 90}Zr{sub 7}B{sub 3}), which lead to a nanocrystalline bcc phase with peculiar soft magnetic properties through primary crystallization. In all samples, the nucleation takes place uniformely throughout the material. The presence of atoms with low diffusivity (Zr, Nb) reduces the grain growth rate so that a small size of crystals is maintained. On the contrary, even extremely fast heating and short heat treatment do not produce nanocrystals in Fe{sub 40}Ni{sub 40}B{sub 20} although the crystallization mechanism is modified. However milling the ribbon leads to nanostructured crystalline phases. The formation of nanophases by crystallization is discussed considering the temperature dependence of nucleation frequency and growth rate. The effects of various thermodynamic and kinetic parameters are analyzed and the most favourable conditions for nanocrystallization are outlined. (orig.)

  2. The crystallization of Al-Sm amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rizzi, P. [Turin Univ. (Italy). Dipt. di Chimica Inorganica; Baricco, M. [Turin Univ. (Italy). Dipt. di Chimica Inorganica; Battezzati, L. [Turin Univ. (Italy). Dipt. di Chimica Inorganica; Schumacher, P. [Cambridge Univ. (United Kingdom). Dept. of Metallurgy and Materials Science; Greer, A.L. [Cambridge Univ. (United Kingdom). Dept. of Metallurgy and Materials Science

    1995-12-31

    Amorphous alloys with composition Al{sub 100-x}Sm{sub x} (8 {<=} x {<=} 14) have been prepared by melt spinning in controlled atmosphere. The quenching conditions significantly influence the microstructure of as-quenched samples and their crystallization mechanisms. The crystallization was followed by means of DSC, XRD, TEM and SEM. Different mechanisms are observed as a function of composition. For low Sm content (Al{sub 92}Sm{sub 8}), a primary crystallization occurs at about 180 C, with the formation of Al nanocrystals with a grain size of about 15 nm. A polymorphic crystallization is found in Al{sub 90}Sm{sub 10}, with the formation of a metastable intermetallic phase at about 220 C. For higher Sm content (Al{sub 88}Sm{sub 12} and Al{sub 86}Sm{sub 14}), a eutectic crystallization at about 230 C gives a mixture of stable (Al and Al{sub 11}Sm{sub 3}) and metastable phases. (orig.)

  3. 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.

  4. Structural studies of the phase separation of amorphous FexGe100-x alloys

    Science.gov (United States)

    Lorentz, Robert D.; Bienenstock, Arthur; Morrison, Timothy I.

    1994-02-01

    Small-angle x-ray scattering and x-ray-absorption near-edge spectroscopy (XANES) experiments have been performed on amorphous FexGe100-x alloys over the composition range 0Janot for the related FexSn100-x system. This phase separation explains the Mossbauer observation of ``magnetic'' and ``nonmagnetic'' Fe atoms in these alloys.

  5. Investigation of Corrosion Resistance Using Positron Annihilation for an Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An amorphous alloy with Ni-(17~19) at. pct P prepared by electrodeposition process was studied using positron annihilation technique (PAT) associated with X-ray diffraction and the measurement of corrosion rate. It is suggested that defect or the interface between precipitates and matrix is one of the important factors which decrease corrosion resistance of the alloy after crystallization.

  6. 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.

  7. CuZrAl amorphous alloys prepared by casting and milling

    Science.gov (United States)

    Tomolya, K.; Janovszky, D.; Sveda, M.; Hegman, N.; Solyom, J.; Roosz, A.

    2009-01-01

    Several preparation methods are available for the production of amorphous alloys. During the experiment described in this paper (Cu58Zr42)100-xAlx (x = 0-14,8; in at%) amorphous alloys were prepared by casting and ball-milling. The ingots were produced by arc melting. Wedge-shaped samples were prepared from the ingots by centrifugal casting into copper mould. The microstructures of these samples were defined by SEM. The amorphous samples were analysed by DSC and the activation energy of the crystallization processes was calculated from the measured temperatures. The master alloys of identical composition were milled by ball-mill for different periods of time. The powders were analysed by XRD in order to define the amorphous fractions.

  8. On amorphization and nanocomposite formation in Al–Ni–Ti system by mechanical alloying

    Indian Academy of Sciences (India)

    K Das; G K Dey; B S Murty; S K Pabi

    2005-11-01

    Amorphous structure generated by mechanical alloying (MA) is often used as a precursor for generating nanocomposites through controlled devitrification. The amorphous forming composition range of ternary Al–Ni–Ti system was calculated using the extended Miedema's semi-empirical model. Eleven compositions of this system showing a wide range of negative enthalpy of mixing (− mix) and amorphization (− amor) of the constituent elements were selected for synthesis by MA. The Al88Ni6Ti6 alloy with relatively small negative mix (−0.4 kJ/mol) and amor (−14.8 kJ/mol) became completely amorphous after 120 h of milling, which is possibly the first report of complete amorphization of an Al-based rare earth element free Al–TM–TM system (TM = transition metal) by MA. The alloys of other compositions selected had much more negative mix and amor; but they yielded either nanocomposites of partial amorphous and crystalline structure or no amorphous phase at all in the as-milled condition, evidencing a high degree of stability of the intermetallic phases under the MA environment. Hence, the negative mix and amor are not so reliable for predicting the amorphization in the present system by MA.

  9. Amorphous TM1−xBx alloy particles prepared by chemical reduction (invited)

    DEFF Research Database (Denmark)

    Linderoth, Søren; Mørup, Steen

    1991-01-01

    Amorphous transition-metal boron (TM-B) alloy particles can be prepared by chemical reduction of TM ions by borohydride in aqueous solutions. ln the last few years systematic studies of the parameters which control the composition, and, in turn, many of the properties of the alloy particles, have...... been performed and are reviewed in the present paper. The most important preparation parameters which influence the composition are the concentration of the borohydride solution and the pH of the TM salt solution. By controlling these parameters it is possible to prepare amorphous alloy samples...

  10. 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.

  11. Structural transformations in wear resistance of iron- and cobalt-based amorphous alloys during abrasive wear

    Science.gov (United States)

    Korshunov, L. G.; Shabashov, V. A.; Chernenko, N. L.

    2010-04-01

    The wear resistance and structural changes in a number of amorphous alloys based on iron and cobalt and in high-carbon tool steels are studied during wear by a fixed abrasive (crondum, Carborundum) at room temperature and -196°C. The abrasive wear resistance of the amorphous alloys is shown to be 1.6-3.1 lower than that of the high-carbon tool steels having a similar hardness. The relatively low level of the abrasive wear resistance of the amorphous alloys is assumed to be caused by strain softening of their surface during wear. A nanocrystalline structure is found to form in local microvolumes in a thin deformed surface layer of the alloys.

  12. Friction and wear behavior of electrodeposited amorphous Fe-Co-W alloy deposits

    Institute of Scientific and Technical Information of China (English)

    何凤姣; 雷惊天; 陆欣; 黄宇宁

    2004-01-01

    The microstructures, friction and wear behavior under dry sliding condition of electrodeposited amorphous Fe-Co-W alloy deposits heat treated at different temperatures were studied. A comparative study of hard chrome deposit under the same testing condition was also made. The experimental results show that the hardness and wear resistance of amorphous Fe-Co-W alloy deposits are improved with the increasing of heat treatment temperature, and reach the maximum value at 800 ℃, then decrease above 800 ℃. Under 40 N load, the wear resistance properties of the alloy deposits heat treated at 800 ℃ are superior to those of hard chrome deposit. The main wear mechanisms of amorphous Fe-Co-W alloy deposits heat treated below 600 ℃ are peeling, plastic and flowing deformation; when the deposits are heat treated above 700 ℃, they are plastic and flowing deformation. While the main wear mechanisms of hard chrome are abrasive wear, fatigue and peeling.

  13. Achieving tailorable magneto-caloric effect in the Gd-Co binary amorphous alloys

    Directory of Open Access Journals (Sweden)

    C. Wu

    2016-03-01

    Full Text Available Tailorable magnetic properties and magneto-caloric effect were achieved in the Gd-Co binary amorphous alloys. It was found that the Curie temperature (Tc of the GdxCo100-x (x=50, 53, 56, 58, 60 metallic glasses can be tuned by changing the concentration of Gd as Tc =708.8-8.83x, and the mechanism involved was investigated. On the other hand, a linear correlation between the peak value of magnetic entropy change (-Δ Smpeak and Tc-2/3 is found in the amorphous alloys with a linear correlation coefficients of above 0.992. Therefore, the -ΔSmpeak of the Gd-Co binary amorphous alloys under different magnetic fields can be easily tailored by adjusting the composition of the alloy.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Amorphous and nanocrystalline phase formation in highly-driven Al-based binary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kalay, Yunus Eren [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    Remarkable advances have been made since rapid solidification was first introduced to the field of materials science and technology. New types of materials such as amorphous alloys and nanostructure materials have been developed as a result of rapid solidification techniques. While these advances are, in many respects, ground breaking, much remains to be discerned concerning the fundamental relationships that exist between a liquid and a rapidly solidified solid. The scope of the current dissertation involves an extensive set of experimental, analytical, and computational studies designed to increase the overall understanding of morphological selection, phase competition, and structural hierarchy that occurs under far-from equilibrium conditions. High pressure gas atomization and Cu-block melt-spinning are the two different rapid solidification techniques applied in this study. The research is mainly focused on Al-Si and Al-Sm alloy systems. Silicon and samarium produce different, yet favorable, systems for exploration when alloyed with aluminum under far-from equilibrium conditions. One of the main differences comes from the positions of their respective T0 curves, which makes Al-Si a good candidate for solubility extension while the plunging T0 line in Al-Sm promotes glass formation. The rapidly solidified gas-atomized Al-Si powders within a composition range of 15 to 50 wt% Si are examined using scanning and transmission electron microscopy. The non-equilibrium partitioning and morphological selection observed by examining powders at different size classes are described via a microstructure map. The interface velocities and the amount of undercooling present in the powders are estimated from measured eutectic spacings based on Jackson-Hunt (JH) and Trivedi-Magnin-Kurz (TMK) models, which permit a direct comparison of theoretical predictions. For an average particle size of 10 {micro}m with a Peclet number of ~0.2, JH and TMK deviate from

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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...

  7. 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...

  8. 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.

  9. EFFECT OF PRE-ALLOYING CONDITION ON THE BULK AMORPHOUS ALLOY ND(60)FE(30)AL(10).

    Energy Technology Data Exchange (ETDEWEB)

    OCONNOR,A.S.; LEWIS,L.H.; MCCALLUM,R.W.; DENNIS,K.W.; KRAMER,M.J.; KIM ANH,D.T.; DAN,N.H.; PHUC,N.X.

    2000-09-10

    Bulk metallic glasses are materials that require only modest cooling rates to obtain amorphous solids directly from the melt. Nd{sub 60}Fe{sub 30}Al{sub 10} has been reported to be a ferromagnetic bulk metallic glass that exhibits high coercivity, a combination unlike conventional Nd-based amorphous magnetic alloys. To clarify the relationship between short-range order and high coercivity in glassy Nd{sub 60}Fe{sub 30}Al{sub 10}, experiments were performed to verify the existence of a homogeneous liquid state prior to rapid solidification. Alloys were prepared by various pre-alloying routes and then melt-spun. Arc-melted alloys were prepared for melt spinning using three different protocols involving: (1) alloying all three elements at once, (2) forming a Nd-Fe alloy which was subsequently alloyed with Al, and (3) forming a Fe-Al alloy for subsequent alloying with Nd. XRD, DTA, and magnetic measurement data from the resultant ribbons indicate significant differences in both the glassy fraction and the crystalline phase present in the as-spun material. These observed differences are attributed to the presence of highly stable nanoscopic aluminide-and/or silicide-phases, or motes, present in the melt prior to solidification. These motes would affect the short-range order and coercivity of the resultant glassy state and are anticipated to provide heterogeneous nucleation sites for crystallization.

  10. Thermophysical Property Measurements of Silicon-Transition Metal Alloys

    Science.gov (United States)

    Banish, R. Michael; Erwin, William R.; Sansoucie, Michael P.; Lee, Jonghyun; Gave, Matthew A.

    2014-01-01

    Metals and metallic alloys often have high melting temperatures and highly reactive liquids. Processing reactive liquids in containers can result in significant contamination and limited undercooling. This is particularly true for molten silicon and it alloys. Silicon is commonly termed "the universal solvent". The viscosity, surface tension, and density of several silicon-transition metal alloys were determined using the Electrostatic Levitator system at the Marshall Space Flight Center. The temperature dependence of the viscosity followed an Arrhenius dependence, and the surface tension followed a linear temperature dependence. The density of the melts, including the undercooled region, showed a linear behavior as well. Viscosity and surface tension values were obtain for several of the alloys in the undercooled region.

  11. Silicon purification using a Cu-Si alloy source

    Science.gov (United States)

    Powell, R. C.; Tejedor, P.; Olson, J. M.

    1986-01-01

    Production of 99.9999% pure silicon from 98% pure metallurgical grade (MG) silicon by a vapor transport filtration process (VTP) is described. The VTF process is a cold wall version of an HCl chemical vapor transport technique using a Si:Cu3Si alloy as the silicon source. The concentration, origin, and behavior of the various impurities involved in the process were determined by chemically analyzing alloys of different purity, the slag formed during the alloying process, and the purified silicon. Atomic absorption, emission spectrometry, inductively coupled plasma, spark source mass spectrometry, and secondary ion mass spectroscopy were used for these analyses. The influence of the Cl/H ratio and the deposition temperature on the transport rate was also investigated.

  12. Effect Of Low-Temperature Annealing On The Properties Of Ni-P Amorphous Alloys Deposited Via Electroless Plating

    Directory of Open Access Journals (Sweden)

    Zhao Guanlin

    2015-06-01

    Full Text Available Amorphous Ni-P alloys were prepared via electroless plating and annealing at 200°C at different times to obtain different microstructures. The effects of low-temperature annealing on the properties of amorphous Ni-P alloys were studied. The local atomic structure of the annealed amorphous Ni-P alloys was analyzed by calculating the atomic pair distribution function from their X-ray diffraction patterns. The results indicate that the properties of the annealed amorphous Ni-P alloys are closely related to the order atomic cluster size. However, these annealed Ni-P alloys maintained their amorphous structure at different annealing times. The variation in microhardness is in agreement with the change in cluster size. By contrast, the corrosion resistance of the annealed alloys in 3.5 wt% NaCl solution increases with the decrease in order cluster size.

  13. Crystallization in Fe- and Co-Based Amorphous Alloys Studied by In-Situ X-Ray Diffraction

    Science.gov (United States)

    Zhang, L. J.; Yu, P. F.; Cheng, H.; Zhang, M. D.; Liu, D. J.; Zhou, Z.; Jin, Q.; Liaw, P. K.; Li, G.; Liu, R. P.

    2016-12-01

    The amorphous alloys, Fe80Si20, Fe78Si9B13, and Fe4Co67Mo1.5Si16.5B11, were prepared by the spinning method in pure argon. The crystallization behaviors of the three amorphous alloys were researched by in-situ X-ray diffraction (XRD), and the crystallization activation energy was calculated, based on the results of differential scanning calorimetry. The crystallization mechanism of the Fe- and Co-based alloys was analyzed, based on the experimental data. The transformation kinetics was described in terms of Johnson-Mehl-Avrami kinetics, except that the Avrami exponent of the Fe78Si9B13 amorphous alloy annealed at 753 K (480 °C) was 4.12; the obtained values for the overall Avrami exponents of the other three amorphous alloys were below 1, as usually found for the Fe-Si amorphous alloys.

  14. 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.

  15. Correlation Between Superheated Liquid Fragility And Onset Temperature Of Crystallization For Al-Based Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Guo J.

    2015-06-01

    Full Text Available Amorphous alloys or metallic glasses have attracted significant interest in the materials science and engineering communities due to their unique physical, mechanical, and chemical properties. The viscous flow of amorphous alloys exhibiting high strain rate sensitivity and homogeneous deformation is considered to be an important characteristic in thermoplastic forming processes performed within the supercooled liquid region because it allows superplastic-like deformation behavior. Here, the correlation between the superheated liquid fragility, and the onset temperature of crystallization for Al-based alloys, is investigated. The activation energy for viscous flow of the liquid is also investigated. There is a negative correlation between the parameter of superheated liquid fragility and the onset temperature of crystallization in the same Al-based alloy system. The activation energy decreases as the onset temperature of crystallization increases. This indicates that the stability of a superheated liquid can affect the thermal stability of the amorphous alloy. It also means that a liquid with a large superheated liquid fragility, when rapidly solidified, forms an amorphous alloy with a low thermal stability.

  16. 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)

  17. Corrosion behavior of Mg-Zn-Ca amorphous alloys with Nd addition in simulated body fluids

    Directory of Open Access Journals (Sweden)

    Qin Chunling

    2014-11-01

    Full Text Available The effects of Nd addition on corrosion behavior of Mg66Zn30Ca4 amorphous alloys in simulated body fluids (SBF were studied in this paper. Electrochemical properties of the samples before and after corrosion were determined. Surface morphologies of samples after immersion in SBF at 37 篊 for different times were observed under scanning electron microscope (SEM. Results show that the corrosion resistance of Mg-based alloys in SBF is improved with the addition of Nd element. The electrochemical properties indicate that microalloying Nd element to the alloys leads to an ennoblement in the open circuit potentials of the alloys and a decrease in the anodic current density in SBF, especially for the Mg66-xZn30Ca4Ndx alloys with Nd content of 1.0at.%-1.5at.%. It was observed that the surface morphologies of the alloys immersed in SBF change with the Nd addition. A flake-like structure parallel to the alloy substrate formed on the surface of 1.0at.% Nd-containing alloy immersed in SBF for 7 days improves the corrosion resistance of the amorphous alloys by blocking the corrosion liquid from attacking the alloys.

  18. 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.)

  19. Synthesis of amorphous Ti-Al alloys by mechanical alloying of elemental powders

    Institute of Scientific and Technical Information of China (English)

    张俊红; 黄伯云; 贺跃辉; 周科朝; 刘咏

    2002-01-01

    Blended elemental powders with the nominal compositions (mole fraction, %) of Ti54Al46, Ti52Al48 and Ti50Al50 were mechanically alloyed in a planetary ball milling system for up to 100h.The structure evolution in these powders was characterized by scanning electron microscope, X-ray diffraction and differential thermal a nalysis techniques. It was found that elemental powders were progressively trans formed into nanocrystalline Ti(Al) supersaturated solid solution, then into amor phous phase. With increasing Al content, the formation of a fully Ti(Al) supersa turated solid solution and amorphous phase were accelerated, which are attributed to the fine grain size. And the grain size condition for formation of amorpho us phase in this system is ≤16 nm.

  20. Electrical properties and degradation behavior of hydrogenated amorphous Si alloys for solar cells

    Science.gov (United States)

    Krühler, W.; Kusian, W.; Karg, F.; Pfleiderer, H.

    1986-12-01

    The electrical properties and the degradation behavior of hydrogenated amorphous silicon alloys (a-Si1- x A x : H, with A=C, Ge, B, P) in designs of pin, pip, nin, and MOS structures are investigated by measuring the dark and light I(V) characteristics and the spectral response as well as the space-charge-limited current (SCLC), the time of flight (TOF) of carriers and the field effect (FE). These investigations give an overview of our recent work combined with new results emphasizing the physics of the a-Si:H pin solar cells. We discuss the stabilizing influence on the degradation behavior achieved by profiling the i layers of the pin solar cells with P and B. Two kinds of pin solar cells, namely glass/SnO2/p(C)in/metal and glass/metal/pin/ITO, are investigated and an explanation of their different spectral response behavior is given. SCLC measurements lead to the conclusion that trapping is also involved in the degradation mechanism, as is recombination. TOF experiments on a-Si1- x Ge x : H pin diodes indicate that the incorporation of Ge widens the tail-state distribution below the conduction band. FE measurements showed densities of gap states of about 5×l016cm-3eV-1.

  1. AMORPHOUS HYDROGENATED ALLOYS : A COMPARATIVE EXAFS STUDY OF a-Si1-xCx : H, a-Si1- xGex : H, a-SiNx : H AT THE SILICON K-EDGE

    OpenAIRE

    1986-01-01

    a-Si1-xCx : H, a-Si1-xGex : H, a-SiNx : H alloys have been studied at the Si K-edge. Si-Si and Si-A (A being C, N, Ge) bond lengths have been determined as a function of composition. The Si-C distance was found to vary significantly, while the Si-Ge and Si-N distances remain almost constant. A high frequency signal has been detected in the a-Si1-xCx : H and a-SiNx : H films at large x due to a second shell contribution. The compositions of the first coordination shell are also reported and di...

  2. Mechanical properties of amorphous alloys ribbons prepared by rapid quenching of the melt after different thermal treatments before quenching

    NARCIS (Netherlands)

    Tabachnikova, ED; Bengus, VZ; Egorov, D V; Tsepelev, VS; Ocelik, Vaclav

    1997-01-01

    The mechanical properties of amorphous alloy are greatly influenced by the thermal treatment of its melt before rapid quenching. The strength and the fracture toughness of some amorphous alloys obtained after melt beating above the melt critical temperature T-CR are essentially higher than those obt

  3. 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)

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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)

  13. 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

  14. Structural transformations of amorphous iron-based alloys upon abrasive and thermal treatments

    Science.gov (United States)

    Korshunov, L. G.; Shabashov, V. A.; Litvinov, A. V.; Chernenko, N. L.

    2010-05-01

    Wear resistance and structural changes have been investigated in amorphous alloys Fe64Co30Si3B3 and Fe73.5Nb3Cu1Si13.5B9 upon wear using a fixed abrasive. The structural studies have been performed by the methods of metallography, electron microscopy, and Mössbauer spectroscopy. It has been shown that the abrasive resistance of amorphous alloys is 1.6-3.1 times lower than that of high-carbon tool steels, which have a close level of hardness. The low abrasive wear resistance of amorphous alloys is caused by the deformation softening of the alloy surface in the process of wear. The major volume of the deformed surface layer of the alloys preserves the amorphous state. Its structural changes upon wear are characterized by the formation of inhomogeneities (fragments with a size of 10-50 nm) and by a decrease in the width of the strongest “halo” in the selected-area electron-diffractions patterns. In the amorphous matrix of the Fe64Co30Si3B3 alloy, a strong magnetic texture is formed and a redistribution of atoms occurs, which leads to an increase in the local shortrange order corresponding to FeB, Fe2B, Fe3B and α-Fe phases. In microvolumes of a thin (several μm) surface layer, the formation of a nanocrystalline structure (on the order of several volume %) was revealed. A tempering of the Fe73.5Cu1Nb3S13.5B9 alloy at temperatures below 500°C does not affect the hardness and wear resistance of the alloy. At 500°C, there occurs an increase in microhardness and wear resistance of the Fe73.5Cu1Nb3S13.5B9 alloy as a result of the formation in it of a nanocrystalline structure with the retention of a certain amount of the amorphous phase. The complete crystallization of the alloy at 540°C increases the brittleness of the alloy, which leads to a sharp reduction in its wear resistance.

  15. Study of The Pd-B/γ-Al2O3 Amorphous Alloy Catalyst

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The Pd-B/γ-Al2O3 amorphous alloy catalyst and Pd/γ-Al2O3 crystalline metal catalyst were prepared by KBH4 reduction and routine impregnation, respectively. Pd-B/γ-A12O3 and Pd/γ-A12O3 catalysts were characterized by XRD and SEM. It was found that the catalytic activity of the Pd-B/γ-A12O3 amorphous alloy catalyst was higher than that of the Pd/γ-A12O3crystalline metal catalyst in the anthraquinone hydrogenation.

  16. Ferromagnetic Fe-based Amorphous Alloy with High Glass-forming Ability

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A ferromagnetic amorphous Fe73Al4Ge2Nb1P10C6B4 alloy with highglass-forming ability was synthesized by melt spinning. The supercooled liquid region before crystallization reaches about 65.7 K. The crystallized structure consists of α-Fe, Fe3B, FeB, Fe3P and Fe3C phases. The Febased amorphous alloy exhibits good magnetic properties with a high saturation magnetization and a low saturated magnetostriction. The crystallization leads to an obvious decrease in the soft magnetic properties.

  17. Effect of Cerium on Chemical Short-Range Order of Al-Fe-Ce Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The chemical short-range order of Al-Fe-Ce amorphous alloy was studied by means of X-ray diffraction(XRD) and differential scanning calorimetry(DSC). It is found that the prepeak position in X-ray diffraction intensity curve shifts to higher angles as the content of Fe increases, but it shifts to smaller angles as the content of Ce increases. The crystallization character of the amorphous alloy changes with the variation of the content of Fe and Ce. Ce can improve the interaction between atoms and the capacity of compound formation, so it is favorable to Al-based glass formability.

  18. Investigation on Crystallization Kinetics of Zr-AI-Based Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    王国明; 李维火; 方守狮; 华勤; 肖学山

    2005-01-01

    Zr65Al10Ni10Cu15, Zr52.5Al10Ni10Cu15Be12.5 and Zr52.5Al10Ni14.6 Cu17.9Ti5bulk amorphous alloys were prepared by copper mould casting. The crystallization kinetics was measured by differential scanning calorimeter(DSC) with different heating rates, and the activation energy was calculated using Kissinger equation. The relationship between thermal stability and rate constant of crystallization reaction is discussed on the view of crystallization kinetics, and the effect of small atom Beryllium on thermal stability of bulk amorphous alloys is also studied.

  19. 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)

  20. 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.%.

  1. 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

  2. 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.

  3. Micromagnetic model for magnetisation processes in RE-TM based-amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Stoleriu, Laurentiu E-mail: lstoler@uaic.ro; Cimpoesu, Dorin; Stancu, Alexandru; Lupu, Nicoleta; Chiriac, Horia

    2004-05-01

    A micromagnetic model and its results for Nd{sub 90-x}Fe{sub x}Al{sub 10} (x=40-50) amorphous alloys are presented. The high coercive field of this type of alloys can be explained using the real values of the materials constants (distances between atoms, magnetic moments and exchange constants). The morphology of the sample plays an important role--the formation of Fe clusters and the cooperative switching behaviour further increase the coercive field value.

  4. Ballistic Impact Properties of Zr-Based Amorphous Alloy Composites Reinforced with Woven Continuous Fibers

    Science.gov (United States)

    Kim, Gyeong Su; Son, Chang-Young; Lee, Sang-Bok; Lee, Sang-Kwan; Song, Young Buem; Lee, Sunghak

    2012-03-01

    This study aims at investigating ballistic impact properties of Zr-based amorphous alloy (LM1 alloy) matrix composites reinforced with woven stainless steel or glass continuous fibers. The fiber-reinforced composites with excellent fiber/matrix interfaces were fabricated without pores and misinfiltration by liquid pressing process, and contained 35 to 41 vol pct of woven continuous fibers homogeneously distributed in the amorphous matrix. The woven-STS-continuous-fiber-reinforced composite consisted of the LM1 alloy layer of 1.0 mm in thickness in the upper region and the fiber-reinforced composite layer in the lower region. The hard LM1 alloy layer absorbed the ballistic impact energy by forming many cracks, and the fiber-reinforced composite layer interrupted the crack propagation and blocked the impact and traveling of the projectile, thereby resulting in the improvement of ballistic performance by about 20 pct over the LM1 alloy. According to the ballistic impact test data of the woven-glass-continuous-fiber-reinforced composite, glass fibers were preferentially fragmented to form a number of cracks, and the amorphous matrix accelerated the fragmentation of glass fibers and the initiation of cracks. Because of the absorption process of ballistic impact energy by forming very large amounts of cracks, fragments, and debris, the glass-fiber-reinforced composite showed better ballistic performance than the LM1 alloy.

  5. 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.

  6. Ideal solution behaviour of glassy Cu–Ti, Zr, Hf alloys and properties of amorphous copper

    Energy Technology Data Exchange (ETDEWEB)

    Ristić, R. [Department of Physics, University of Osijek, Trg Ljudevita Gaja 6, HR-3100 Osijek (Croatia); Cooper, J.R. [Department of Physics, Cavendish Laboratory, J.J. Thomson Avenue, CB3 0HE Cambridge (United Kingdom); Zadro, K.; Pajić, D. [Department of Physics, Faculty of Science, Bijenička cesta 32, HR-10002 Zagreb (Croatia); Ivkov, J. [Institute of Physics, Bijenička cesta 46, HR-10002 Zagreb (Croatia); Babić, E. [Department of Physics, Faculty of Science, Bijenička cesta 32, HR-10002 Zagreb (Croatia)

    2015-02-05

    Highlights: • Ideal solution behaviour (ISB) is established in all Cu–Ti, Zr, Hf glassy alloys. • ISB enables reliable estimates for various properties of amorphous Cu. • ISB also impacts glass forming ability in these and probably other similar alloys. - Abstract: A comprehensive study of selected properties of amorphous (a) Cu–TE alloys (TE = Ti, Zr and Hf) has been performed. Data for average atomic volumes of a-Cu–Hf, Ti alloys combined with literature data show that ideal solution behaviour (Vegard’s law) extends over the whole glass forming range (GFR) in all a-Cu–TE alloys. This enables one to obtain an insight into some properties and probable atomic arrangements for both, a-TEs (Ristić et al., 2010) and a-Cu by extrapolation of the data for alloys. Indeed the atomic volumes and other properties studied for all a-Cu–TE alloys extrapolate to the same values for a-Cu. Depending on the property, these values are either close to those of crystalline (c) Cu, or are close to those for liquid (L) Cu. In particular, the electronic transport properties of a-Cu seem close to those of L-Cu, whereas the static properties, such as the density of states, and Young’s modulus, converge to those of c-Cu. The possible impact of these results on our understanding of a-Cu–TE alloys, including glass forming ability, is discussed.

  7. Structural transformations and tribological properties of amorphous alloys upon wear at room and cryogenic temperatures

    Science.gov (United States)

    Korshunov, L. G.; Chernenko, N. L.; Goikhenberg, Yu. N.

    2009-09-01

    The abrasive wear resistance of the Fe64Co30Si3B3, Co86.5Cr4Si7B2.5, Fe73.5Nb3Cu1Si13.5B9, and Fe82.6Nb5Cu3Si8B1.4 commercial amorphous alloys (ribbon 0.03 mm thick and 12 mm wide) has been investigated under the conditions of abrasive and adhesive wear upon sliding friction. The character of fracture of the surface and structural transformations that occur in these materials upon wear have been studied by the metallographic and electron-microscopic methods. It has been shown that at room and cryogenic (-196°C) temperatures of tests the abrasive wear resistance of the amorphous alloys is two-three times lower than that of tool steels Kh12M and U8. A comparatively small abrasive wear resistance of the amorphous alloys is explained by local softening of these materials in the process of wear. Under the conditions of adhesive wear of like friction pairs at room temperature in air and argon, the amorphous alloys are characterized by the rate of wear that is smaller approximately by an order of magnitude than in steels 12Kh13 and 12Kh18N9. It has been established that upon wear the deformed surface layer of the alloys under study retains a predominantly amorphous state but in local sections of this layer nanocrystalline structures that consist of crystals of bcc and fcc phases and borides are formed. The possible effects of this partial crystallization on the microhardness, friction coefficient, and wear resistance of these alloys have been considered.

  8. 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.

  9. 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.

  10. Magnetocaloric response of amorphous and nanocrystalline Cr-containing Vitroperm-type alloys

    Energy Technology Data Exchange (ETDEWEB)

    Moreno-Ramírez, L.M.; Blázquez, J.S.; Franco, V.; Conde, A. [Dpto. Física de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Marsilius, M.; Budinsky, V.; Herzer, G. [Vacuumschmelze GmbH & Co KG, Grüner Weg 37, D-63450 Hanau (Germany)

    2016-07-01

    The broad compositional range in which transition metal (TM) based amorphous alloys can be obtained, yields an easily tunable magnetocaloric effect (MCE) in a wide temperature range. In some TM-based alloys, anomalous behaviors are reported, as a non-monotonous trend with magnetic moment (e.g. FeZrB alloys). Moreover, in certain Cr-containing Vitroperm alloys anomalously high values of the magnetic entropy change were published. In this work, a systematic study on MCE response of Cr-containing amorphous alloys of composition Fe{sub 74-x}Cr{sub x}Cu{sub 1}Nb{sub 3}Si{sub 15.5}B{sub 6.5} (with x=2, 8, 10, 12, 13, 14 and 20) has been performed in a broad Curie temperature range from 100 K to 550 K. Curie temperature and magnetic entropy change peak of the amorphous alloys decrease with the increase of Cr content at rates of −25.6 K/at% Cr and −54 mJ kg{sup −1} K{sup −1}/at% Cr, respectively, following a linear trend with the magnetic moment in both cases. The presence of nanocrystalline phases has been considered as a possible cause in order to explain the anomalies. The samples were nanocrystallized in different stages, however, the magnetocaloric response decreases as crystallization progresses due to the large separation of the Curie temperatures of the two phases. - Highlights: • Study of magnetocaloric effect of amorphous and nanocrystalline Cr-Vitroperm alloys. • Cr content decreases the magnetocaloric response and the Curie temperature. • Nanocrystallization reduces MCE and modifies T{sub C} in a non-monotonous way. • The large difference between T{sub C} of phases decreases MCE of composite.

  11. Evidence of eutectic crystallization and transient nucleation in Al89La6Ni5 amorphous alloy

    DEFF Research Database (Denmark)

    Zhuang, Yanxin; Jiang, Jianzhong; Lin, Z. G.;

    2001-01-01

    The phase evolution with the temperature and time in the process of crystallization of Al89La6Ni5 amorphous alloy has been investigated by in situ high-temperature and high-pressure x-ray powder diffraction using synchrotron radiation. Two crystalline phases, fcc-Al and a metastable bcc-(AlNi)(11...

  12. A New Physical Metallurgy Phenomenon-the Shock Wave Nanocrystallization of Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Some results of amorphous alloy nanocrystallization by shock wave are presented. Compared with the well knownannealing crystallization, these results seem novel and are very difficult to be explained by the diffusion theory, such asnucleation and growth mechanism in the solid state phase transitions. The shock wave crystallization of amorphousalloy is a new metallurgical phenomenon with possibilities for improving the crystallization theory in physics.

  13. Annealing crystallization and catalytic activity of ultrafine NiB amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Annealing crystallization of ultrafine NiB amorphous alloy prepared by the chemical reduction method was studied by DTA,XRD and XAFS techniques. The XRD and XAFS results have revealed that the crystallization process of ultrafine NiB amorphous alloy proceeds in two steps. First,ultrafine NiB amorphous alloy is crystallized to form metastable nanocrystalline Ni3B at an annealing temperature of 325℃. Second,the nanocrystalline Ni3B is further decom-posed into crystalline Ni at 380℃ or higher tempera ture,the local structure around Ni atoms in resultant product is similar to that in Ni foil. It was found that the catalytic ac-tivity of nanocrystalline Ni3B for benzene hydrogenation is much higher than that of ultrafine NiB amorphous alloy or crystalline Ni. The result indicates that the active sites of nanocrystalline Ni3B for benzene hydrogenation are com-posed of both Ni and B with proper geometry configuration.

  14. Superconductivity in the amorphous phase of topological insulator Bi x Sb100-x alloys

    Science.gov (United States)

    Barzola-Quiquia, J.; Lauinger, C.; Zoraghi, M.; Stiller, M.; Sharma, S.; Häussler, P.

    2017-01-01

    In this work we investigated the electrical properties of rapidly quenched amorphous Bi x Sb{}100-x alloys in the temperature range of 1.2 K to 345 K. The resistance reveals that for a broad range of different compositions, including that for the topological insulator (TI), a superconducting state in the amorphous phase is present. After crystallization and annealing at an intermediate temperature, we found that in pure Bi and Bi x Sb{}100-x alloys with composition corresponding to the TI, the superconductivity persists, but the transition shifts to a lower temperature. The highest superconducting transition temperature {T}{{C}0} was found for pure Bi and those TI’s, with a shift to low temperatures when the Sb content is increased. After annealing at a maximum temperature of T = 345 K, the samples are non-superconducting within the experimental range and the behavior changes from semiconducting-like for pure Bi, to metallic-like for pure Sb. Transition temperature {T}{{C}0} of the amorphous Bi x Sb{}100-x alloys have been calculated in the BCS-Eliashberg-McMillan framework, modified for binary alloys. The results can explain the experimental results and show that amorphous Bi x Sb{}100-x exhibits a strong to intermediate electron-phonon coupling.

  15. 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.

  16. Molecular dynamics simulation of amorphous segregation inAg-Rh alloys

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jingxiang; BIAN Xiufang

    2003-01-01

    Molecular dynamics simulation was carried out to investigate the liquid and amorphous microstructures of binary Agx-Rh(100-x) (x = 25, 50, 75 in atom fraction) alloys. Segregation feature of homogeneous interatomic binding of Ag-Rh liquid was found and probed, which can be retained into amorphous solids upon rapid cooling. Homogeneous binding may occur when the difference in the elemental atomic sizes is less than 10%. The icosahedra in liquid before the formation of amorphous state exist in a stable state and the network formed by 1551-clusters in molten alloys would inhibit the crystallization and diffusion of atoms. A higher degree of 155 1-clusters will be favorable to form metallic glasses.

  17. Amorphization Induced High Magneto-Caloric Effect of Gd55A120Ni25 Ternary Alloy

    Institute of Scientific and Technical Information of China (English)

    DING Ding; XIA Lei; YU Zhong-Hua; DONG Yuan-Da

    2008-01-01

    We report the amorphization induced high magneto-caloric effect (MCE) of recently developed Gd55Al15Ni30 bulk metallic glass (BMG). The magnetic properties of the Gd55Al15Ni30 BMG are investigated in comparison with that of its crystalline counterpart. It is found that amorphization can increase the saturation magnetization and decrease the hysteresis of Gd55Al15Ni30 alloys, which indicate the possible enhancement of MCE. The magnetic entropy changes and the refrigerant capacity of the BMG as well as the crystalline samples is calculated directly from isothermal magnetic measurements. The results show the amorphization induced high MCE of the alloy and the excellent refrigerant efficiency of Gd55A115Ni30 bulk metallic glass.

  18. Formation and structure of V-Zr amorphous alloy thin films

    KAUST Repository

    King, Daniel J M

    2015-01-01

    Although the equilibrium phase diagram predicts that alloys in the central part of the V-Zr system should consist of V2Zr Laves phase with partial segregation of one element, it is known that under non-equilibrium conditions these materials can form amorphous structures. Here we examine the structures and stabilities of thin film V-Zr alloys deposited at room temperature by magnetron sputtering. The films were characterized by X-ray diffraction, transmission electron microscopy and computational methods. Atomic-scale modelling was used to investigate the enthalpies of formation of the various competing structures. The calculations confirmed that an amorphous solid solution would be significantly more stable than a random body-centred solid solution of the elements, in agreement with the experimental results. In addition, the modelling effort provided insight into the probable atomic configurations of the amorphous structures allowing predictions of the average distance to the first and second nearest neighbours in the system.

  19. A resistivity study of crystallization of some FeNiB-based amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Riontino, G.; Baricco, M.; Marino, F.

    1986-07-01

    The amorphous-to-crystalline transformations has been studied extensively since the discovery of glassy alloys. Many physical and chemical properties vary drastically in the course of thermal treatments leading to crystallization, and this seems to be a limit to the applications of these materials. Nevertheless, the intermediate metastable crystallization products, in some cases, or the final crystalline phases show, in several cases, interesting properties. Among the very large number of amorphous systems up to now investigated, Metglas 2826 and 2826A (from Allied Chemical) have received particular attention, because of their magnetic and anticorrosive properties. In the present paper the authors discuss some results on amorphous alloys having compositions similar to the commercial ones and, in particular, they discuss the influence of phosphorus and chromium content on the electrical resistivity variations during thermal treatments up to crystallization.

  20. 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.

  1. Copper-Silicon-Magnesium Alloys for Latent Heat Storage

    Science.gov (United States)

    Gibbs, P. J.; Withey, E. A.; Coker, E. N.; Kruizenga, A. M.; Andraka, C. E.

    2016-12-01

    The systematic development of microstructure, solidification characteristics, and heat of solidification with composition in copper-silicon-magnesium alloys for thermal energy storage is presented. Differential scanning calorimetry was used to relate the thermal characteristics to microstructural development in the investigated alloys and clarifies the location of one of the terminal three-phase eutectics. Repeated thermal cycling highlights the thermal storage stability of the transformation through multiple melting events. Two near-terminal eutectic alloys display high enthalpies of solidification, relatively narrow melting ranges, and stable transformation hysteresis behaviors suited to thermal energy storage.

  2. Annealing temperature effect on microstructure, magnetic and microwave properties of Fe-based amorphous alloy powders

    Energy Technology Data Exchange (ETDEWEB)

    He Jinghua; Wang Wei; Wang Aimin [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Guan Jianguo, E-mail: guanjg@whut.edu.cn [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

    2012-09-15

    Fe{sub 74}Ni{sub 3}Si{sub 13}Cr{sub 6}W{sub 4} amorphous alloy powders were annealed at different temperature (T) for 1.5 h to fabricate the corresponding amorphous and nanocrystalline powders. The influences of T on the crystalline structure, morphology, magnetic and microwave electromagnetic properties of the resultant samples were investigated via X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer and vector network analyzer. The results show that the powder samples obtained at T of 650 Degree-Sign C or more are composed of lots of ultra-fine {alpha}-Fe(Si) grains embedded in an amorphous matrix. When T increases from 350 to 750 Degree-Sign C, the saturated magnetization and coercivity of the as-annealed powder samples both increase monotonously whereas the relative real permittivity shows a minimal value and the relative real permeability shows a maximal value at T of 650 Degree-Sign C. Thus the powder samples annealed at 650 Degree-Sign C show optimal reflection loss under -10 dB in the whole C-band. These results here suggest that the annealing heat treatment of Fe-based amorphous alloy is an effective approach to fabricate high performance microwave absorber with reasonable permittivity and large permeability simultaneously via adjusting T. - Highlights: Black-Right-Pointing-Pointer The annealing temperature effect of Fe-based amorphous alloy was studied. Black-Right-Pointing-Pointer Fe-based amorphous and nanocrystalline alloy has a good absorbing property in C-band. Black-Right-Pointing-Pointer There exists a correspondence between microwave properties and microstructure.

  3. Magneto-caloric effect of a Gd50Co50 amorphous alloy near the freezing point of water

    Directory of Open Access Journals (Sweden)

    L. Xia

    2015-09-01

    Full Text Available In the present work, we report the magneto-caloric effect (MCE of a binary Gd50Co50 amorphous alloy near the freezing temperature of water. The Curie temperature of Gd50Co50 amorphous ribbons is about 267.5 K, which is very close to room temperature. The peak value of the magnetic entropy change (-ΔSmpeak and the resulting adiabatic temperature rise (ΔTad. of the Gd50Co50 amorphous ribbons is much higher than that of any other amorphous alloys previously reported with a Tc near room temperature. On the other hand, although the -ΔSmpeak of Gd50Co50 amorphous ribbons is not as high as those of crystalline alloys near room temperature, its refrigeration capacity (RC is still much larger than the RC values of these crystalline alloys. The binary Gd50Co50 amorphous alloy provides a basic alloy for developing high performance multi-component amorphous alloys near room temperature.

  4. Wear mechanism of electrodeposited amorphous Ni-Fe-P alloys

    Institute of Scientific and Technical Information of China (English)

    高诚辉; 赵源

    2004-01-01

    The wear mechanism of amorphous Ni-Fe-P coating was discussed. The wear resistance of the amor phous Ni-Fe-P coatings was tested on a Timken wear apparatus, and the wear track of the amorphous Ni-Fe-P coat ings as-deposited and heated at various temperatures was observed by SEM. The results show that the wear resistthe coating will change with the heating temperature increasing from pitting+plowing at 200 ℃ to pitting at 400 ℃,and to plowing at 600 ℃. The pits on the worn surface of the amorphous Ni-Fe-P coating result from the tribo-fatigue fracture. The cracks of spalling initiate at pits and propagate at certain angle with the sliding direction on sur face, and then extend into sub-surface along the poor P layers or the interface between layers. Finally under repeated action of the stress in the rubbing process the cracks meet and the debris forms. The generation of the pits and spal-ling is related with the internal stress, brittleness and layer structure of the amorphous Ni-Fe-P coating.

  5. Properties of amorphous FeCoB alloy particles (abstract)

    DEFF Research Database (Denmark)

    Charles, S. W.; Wells, S.; Meagher, A.

    1988-01-01

    -ray diffraction. Magnetic measurements of the saturation magnetization, coercivity, and remanence of the particles have been measured. The transition from the amorphous-to-crystalline state has been studied using differential scanning calorimetry (DSC) and thermomagnetometry up to a temperature of 450 °C (see Fig...

  6. Amorphization of Ni61 Nb39 Alloy by Laser Surface Treatment

    Institute of Scientific and Technical Information of China (English)

    Zhong-xiang LU; Ran LI; Yan LI; Tao ZHANG

    2016-01-01

    The surface of Ni61 Nb39 crystalline ingot was treated by laser surface melting with different processing parame-ters.A fully amorphous layer with a thickness of approximately 10 μm could be produced on the top surface under optimal parameters.An amorphous-crystalline composite layer with the depth from 10 to 50 μm,consisting of amor-phous matrix and intermetallic phases of Ni3 Nb and Ni6 Nb7 ,could be formed.The micro-hardness (about 831 HV) of the treated surface was remarkably improved by nearly 100% compared with the value of the crystalline substrate caused by the formation of the fully amorphous structure.A finite volume simulation was adopted to evaluate the temperature distribution in the laser-affected zone of Ni6 1 Nb3 9 alloys and to reveal the mechanism of glass formation in the laser-affected zone.

  7. 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.

  8. Mg amorphous alloys for biodegradable implants; Ligas amorfas de magnesio utilizadas em implantes consumiveis

    Energy Technology Data Exchange (ETDEWEB)

    Danez, G.P., E-mail: gabidanez@hotmail.co [Universidade Federal de Sao Carlos (PPG-CEMUFSCar), SP (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Koga, G.Y.; Tonucci, S.; Bolfarini, C.; Kiminami, C.S.; Botta Filho, W.J. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    The use of implants made from amorphous alloys magnesium-based with additions of zinc and calcium are promising. Properties such as biocompatibility, low density, high mechanical strength, low modulus (as compared to alloys such as stainless steel and titanium), corrosion resistance and wear resistance make it attractive for use in implants. Moreover, the by-products of corrosion and wear are not toxic and may contribute to fixation. Aiming to understand the tendency of this amorphous ternary (Mg-Zn-Ca) and expand the information about this system, this work involved the use of the topological criterion of instability ({lambda}) and the criterion of electronegativity ({Delta}e) to the choice of compositions. The alloys were processed into wedge-shaped and analyzed structurally and in X-ray diffraction and scanning electron microscopy. (author)

  9. Surface modification of Zr-based bulk amorphous alloys by using ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, M., E-mail: miqbalchishti@yahoo.com [Physics Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), P.O. Nilore, Islamabad, 45650 (Pakistan); Qayyum, A.; Akhter, J.I. [Physics Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), P.O. Nilore, Islamabad, 45650 (Pakistan)

    2011-02-10

    Research highlights: > Ion irradiations of two multicomponent bulk amorphous alloys have been done. Ion irradiation produced crystalline phases in the amorphous matrix due to which mechanical properties enhanced. Considerable increase in hardness and elastic modulus was observed. The results are verified, authentic and confirmed. - Abstract: Surfaces of the [Zr{sub 0.65}Cu{sub 0.18}Ni{sub 0.09}Al{sub 0.08}]{sub 98}M{sub 2} (M = Er and Gd) bulk amorphous alloys were modified by irradiation with energetic singly charged argon (Ar{sup +}) ions. Samples of both the alloys were irradiated with 2.17 x 10{sup 17} argon ions of 10 keV energy. As cast and ion irradiated samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Mechanical properties like Vicker's hardness, nanohardness, elastic modulus and elastic recovery were measured. Considerable increase in elastic modulus and hardness was observed because of ion irradiation in these alloys. The ion irradiated samples of the [Zr{sub 0.65}Cu{sub 0.18}Ni{sub 0.09}Al{sub 0.08}]{sub 98}Er{sub 2} alloy showed better properties as compared to [Zr{sub 0.65}Cu{sub 0.18}Ni{sub 0.09}Al{sub 0.08}]{sub 98}Gd{sub 2} alloy. CuZr{sub 2} phase was detected in ion irradiated alloys by XRD and confirmed by EDS. The range of Ar{sup +} ions was found to be approximately 9.3 {+-} 5.4 nm in both alloys.

  10. 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...

  11. 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.

  12. 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%.

  13. 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.

  14. 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.……

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  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. 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).

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Amorphous metallic alloys for oxygen reduction reaction in a polymer electrolyte membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Huerta, R.; Guerra-Martinez, I.; Lopez, J.S. [Inst. Politecnico Nacional, ESIQIE, Mexico City (Mexico). Lab. de Electroquimica; Pierna, A.R. [Basque Country Univ., San Sebastian (Spain). Dept. of Chemical Engineering and Environment; Solorza-Feria, O. [Inst. Politenico Nacional, Centro de Investigacion y de Estudios Avanzados, Mexico City (Mexico). Dept. de Quimica

    2010-07-15

    Direct methanol fuel cells (DMFC) and polymer electrolyte membrane fuel cells (PEMFC) represent an important, environmentally clean energy source. This has motivated extensive research on the synthesis, characterization and evaluation of novel and stable oxygen reduction electrocatalysts for the direct four-electron transfer process to water formation. Studies have shown that amorphous alloyed compounds can be used as electrode materials in electrochemical energy conversion devices. Their use in PEMFCs can optimize the electrocatalyst loading in the membrane electrode assembly (MEA). In this study, amorphous metallic PtSn, PtRu and PtRuSn alloys were synthesized by mechanical milling and used as cathodes for the oxygen reduction reaction (ORR) in sulphuric acid and in a single PEM fuel cell. Two different powder morphologies were observed before and after the chemical activation in a hydrofluoric acid (HF) solution at 25 degrees C. The kinetics of the ORR on the amorphous catalysts were investigated. The study showed that the amorphous metallic PtSn electrocatalyst was the most active of the 3 electrodes for the cathodic reaction. Fuel cell experiments were conducted at various temperatures at 30 psi for hydrogen (H{sub 2}) and at 34 psi for oxygen (O{sub 2}). MEAs made of Nafion 115 and amorphous metallic PtSn dispersed on carbon powder in a PEMFC had a power density of 156 mW per cm{sup 2} at 0.43V and 80 degrees C. 12 refs., 1 tab., 5 figs.

  11. 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.

  12. Amorphous metal nanocrystallization changes due to mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Bonastre, Jordi; Escoda, Lluisa; Sunol, Joan Josep [GRMT, EPS, Campus Montilivi s/n, Girona University, 17071 Girona (Spain); Hernando, Blanca; Sanchez-Llamazares, Jose Luis [Dept. Fisica, Univ. Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain)

    2010-11-15

    A detailed knowledge of the temperature dependence of the transformed fraction is an essential issue in the development of nanomaterials and the control of their microstructure. In technical applications, the thermal stability of nanocrystalline alloys is a problem of fundamental interest in order to determine the useful working temperature ranges. The transformation diagrams give information relative to the stability and applicability of these materials. In this work the temperature-heating rate transformation diagram of a Co-rich alloy obtained by mechanical alloying or rapid solidification was built using an isoconversional approach in order to obtain a good prediction even for low transformed fractions (0.1). (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Electrocatalytic properties of Ni-Zr based amorphous and nanocrystalline alloys

    Energy Technology Data Exchange (ETDEWEB)

    Baricco, M.; Minichilli, F. [Torino Univ. (Italy). Dipt. di Chimica; Angelini, E.; Spriano, S.; Rosalbino, F.; Spinelli, P.; Antonione, C. [Dipt. di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino (Italy)

    1997-12-31

    The electrocatalytic activity of Ni-Zr based crystalline and amorphous alloys has been tested for the hydrogen evolution reaction. Ni{sub 36}Zr{sub 64} and Ni{sub 27}Zr{sub 48}Al{sub 25} amorphous alloys have been produced in ribbon form by rapid solidification. The amorphous-to-crystalline transformation has been followed by DSC, XRD and TEM. The various samples have been subjected to electrochemical tests by means of cathodic polarization curves in 1 M KOH at 25 C and the obtained exchange current density has been taken as a measure of catalytic efficiency. Surface activation treatments have been performed by chemical etching in HF or by leaching in KOH and a morphological and compositional analysis of the surfaces has been performed by SEM/EDS. The electrochemical behaviour of pure elements (Ni and Zr) has also been considered for comparison. All the samples need a chemical pre-treatment in order to become active. A higher electrocatalytic activity has been observed for amorphous with respect to crystalline alloys with the same composition. For a nanocrystalline microstructure, obtained by partial crystallization of amorphous Zr{sub 64}Ni{sub 36}, an electrocatalytic efficiency comparable to that of the amorphous phase has been observed. Treatments with concentrated HF solutions enhance the electrocatalytic activity and this effect has been related to the formation of nanocrystalline Ni at the surfaces. The leaching of Zr{sub 48}Ni{sub 27}Al{sub 25} produces also small Ni particles owing to the dissolution of Al. (orig.) 15 refs.

  14. Effects of TM on stability of structure corresponding to prepeak of amorphous Al90TM5Ce5 Alloys

    Institute of Scientific and Technical Information of China (English)

    赵芳; 吴佑实

    2002-01-01

    X-ray diffraction and DSC were used to investigate the crystallization process of amorphous Al90Fe5Ce5 and Al90Ni5Ce5 alloys, and the stability of the structure corresponding to the prepeak. Both these amorphous alloys are crystallized by two stages. The stability of the structure corresponding to the prepeak has a large difference. The structure corresponding to the prepeak for amorphous Al90Fe5Ce5 alloy is more stable than the amorphous matrix. However, it is not stable for amorphous Al90Ni5Ce5 alloys during the first crystallization stage. The prepeak position of amorphous Al90Ni5Ce5 alloys is very close to that of amorphous Al90Fe5Ce5 alloys. It is estimated that the prepeak is also due to diffraction peak broadening caused by very fine quasi-crystalline structure and the structural unit is an icosahedral quasi-crystalline structure with Ni as the central atom. The large difference of the stability of the structure corresponding to the prepeak is likely caused by different stability of the quasi-crystalline structure.

  15. Developments in the Ni-Nb-Zr amorphous alloy membranes. A review

    Energy Technology Data Exchange (ETDEWEB)

    Sarker, S.; Chandra, D. [University of Nevada, Materials Science and Engineering, Reno, NV (United States); Hirscher, M. [Max-Planck-Institut fuer Intelligente Systeme, Stuttgart (Germany); Dolan, M.; Viano, D. [CSIRO, QCAT, Energy, Pullenvale, QLD (Australia); Isheim, D. [Northwestern University, Materials Science and Engineering, Evanston, IL (United States); Wermer, J. [Los Alamos National Laboratory, Los Alamos, NM (United States); Baricco, M. [University of Turin, Department of Chemistry and NIS, Turin (Italy); Udovic, T.J. [National Institute of Standards and Technology, Gaithersburg, MD (United States); Grant, D. [University of Nottingham, Nottingham (United Kingdom); Palumbo, O.; Paolone, A. [CNR-ISC, U.O.S. La Sapienza, Rome (Italy); Cantelli, R. [University of Rome, La Sapienza, Roma (Italy)

    2016-03-15

    Most of the global H{sub 2} production is derived from hydrocarbon-based fuels, and efficient H{sub 2}/CO{sub 2} separation is necessary to deliver a high-purity H{sub 2} product. Hydrogen-selective alloy membranes are emerging as a viable alternative to traditional pressure swing adsorption processes as a means for H{sub 2}/CO{sub 2} separation. These membranes can be formed from a wide range of alloys, and those based on Pd are the closest to commercial deployment. The high cost of Pd (USD ∝31,000 kg{sup -1}) is driving the development of less-expensive alternatives, including inexpensive amorphous (Ni{sub 60}Nb{sub 40}){sub 100-x} Zr{sub x} alloys. Amorphous alloy membranes can be fabricated directly from the molten state into continuous ribbons via melt spinning and depending on the composition can exhibit relatively high hydrogen permeability between 473 and 673 K. Here we review recent developments in these low-cost membrane materials, especially with respect to permeation behavior, electrical transport properties, and understanding of local atomic order. To further understand the nature of these solids, atom probe tomography has been performed, revealing amorphous Nb-rich and Zr-rich clusters embedded in majority Ni matrix whose compositions deviated from the nominal overall composition of the membrane. (orig.)

  16. Preparation of casting alloy ZL101 with coarse aluminum-silicon alloy

    Institute of Scientific and Technical Information of China (English)

    YOU Jing; WANG Yao-wu; FENG Nai-xiang; YANG Ming-sheng

    2008-01-01

    The coarse Al-Si alloy produced by carbothermal reduction of aluminous ore contains 55% Al, 25% Si and some impurities. The main impurities are slag and iron. The process of manufacturing casting Al-Si alloy ZL101 with the coarse Al-Si alloy was studied. The phase constitution and microstructure of the coarse Al-Si alloy, slag and ZL101 were examined by X-ray diffractometry and scanning electron microscopy. The results show that the content of silicon and iron in the casting alloy reduces with the increase of the dosage of purificant and manganese, but increases with the rise of filtering temperature. It is found that casting Al-Si alloy conforming to industrial standard can be produced after refining by using purificant, and removing iron by using manganese and added magnesium.

  17. Corrosion resistance of amorphous and crystalline Pd40Ni40P20 alloys in aqueous solutions

    DEFF Research Database (Denmark)

    Wu, Y.F.; Chiang, Wen-Chi; Chu, J.;

    2006-01-01

    The corrosion behaviors of amorphous and crystalline Pd40Ni40P20 alloys in various aqueous solutions are reported in this paper. The corrosion resistance of crystalline (annealed) Pd40Ni40P20 is better than that of amorphous Pd40Ni40P20 in various corrosive solutions, due to crystalline Pd40Ni40P20...... and mainly consists of inert Pd5P2, NI3P, Ni2Pd2P and noble Pd phases. These inert and noble properties result in a higher corrosion resistance in crystalline Pd40Ni40P20....

  18. Research on stable, high-efficiency, amorphous silicon multijunction modules

    Energy Technology Data Exchange (ETDEWEB)

    Catalano, A.; Bennett, M.; Chen, L.; D' Aiello, R.; Fieselmann, B.; Li, Y.; Newton, J.; Podlesny, R.; Yang, L. (Solarex Corp., Newtown, PA (United States). Thin Film Div.)

    1992-08-01

    This report describes work to demonstrate a multijunction module with a stabilized'' efficiency (600 h, 50{degrees}C, AM1.5) of 10.5%. Triple-junction devices and modules using a-Si:H alloys with carbon and germanium were developed to meet program goals. ZnO was used to provide a high optical transmission front contact. Proof of concept was obtained for several important advances deemed to be important for obtaining high (12.5%) stabilized efficiency. They were (1) stable, high-quality a-SiC:H devices and (2) high-transmission, textured ZnO. Although these developments were not scaled up and included in modules, triple-junction module efficiencies as high as 10.85% were demonstrated. NREL measured 9.62% and 9.00% indoors and outdoors, respectively. The modules are expected to lose no more than 20% of their initial performance. 28 refs.

  19. 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.

  20. Magnetocaloric effect in amorphous and partially crystallized Fe40Ni38Mo4B18 alloys

    Directory of Open Access Journals (Sweden)

    T. Thanveer

    2016-05-01

    Full Text Available A study of magnetocaloric effect in amorphous and partially crystallized Fe40Ni38Mo4B18 alloys is reported. Amorphous Fe40Ni38Mo4B18, near its magnetic ordering temperature (600K showed a magnetic entropy change ΔSM of 1.1 J/KgK and a relative cooling power of 36J/Kg in a field change of 10 kOe. Amorphous samples were partially crystallized by annealing at 700 K at different time intervals. Partially crystallized samples showed two distinct magnetic ordering temperature, one corresponding to the precipitated FeNi nanocrystals and the other one corresponding to the boron rich amorphous matrix. Magnetic ordering temperature of the residual amorphous matrix got shifted to the lower temperatures on increasing the annealing duration. Partially crystallised samples showed a magnetic entropy change of about 0.27J/kgK near the magnetic ordering temperature of the amorphous matrix (540K in a field change of 10 kOe. The decrease in ΔSM on partial crystallisation is attributed to the biphasic magnetic nature of the sample.

  1. 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.

  2. 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).

  3. 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

  4. 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 (

  5. Hard rhenium–boron–cobalt amorphous alloys with a wide supercooled liquid region

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jianfeng, E-mail: jfwang316@zzu.edu.cn [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Zhu, Shijie; Wang, Liguo; Guan, Shaokang [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Li, Ran; Zhang, Tao [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

    2015-10-01

    Novel Re–B–Co amorphous alloys with compositions of Re{sub 65−x}B{sub 35}Co{sub x} (at%, x=25, 30, 35, 40, 45, and 50) were fabricated by single-roller melt spinning. These alloys were found to exhibit a clear glass transition phenomenon. The width of supercooled liquid region (ΔT{sub x}) is in the range of 52–71 K. Such a large ΔT{sub x} allows us to produce amorphous alloy bulks by thermoplastic forming. The Vickers hardness is up to 19.10 GPa for the Re{sub 40}B{sub 35}Co{sub 25} alloy, which is close to that reported for some hard covalent crystals. Thus, the present alloys with a combination of large ΔT{sub x} and high hardness are expected to be used as a new type of structural materials. Furthermore, the relationships of hardness with glass transition temperature and Young's modulus were also discussed.

  6. High-strength Zr-based bulk amorphous alloys containing nanocrystalline and nanoquasicrystalline particles

    Directory of Open Access Journals (Sweden)

    A Inoue, C Fan, J Saida and T Zhang

    2000-01-01

    Full Text Available It was recently found that the addition of special elements leading to the deviation from the three empirical rules for the achievement of high glass-forming ability causes new mixed structures consisting of the amorphous phase containing nanoscale compound or quasicrystal particles in Zr–Al–Ni–Cu–M (M=Ag, Pd, Au, Pt or Nb bulk alloys prepared by the copper mold casting and squeeze casting methods. In addition, the mechanical strength and ductility of the nonequilibrium phase bulk alloys are significantly improved by the formation of the nanostructures as compared with the corresponding amorphous single phase alloys. The composition ranges, formation factors, preparation processes, unique microstructures and improved mechanical properties of the nanocrystalline and nanoquasicrystalline Zr-based bulk alloys are reviewed on the basis of our recent results reported over the last two years. The success of synthesizing the novel nonequilibrium, high-strength bulk alloys with good mechanical properties is significant for the future progress of basic science and engineering.

  7. FORCED VOLUME MAGNETOSTRICTION IN AMORPHOUS Co-Si-B ALLOYS

    OpenAIRE

    Baczewski, L.

    1985-01-01

    The room temperature forced volume magnetostriction constant σω/σH was calculated from the field dependence of saturation magnetostriction for the magnetic field parallel and perpendicular to the length of ribbons. Compositional dependences of forced volume magnetostriction - both as a function of Co and Si content - were determined. On the basis of the thermodynamical relations the pressure dependence of Curie temperature for the studied alloys from σω/σH measurements was derived.

  8. Oxygen Behavior in Bulk Amorphous Zr-base Alloy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Bulk Zr55Al10Ni5Cu30 metallic glass plates with a dimension of 85 mm×35mm×4 mm and a complicated plate werefabricated by injecting casting method using spongy zirconium and industrial purity aluminum, nickel and copper asraw materials. It was shown that the holding time of liquid metals at elevated temperatures had a great influence onthe oxygen content of the plates due to the contamination resulting from the atmosphere. Increasing holding timeresulted in the increase of oxygen content in the injected alloy. The glass transition temperatures of the bulk metallicglass plates are higher than that reported in the literature and crystallization temperature is lower for the one withhigher oxygen content at the same heating rate. The extension of the undercooled liquid region △Tx reaching about87 K is 3 K higher than that previously reported and 26 K higher than that with oxygen content of 0.076 wt pct forthe one with oxygen content as high as 0.065 wt pct. Therefore the oxygen content of the alloy has a significantinfluence on the glass forming ability and thermal stability of bulk metal glass. It is suggested that direct correlationbetween high glass forming ability and large △Tx is only valid for a well-defined Iow oxygen concentration or has tobe reconsidered by incorporating oxygen as an additional alloying element.

  9. Hydrogen diffusion in Zr35Ni55V10 amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    CHENG Xiao-ying; WAHG Fang

    2007-01-01

    Hydrogen diffusion in Zr35Ni55V10 amorphous alloy was measured by chronopotentiometry. The results show that at lower molar ratio of hydrogen (x<0.06, x=n(H)/n(M)), the diffusivity of hydrogen increases rapidly with increasing the molar ratio of hydrogen. However, when x(H)>0.1, the diffusivity of hydrogen decreases slightly with increasing the molar ratio of hydrogen, which is similar to the change in crystalline alloy. It is proposed that hydrogen atoms mainly occupy the sites corresponding to tetrahedra with 4 Zr atoms at lower molar ratio of hydrogen. When the molar ratio of hydrogen is higher, the additional hydrogen atoms are in sites with higher energy and these sites in amorphous state are similar to these in crystalline states.

  10. Chemical preparation and investigation of Fe-P-B ultrafine amorphous alloy particles

    Institute of Scientific and Technical Information of China (English)

    胡征; 吴勇; 范以宁; 颜其洁; 陈懿

    1997-01-01

    A series of Fe-P-B ultrafine amorphous alloy particles has been prepared by the chemical reduction method The composition and size of the particles have been effectively adjusted.Mossbauer spectroscopy in addition to sonic other techniques has been used to investigate the reaction process,the factors that influence the preparation,the crystallization of the particles,and the interactions between the components within them.The results indicate that the co-deposition of iron,phosphorus and boron atoms in the solution at room temperature forms Fe-P-B amorphous alloy particles,and a preferential bonding of Fe-P bond to Fe-B one exists in the particles.

  11. Nanocrystallization of Al80Ni6Y8Co4Cu2 amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    边赞; 孙玉峰; 何国; 陈国良

    2001-01-01

    Nanoscale α(Al) phase with a size of 15  nm was precipitated from Al80Ni6Y8Co4Cu2 amorphous ribbons after annealing. The microhardness increases with increasing the crystallization volume fraction of nanoscale α(Al) phase. The combination effect of alloy strengthening and dispersion strengthening is main reason for the increase of microhardness. The formation of intermetallic compound (Al3Ni) with a small volume fraction leads to the decrease of microhardness resulting from the depletion of the solute elements in the residual amorphous matrix and the weakening of alloy strengthening. With increasing the volume fraction of intermetallic compound, microhardness increases again due to dispersion strengthening of nanoscale intermetallic compound.

  12. Mossbauer studies of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy

    DEFF Research Database (Denmark)

    Jiang, Jianzhong

    1996-01-01

    This paper reports a Mossbauer study of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy between 10 and 673 K. The Curie temperature Tc is found to be 620-+ 1 K. The temperature dependence of the reduced average hyperfine field can be explained on the basis of Handrich's model of amorphous ferromagnetism...

  13. Amorphous Fe-B alloys in B-Fe-Ag multilayers studied by magnetization and Mössbauer measurements

    DEFF Research Database (Denmark)

    Kiss, L. F.; Balogh, J.; Bujdoso, L.;

    2011-01-01

    –B layers, which depends on the thickness of the Ag barrier layers. The magnetization measurements indicate ferromagnetic behaviour of the ultra-thin amorphous layers with the presence of less than 10% superparamagnetic moments for x = 5 and 10. The average B concentration of the amorphous Fe–B alloy...

  14. Preparation of Uniform Ni-B Amorphous Alloy Catalyst on CNTs and its Performance for Acetylene Selective Hydrogenation

    Institute of Scientific and Technical Information of China (English)

    Chang Yuan HU; Feng Yi LI; Rong Bin ZHANG; Li HUA

    2006-01-01

    Uniform Ni-B amorphous alloys about 14 nm have been prepared on CNTs-A support,named Ni-B/CNTs-A. In comparison with the Ni-B/CNTs amorphous catalyst, Ni-B/CNTs-A showed higher nickel loading, determined by ICP and better catalytic activity and ethylene selectivity in the acetylene hydrogenation reaction.

  15. Icosahedral medium-range orders and backbone formation in an amorphous alloy

    Science.gov (United States)

    Lee, Mirim; Kim, Hong-Kyu; Lee, Jae-Chul

    2010-12-01

    Analyses of metallic amorphous solids constructed using molecular dynamics (MD) simulations have demonstrated that individual short-range orders (SROs) are linked with neighboring SROs and form various medium-range orders (MROs). These MROs have been observed to have different structural stability depending on their linking patterns. On the basis of the assessment of the structural stability of various MROs, we propose new types of structural organization, namely, icosahedral medium-range orders (I-MROs) and their extended-range order that forms the backbone of amorphous solids. We also discuss why the atomic-scale structure of an amorphous alloy can be more appropriately described in terms of I-MROs, rather than by the degree of short-range ordering as characterized by the fractions of SROs.

  16. Hydrogen-induced phase separation of an amorphous cerium-copper alloy

    Energy Technology Data Exchange (ETDEWEB)

    Felsch, W.; Volkmer, H.; Schneider, S.; Kohlmann, J.; Regenbrecht, A.; Samwer, K. (Goettingen Univ. (Germany, F.R.). 1. Physikalisches Inst.)

    1989-01-01

    X-ray diffraction and differential scanning calorimetry show that the amorphous alloy Ce{sub 26}Cu{sub 74} decomposes gradually into a two-phase amorphous structure by the absorption of hydrogen. There is evidence that these phases are close, in their metallic composition, to the intermetallic compounds CeCu{sub 2} and CeCu{sub 6}. Hydrogen is absorbed almost entirely by the amorphous phase related to CeCu{sub 2}. The electrical resistivity increases steeply by a factor of 3 near H/M=0.4. While the magnetic susceptibility shows a small reduction only on the spin-glass temperature due to hydrogen absorption, the low-temperature specific heat is substantially modified, indicating a considerably diminished exchange coupling between the Ce-4f and conduction electrons. (orig.).

  17. Preparation and Characterization of Amorphous Layer on Aluminum Alloy Formed by Plasma Electrolytic Deposition (PED)

    Institute of Scientific and Technical Information of China (English)

    GUAN Yong-jun; XIA Yuan

    2004-01-01

    In this investigation, protective layers were formed on aluminum substrate by Plasma Electrolytic Deposition (PED) using sodium silicate solution. The relation between the thickness of the layer and process time were studied. XRD,SEM, EDS were used to study the layer's structure, composition and micrograph. The results show that the deposited layers are amorphous and contain mainly oxygen, silicon, and aluminum. The possible formation mechanism of amorphous [Al-Si-O] layer was proposed: During discharge periods, Al2O3 phase of the passive film and SiO32-near the substrate surface are sintered into xSiO2(1-x)Al2O3 and then transformed into amorphous [Al-Si-O] phase.

  18. Thermal relaxation of magnetic clusters in amorphous Hf_{57}Fe_{43} alloy

    OpenAIRE

    Pajic, Damir; Zadro, Kreso; Ristic, Ramir; Zivkovic, Ivica; Skoko, Zeljko; Babic, Emil

    2006-01-01

    The magnetization processes in binary magnetic/nonmagnetic amorphous alloy Hf_{57}Fe_{43} are investigated by the detailed measurements of magnetic hysteresis loops, temperature dependence of magnetization, relaxation of magnetization and magnetic ac susceptibility, including a nonlinear term. Blocking of magnetic moments at lower temperatures is accompanied with the slow relaxation of magnetization and magnetic hysteresis loops. All of the observed properties are explained with the superpara...

  19. A Novel Ultrafine Ru-B Amorphous Alloy Catalyst for Glucose Hydrogenation to Sorbitol

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    An ultrafine Ru-B amorphous alloy catalyst was prepared by chemical reduction with KBH4 in aqueous solution, which exhibited perfect selectivity to sorbitol (~100%) and very high activity during the liquid phase glucose hydrogenation, much higher than the corresponding crystallized Ru-B, the pure Ru powder, and Raney Ni catalysts. The correlation of the catalytic activity to both the structural and surface electronic characteristics was discussed briefly.

  20. Influence of the Quenching Rate on the Structure and Magnetic Properties of the Fe-Based Amorphous Alloy

    Directory of Open Access Journals (Sweden)

    Nabiałek M.

    2016-03-01

    Full Text Available This paper presents the results of investigations into the structure, microstructure and magnetic properties of Fe61Co10Y8W1B20 amorphous alloy. The alloy samples were in two physical forms: (1 plates of approximate thickness 0.5 mm (so-called bulk amorphous alloys and (2 a ribbon of approximate thickness 35 μm (so-called classic amorphous alloy. The investigations comprised: X-ray diffractometry, Mössbauer spectrometry, transmission electron microscopy, and selected magnetic measurements; all of the investigations were carried out on samples in the as-quenched state. Analysis of the obtained SEM and TEM images, X-ray diffraction patterns, Mössbauer spectrometry results and measurements of the magnetisation in a high magnetic field facilitated collectively the detailed description of the structure of the investigated alloy, which was found to depend on the quenching speed.

  1. Amorphous Alloy Membranes Prepared by Melt-Spin methods for Long-Term use in Hydrogen Separation Applications

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Dhanesh; Kim, Sang-Mun; Adibhatla, Anasuya; Dolan, Michael; Paglieri, Steve; Flanagan, Ted; Chien, Wen-Ming; Talekar, Anjali; Wermer, Joseph

    2013-02-28

    Amorphous Ni-based alloy membranes show great promise as inexpensive, hydrogenselective membrane materials. In this study, we developed membranes based on nonprecious Ni-Nb-Zr alloys by adjusting the alloying content and using additives. Several studies on crystallization of the amorphous ribbons, in-situ x-ray diffraction, SEM and TEM, hydrogen permeation, hydrogen solubility, hydrogen deuterium exchange, and electrochemical studies were conducted. An important part of the study was to completely eliminate Palladium coatings of the NiNbZr alloys by hydrogen heattreatment. The amorphous alloy (Ni0.6Nb0.4)80Zr20 membrane appears to be the best with high hydrogen permeability and good thermal stability.

  2. Microstructure and properties of hydrophobic films derived from Fe-W amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    Song Wang; Yun-han Ling; Jun Zhang; Jian-jun Wang; Gui-ying Xu

    2014-01-01

    Amorphous metals are totally different from crystalline metals in regard to atom arrangement. Amorphous metals do not have grain boundaries and weak spots that crystalline materials contain, making them more resistant to wear and corrosion. In this study, amorphous Fe-W alloy films were first prepared by an electroplating method and were then made hydrophobic by modification with a water repellent (heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane. Hierarchical micro-nano structures can be obtained by slightly oxidizing the as-deposited alloy, accompanied by phase transformation from amorphous to crystalline during heat treatment. The mi-cro-nano structures can trap air to form an extremely thin cushion of air between the water and the film, which is critical to producing hydrophobicity in the film. Results show that the average values of capacitance, roughness factor, and impedance for specific surface areas of a 600°C heat-treated sample are greater than those of a sample treated at 500°C. Importantly, the coating can be fabricated on various metal substrates to act as a corrosion retardant.

  3. Structural relaxation in Fe(Co)SiAlGaPCB amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Borrego, J.M., E-mail: jmborrego@us.es [Dpto. Física de la Materia Condensada, Instituto de Ciencia de Materiales, C.S.I.C., Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Blázquez, J.S. [Dpto. Física de la Materia Condensada, Instituto de Ciencia de Materiales, C.S.I.C., Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Lozano-Pérez, S.; Kim, J.S. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Conde, C.F.; Conde, A. [Dpto. Física de la Materia Condensada, Instituto de Ciencia de Materiales, C.S.I.C., Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain)

    2014-01-25

    Highlights: • Structural relaxation of a Fe(Co)SiAlGaPCB amorphous alloys was studied by DSC. • Two relaxation times were use to fit the experimental values of different magnitudes. • HRTEM images suggest some medium range structural order in the amorphous. -- Abstract: The structural relaxation of multicomponent Fe(Co)SiAlGaPCB amorphous alloys was investigated calorimetrically for annealed samples over a wide temperature range below the glass transition temperature. Upon heating, the annealed samples exhibit an endothermic reaction (enthalpy relaxation) starting around the annealing temperature and continuing over a temperature range of about 50–140 K, that it is followed by a broad exothermic reaction. Changes in the heat flow curves with annealing temperature and time were analyzed. Experimental values of the overall enthalpy change, ΔH, the peak temperature of the difference in heat flow between the annealed and the as-quenched samples, T{sub p}, and Curie temperature, T{sub C}, were fitted by exponential functions including two relaxation times. Values of the two relaxation times are the same for different annealing temperatures regardless the considered property. Saturation values of these magnitudes show a linear dependence with the inverse of the annealing temperature. Tiny domains (2–3 nm in diameter) in the matrix observed by spherical aberration corrected high-resolution transmission electron microscopy could be attributed to some medium-range order in the atomic structure of these quenched alloys.

  4. New Approaches to the Computer Simulation of Amorphous Alloys: A Review

    Directory of Open Access Journals (Sweden)

    Fernando Alvarez-Ramirez

    2011-04-01

    Full Text Available In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties.

  5. Glass Forming Ability and Magnetic Property of Fe74Al4Sn2(PSiB)20 Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    CHEN Fei-fei; ZHOU Shao-xiong

    2004-01-01

    Amorphous ribbons of Fe74Al4Sn2(PSiB)20 alloy have been synthesized by melt spinning and axial design method. The thermal properties of the amorphous ribbons have been measured by differential scanning calorimeter (DSC). The DSC results show that the Fe74Al4Sn2P12Si4B4 amorphous alloy has relatively wider supercooled liquid region with a temperature interval of 40.38 K (ΔTx=Tx-Tg). The alloys with a higher phosphorous content in the metalloid element composition triangle of Fe74Al4Sn2(PSiB)20 have high glass forming ability. The amorphous alloys also show good magnetic properties in which Fe74Al4Sn2P6.67Si6.67B6.67 alloy has a large maximum permeability (μm), Fe78Al4Sn2P3Si3B10 alloy exhibits a high square ratio (Br/B10) and Fe74Al4Sn2P4Si12B4 shows a low core loss (P0.5/1.3T). High glass forming ability and good magnetic properties make Fe74Al4Sn2(PSiB)20 amorphous alloys valuable in future research.

  6. 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.

  7. 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)

  8. 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.

  9. 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.

  10. 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).

  11. 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.

  12. Skeletal Amorphous Nickel Based Alloy Catalysts and Magnetically Stabilized Bed Hydrogenation Technology

    Institute of Scientific and Technical Information of China (English)

    Min Enze

    2004-01-01

    Looking toward 21 century, smaller, cleaner and more energy-efficient technology will be an important trend in the development of chemical industry. In light of the new process requirements,a number of technology breakthroughs have occurred. One of these discoveries, the magnetically stabilized bed (MSB), has been proven a powerful process for intensification. Since its initial research in the late 1980's at Research Institute of Petroleum Processing (RIPP), the MSB technology and related catalytic material have matured rapidly through an intensive research and engineering program, primarily focused on its scaling-up.In this paper, we report the discovery of a novel skeletal amorphous nickel-based alloy and its use in magnetically stabilized bed (MSB). Amorphous alloys are new kinds of catalytic materials with short-range order but long-range disorder structure. In comparison with Raney Ni, the skeletal amorphous nickel-based alloy has an increasingly higher activity in the hydrogenation of reactive groups and compounds including nitro, nitrile, olefin, acetylene, aromatics, etc. Up to now, the amorphous nickel based alloy catalysts, SRNA series catalyst, one with high Ni ratio have been commercially manufactured more than four year. The new SRNA catalyst has been successfully implemented for hydrogenation applications in slurry reactor at Balin Petrochemical, SINOPEC.SRNA catalyst with further improvement in catalytic activity and stability raise its relative stability to 2~4 times of that of conventional catalyst. In the course of the long-cycle operation of SRNA-4 the excellent catalyst activity and stability can bring about such advantage as low reaction temperature, good selectivity and low catalyst resumption.Magnetically stabilized bed (MSB), a fluidized bed of magnetizable particles by applying a spatially uniform and time-invariant magnetic field oriented axially relative to the fluidizing fluid flow, had many advantages such as the low pressure drop and

  13. Crystallization Process of Heat-treated Amorphous Ni-P Alloy Coating

    Directory of Open Access Journals (Sweden)

    JIN Shi-wei

    2016-09-01

    Full Text Available Amorphous Ni-P alloy coatings were prepared on 45 carbon steel blocks using electrodeposition method. The thermal effect and quality change of Ni-P alloy coating under heating rate of 20℃/min were analyzed by differential scanning calorimetry (DSC and thermogravimetry (TG. Coatings were heat-treated at 300℃ and 400℃ for 0, 15, 30, 45, 60, 75min respectively, coating surface was characterized by scanning electron microscope (SEM, energy dispersive spectrometer (EDS, X-ray diffraction (XRD, microhardness tester. The result shows that the exothermic peak of Ni-P alloy coating appears at 284.8℃, coating quality and elemental composition are stable during the heat treatment. Crystallization process experiences a transformation of amorphous, metastable state NiP and Ni5P2, stable state Ni3P. The microhardness of coating can be improved remarkably after heat treatment, namely, the maximum value of heat-treated coating is 1036.56HV, which is nearly 2 times as hard as as-deposited coating. The corrosion resistance of heat-treated Ni-P alloy coating in NaCl solution is inferior to as-deposited coating, but they are both much better than 45 carbon steel substrate.

  14. Study of Critical Behavior in Amorphous Fe85Sn5Zr10 Alloy Ribbon

    Science.gov (United States)

    Han, L. A.; Hua, X. H.; Zhu, H. Z.; Yang, J.; Yang, H. P.; Yan, Z. X.; Zhang, T.

    2016-10-01

    We have investigated the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon prepared using a single-roller melt-spinning method. This alloy shows a second-order magnetic transition from paramagnetic to ferromagnetic (FM) state at the Curie temperature T C (˜306 K). To obtain more information on the features of the magnetic transition, a detailed critical exponent study was carried out using isothermal magnetization M (H, T) data in the vicinity of the T C. Modified Arrott plot, Kouvel-Fisher plot, Widom's scaling relation and critical isotherm analysis techniques were used to investigate the critical behavior of this alloy system around its phase transition point. The values of critical exponents determined using the above methods are self-consistent. The estimated critical exponents are fairly close to the theoretical prediction of the three-dimensional (3D) Heisenberg model, implying that short-range FM interactions dominate the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon.

  15. Study of Critical Behavior in Amorphous Fe85Sn5Zr10 Alloy Ribbon

    Science.gov (United States)

    Han, L. A.; Hua, X. H.; Zhu, H. Z.; Yang, J.; Yang, H. P.; Yan, Z. X.; Zhang, T.

    2017-02-01

    We have investigated the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon prepared using a single-roller melt-spinning method. This alloy shows a second-order magnetic transition from paramagnetic to ferromagnetic (FM) state at the Curie temperature T C (˜306 K). To obtain more information on the features of the magnetic transition, a detailed critical exponent study was carried out using isothermal magnetization M ( H, T) data in the vicinity of the T C. Modified Arrott plot, Kouvel-Fisher plot, Widom's scaling relation and critical isotherm analysis techniques were used to investigate the critical behavior of this alloy system around its phase transition point. The values of critical exponents determined using the above methods are self-consistent. The estimated critical exponents are fairly close to the theoretical prediction of the three-dimensional (3D) Heisenberg model, implying that short-range FM interactions dominate the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon.

  16. 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.

  17. Band gap tuning of amorphous Al oxides by Zr alloying

    DEFF Research Database (Denmark)

    Canulescu, Stela; Jones, N. C.; Borca, C. N.;

    2016-01-01

    minimum changes non-linearly as well.Fitting of the energy band gap values resulted in a bowing parameter of 2 eV. The band gap bowing of themixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction bandminimum of anodized Al2O3.......The optical band gap and electronic structure of amorphous Al-Zr mixed oxides, with Zr content ranging from4.8 to 21.9% were determined using vacuum ultraviolet (VUV) and X-ray absorption spectroscopy (XAS). Thelight scattering by the nano-porous structure of alumina at low wavelengths...... was estimated based on the Miescattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on Zr content deviatesfrom linearity and decreases from 7.3 eV for pure anodized Al2O3 to 6.45 eV for Al-Zr mixed oxide with Zrcontent of 21.9%. With increasing Zr content, the conduction band...

  18. Critical behavior of electrical resistivity in amorphous Fe–Zr alloys

    Indian Academy of Sciences (India)

    A Perumal

    2001-04-01

    Electrical resistivity (ρ) of the amorphous (a-)Fe100-Zr ( = 8.5, 9.5 and 10) alloys has been measured in the temperature range 77 to 300 K, which embraces the second-order magnetic phase transition at the Curie temperature point . Analysis of the resistivity data particularly in the critical region reveals that these systems have a much wider range of critical region compared to other crystalline ferromagnetic materials. The value of and specific heat critical exponent, has the same values as those determined from our earlier magnetic measurements. The value of for all the present investigated alloys are in close agreement with the values predicted for three-dimensional (3D) Heisenberg ferromagnet systems, which gives contradiction to the earlier results on similar alloys. It is observed from the analysis that the presence of quenched disorder does not have any influence on critical behavior.

  19. The corrosion resistance and neutron-absorbing properties of coatings based on amorphous alloys

    Science.gov (United States)

    Sevryukov, O. N.; Polyansky, A. A.

    2016-04-01

    The object of the present study was the corrosion-resistant amorphizing alloys with an increased content of boron for cladding the surface of metals, rapidly quenched alloys without boron for protective coatings on a high-boron cladding layer, as well as steel samples with a protective coating with a high content of boron and without boron. The aim of the work is to investigate the corrosion resistance of a coating in water at the temperature of 40 °C in conditions of an open access of oxygen for 1000 h, as well as the features of the microstructure of clad samples before and after the corrosion tests. New data on the corrosion resistance of Cr18Ni10Ti steel samples with a protective layer from a rapidly quenched alloy Ni-19Cr-10Si (in wt.%) on a high-boron coating have been obtained.

  20. Control and optimization of baths for electrodeposition of Co-Mo-B amorphous alloys

    Directory of Open Access Journals (Sweden)

    S. Prasad

    2000-12-01

    Full Text Available Optimization and control of an electrodeposition process for depositing boron-containing amorphous metallic layer of cobalt-molybdenum alloy onto a cathode from an electrolytic bath having cobalt sulfate, sodium molybdate, boron phosphate, sodium citrate, 1-dodecylsulfate-Na, ammonium sulfate and ammonia or sulfuric acid for pH adjustments has been studied. Detailed studies on bath composition, pH, temperature, mechanical agitation and cathode current density have led to optimum conditions for obtaining satisfactory alloy deposits. These alloys were found to have interesting properties such as high hardness, corrosion resistance, wear resistance and also sufficient ductility. A voltammetric method for automatic monitoring and control of the process has been proposed.

  1. 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)

  2. Soft magnetic and microstructural investigation in Fe-based amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nabiałek, Marcin, E-mail: nmarcell@wp.pl

    2015-09-05

    Highlights: • Samples were obtained using the injection-casting method. • The samples were manufactured in the shape of plates of the thickness 0.5 mm. • The amorphous and nanocrystalline structure was confirmed using XRD, SEM, TEM, CT. • Magnetic properties were analysed in terms of contents of the spin waves stiffness parameter b. - Abstract: In this paper, the results of investigations concerning Fe{sub 61}Co{sub 10}Y{sub 8}W{sub 1}B{sub 20} alloy are presented. The alloy samples were produced, using an injection-casting method, in the form of plates of approximate thickness 0.5 mm. Analysis of the results facilitates the description of structural transformations which occurred within the amorphous material as a result of isothermal annealing, the latter having been carried out under specified conditions. This thermal treatment led to the creation within the amorphous matrix of evenly distributed nanometric sized crystalline grains. The structure and microstructure of the samples in the as-quenched and nanocrystalline states were analysed by means of: X-ray diffractometry (XRD), scanning and transmission electron microscopy (SEM and TEM) and computer tomography (CT). The influence of the structural changes on the magnetic properties was studied using a vibrating sample magnetometer (VSM). Detailed analysis of the microstructure was performed on the ferromagnetic alloy samples with amorphous and nanocrystalline structure; this, in connection with the magnetic studies, facilitated full description of the influence of changes in the microstructure, and imperfections created during the production process, on the magnetic properties.

  3. Amorphous Structures in Laser Cladding of ZL111 Aluminum Alloy:Semi-quantitative Study by Differential Thermal Analysis (DTA)

    Institute of Scientific and Technical Information of China (English)

    LI Xianqin; CHENG Zhaogu; XIA Jin'an; XU Guoliang; LIANG Gongying

    2000-01-01

    This paper deals with amorphous structures in the laser cladding. ZL111 alloy is the substrate and Ni-Cr-Al alloy is sprayed on the substrate as the coating material. The coating is clad by a 5 kW transverse flow CO2 laser. The observation of SEM and TEM reveal that in the laser cladding there are amorphous structures of two different morphologies: one is space curved flake-like, and exists in the white web-like structures; the other is fir leaf-like, and exists in the grain-like structures. Differential thermal analysis (DTA) is used to semi-quantitatively determine the content of the amorphous structures. A relation is obtained between the content of amorphous structures and the dimensionless laser cladding parameter C. We also show the changes of the amorphous structures after annealing.

  4. Survey of BGFA Criteria for the Cu-Based Bulk Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    D. Janovszky

    2011-01-01

    Full Text Available To verify the effect of composition on the bulk glass forming ability (BGFA of Cu-based alloys, properties have been collected from the literature (~100 papers, more than 200 alloys. Surveying the BGFA criteria published so far, it has been found that the atomic mismatch condition of Egami-Waseda is fulfilled for all the Cu-based BGFAs, the value being above 0,3. The Zhang Bangwei criterion could be applied for the binary Cu-based alloys. The Miracle and Senkov criteria do not necessarily apply for Cu based bulk amorphous alloys. The critical thickness versus =/(+ plot of Lu and Liu extrapolates to =0.36, somewhat higher than the 0.33 value found in other BGFA alloys. The Park and Kim parameter correlates rather poorly with the critical thickness for Cu based alloys. The Cheney and Vecchino parameter is a good indicator to find the best glass former if it is possible to calculate the exact liquids projection. In 2009 Xiu-lin and Pan defined a new parameter which correlates a bit better with the critical thickness. Based on this survey it is still very difficult to find one parameter in order to characterize the real GFA without an unrealized mechanism of crystallization.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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%.

  10. 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)

  11. 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...

  12. 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.

  13. 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...

  14. Methods of quantum chemistry and nanotechnology as applied to the study of the energy states of amorphous tetrahedral structures

    Directory of Open Access Journals (Sweden)

    B. A. Golodenko

    2013-01-01

    Full Text Available The technique and results of an experimental research of power conditions of amorphous alloy hydrogenated carbide silicon is described. Application of power spectra of a silicon valence zone for definition phase structure of its amorphous hydrogenated carbide is shown. Quantitative dependence of a share carbide phases of silicon in structure of its alloy from the maintenance of methane in an initial gas mix is established.

  15. Crystallisation of partially amorphized Ni-Mo alloy

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Sanchez, R.; Diaz de la Torre, S.; Espinosa-Magana, F. [Centro de Investigacion en Materiales Avanzados (CIMAV), Chihuahua (Mexico); Bejar Gomez, L. [Centro de Investigacion en Materiales Avanzados (CIMAV), Chihuahua (Mexico); Univ. Michoacana de San Nicolas de Hidalgo, Morelia (Mexico); Cabanas-Moreno, J.G. [Inst. Politecnico Nacional, ESFM, UPALM-Zacatenco, Mexico D.F. (Mexico)

    2001-07-01

    The Ni-Mo system processed through mechanical alloying (MA) technique has been widely investigated. Complete or partial amorphisation in this binary system mainly depends on the concentration of the elements. A new microstructural phase, called ''Y'' has been reported upon crystallisation of the powder. Although the ''Y'' phase formation has been attributed to the presence of C, O or N contaminants, its identification and characteristics remains unclear. In this work, an oxicarbide (Ni{sub 6}Mo{sub 6}(C,O){sub 1.06}) has been identified in samples in the as-heated condition and has been found as the crystallised phase in major amount in the final product. The XRD pattern of this oxicarbide is very similar to that reported before for a new phase called ''Y''. The simulated XRD pattern of oxicarbide (Ni{sub 6}Mo{sub 6}(C,O){sub 1.06}) is in good agreement with that experimentally found in this work. The activation energy required to induce crystallisation ({proportional_to}336 kJ/mol) matches well to the values reported in literature. (orig.)

  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. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Ion-implantation-induced amorphization of InxGa1-xP alloys as functions of stoichiometry and temperature

    Science.gov (United States)

    Hussain, Z. S.; Wendler, E.; Wesch, W.; Schnohr, C. S.; Ridgway, M. C.

    2016-05-01

    Rutherford Backscattering Spectrometry/Channeling and Extended X-ray Absorption Fine Structure measurements have been combined to investigate the amorphization of InxGa1-xP alloys at 15 and 300 K for selected stoichiometries representative of the entire stoichiometric range. The amorphization kinetics differs considerably for the two temperatures: at 15 K, the amorphization kinetics of InxGa1-xP is intermediate between the two binary extremes while at 300 K, InxGa1-xP is more easily amorphized than both InP and GaP. Direct impact and stimulated amorphization both contribute to the amorphization process at 15 K. Dynamic annealing via thermally induced Frenkel pair recombination reduces the influence of direct impact amorphization at 300 K such that the stimulated amorphization is dominant. At this temperature, stimulated amorphization in ternary InxGa1-xP alloys is supported by the structural disorder inherent from the bimodal bond length distribution.

  2. 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.)

  3. 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.

  4. 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.

  5. Crystallization kinetics of an amorphous Co77Si11.5B11.5 alloy

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2006-04-01

    Full Text Available Purpose: This paper describes crystallization kinetics and changes magnetic properties involved by process of crystallization Co-Si-B amorphous alloy.Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD, electrical resistivity in situ measurements (four-point probe static and dynamic measurements of magnetic properties (magnetic balance, fluxmeter, Maxwell-Wien bridge.Findings: In this work has been performed influence of thermal annealing on crystallization kinetics and magnetic properties amorphous Co77Si11.5B11.5 alloy.Practical implications: The attractive properties of Co-Si-B alloy are of special interest for basic research on the materials as well as for their potential applications, like magnetic sensors. The Co soft magnetic material is used in noise filters, saturable reactors, miniature inductance elements for abating spike noise, mains transformers, choke coils, zero-phase current transformers, and magnetic heads etc., i.e., devices which are expected to exhibit high levels of permeability at high frequencies.Originality/value: It has been shown that thermal annealing at temperature close to the crystallization temperature leads to a significant increase of the initial magnetic permeability.

  6. Annealed Crystallization and Catalytic activity of Ultrafine NiB Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    WEIShiqing; HUTiandou; 等

    2001-01-01

    A Ultrafine amorphous NiB alloy was prepared via chemical reduction method;Its structures during the crystallizatioin precess was characterized by such techniques as Differential thermal analysis (DTA),X-ray absorption fine structure (XAFS) and X-ray diffraction(XRD),and correlated to the catalytic properties for benzene hydrogenation.It was found that the crystallization of amorphous NiB alloy was carried out in two steps,as indicated by two exothermic peaks centered at 598 and 652K respectively.During the first step.two metastable crystalline phases,i.e.,Ni3B and a noaocrstalline Ni phase(Ni-rich NiB alloy),were formed.Further annealing at higher temperature of 652 K may result in the decomposition of crystalline Ni3B and aggregation of nanocrystalline Ni,the benzene hydrogenation is optimized around the annealing temperature of 623K.It most probably results from the maximum amount of active site on nanocrystalline Ni formed by thermal treatment at appropriate annealing temperature.

  7. Reactive wetting of amorphous silica by molten Al-Mg alloys and their interfacial structures

    Science.gov (United States)

    Shi, Laixin; Shen, Ping; Zhang, Dan; Jiang, Qichuan

    2016-07-01

    The reactive wetting of amorphous silica substrates by molten Al-Mg alloys over a wide composition range was studied using a dispensed sessile drop method in a flowing Ar atmosphere. The effects of the nominal Mg concentration and temperature on the wetting and interfacial microstructures were discussed. The initial contact angle for pure Al on the SiO2 surface was 115° while that for pure Mg was 35° at 1073 K. For the Al-Mg alloy drop, it decreased with increasing nominal Mg concentration. The reaction zone was characterized by layered structures, whose formation was primarily controlled by the variation in the alloy concentration due to the evaporation of Mg and the interfacial reaction from the viewpoint of thermodynamics as well as by the penetration or diffusion of Mg, Al and Si from the viewpoint of kinetics. In addition, the effects of the reaction and the evaporation of Mg on the movement of the triple line were examined. The spreading of the Al-Mg alloy on the SiO2 surface was mainly attributed to the formation of Mg2Si at the interface and the recession of the triple line to the diminishing Mg concentration in the alloy.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.)

  17. 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.)

  18. 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).

  19. 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.

  20. 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.

  1. A Novel Carbon Nanotube-Supported NiP Amorphous Alloy Catalyst and Its Hydrogenation Activity

    Institute of Scientific and Technical Information of China (English)

    Yan Ju; Fengyi Li

    2006-01-01

    A carbon nanotube-supported NiP amorphous catalyst (NiP/CNT) was prepared by induced reduction. Benzene hydrogenation was used as a probe reaction for the study of catalytic activity. The effects of the support on the activity and thermal stability of the supported catalyst were discussed based on various characterizations, including XRD, TEM, ICP, XPS, H2-TPD, and DTA. In comparison with the NiP amorphous alloy, the benzene conversion on NiP/CNT catalyst was lower, but the specific activity of NiP/CNT was higher, which is attributed to the dispersion produced by the support, an electron-donating effect, and the hydrogen-storage ability of CNT. The NiP/CNT thermal stability was improved because of the dispersion and electronic effects and the good heat-conduction ability of the CNT support.

  2. Fabrication of silicon-based shape memory alloy micro-actuators

    Science.gov (United States)

    Johnson, A. David; Busch, John D.; Ray, Curtis A.; Sloan, Charles L.

    1992-01-01

    Thin film shape memory alloy has been integrated with silicon in a new actuation mechanism for microelectromechanical systems. This paper compares nickel-titanium film with other actuators, describes recent results of chemical milling processes developed to fabricate shape memory alloy microactuators in silicon, and describes simple actuation mechanisms which have been fabricated and tested.

  3. Processing and characterization of amorphous magnesium based alloy for application in biomedical implants

    Directory of Open Access Journals (Sweden)

    Telma Blanco Matias

    2014-07-01

    Full Text Available Magnesium-based bulk metallic glasses are attractive due to their single-phase, chemically homogeneous alloy system and the absence of second-phase, which could impair the mechanical properties and corrosion resistance. However, one of the unsolved problems for the manufacturability and the applications of bulk metallic glasses is that their glass-forming ability is very sensitive to the preparation techniques and impurity of components since oxygen in the environment would markedly deteriorate the glass-forming ability. Therefore, the aim of this study was to establish proper processing conditions to obtain a magnesium-based amorphous ternary alloy and its characterization. The final composition was prepared using two binary master alloys by melting in an induction furnace. Carbon steel crucible was used in argon atmosphere with and without addition of SF6 gas in order to minimize the oxygen contamination. The microstructure, amorphous nature, thermal properties and chemical analysis of samples were investigated by scanning electron microscopy (SEM, X-ray diffraction (XRD, differential scanning calorimetry (DSC and inductively coupled plasma emission spectrometry, respectively. The oxygen content of the as-cast samples was chemically analyzed by using carrier gas hot extraction (O/N Analyzer TC-436/LECO and was kept bellow 25 ppm (without SF6 and 10 ppm (with SF6. Bulk samples were produced by rapid cooling in a cooper mold until 1.5 mm thickness, with amorphous structures being observed up to 2.5 mm.

  4. Magnetoelectric effect in layered structures of amorphous ferromagnetic alloy and gallium arsenide

    Science.gov (United States)

    Bichurin, M. I.; Petrov, V. M.; Leontiev, V. S.; Ivanov, S. N.; Sokolov, O. V.

    2017-02-01

    A paper devotes to theoretical and experimental studying the magnetoelectric interaction in layered structures of amorphous ferromagnetic alloy and single- crystal gallium arsenide. The authors investigated the magnetoelectric effect in the (100) plane of gallium arsenide in the electromechanical resonance range of 200-240 kHz and obtained maximal ME voltage coefficient of 120 V/A at bias field equaled 3.6 kA/m for the direction parallel to the [011] axis. Also the magnetoelectric effect in the (110) and (111) planes is discussed. The results can be used for design of new electronic devices based on the magnetostrictive-semiconductor materials.

  5. Nanoscale order and crystallization in nitrogen-alloyed amorphous GeTe

    Energy Technology Data Exchange (ETDEWEB)

    Darmawikarta, Kristof; Abelson, John R., E-mail: abelson@illinois.edu [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, Illinois 61801 (United States); Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, 1308 W. Main St., Urbana, Illinois 61801 (United States); Raoux, Simone [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Route 134, Yorktown Heights, New York 10598 (United States); Bishop, Stephen G. [Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, 1308 W. Main St., Urbana, Illinois 61801 (United States); Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 1406 W. Green St., Urbana, Illinois 61801 (United States)

    2014-11-10

    The nanoscale order in amorphous GeTe thin films is measured using fluctuation transmission electron microscopy (FTEM). The order increases upon annealing at 145 °C, which indicates a coarsening of subcritical nuclei. This correlates with a reduction in the nucleation delay time in laser crystallization. A shift in the FTEM peak positions may indicate a transformation in local bonding. In samples alloyed with 12 at. % nitrogen, the order does not change upon annealing, the peak does not shift, and the nucleation time is longer. The FTEM data indicate that nitrogen suppresses the structural evolution necessary for the nucleation process and increases the thermal stability of the material.

  6. Magnetically stabilized bed reactor for selective hydrogenation of olefins in reformate with amorphous nickel alloy catalyst

    Institute of Scientific and Technical Information of China (English)

    Xuhong Mu; Enze Min

    2007-01-01

    A magnetically stabilized bed (MSB) reactor for selective hydrogenation of olefins in reformate was developed by combining the advantages of MSB and amorphous nickel alloy catalyst. The effects of operating conditions, such as temperature, pressure, liquid space velocity, hydrogen-to-oil ratio, and magnetic field intensity on the reaction were studied. A mathematical model of MSB reactor for hydrogenation of olefins in reformate was established. A reforming flow scheme with a post-hydrogenation MSB reactor was proposed. Finally, MSB hydrogenation was compared with clay treatment and conventional post-hydrogenation.

  7. Kinetics of glass transition and crystallization in multicomponent bulk amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    庄艳歆[1; 赵德乾[2; 张勇[3; 汪卫华[4; 潘明祥[5

    2000-01-01

    Differential scanning calorimeter (DSC) is used to investigate apparent activation energy of glass transition and crystallization of Zr-based bulk amorphous alloys by Kissinger equation under non-isothermal condition. It is shown that the glass transition behavior as well as crystallization reaction depends on the heating rate and has a characteristic of kinetic effects. After being isothermally annealed near glass transition temperature, the apparent activation energy of glass transition increases and the apparent activation energy of crystallization reaction decreases. However, the kinetic effects are independent of the pre-annealing.

  8. Identifying Electronic Properties Relevant to Improving the Performance and Stability of Amorphous Silicon Based Photovoltaic Cells: Final Subcontract Report, 27 November 2002--31 March 2005

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, J. D.

    2005-11-01

    A major effort during this subcontract period has been to evaluate the microcrystalline Si material under development at United Solar Ovonics Corporation (USOC). This material is actually a hydrogenated nanocrystalline form of Si and it will be denoted in this report as nc-Si:H. Second, we continued our studies of the BP Solar high-growth samples. Third, we evaluated amorphous silicon-germanium alloys produced by the hot-wire chemical vapor deposition growth process. This method holds some potential for higher deposition rate Ge alloy materials with good electronic properties. In addition to these three major focus areas, we examined a couple of amorphous germanium (a-Ge:H) samples produced by the ECR method at Iowa State University. Our studies of the electron cyclotron resonance a-Ge:H indicated that the Iowa State a Ge:H material had quite superior electronic properties, both in terms of the drive-level capacitance profiling deduced defect densities, and the transient photocapacitance deduced Urbach energies. Also, we characterized several United Solar a Si:H samples deposited very close to the microcrystalline phase transition. These samples exhibited good electronic properties, with midgap defect densities slightly less than 1 x 1016 cm-3 in the fully light-degraded state.

  9. Fe-Zr-Nd-Y-B permanent magnet derived from crystallization of bulk amorphous alloy

    Science.gov (United States)

    Tan, Xiaohua; Xu, Hui; Bai, Qin; Dong, Yuanda

    2007-12-01

    The microstructure and magnetic properties of Nd2Fe14B/(Fe3B,α-Fe) nanocomposite magnet derived form crystallization of bulk amorphous Fe68Zr2Y4B21Nd5 alloy, which was prepared by copper mold casting, have been investigated. The obtaining maximum values of Ms, Mr, Hci, and (BH)max annealed at 963K for Fe68Zr2Nd5Y4B21 alloy are 86Am2/kg, 49Am2/kg, 380kA/m, and 43kJ/m3, respectively. δM plot, high resolution transmission electron microscopy observation, and three-dimensional atom probe technique clarified that the hard magnetic behavior is due to the exchange coupling between soft and hard magnetic nanophases.

  10. Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying

    DEFF Research Database (Denmark)

    Canulescu, Stela; Rechendorff, K.; Borca, C. N.;

    2014-01-01

    The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. %. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms...... are not located in a TiO2 unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2 eV (300–135 nm). The results indicate that amorphous anodic Al2O3 has a direct...

  11. Effect of Pd on GFA and Thermal Stability of Zr-based Bulk Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    Fengxiang QIN; Haifeng ZHANG; Aimin WANG; Bingzhe DING; Zhuangqi HU

    2004-01-01

    The effect of Pd addition on the glass-forming ability and thermal stability of the Zr5sAl10Cus0Nis-xPdx (x=0, 1, 3,5 at. Pct) alloys upon copper-mold casting has been investigated. The structure, thermal stability and microstructure were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. It was identified that a new bulk amorphous alloy with the larger supercooled liquid region Atx of 100 K is obtained with substituting Ni by 1 at. Pct Pd. Furthermore, the origins that thermal stability and GFA change with increasing of Pd have also beer discussed.

  12. Effect of high pressure on microstructure of crystallizing amorphous Nd9Fe85B6 alloy

    Institute of Scientific and Technical Information of China (English)

    WU Wei; LI Hui; XIE Yanwu; ZHANG Xiangyi

    2008-01-01

    The effect of high pressure on the microstructure of annealed amorphous NdgFegsB6 alloy was studied. It was found that applica- tion of high pressure made the microstructure of the crystallized alloy much more homogeneous. The average grain size of the Nd2Fe14B phase decreased with the increase of pressure, whereas, the size of the α-Fe first increased when a pressure of 1 Gpa was applied and then decreased with further increase of pressure. Pressure-induced (410) texture of the Nd2Fe14B phase was also observed. The present study sug-gested an effective route for controlling the microstructure in a nanoscale solid.

  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. 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.

  15. A review of ordering phenomena in iron-silicon alloys

    Directory of Open Access Journals (Sweden)

    González, F.

    2013-06-01

    Full Text Available Silicon steel is an industrially-desired alloy of iron and silicon, characterised by soft magnetic properties, low eddy-current losses, and low magnetostriction. Silicon steels have narrow hysteresis cycles, making them particularly advantageous in applications using electromagnetic fields, such as transformers, generators, electric motor cores, and few other components in industry. Despite its incontestable industrial value, there is not much agreement on the atomic structure of silicon steel. Gaining better understanding of e.g. ordering processes in Fe-Si alloys could not only explain their magnetic properties, but also open opportunities to reduce their weaker characteristics, such as brittleness that adversely affects silicon steel workability and its associated high production costs. This review summarises the state-of-the-art knowledge about ordering in silicon steel and describes the most relevant experimental techniques used for studying its microstructure. In addition, the process of building the iron rich part of the Fe-Si phase diagram is explained. Lastly, the influence of order on the alloy’s magnetic and mechanical properties is illustrated.El acero al silicio es una aleación de importancia industrial, caracterizada por propiedades magnéticas blandas, bajas pérdidas por corrientes de Foucault y baja magnetostricción. Los aceros al silicio tienen ciclo de histéresis estrecho, lo que es una ventaja en aplicaciones con campos electromagnéticos, como transformadores, generadores, núcleos de motores eléctricos y otros componentes industriales. A pesar de su incomparable valor industrial, no hay convenio sobre la estructura atómica del acero al silicio. Obtener mayor conocimiento sobre los procesos de orden no sólo podría explicar las propiedades magnéticas sino que también podría abrir vías para la reducción de sus características más débiles, como su fragilidad, la cual afecta negativamente a la fabricación del

  16. The features of CNT growth on catalyst-content amorphous alloy layer by CVD-method

    Science.gov (United States)

    Dubkov, S.; Bulyarskii, S.; Pavlov, A.; Trifonov, A.; Kitsyuk, E.; Mierczynski, P.; Maniecki, T.; Ciesielski, R.; Gavrilov, S.; Gromov, D.

    2016-12-01

    This work is devoted to the CVD-synthesis of arrays of carbon nanotubes (CNTs) on Co-Zr-N-(O), Ni-Nb-N-(O), Co- Ta-N-(O) catalytic alloy films from gas mixture of C2H2+NH3+Ar at a substrate temperature of about 550°C.Heating of the amorphous alloy causes its crystallization and squeezing of the catalytic metal onto the surface. As a result, small catalyst particles are formed on the surface. The CNT growth takes place after wards on these particles. It should be noted that the growth of CNT arrays on these alloys is insensitive to the thickness of alloy film, which makes this approach technically attractive. In particular, the possibility of local CNT growth at the ends of the Co-Ta-N-(O) film and three-level CNT growth at the end of more complex structure SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2 is demonstrated.

  17. Atomic structure and crystallization processes of amorphous (Co,Ni)–P metallic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Modin, Evgeny B., E-mail: modin.eb@dvfu.ru [Far Eastern Federal University, Shukhanova 8, Vladivostok 690950 (Russian Federation); Pustovalov, Evgeny V.; Fedorets, Aleksander N.; Dubinets, Aleksander V.; Grudin, Boris N.; Plotnikov, Vladimir S. [Far Eastern Federal University, Shukhanova 8, Vladivostok 690950 (Russian Federation); Grabchikov, Sergey S. [Scientific and Practical Centre of Material Science, Belarus National Academy of Sciences, P. Brovki 19, Minsk 220072 (Belarus)

    2015-08-25

    Highlights: • The CoP–CoNiP amorphous alloys were studied by the Cs-corrected high resolution transmission electron microscopy. • In situ heating experiments showed that crystallization starts at 200–250 °C on the network frame and cell boundaries. • Crystal growth occurs at the free surface, then the remaining material in the volume is crystallized. • Adding nickel to the CoP alloy leads to higher thermal stability. • At the beginning of crystallization there are high diffusion coefficients, 1.2–2.4 ∗ 10{sup −18} m{sup 2}/s at 250 °C. - Abstract: This work concerns the in situ investigation of the atomic structure of (Co,Ni)–P alloys during relaxation and crystallization by high resolution transmission electron microscopy. The CoP–CoNiP alloys, in the initial state, have a hierarchical network-like disordered structure. Crystallization starts at 200–250 °C on the network frame and cell boundaries. In the early stages, crystal growth occurs at the free surface, then the remaining material in the volume is crystallized. The diffusion coefficient at the start of crystallization is 1.2–2.4 × 10{sup −18} m{sup 2}/s at 250 °C and we assume that the high diffusion speed is due to surface diffusion.

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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

  3. Preparation of Mg55Ni35Si10 Amorphous Powders by Mechanical Alloying and Consolidation by Vacuum Hot Pressing

    Institute of Scientific and Technical Information of China (English)

    YANG Deng-Ke; WEN Cui-E; HAN Fu-Sheng; WANG Qing-Zhou; LI Hai-Jin

    2006-01-01

    @@ Amorphous Mg55Ni35Si10 powders are fabricated by using a mechanical alloying technique. The amorphous powders are found to exhibit a relatively high crystallization temperature of 380℃. The as-milled amorphous Mg55Ni35Si10 powders are consolidated successfully into bulk body by vacuum hot pressing technique. Limited nanocrystallization is noticed. The Vickers microhardness range of the Mg55Ni35Si10 bulk sample is 7834 to 8048 Mpa. Its bending strength and compressive strength are 529 Mpa and 1466 Mpa, respectively.

  4. Silicon spheroidization treatment of thixoformed Al-Si-Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ogris, E.; Uggowitzer, P.J. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. of Metallurgy; Luechinger, H. [SAG-Aluminium Lend GmbH und Co KG and THIXALLOY trademark Components GmbH und Co KG, Lend (Austria)

    2002-07-01

    Al-Si-Mg alloys are commonly used in the automobile industry because of their outstanding mechanical properties and corrosion resistance. The need of lighter and safer cars is the driving force behind research in the area of high strength light metal safety part applications. The strength level can be tuned by varying the amount of alloyed magnesium. Usually if strength is increased, ductility will decrease. Following the demands of the automotive industry, safety parts should have a minimum fracture elongation of 15% and a minimum yield strength of 150 MPa. The huge hurdle is the 15% fracture elongation which can not be reached by sand or die casting, but some relatively new alternative casting technologies, like Thioxocasting or New Rheocasting, yield encouraging ductility values. Recent research activity has focused on increasing strength and ductility, but so far the results have not yet been satisfying. This paper presents investigations on the spheroidization process of eutectic silicon and its positive effect on mechanical properties. It is shown that the spheroidization process is already finished after minutes of exposure to heat treatment. Metallographical and quantitative microstructural analysis is used to describe the growth and spheroidization process of the silicon crystals. Specimens of THIXALLOY trademark 630 (A356) thixocast components were heat treated for varied periods of time, aged and tested. Results show amazing improvements of ductility and strength in comparison to the as cast state. Maximum values of 18% fracture elongation and 230 MPa yield strength are reached. (orig.)

  5. Stoichiometry dependence of resistance drift phenomena in amorphous GeSnTe phase-change alloys

    Science.gov (United States)

    Luckas, J.; Piarristeguy, A.; Bruns, G.; Jost, P.; Grothe, S.; Schmidt, R. M.; Longeaud, C.; Wuttig, M.

    2013-01-01

    In phase-change materials, the amorphous state resistivity increases with time following a power law ρ ∝ (t/t0)αRD. This drift in resistivity seriously hampers the potential of multilevel-storage to achieve an increased capacity in phase-change memories. This paper presents the stoichiometric dependence of drift phenomena in amorphous GeSnTe systems (a-GeSnTe) and other known phase-change alloys with the objective to identify low drift materials. The substitution of Ge by Sn results in a systematic decrease of the drift parameter from a-GeTe (αRD = 0.129) to a-Ge2Sn2Te4 (αRD = 0.053). Furthermore, with increasing Sn content a decrease in crystallization temperature, trap state density, optical band gap, and activation energy for electronic conduction is observed. In a-GeSnTe, a-GeSbTe, and a-AgInSbTe alloys as well, the drift parameter αRD correlates to the activation energy for electronic conduction. This study indicates that low drift materials are characterized by low activation energies of electronic conduction. The correlation found between drift and activation energy of electronic conduction manifests a useful criterion for material optimization.

  6. First-principles study of amorphous Ga4Sb6Te3 phase-change alloys

    Science.gov (United States)

    Bouzid, Assil; Gabardi, Silvia; Massobrio, Carlo; Boero, Mauro; Bernasconi, Marco

    2015-05-01

    First-principles molecular dynamics simulations within the density functional theory framework were performed to generate amorphous models of the Ga4Sb6Te3 phase change alloy by quenching from the melt. We find that Ga-Sb and Ga-Te are the most abundant bonds with only a minor amount of Sb-Te bonds participating to the alloy network. Ga and four-coordinated Sb atoms present a tetrahedral-like geometry, whereas three-coordinated Sb atoms are in a pyramidal configuration. The tetrahedral-like geometries are similar to those of the crystalline phase of the two binary compounds GaTe and GaSb. A sizable fraction of Sb-Sb bonds is also present, indicating a partial nanoscale segregation of Sb. Despite the fact that the composition Ga4Sb6Te3 lies on the pseudobinary Ga Sb -Sb2Te3 tie line, the amorphous network can be seen as a mixture of the two binary compounds GaTe and GaSb with intertwined elemental Sb.

  7. Room-temperature amorphous alloy field-effect transistor exhibiting particle and wave electronic transport

    Energy Technology Data Exchange (ETDEWEB)

    Fukuhara, M., E-mail: fukuhara@niche.tohoku.ac.jp [New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579 (Japan); Kawarada, H. [Research and Development Center, Waseda University, Tokyo 162-0041 (Japan)

    2015-02-28

    The realization of room-temperature macroscopic field effect transistors (FETs) will lead to new epoch-making possibilities for electronic applications. The I{sub d}-V{sub g} characteristics of the millimeter-sized aluminum-oxide amorphous alloy (Ni{sub 0.36}Nb{sub 0.24}Zr{sub 0.40}){sub 90}H{sub 10} FETs were measured at a gate-drain bias voltage of 0–60 μV in nonmagnetic conditions and under a magnetic fields at room temperature. Application of dc voltages to the gate electrode resulted in the transistor exhibiting one-electron Coulomb oscillation with a period of 0.28 mV, Fabry-Perot interference with a period of 2.35 μV under nonmagnetic conditions, and a Fano effect with a period of 0.26 mV for Vg and 0.2 T under a magnetic field. The realization of a low-energy controllable device made from millimeter-sized Ni-Nb-Zr-H amorphous alloy throws new light on cluster electronics.

  8. 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%.

  9. Nanocrystals and amorphous matrix phase studies of Finemet-like alloys containing Ge

    Energy Technology Data Exchange (ETDEWEB)

    Moya, J.A., E-mail: jmoya.fi.uba@gmail.co [IESIING, Facultad de Ingenieria e Informatica, UCASAL, A4402FYP Salta (Argentina); Lab. Solidos Amorfos, Facultad de Ingenieria, INTECIN, UBA-CONICET (Argentina); CONICET (Argentina)

    2010-07-15

    Two simple models were developed in order to determine the chemical composition of both nanocrystals and intergranular amorphous phases in nanocrystallized Fe{sub 73.5}Si{sub 13.5}B{sub 9}Nb{sub 3}Cu{sub 1} containing Ge using data from X-ray diffraction and Moessbauer spectroscopy techniques. Saturation magnetization of the amorphous intergranular matrix (M{sub s}{sup am}) was calculated considering the contribution of the alpha-Fe(Si,Ge) nanocrystals and saturation magnetization of the alloys. The behavior of M{sub s}{sup am} with the iron content of the matrix was obtained and discussed. The exchange stiffness constant for the nanograins and for the amorphous phases was determined. The increment in the coercive field (H{sub c}) with increasing Ge content was evaluated using two theoretical models for the random magnetocrystalline anisotropy constant (). Results show that the magnetic hardening observed could not be attributed to an increase in but mainly to an important increment of the magnetostriction constant of the alpha-Fe(Si,Ge) nanocrystals (lambda{sub s}{sup cr}). Values for lambda{sub s}{sup cr} are proposed.

  10. Ultrafast all-optical arithmetic logic based on hydrogenated amorphous silicon microring resonators

    Science.gov (United States)

    Gostimirovic, Dusan; Ye, Winnie N.

    2016-03-01

    For decades, the semiconductor industry has been steadily shrinking transistor sizes to fit more performance into a single silicon-based integrated chip. This technology has become the driving force for advances in education, transportation, and health, among others. However, transistor sizes are quickly approaching their physical limits (channel lengths are now only a few silicon atoms in length), and Moore's law will likely soon be brought to a stand-still despite many unique attempts to keep it going (FinFETs, high-k dielectrics, etc.). This technology must then be pushed further by exploring (almost) entirely new methodologies. Given the explosive growth of optical-based long-haul telecommunications, we look to apply the use of high-speed optics as a substitute to the digital model; where slow, lossy, and noisy metal interconnections act as a major bottleneck to performance. We combine the (nonlinear) optical Kerr effect with a single add-drop microring resonator to perform the fundamental AND-XOR logical operations of a half adder, by all-optical means. This process is also applied to subtraction, higher-order addition, and the realization of an all-optical arithmetic logic unit (ALU). The rings use hydrogenated amorphous silicon as a material with superior nonlinear properties to crystalline silicon, while still maintaining CMOS-compatibility and the many benefits that come with it (low cost, ease of fabrication, etc.). Our method allows for multi-gigabit-per-second data rates while maintaining simplicity and spatial minimalism in design for high-capacity manufacturing potential.

  11. Nanometric Cutting of Silicon with an Amorphous-Crystalline Layered Structure: A Molecular Dynamics Study

    Science.gov (United States)

    Wang, Jinshi; Fang, Fengzhou; Zhang, Xiaodong

    2017-01-01

    Materials with specific nanometric layers are of great value in both theoretical and applied research. The nanometric layer could have a significant influence on the response to the mechanical loading. In this paper, the nanometric cutting on the layered systems of silicon has been studied by molecular dynamics. This kind of composite structure with amorphous layer and crystalline substrate is important for nanomachining. Material deformation, stress status, and chip formation, which are the key issues in nano-cutting, are analyzed. A new chip formation mechanism, i.e., the mixture of extrusion and shear, has been observed. In addition, from the perspective of engineering, some specific composite models show the desired properties due to the low subsurface damage or large material removal rate. The results enrich the cutting theory and provide guidance on nanometric machining.

  12. Using amorphous silicon solar cells to boost the viability of luminescent solar concentrators

    Energy Technology Data Exchange (ETDEWEB)

    Farrell, Daniel J. [Physics Department, Imperial College London, South Kensington campus, SW7 2AZ, London (United Kingdom); Sark, Wilfried G.J.H.M. van [Utrecht University, Faculty of Science, Debye Institute for Nanomaterials Science, Nanophotonics - Physics of Devices, P.O. Box 80000, 3508 TA Utrecht (Netherlands); Utrecht University, Copernicus Institute for Sustainable Development and Innovation, Science, Technology and Society, Heidelberglaan 2, 3584 CS Utrecht (Netherlands); Velthuijsen, Steven T.; Schropp, Ruud E.I. [Utrecht University, Faculty of Science, Debye Institute for Nanomaterials Science, Nanophotonics - Physics of Devices, P.O. Box 80000, 3508 TA Utrecht (Netherlands)

    2010-04-15

    We have, for the first time, designed and fabricated hydrogenated amorphous silicon solar cells to be used in conjunction with Luminescent Solar Concentrators (LSCs). LSCs are planar plastic sheets doped with organic dyes that absorb solar illumination and down shift the energy to narrowband luminescence which is collected by solar cells attached to the sheet edge. We fabricated an LSC module with two bonded solar cells and performed characterisation with the cells connected in series and parallel configurations. We find that the LSC module has an optical collection efficiency of 9.5% and an optimum power conversion efficiency of approaching 1% when the cells are in a parallel connection. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Serially Connected Micro Amorphous Silicon Solar Cells for Compact High-Voltage Sources

    Directory of Open Access Journals (Sweden)

    Jiyoon Nam

    2016-01-01

    Full Text Available We demonstrate a compact amorphous silicon (a-Si solar module to be used as high-voltage power supply. In comparison with the organic solar module, the main advantages of the a-Si solar module are its compatibility with photolithography techniques and relatively high power conversion efficiency. The open circuit voltage of a-Si solar cells can be easily controlled by serially interconnecting a-Si solar cells. Moreover, the a-Si solar module can be easily patterned by photolithography in any desired shapes with high areal densities. Using the photolithographic technique, we fabricate a compact a-Si solar module with noticeable photovoltaic characteristics as compared with the reported values for high-voltage power supplies.

  14. 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.

  15. Direct visualization of photoinduced glassy dynamics on the amorphous silicon carbide surface by STM movies

    Science.gov (United States)

    Nguyen, Duc; Nienhaus, Lea; Haasch, Richard T.; Lyding, Joseph; Gruebele, Martin

    2015-03-01

    Glassy dynamics can be controlled by light irradiation. Sub- and above-bandgap irradiation cause numerous phenomena in glasses including photorelaxation, photoexpansion, photodarkening and pohtoinduced fluidity. We used scanning tunneling microscopy to study surface glassy dynamics of amorphous silicon carbide irradiated with above- bandgap 532 nm light. Surface clusters of ~ 4-5 glass forming unit in diameter hop mostly in a two-state fashion, both without and with irradiation. Upon irradiation, the average surface hopping activity increases by a factor of 3. A very long (~1 day) movie of individual clusters with varying laser power density provides direct evidence for photoinduced enhanced hopping on the glass surfaces. We propose two mechanisms: heating and electronic for the photoenhanced surface dynamics.

  16. 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.

  17. 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.

  18. 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.

  19. Mapping between atomistic simulations and Eshelby inclusions in the shear deformation of an amorphous silicon model

    Science.gov (United States)

    Albaret, T.; Tanguy, A.; Boioli, F.; Rodney, D.

    2016-05-01

    In this paper we perform quasistatic shear simulations of model amorphous silicon bulk samples with Stillinger-Weber-type potentials. Local plastic rearrangements identified based on local energy variations are fitted through their displacement fields on collections of Eshelby spherical inclusions, allowing determination of their transformation strain tensors. The latter are then used to quantitatively reproduce atomistic stress-strain curves, in terms of both shear and pressure components. We demonstrate that our methodology is able to capture the plastic behavior predicted by different Stillinger-Weber potentials, in particular, their different shear tension coupling. These calculations justify the decomposition of plasticity into shear transformations used so far in mesoscale models and provide atomic-scale parameters that can be used to limit the empiricism needed in such models up to now.

  20. 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)

  1. 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

  2. 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.

  3. Band-gap engineering by molecular mechanical strain-induced giant tuning of the luminescence in colloidal amorphous porous silicon nanostructures

    KAUST Repository

    Mughal, Asad Jahangir

    2014-01-01

    Nano-silicon is a nanostructured material in which quantum or spatial confinement is the origin of the material\\'s luminescence. When nano-silicon is broken into colloidal crystalline nanoparticles, its luminescence can be tuned across the visible spectrum only when the sizes of the nanoparticles, which are obtained via painstaking filtration methods that are difficult to scale up because of low yield, vary. Bright and tunable colloidal amorphous porous silicon nanostructures have not yet been reported. In this letter, we report on a 100 nm modulation in the emission of freestanding colloidal amorphous porous silicon nanostructures via band-gap engineering. The mechanism responsible for this tunable modulation, which is independent of the size of the individual particles and their distribution, is the distortion of the molecular orbitals by a strained silicon-silicon bond angle. This mechanism is also responsible for the amorphous-to-crystalline transformation of silicon. This journal is

  4. Band-gap engineering by molecular mechanical strain-induced giant tuning of the luminescence in colloidal amorphous porous silicon nanostructures.

    Science.gov (United States)

    Mughal, A; El Demellawi, J K; Chaieb, Sahraoui

    2014-12-14

    Nano-silicon is a nanostructured material in which quantum or spatial confinement is the origin of the material's luminescence. When nano-silicon is broken into colloidal crystalline nanoparticles, its luminescence can be tuned across the visible spectrum only when the sizes of the nanoparticles, which are obtained via painstaking filtration methods that are difficult to scale up because of low yield, vary. Bright and tunable colloidal amorphous porous silicon nanostructures have not yet been reported. In this letter, we report on a 100 nm modulation in the emission of freestanding colloidal amorphous porous silicon nanostructures via band-gap engineering. The mechanism responsible for this tunable modulation, which is independent of the size of the individual particles and their distribution, is the distortion of the molecular orbitals by a strained silicon-silicon bond angle. This mechanism is also responsible for the amorphous-to-crystalline transformation of silicon.

  5. 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.

  6. 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...

  7. 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.

  8. Prediction of Failure Due to Thermal Aging, Corrosion and Environmental Fracture in Amorphous and Titanium Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C

    2003-04-15

    DARPA is exploring a number of advanced materials for military applications, including amorphous metals and titanium-based alloys. Equipment made from these materials can undergo degradation due to thermal aging, uniform corrosion, pitting, crevice corrosion, denting, stress corrosion cracking, corrosion fatigue, hydrogen induced cracking and microbial influenced corrosion. Amorphous alloys have exceptional resistance to corrosion, due in part to the absence of grain boundaries, but can undergo crystallization and other phase instabilities during heating and welding. Titanium alloys are extremely corrosion resistant due to the formation of a tenacious passive film of titanium oxide, but is prone to hydrogen absorption in crevices, and hydrogen induced cracking after hydrogen absorption. Accurate predictions of equipment reliability, necessary for strategic planning, requires integrated models that account for all relevant modes of attack, and that can make probabilistic predictions. Once developed, model parameters must be determined experimentally, and the validity of models must be established through careful laboratory and field tests. Such validation testing requires state-of-the-art surface analytical techniques, as well as electrochemical and fracture mechanics tests. The interaction between those processes that perturb the local environment on a surface and those that alter metallurgical condition must be integrated in predictive models. The material and environment come together to drive various modes of corrosive attack (Figure 1). Models must be supported through comprehensive materials testing capabilities. Such capabilities are available at LLNL and include: the Long Term Corrosion Test Facility (LTCTF) where large numbers of standard samples can be exposed to realistic test media at several temperature levels; a reverse DC machine that can be used to monitor the propagation of stress corrosion cracking (SCC) in situ; and banks of potentiostats with

  9. 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

  10. Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625), Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219), and Nickel-Chromium-Molybdenum-Tungsten Alloy (UNS N06650) Rod and Bar

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2014-01-01

    Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625), Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219), and Nickel-Chromium-Molybdenum-Tungsten Alloy (UNS N06650) Rod and Bar

  11. Kinetics of crystallization of a Fe-based multicomponent amorphous alloy

    Indian Academy of Sciences (India)

    Arun Pratap; T Lilly Shanker Rao; Kinnary Patel; Mukesh Chawda

    2009-10-01

    The Fe-based multicomponent amorphous alloys (also referred to as metallic glasses) are known to exhibit soft magnetic properties and, it makes them important for many technological applications. However, metallic glasses are in a thermodynamically metastable state and in case of high temperature operating conditions, the thermally activated crystallization would be detrimental to their magnetic properties. The study of crystallization kinetics of metallic glasses gives useful insight about its thermal stability. In the present work, crystallization study of Fe67Co18B14Si1 (2605CO) metallic glass has been carried out using differential scanning calorimetry (DSC) technique. Mössbauer study has also been undertaken to know the phases formed during the crystallization process. The alloy shows two-stage crystallization. The activation energy has been derived using the Kissinger method. It is found to be equal to 220 kJ/mol and 349 kJ/mol for the first and second crystallization peaks, respectively. The Mössbauer study indicates the formation of -(Fe, Co) and (Fe, Co)3B phases in the alloy.

  12. The Effects of Hydrogen on the Potential-Energy Surface of Amorphous Silicon

    Science.gov (United States)

    Joly, Jean-Francois; Mousseau, Normand

    2012-02-01

    Hydrogenated amorphous silicon (a-Si:H) is an important semiconducting material used in many applications from solar cells to transistors. In 2010, Houssem et al. [1], using the open-ended saddle-point search method, ART nouveau, studied the characteristics of the potential energy landscape of a-Si as a function of relaxation. Here, we extend this study and follow the impact of hydrogen doping on the same a-Si models as a function of doping level. Hydrogen atoms are first attached to dangling bonds, then are positioned to relieve strained bonds of fivefold coordinated silicon atoms. Once these sites are saturated, further doping is achieved with a Monte-Carlo bond switching method that preserves coordination and reduces stress [2]. Bonded interactions are described with a modified Stillinger-Weber potential and non-bonded Si-H and H-H interactions with an adapted Slater-Buckingham potential. Large series of ART nouveau searches are initiated on each model, resulting in an extended catalogue of events that characterize the evolution of potential energy surface as a function of H-doping. [4pt] [1] Houssem et al., Phys Rev. Lett., 105, 045503 (2010)[0pt] [2] Mousseau et al., Phys Rev. B, 41, 3702 (1990)

  13. Numerical Analysis of Lamellar Gratings for Light-Trapping in Amorphous Silicon Solar Cells

    CERN Document Server

    Gablinger, David I

    2015-01-01

    In this paper, we calculate the material specific absorption accurately using a modal method by determining the integral of the Poynting vector around the boundary of a specific material. Given that the accuracy of our method is only determined by the number of modes included, the material specific absorption can be used as a quality measure for the light-trapping performance. We use this method to investigate metallic gratings and find nearly degenerate plasmons at the interface between metal and amorphous silicon (a-Si). The plasmons cause large undesired absorption in the metal part of a grating as used in a-Si cells. We explore ways to alleviate the parasitic absorption in the metal by appropriate choice of the geometry. Separating the diffraction grating from the back reflector helps, lining silver or aluminum with a dielectric helps as well. Gratings with depth > 60nm are preferred, and periods > 600nm are not useful. Maximum absorption in silicon can occur for less thick a-Si than is standard. We also ...

  14. 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.

  15. Synthesis and characterization of Mg-based amorphous alloys and their use for decolorization of Azo dyes

    Science.gov (United States)

    Iqbal, M.; Wang, W. H.

    2014-06-01

    Mg-based alloys are light weight and have wide range of applications in the automotive industry. These alloys are widely used because of their very attractive physical and mechanical properties and corrosion resistance. The properties and applications can be further improved by changing the nature of materials from crystalline to amorphous. In this study, melt spun ribbons (MSRs) of Mg70Zn25Ca5 Mg68Zn27Ca5 alloys were prepared by melt spinning technique by using 3-4N pure metals. Characterization of the samples was done by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and energy dispersive x-ray analyzer (EDAX). Microstructural investigations were conducted by using scanning electron microscopy (SEM), atomic force microscopy (AFM) as well as optical and stereo scan microscopy techniques. DSC results showed multistage crystallization. Activation energy was found to be 225 kJ/mol by Kissinger method indicating good thermal stability against crystallization. XRD, DSC, SEM and EDS (energy dispersive spectroscopy) results are agreed very well. In order to study decolorization, the MSRs of Mg70Zn25Ca5 Mg68Zn27Ca5 alloys were treated repeatedly with various azo dyes at room temperature. In order to compare the results, MSRs of amorphous Zr- and Ni-based metallic glasses were also treated. Reaction of MSRs with azo dyes results in their decolorization in a few hours. Decolorization of azo dyes takes place by introducing amorphous MSRs which results in breaking the -N=N- bonds that exist in dye contents. It is concluded that Mg-based alloys are useful for paint and dye industries and will be beneficial to control water pollution. Comparison of results showed that Mg-based alloys are more efficient than Zr- and Ni-based amorphous alloys for decolorization of azo dyes.

  16. Local structure of amorphous GaN{sub 1-x}As{sub x} semiconductor alloys across the composition range

    Energy Technology Data Exchange (ETDEWEB)

    Levander, A. X.; Dubon, O. D.; Wu, J. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States); Yu, K. M.; Liliental-Weber, Z.; Walukiewicz, W. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Novikov, S. V.; Foxon, C. T. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2013-06-28

    Typically only dilute (up to {approx}10%) highly mismatched alloys can be grown due to the large differences in atomic size and electronegativity of the host and the alloying elements. We have overcome the miscibility gap of the GaN{sub 1-x}As{sub x} system using low temperature molecular beam epitaxy. In the intermediate composition range (0.10 < x < 0.75), the resulting alloys are amorphous. To gain a better understanding of the amorphous structure, the local environment of the As and Ga atoms was investigated using extended x-ray absorption fine structure (EXAFS). The EXAFS analysis shows a high concentration of dangling bonds compared to the crystalline binary endpoint compounds of the alloy system. The disorder parameter was larger for amorphous films compared to crystalline references, but comparable with other amorphous semiconductors. By examining the Ga local environment, the dangling bond density and disorder associated with As-related and N-related bonds could be decoupled. The N-related bonds had a lower dangling bond density and lower disorder.

  17. 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%)

  18. 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.

  19. Short-range order in ab initio computer generated amorphous and liquid Cu–Zr alloys: A new approach

    Energy Technology Data Exchange (ETDEWEB)

    Galván-Colín, Jonathan, E-mail: jgcolin@ciencias.unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México, D.F. 04510, México (Mexico); Valladares, Ariel A., E-mail: valladar@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México, D.F. 04510, México (Mexico); Valladares, Renela M.; Valladares, Alexander [Facultad de Ciencias, Universidad Nacional Autónoma de México, Apartado Postal 70-542, México, D.F. 04510, México (Mexico)

    2015-10-15

    Using ab initio molecular dynamics and a new approach based on the undermelt-quench method we generated amorphous and liquid samples of Cu{sub x}Zr{sub 100−x} (x=64, 50, 36) alloys. We characterized the topology of our resulting structures by means of the pair distribution function and the bond-angle distribution; a coordination number distribution was also calculated. Our results for both amorphous and liquids agree well with experiment. Dependence of short-range order with the concentration is reported. We found that icosahedron-like geometry plays a major role whenever the alloys are Cu-rich or Zr-rich disregarding if the samples are amorphous or liquid. The validation of these results, in turn would let us calculate other properties so far disregarded in the literature.

  20. Microstructure of Cu-based Amorphous Composite Coatings on AZ91D Magnesium Alloy by Laser Cladding

    Institute of Scientific and Technical Information of China (English)

    Kaijin Huang; Changsheng Xie; T.M.Yue

    2009-01-01

    To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of Cu47Ti34Zr11Ni8 and Cu47Ti34Zr11Ni8+20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM (scanning electron microscopy), EDS (energy dispersive X-ray spectroscopy), XRD (X-ray diffraction) and TEM (transmission electron microscopy) techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.

  1. Effect of heat treatments in the silicon eutectic crystal evolution in Al-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Forn, A.; Baile, M.T.; Martin, E.; Ruperez, E. [Light Alloys and Surface Treatments Design Centre (CDAL), Univ. Politecnica de Catalunya, Vilanova I la Geltru (Spain)

    2005-07-01

    This paper describes the heat treatment effect on the eutectic silicon evolution in the A357 alloy, obtained by semisolid forming process (SSM). The coarsening rate of the silicon was determined by image analysis technique in specimens from rheocasting ingots and thixocasting components. The study was realized in the temperature range from 450 to 550 C by applying heating times between 1 and 24 hours. The results show that during the heat treatment the coarsening and sphereodization of the silicon particles is produced and the fragmentation stages, which are observed in conventional alloys, do not appear. Kinetic silicon growth has been adjusted to the Oswald's ripening equation. (orig.)

  2. 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.

  3. A critical appraisal of the factors affecting energy production from amorphous silicon photovoltaic arrays in a maritime climate

    Energy Technology Data Exchange (ETDEWEB)

    Gottschalg, R.; Betts, T.R.; Williams, S.R.; Sauter, D.; Infield, D.G. [Loughborough University (United Kingdom). Department of Electronic and Electrical Engineering, Centre for Renewable Energy Systems Technology; Kearney, M.J. [University of Surrey, Guildford (United Kingdom). School of Electronics and Physical Sciences, Advanced Technology Institute

    2004-12-01

    Contradictory reports exist in the literature regarding the energy production from amorphous silicon photovoltaic arrays. The majority claims high-energy output compared to crystalline silicon arrays of the same power rating (i.e. high kW h/kW{sub p}), but some reports point to less favourable comparisons. The reasons for these conflicting reports are investigated using long-term measurements of the I-V characteristics of a number of amorphous silicon devices, in conjunction with in situ measurements of the solar spectrum and other relevant environmental parameters. It is shown that the variation in the performance of devices produced by different manufacturers is so significant that one cannot speak of the performance of amorphous silicon devices in general; one has to investigate each type of amorphous silicon panel separately. The causes of differences in energy production are investigated in detail. The major factor impacting on the seasonal performance in the UK is identified to be variations in the solar spectrum. Single junction devices exhibit some seasonal thermal annealing but multi-junctions do not show this effect at a significant level. Scope for further improvement is identified, largely in the photon absorption. The response to different spectra can be modified to some extent, which would bridge the gap between the best and the worst performers in the field. It is also shown that in the case of multi-junction devices an optimised current matching might bring a 5% increase in energy production for this location. Differences in the magnitude of the fill factor have been identified to be the second most significant cause for performance variation between the different samples in the test, suggesting additional scope for improvement. (author)

  4. Electronic structure and sign reversal of the Hall coefficient in amorphous CuZr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Manh, D.N.; Pavuna, D.; Cyrot-Lackmann, F.; Mayou, D.; Pasturel, A.

    1986-04-15

    We present calculated densities of states (DOS) for Cu/sub x/Zr/sub 1-x/ amorphous alloys across the compositional range. We find that for x<80 at. % Cu there is no ordering and the Fermi level E/sub F/ is dominated by the Zr 4d subband, while above 80 at. % Cu the local order increases and the DOS at E/sub F/ abruptly decreases and is dominated by the s states. These changes in DOS and the fact that the energy derivative of the self-energy changes its sign (implying a change of sign of the Fermi velocity) gives further insight into the experimentally observed sign reversal of the Hall coefficient which occurs for 80< or =x< or =85 at. % Cu.

  5. A thermodynamic approach towards glass-forming ability of amorphous metallic alloys

    Indian Academy of Sciences (India)

    Sonal R Prajapati; Supriya Kasyap; Arun Pratap

    2015-12-01

    A quantitative measure of the stability of a glass as compared to its corresponding crystalline state can be obtained by calculating the thermodynamic parameters, such as the Gibbs free energy difference (), entropy difference () and the enthalpy difference () between the super-cooled liquid and the corresponding crystalline phase. is known as the driving force of crystallization. The driving force of crystallization () provides very important information about the glass-forming ability (GFA) of metallic glasses (MGs). Lesser the driving force of crystallization more is the GFA. The varies linearly with the critical size (). According to Battezzati and Garonne the parameter ( = (1−(/))/(1−( / ))) in the expression for should be a constant (i.e., 0.8), but its uniqueness is not observed for all MGs. The thermal stability of various alloy compositions is studied by their undercooled liquid region ( = − ). Large implies greater stability against crystallization of the amorphous structure. Other GFA parameters are also calculated and correlated with critical size ().

  6. Kinetic Characteristic of Hydrogenation Zr-Ti-Cu-Ni-Be Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    Delin PENG; Jun SHEN; Jianfei SUN; Yuyong CHEN

    2004-01-01

    The relationship between the hydrogen content and the microhardness and the charging period, the effect of hydrogen on the activation energy, the kinetics of glass transition and crystallization of Zr-Ti-Cu-Ni-Be bulk amorphous alloy were studied by differential scanning calorimetry (DSC) and the Kissinger equation. It shows that both of the hydrogen content and the microhardness are related to the charging period, and that the glass transition and crystallization behavior are associated with the heating rate, and possess the kinetic effect. Hydrogen increases the glass transition temperature and the crystallization temperature, decreasing the enthalpies in the different stages of crystallization.Hydrogen increases the activation energies of the glass transition and the crystallization and changes the kinetic effect. The dependent extent between the glass transition, the crystallization and heating rate decreases after hydrogen charging.

  7. Influence of composition and heat treatments on corrosion resistance of Fe-Co-BSi amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Angelini, E.; Antonione, C.; Baricco, M.; Rosalbino, F.; Zucchi, F. (Ist. Elettrotecnico Nazionale Galileo Ferraris, Turin (Italy) Turin Univ. (Italy) Politecnico di Torino (Italy))

    This paper studies the influence of composition and heat treatments on the corrosion resistance, in a solution of Na/sub 2/SO/sub 4/ 0.05M + H/sub 2/SO/sub 4/ 0.05M, at 1.5 pH, of a series of iron base amorphous alloys with increasing cobalt content, i.e., Fe/sub 80-x/Co/sub x/B/sub 10/Si/sub 10/ with x=0, 30, and 80. The treatments were carried out in an argon atmosphere over increasing time durations: 30, 60, 120, and 240 minutes, and increasing temperatures: 350, 400, 450 and 500 degrees C respectively. It was possible to observe that, independent of heat treatment, the corrosion resistance increased with increasing cobalt concentration. In comparing samples having the same chemical composition, it was noted that their electrochemical behaviour worsened with increasing temperature and time.

  8. Synthesis and Electro-Magneto-Mechanical Properties of Graphene Aerogels Functionalized with Co-Fe-P Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Guang-Ping Zheng

    2016-07-01

    Full Text Available Graphene aerogels (GAs are functionalized with Fe-Co-P alloy using an electro-deposition method. The Fe-Co-P alloy coated on the graphene nanosheets is found to possess an amorphous structure and a nanoporous architecture of GAs. The electro-mechanical properties of GAs are significantly affected by the Fe-Co-P nanoparticles embedded inside GAs. The electro-mechanical responses of GA/Fe-Co-P nanoporous hybrid structures are sensitive to an applied magnetic field, demonstrating that they are promising for electro-magneto-mechanical applications. The light-weight, high-strength and nanoporous GAs functionalized with Fe-Co-P amorphous alloys are desirable sensors, actuators, and nano-electro-mechanical systems that could be controlled or manipulated by mechanical, electric and magnetic fields.

  9. 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

  10. Glass-forming ability analysis of selected Fe-based bulk amorphous alloys

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2010-09-01

    Full Text Available Purpose: The paper mainly aims to present the structure and thermal stability of selected Fe-based bulk metallic glasses: Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4.Design/methodology/approach: The investigated samples were cast in form of the rods by the pressure die casting method. The structure analysis of the studied materials in as-cast state was carried out using XRD and TEM methods. The thermal stability associated with glass transition temperature (Tg, onset (Tx and peak (Tp crystallization temperature was examined by differential scanning calorimetry (DSC. Several parameters have been used to determine the glass-forming ability of studied alloys. The parameters of GFA included reduced glass transition temperature (Trg, supercooled liquid region (ΔTx, the stability (S and (Kgl parameter.Findings: The XRD and TEM investigations revealed that the studied as-cast metallic glasses were fully amorphous. Changes of the onset and peak crystallization temperature and the glass transition temperature as a function of glassy samples thickness were stated. The good glass-forming ability (GFA enabled casting of the Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4 glassy rods.Practical implications: The obtained examination results confirm the utility of applied investigation methods in the thermal stability analysis of examined bulk amorphous alloys. It is evident that parameters Trg, ΔTx, Kgl, S could be used to determine glass-forming ability of studied bulk metallic glasses.Originality/value: The success of fabrication of studied Fe-based bulk metallic glasses in form of rods with diameter up to 3 mm is important for the future progress in research of this group of materials.

  11. Influence of bath composition on the electrodeposition of cobalt-molybdenum amorphous alloy thin films

    Institute of Scientific and Technical Information of China (English)

    Qiaoying Zhou; Hongliang Ge; Guoying Wei; Qiong Wu

    2008-01-01

    Cobalt-molybdenum (Co-Mo) amorphous alloy thin films were deposited on copper substrates by the electrochemical method at pH 4.0. Among the experimental electrodeposition parameters, only the concentration ratio of molybdate to cobalt ions ([ MoO2-4 ]/[CO2+]) was varied to analyze its influence on the mechanism of induced cobalt-molybdenum codeposition. Voltammetry was one of the main techniques, which was used to examine the voltammetric response, revealing that cobalt-molybdenum codeposi-tion depended on the nature of the species in solution. To correlate the type of the film to the electrochemical response, various co-bait-molybdenum alloy thin films obtained from different [ MoO2-4]/[Co2+] solutions were tested. Crack-free homogeneous films could be easily obtained from the low molybdate concentrations ([ MoO2-4]/[Co2+]≈0.05) applying low deposition potentials.Moreover, the content of molybdenum up to 30wt% could be obtained from high molybdate concentration; in this case, the films showed cracks. The formation of these cracked films could be predicted from the observed distortions in the curves of electric cur-rent-time (j-t) deposition transients. The films with amorphous stmeture were obtained. The hysteresis loops suggested that the easily film were obtained when the deposition potential was -1025 mV, and [ MoO2-4]/[Co2+] was 0.05 in solution, which exhibited a nicer soft-magnetic response.

  12. First-principles study of the structural and dynamic properties of the liquid and amorphous Li–Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Han-Hsin; Kuo, Chin-Lung, E-mail: chinlung@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Lu, Jian-Ming [National Center for High-Performance Computing, Tainan 74147, Taiwan (China)

    2016-01-21

    We have performed density functional theory calculations and ab initio molecular dynamics to investigate the structures and dynamic properties of the liquid and amorphous Li{sub x}Si alloys over a range of composition from x = 1.0 − 4.8. Our results show that Si atoms can form a variety of covalently bonded polyanions with diverse local bonding structures in the liquid alloys. Like in c-LiSi, Si atoms can form a continuous bond network in liquid Li{sub 1.0}Si at 1050 K, while it gradually disintegrates into many smaller Si polyanions as the Li content increases in the alloys. The average sizes of Si polyanions in these liquid alloys were found to be relatively larger than those in their crystalline counterparts, which can even persist in the highly lithiated Li{sub 4.81}Si alloy at 1500 K. Our results also show that amorphous Li{sub x}Si alloys have similar local bonding structures but a largely increased short-range order as compared to their liquid counterparts. The differences between the average coordination number of each atomic pair in amorphous solids and that in the liquids are less than 1.1. Furthermore, our calculations reveal that Li and Si atoms can exhibit very distinct dynamic behaviors in the liquids and their diffusivities appear to be largely dependent on the chemical composition of the alloys. The diffusivity of Li was found to increase with the Li content in the alloys primarily because of the reduced interactions between Li and Si atoms, while the Si diffusivity also increases due to the gradual disintegration of the strongly interconnected Si bond network. The diffusivity of Li in amorphous Li{sub x}Si was predicted to lie in the range between 10{sup −7} and 10{sup −9} cm{sup 2}/s at 300 K, which is more than 20-fold larger than that of Si over the composition range considered. Our calculations further show that the diffusivities of both Li and Si can increase by two orders of magnitude as x increases from 1.0 to 3.57 in amorphous Li

  13. First-principles study of the structural and dynamic properties of the liquid and amorphous Li-Si alloys.

    Science.gov (United States)

    Chiang, Han-Hsin; Lu, Jian-Ming; Kuo, Chin-Lung

    2016-01-21

    We have performed density functional theory calculations and ab initio molecular dynamics to investigate the structures and dynamic properties of the liquid and amorphous LixSi alloys over a range of composition from x = 1.0 - 4.8. Our results show that Si atoms can form a variety of covalently bonded polyanions with diverse local bonding structures in the liquid alloys. Like in c-LiSi, Si atoms can form a continuous bond network in liquid Li1.0Si at 1050 K, while it gradually disintegrates into many smaller Si polyanions as the Li content increases in the alloys. The average sizes of Si polyanions in these liquid alloys were found to be relatively larger than those in their crystalline counterparts, which can even persist in the highly lithiated Li4.81Si alloy at 1500 K. Our results also show that amorphous LixSi alloys have similar local bonding structures but a largely increased short-range order as compared to their liquid counterparts. The differences between the average coordination number of each atomic pair in amorphous solids and that in the liquids are less than 1.1. Furthermore, our calculations reveal that Li and Si atoms can exhibit very distinct dynamic behaviors in the liquids and their diffusivities appear to be largely dependent on the chemical composition of the alloys. The diffusivity of Li was found to increase with the Li content in the alloys primarily because of the reduced interactions between Li and Si atoms, while the Si diffusivity also increases due to the gradual disintegration of the strongly interconnected Si bond network. The diffusivity of Li in amorphous LixSi was predicted to lie in the range between 10(-7) and 10(-9) cm(2)/s at 300 K, which is more than 20-fold larger than that of Si over the composition range considered. Our calculations further show that the diffusivities of both Li and Si can increase by two orders of magnitude as x increases from 1.0 to 3.57 in amorphous LixSi, indicating a more profound dependence on the

  14. Amorphous Nickel Based Alloy Catalysts and Magnetically Stabilized Bed Hydrogenation Technology

    Institute of Scientific and Technical Information of China (English)

    MuXuhong; ZongBaoning; 等

    2002-01-01

    Amorphous nickel based alloy catalysts(denoted as the SRNA series catalysts)were prepared via rapid quenching method followed by alkali leaching and other activation procedures.The physicochemical characterizations show that nickel,the active component in these catalysts,exists in the amorphous state,and the catalyst particles possess many nanosized voids leading to large surface area(the highest is 145m2/g).The evaluation results in some model reactions show that the SRNA series catalysts have 2 to 4 times higher activity and selectivity than conventional Raney Ni catalyst for the hydrogenation of compounds with unsatur-ated functional groups.At present,the SRNA series catalysts have been successfully used in hydrogenation of glucose,hydrogenation of pharmaceutical intermediates and purification of caprolactam.In order to use these catalysts efficiently,a magnetically stabilized bed(MSB) technology has been developed by combining the ferromagnetic property of the catalyst with the good mass transfer characteristics of MSB.The demonstration unit of MSB hydrogenation technology has been set up and has kept running for 2800 hours.The results show that,after running 2800 hours,the catalyst still retained good activity; meanwhile,the hydrogenation effi-ciency had been improved 10 times in comparison with the traditional CSTR process.

  15. Amorphous Nickel Based Alloy Catalysts and Magnetically Stabilized Bed Hydrogenation Technology

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Amorphous nickel based alloy catalysts (denoted as the SRNA series catalysts) were prepared viarapid quenching method followed by alkali leaching and other activation procedures. The physicochemicalcharacterizations show that nickel, the active component in these catalysts, exists in the amorphous state, andthe catalyst particles possess many nanosized voids leading to large surface area (the highest is 145m2/g). Theevaluation results in some model reactions show that the SRNA series catalysts have 2 to 4 times higheractivity and selectivity than conventional Raney Ni catalyst for the hydrogenation of compounds with unsatur-ated functional groups. At present, the SRNA series catalysts have been successfully used in hydrogenation ofglucose, hydrogenation of pharmaceutical intermediates and purification of caprolactam. In order to use thesecatalysts efficiently, a magnetically stabilized bed (MSB) technology has been developed by combining theferromagnetic property of the catalyst with the good mass transfer characteristics of MSB. The demonstrationunit of MSB hydrogenation technology has been set up and has kept running for 2800 hours. The results showthat, after running 2800 hours, the catalyst still retained good activity; meanwhile, the hydrogenation effi-ciency had been improved 10 times in comparison with the traditional CSTR process.

  16. Amorphous Nickel Based Alloy Catalysts and Magnetically Stabilized Bed Hydrogenation Technology

    Institute of Scientific and Technical Information of China (English)

    Mu Xuhong; Zong Baoning; Meng Xiangkun; Min Enze

    2002-01-01

    Amorphous nickel based alloy catalysts (denoted as the SRNAseries catalysts) were prepared viarapid quenching method followed by alkali leaching and other activation procedures. The physicochemicalcharacterizations show that nickel, the active component in these catalysts, exists in the amorphous state, andthe catalyst particles possess many nanosized voids leading to large surface area (the highest is 145m2/g). Theevaluation results in some model reactions show that the SRNA series catalysts have 2 to 4 times higheractivity and selectivity than conventional Raney Ni catalyst for the hydrogenation of compounds with unsatur-ated functional groups. At present, the SRNA series catalysts have been successfully used in hydrogenation ofglucose, hydrogenation of pharmaceutical intermediates and purification of caprolactam. In order to use thesecatalysts efficiently, a magnetically stabilized bed (MSB) technology has been developed by combining theferromagnetic property of the catalyst with the good mass transfer characteristics of MSB. The demonstrationunit of MSB hydrogenation technology has been set up and has kept running for 2800 hours. The results showthat, after running 2800 hours, the catalyst still retained good activity; meanwhile, the hydrogenation effi-ciency had been improved 10 times in comparison with the traditional CSTR process.

  17. 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.

  18. Observation by conductive-probe atomic force microscopy of strongly inverted surface layers at the hydrogenated amorphous silicon/crystalline silicon heterojunctions

    Science.gov (United States)

    Maslova, O. A.; Alvarez, J.; Gushina, E. V.; Favre, W.; Gueunier-Farret, M. E.; Gudovskikh, A. S.; Ankudinov, A. V.; Terukov, E. I.; Kleider, J. P.

    2010-12-01

    Heterojunctions made of hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) are examined by conducting probe atomic force microscopy. Conductive channels at both (n )a-Si:H/(p)c-Si and (p)a-Si:H/(n)c-Si interfaces are clearly revealed. These are attributed to two-dimension electron and hole gases due to strong inversion layers at the c-Si surface in agreement with previous planar conductance measurements. The presence of a hole gas in (p )a-Si:H/(n)c-Si structures implies a quite large valence band offset (EVc-Si-EVa-Si:H>0.25 eV).

  19. Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon

    Science.gov (United States)

    Puerto, Daniel; Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

    2016-07-01

    Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N eff) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics.

  20. Bulk amorphous Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} alloys fabricated by consolidation of mechanically alloyed amorphous powders

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Bo; Wang, Xinfu; Li, Xianyu; Wang, Dan; Qin, Yong; Han, Fusheng, E-mail: fshan@issp.ac.cn

    2014-02-15

    Highlights: • Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} (x = 0, 6.25, and 12.5 at%) amorphous powders were synthesized by MA. • Bulk Al{sub 75}V{sub 12.5}Fe{sub 12.5} amorphous alloy is obtained by means of hydraulic pressing. • The Vickers microhardness of bulk sample is in the range of 821-927 HV. -- Abstract: Hydraulic press was used to produce bulk amorphous Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} (x = 0, 6.25, and 12.5) (at.%) alloy by consolidation of mechanically alloyed amorphous powder. The as-milled powders and bulk alloy were examined by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The glass-forming ability was evaluated in accordance with the milling time. The results show that the glass-forming ability of the mechanical-alloyed Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} powders decreases with the increase of x. The onset crystallization temperatures (T{sub x}{sup onset}) of the three powders are 749 K, 771 K and 712 K, respectively. The results also indicate that the quality of consolidation is very good and the product’s Vickers microhardness is relatively high (821–927 HV)

  1. The effect of minor addition of insoluble elements on transformation kinetics in amorphous Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Y.; Perepezko, J.H., E-mail: perepezk@engr.wisc.edu

    2015-09-15

    Highlights: • By doping Pb or In in AlYFe alloys, the primary crystallization of Al is promoted. • The catalytic effect is based on the good wetting behavior between Al and Pb. • Pb promotes crystallization by providing heterogeneous nucleation sites. • Through doping 0.5–2 at.% of In, T{sub x} decreases by 35–47 °C. • The coherent interface shows a good contacting behavior between Al and In. - Abstract: Nanocrystalline metallic materials based on partial devitrification of amorphous aluminum alloys show an attractive combination of high strength and low density. A key feature concerning the improved mechanical properties is the high number density of Al nanocrystals (10{sup 22}–10{sup 23} m{sup −3}) that precipitate within the amorphous precursor structure upon low temperature annealing. For Al{sub 87}Y{sub 7}Fe{sub 5}Pb, the melt-spun ribbons consisted of an amorphous matrix with a dispersion of Pb nanoparticles (10 nm diameter). HRTEM images of the Pb–Al interface revealed a good wetting behavior between the Al and the Pb nanoparticles. Isothermal annealing for Al{sub 87}Y{sub 7}Fe{sub 5}Pb showed no transient stage even though the crystallization onset, T{sub x}, was at a much lower temperature (247 °C) compared with Al{sub 88}Y{sub 7}Fe{sub 5} (267 °C). For Al{sub (88−x)}Y{sub 7}Fe{sub 5}In{sub x} (x = 0.5, 1.0, 1.5, 2.0), the DSC results indicated that T{sub x} continuously decreased from 232 °C to 220 °C as the indium level increases from 0.5 at.% to 2.0 at.%. Under STEM, the image showed a coherent interface between Al and In particles. In the analysis of the transformation kinetics, the addition of minor elements can effectively promote additional nucleation of Al nanocrystals by providing heterogeneous nucleation sites. These developments offer new opportunities for the control of nanoscale microstructures.

  2. The Temperature Dependence Coefficients of Amorphous Silicon and Crystalline Photovoltaic Modules Using Malaysian Field Test Investigation

    Directory of Open Access Journals (Sweden)

    Sulaiman Shaari

    2009-01-01

    Full Text Available The temperature dependence coefficients of amorphous silicon and crystalline photovoltaic (PV modules using Malaysian field data have been obtained using linear regression technique. This is achieved by studying three test stand-alone PV-battery systems using 62 Wp a-Si, 225 Wp multi-crystalline and 225 Wp mono-crystalline PV modules. These systems were designed to provide electricity for rural domestic loads at 200 W, 500 W and 530 W respectively. The systems were installed in the field with data monitored using data loggers. Upon analysis, the study found that the normalized power output per operating array temperature for the amorphous silicon modules, multi-crystalline modules and mono-crystalline modules were: +0.037 per°C, +0.0225 per °C and +0.0263 per °C respectively. In addition, at a solar irradiance value of 500 Wm-2, the current, voltage, power and efficiency dependence coefficients on operating array temperatures obtained from linear regression were: +37.0 mA per °C, -31.8 mV per °C, -0.1036 W per °C and -0.0214% per °C, for the a-Si modules, +22.5 mA per °C, -39.4 mV per °C, -0.2525 W per °C, -0.072 % per °C for the multi-crystalline modules and +26.3 mA per °C, -32.6 mV per °C, -0.1742 W per °C, -0.0523 % per °C for the mono-crystalline modules. These findings have a direct impact on all systems design and sizing in similar climate regions. It is thus recommended that the design and sizing of PV systems in the hot and humid climate regions of the globe give due address to these findings.

  3. Photostability Assessment in Amorphous-Silicon Solar Cells; Determinacion de la Fotoestabilidad en Celulas Solares de Silicio Amorfo

    Energy Technology Data Exchange (ETDEWEB)

    Gandia, J. J.; Carabe, J.; Fabero, F.; Jimenez, R.; Rivero, J. M. [Ciemat, Madrid (Spain)

    2000-07-01

    The present status of amorphous-silicon-solar-cell research and development at CIEMAT requires the possibility to characterise the devices prepared from the point of view of their stability against sunlight exposure. Therefore a set of tools providing such a capacity has been developed. Together with an introduction to photovoltaic applications of amorphous silicon and to the photodegradation problem, the present work describes the process of setting up these tools. An indoor controlled-photodegradation facility has been designed and built, and a procedure has been developed for the measurement of J-V characteristics in well established conditions. This method is suitable for a kinds of solar cells, even for those for which no model is still available. The photodegradation and characterisation of some cells has allowed to validate both the new testing facility and method. (Author) 14 refs.

  4. 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].

  5. 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.

  6. 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.

  7. Optimization of transparent and reflecting electrodes for amorphous silicon solar cells. Annual technical report, April 1, 1995--March 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, R.G.; Sato, H.; Liang, H.; Liu, X.; Thornton, J. [Harvard Univ., Cambridge, MA (United States)

    1996-08-01

    The general objective is to develop methods to deposit materials which can be used to make more efficient solar cells. The work is organized into three general tasks: Task 1. Develop improved methods for depositing and using transparent conductors of fluorine-doped zinc oxide in amorphous silicon solar cells Task 2. Deposit and evaluate titanium oxide as a reflection-enhancing diffusion barrier between amorphous silicon and an aluminum or silver back-reflector. Task 3. Deposit and evaluate electrically conductive titanium oxide as a transparent conducting layer on which more efficient and more stable superstrate cells can be deposited. About one-third of the current project resources are allocated to each of these three objectives.

  8. Ni-WC composite coatings by carburizing electrodeposited amorphous and nanocrystalline Ni-W alloys

    Science.gov (United States)

    Latif, Saadia; Mehmood, Mazhar; Ahmad, Jamil; Aslam, Muhammad; Ahmed, Maqsood; Zhang, Zhi-dong

    2010-03-01

    In situ formation of tungsten carbide in the matrix of FCC nickel has been achieved by carburizing of the electrodeposited Ni-W alloy coatings. The size of the carbide particles ranges between 100 and 500 nm. The carbide phase is also present in the form of very small precipitates inside the nickel grains. The size of such precipitates is between 10 and 40 nm. The carburizing environment was created by introducing a flowing mixture of vaporized 95.5% alcohol (0.25 ml/min, liquid) and argon (0.5 L/min, gas) into the carburizing furnace. Supersaturated nature of electrodeposited amorphous and nanocrystalline alloys, in addition to high diffusivity, have been attributed for the formation of carbide phase in the deposits at a temperature range of 700-850 °C. The carbide-metal interface is clean and the composite coatings are compact. Hardness values up to about 1100 KHN are achieved. Hardness increases with tungsten content and carburizing temperature.

  9. Ni-WC composite coatings by carburizing electrodeposited amorphous and nanocrystalline Ni-W alloys

    Energy Technology Data Exchange (ETDEWEB)

    Latif, Saadia [National Centre for Nanotechnology, Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650 (Pakistan); Mehmood, Mazhar, E-mail: mazhar@pieas.edu.pk [National Centre for Nanotechnology, Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650 (Pakistan); Ahmad, Jamil; Aslam, Muhammad [National Centre for Nanotechnology, Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650 (Pakistan); Ahmed, Maqsood [Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Zhang Zhidong [Institute of Metals Research, Chinese Academy of Science, Shenyang (China)

    2010-03-01

    In situ formation of tungsten carbide in the matrix of FCC nickel has been achieved by carburizing of the electrodeposited Ni-W alloy coatings. The size of the carbide particles ranges between 100 and 500 nm. The carbide phase is also present in the form of very small precipitates inside the nickel grains. The size of such precipitates is between 10 and 40 nm. The carburizing environment was created by introducing a flowing mixture of vaporized 95.5% alcohol (0.25 ml/min, liquid) and argon (0.5 L/min, gas) into the carburizing furnace. Supersaturated nature of electrodeposited amorphous and nanocrystalline alloys, in addition to high diffusivity, have been attributed for the formation of carbide phase in the deposits at a temperature range of 700-850 deg. C. The carbide-metal interface is clean and the composite coatings are compact. Hardness values up to about 1100 KHN are achieved. Hardness increases with tungsten content and carburizing temperature.

  10. Effect of Co content on structure and magnetic behaviors of high induction Fe-based amorphous alloys

    Science.gov (United States)

    Roy, Rajat K.; Panda, Ashis K.; Mitra, Amitava

    2016-11-01

    The replacement of Fe with Co is investigated in the (Fe1-xCox)79Si8.5B8.5Nb3Cu1 (x=0, 0.05, 0.2, 0.35, 0.5) amorphous alloys. The alloys are synthesized in the forms of ribbons by single roller melt spinning technique, and the structural and magnetic properties of annealed ribbons are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), B-H curve tracer, respectively. All as-cast alloys are structurally amorphous, however, their magnetic properties are varying with Co addition. The Co addition within 5-20 at% results in moderate thermal stability, saturation induction, Curie temperature and lowest coercivity, while 35 at% Co causes highest saturation induction, coercivity, Curie temperature and lowest thermal stability. On devitrification, the magnetic properties change with the generation of α-FeCo nanocrystallites and (FeCo)23B6, Fe2B phases during primary and secondary crystallization stages, respectively. A small amount Co is advantageous for maintaining finer nanocrystallites in amorphous matrix even after annealing at 600 °C, leading to high saturation magnetization (>1.5 T) and low coercivity (~35 A/m). The improved magnetic properties at elevated temperatures indicate these alloys have a potential for high frequency transformer core applications.

  11. Influence of pulsing current on the glass transition and crystallizing kinetics of a Zr base bulk amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    WU Wenfei; YAO Kefu; ZHAO Zhankui

    2004-01-01

    Based on the thermal analysis, the influence of pulsing current on the glass transition and crystallizing kinetics of Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy has been studied. The obtained results show that after the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy was pretreated by high-density pulsing current at low temperature, its glass transition temperature Tg, the initial crystallizing temperature Tx and the corresponding exothermic peak of crystallization Tpi were reduced. But the temperature range of supercooled liquid ΔT=Tx-Tg is almost the same. The calculated results with Kissinger equation show that the activation energy of glass transition of the alloy pretreated is reduced significantly, while the activation energy of crystallization is basically unchanged. The influence of pulsing current on the glass transition and crystallization of the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy is believed to be related with the structure relaxation of the glass caused by the current.

  12. Morphological Change and Its Mechanism of Eutectic Silicon for Strontium-Modified Alloy A357

    Institute of Scientific and Technical Information of China (English)

    GUO Jian-ting; DU Xing-hao

    2004-01-01

    The microstructure evolution for alloy A357 modified by original Al-10Sr alloy was systematically investigated. The results show that the eutectic silicon phase becomes finer and more homogeneous with the increase of strontium concentration and modifying temperature. The mechanism of microstructure evolution was also investigated by TEM observation.

  13. Vacuum Brazing TC4 Titanium Alloy to 304 Stainless Steel with Cu-Ti-Ni-Zr-V Amorphous Alloy Foil

    Science.gov (United States)

    Dong, Honggang; Yang, Zhonglin; Wang, Zengrui; Deng, Dewei; Dong, Chuang

    2014-10-01

    Dissimilar metal vacuum brazing between TC4 titanium alloy and 304 stainless steel was conducted with newly designed Cu-Ti-Ni-Zr-V amorphous alloy foils as filler metals. Solid joints were obtained due to excellent compatibility between the filler metal and stainless steel substrate. Partial dissolution of stainless steel substrate occurred during brazing. The shear strength of the joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25 foil was 105 MPa and that with Cu37.5Ti25Ni12.5Zr12.5V12.5 was 116 MPa. All the joints fractured through the gray layer in the brazed seam, revealing brittle fracture features. Cr4Ti, Cu0.8FeTi, Fe8TiZr3 and Al2NiTi3C compounds were found in the fractured joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25 foil, and Fe2Ti, TiCu, Fe8TiZr3 and NiTi0.8Zr0.3 compounds were detected in the joint brazed with Cu37.5Ti25Ni12.5Zr12.5V12.5 foil. The existence of Cr-Ti, Fe-Ti, Cu-Fe-Ti, and Fe-Ti-V intermetallic compounds in the brazed seam caused fracture of the resultant joints.

  14. 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.

  15. 25th anniversary article: organic field-effect transistors: the path beyond amorphous silicon.

    Science.gov (United States)

    Sirringhaus, Henning

    2014-03-05

    Over the past 25 years, organic field-effect transistors (OFETs) have witnessed impressive improvements in materials performance by 3-4 orders of magnitude, and many of the key materials discoveries have been published in Advanced Materials. This includes some of the most recent demonstrations of organic field-effect transistors with performance that clearly exceeds that of benchmark amorphous silicon-based devices. In this article, state-of-the-art in OFETs are reviewed in light of requirements for demanding future applications, in particular active-matrix addressing for flexible organic light-emitting diode (OLED) displays. An overview is provided over both small molecule and conjugated polymer materials for which field-effect mobilities exceeding > 1 cm(2) V(-1) s(-1) have been reported. Current understanding is also reviewed of their charge transport physics that allows reaching such unexpectedly high mobilities in these weakly van der Waals bonded and structurally comparatively disordered materials with a view towards understanding the potential for further improvement in performance in the future.

  16. Morphological and Chemical Analysis Of Degraded Single Junction Amorphous Silicon Module.

    Science.gov (United States)

    Osayemwenre, Gilbert; Meyer, Edson; Mamphweli, Sampson

    2017-01-01

    Photovoltaic solar modules have different defects and degradation characteristic modes. These defects/degradation modes normally heats up some regions in the PV module, depending on the degree and size of the localised heat or hot spot, the localized heat can rise above the temperature limit of the module thereby cause damage to the structural orientation. The presence of severe defect and degradation correlates with high temperature gradients that usually results in morphological damage especially under outdoor conditions. The present study investigates the effect of defect/degradation on the surface morphology of the single junction amorphous silicon modules (a-Si:H) during outdoor deployment. The observed structural damage was analysed using scanning electron microscope (SEM) and energy dispersion X-ray (EDX) to ascertain the elemental composition. Results show huge discrepancies in the chemical composition constitute alone different regions. The presence of high concentration of carbon and oxygen was found in the affected region. The authors sincerely thank GMDRC University of Fort Hare for financial support. The authors also wish to thank Eskom for financing this project.

  17. Field collapse due to band-tail charge in amorphous silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qi; Crandall, R.S. [National Renewable Energy Lab., Golden, CO (United States); Schiff, E.A. [Syracuse Univ., NY (United States)

    1996-05-01

    It is common for the fill factor to decrease with increasing illumination intensity in hydrogenated amorphous silicon solar cells. This is especially critical for thicker solar cells, because the decrease is more severe than in thinner cells. Usually, the fill factor under uniformly absorbed red light changes much more than under strongly absorbed blue light. The cause of this is usually assumed to arise from space charge trapped in deep defect states. The authors model this behavior of solar cells using the Analysis of Microelectronic and Photonic Structures (AMPS) simulation program. The simulation shows that the decrease in fill factor is caused by photogenerated space charge trapped in the band-tail states rather than in defects. This charge screens the applied field, reducing the internal field. Owing to its lower drift mobility, the space charge due to holes exceeds that due to electrons and is the main cause of the field screening. The space charge in midgap states is small compared with that in the tails and can be ignored under normal solar-cell operating conditions. Experimentally, the authors measured the photocapacitance as a means to probe the collapsed field. They also explored the light intensity dependence of photocapacitance and explain the decrease of FF with the increasing light intensity.

  18. 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.

  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. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Electric properties of undoped hydrogenated amorphous silicon semiconductors irradiated with self-ions

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Shin-ichiro, E-mail: sato.shinichiro@jaea.go.jp [Japan Atomic Energy Agency (JAEA), 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Sai, Hitoshi [National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Ohshima, Takeshi [Japan Atomic Energy Agency (JAEA), 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Imaizumi, Mitsuru; Shimazaki, Kazunori [Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505 (Japan); Kondo, Michio [National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2012-08-15

    This paper reports dark conductivity (DC), photoconductivity (PC), and Seebeck coefficient variations of undoped hydrogenated amorphous silicon semiconductors irradiated with protons and Si ions. Both the DC and PC values show nonmonotonic variations with increasing a fluence in the case of proton irradiation, whereas the monotonic decreases are observed in the case of Si ion irradiation. From results of the Seebeck coefficient variation due to proton irradiation, it is shown that the increase in DC and PC in the low fluence regime is caused by donor-center generation. Also, it is shown by analyzing the proton energy dependence and the energy deposition process that the donor-center generation is based on the electronic excitation effect. On the other hand, the decrease in DC and PC in the high fluence regime is attributed to the carrier removal effect and the carrier lifetime decrease due to the accumulation of dangling bonds, respectively. The dangling bond generation due to ion irradiation is mainly caused by the displacement damage effect and therefore it is different from the generation process in the Staebler-Wronski effect.

  6. Anomalous enhancement in radiation induced conductivity of hydrogenated amorphous silicon semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Shin-ichiro, E-mail: sato.shinichiro@jaea.go.jp [Japan Atomic Energy Agency (JAEA), 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Sai, Hitoshi [National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Ohshima, Takeshi [Japan Atomic Energy Agency (JAEA), 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Imaizumi, Mitsuru; Shimazaki, Kazunori [Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505 (Japan); Kondo, Michio [National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2012-09-01

    Electric conductivity variations of undoped hydrogenated amorphous silicon (a-Si:H) semiconductors induced by swift protons are investigated. The results show that the conductivity drastically increases at first and then decreases on further irradiation. The conductivity enhancement is observed only in the low fluence regime and lasts for a prolonged period of time when proton irradiation stops in this fluence regime. On the other hand, the photosensitivity has a minimum value around the conductivity peak. This fact indicates that non-equilibrium carriers do not play a dominant role in the electric conduction in this fluence regime. It is found that the anomalous conductivity enhancement in the low fluence regime is dominated by donor center generation. At higher fluences the conductivity during irradiation is dominated by non-equilibrium carriers as the generated donor centers disappear. It is also found that the RIC in the high fluence regime is proportional to the carrier generation rate. This indicates that the recombination process of non-equilibrium carriers is dominated by indirect recombination via defect levels.

  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. In vivo Characterization of Amorphous Silicon Carbide As a Biomaterial for Chronic Neural Interfaces.

    Science.gov (United States)

    Knaack, Gretchen L; McHail, Daniel G; Borda, German; Koo, Beomseo; Peixoto, Nathalia; Cogan, Stuart F; Dumas, Theodore C; Pancrazio, Joseph J

    2016-01-01

    Implantable microelectrode arrays (MEAs) offer clinical promise for prosthetic devices by enabling restoration of communication and control of artificial limbs. While proof-of-concept recordings from MEAs have been promising, work in animal models demonstrates that the obtained signals degrade over time. Both material robustness and tissue response are acknowledged to have a role in device lifetime. Amorphous Silicon carbide (a-SiC), a robust material that is corrosion resistant, has emerged as an alternative encapsulation layer for implantable devices. We systematically examined the impact of a-SiC coating on Si probes by immunohistochemical characterization of key markers implicated in tissue-device response. After implantation, we performed device capture immunohistochemical labeling of neurons, astrocytes, and activated microglia/macrophages after 4 and 8 weeks of implantation. Neuron loss and microglia activation were similar between Si and a-SiC coated probes, while tissue implanted with a-SiC displayed a reduction in astrocytes adjacent to the probe. These results suggest that a-SiC has a similar biocompatibility profile as Si, and may be suitable for implantable MEA applications as a hermetic coating to prevent material degradation.

  10. Memory effect in MOS structures containing amorphous or crystalline silicon nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Meier, Sebastian; Brueggemann, Rudolf; Bauer, Gottfried Heinrich [Institute of Physics, Carl von Ossietzky University Oldenburg, D-26111 Oldenburg (Germany); Nedev, Nicola [Istituto de Ingenieria, Universidad Autonoma de Baja California, Benito Juarez Blvd., s/n, C.P. 21280, Mexicali, Baja California (Mexico); Manolov, Emmo; Nesheva, Diana; Levi, Zelma [Insitute of Solid State Physics, Bulgarian Academy of Science, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria)

    2008-07-01

    Amorphous and crystalline silicon nanoparticles (Si-NPs) embedded in a SiO{sub 2} matrix are fabricated by thermal annealing of Metal/SiO{sub 2}/SiO{sub x}/c-Si structures (x=1.15) at 700 C or 1000 C in N{sub 2} atmosphere for 30 or 60 minutes. High frequency C-V measurements show that the samples can be charged negatively or positively by applying a positive or negative bias voltage to the gate. A memory effect, due to the Si-NPs in the SiO{sub 2} matrix, is observed. The method of measurement with open circuit between two measurements leads to the retention characteristic where the structures retain about 50% of negative charge trapped in Si-NPs for 24 hours. A second method, where the flat-band voltage is applied as bias voltage, shows shorter retention characteristics. There the Si-NPs retain 50% of their charge after 10 hours.

  11. Amorphous silicon under mechanical shear deformations: Shear velocity and temperature effects

    Science.gov (United States)

    Kerrache, Ali; Mousseau, Normand; Lewis, Laurent J.

    2011-04-01

    Mechanical shear deformations lead, in some cases, to effects similar to those resulting from ion irradiation. Here we characterize the effects of shear velocity and temperature on amorphous silicon (a-Si) modeled using classical molecular-dynamics simulations based on the empirical environment-dependent interatomic potential (EDIP). With increasing shear velocity at low temperature, we find a systematic increase in the internal strain leading to the rapid appearance of structural defects (fivefold-coordinated atoms). The impacts of externally applied strain can be almost fully compensated by increasing the temperature, allowing the system to respond more rapidly to the deformation. In particular, we find opposite power-law relations between the temperature and the shear velocity and the deformation energy. The spatial distribution of defects is also found to depend strongly on temperature and strain velocity. For low temperature or high shear velocity, defects are concentrated in a few atomic layers near the center of the cell, while with increasing temperature or decreasing shear velocity, they spread slowly throughout the full simulation cell. This complex behavior can be related to the structure of the energy landscape and the existence of a continuous energy-barrier distribution.

  12. Low-level boron doping and light-induced effects in amorphous silicon pin solar cells

    Science.gov (United States)

    Moeller, M.; Rauscher, B.; Kruehler, W.; Plaettner, R.; Pfleiderer, H.

    Amorphous silicon solar cells with the structure pin/ITO produced in the laboratory show an AM1 efficiency of up to 7.4 percent on 6 sq mm. The impact of doping the i-layer slightly with boron on the cell performance was studied together with its possible influence on the cell stability. Cells exposed to continuous AM1 illumination (up to 2000 hours) show a degradation of the efficiency. Differences in the bias-voltage during the deposition lead to significant differences in the stability whereas the influence of boron doping was not so prominent. The nu-tau-products for electrons and holes were shown to degrade differently through light-soaking for different doping-level. A further investigation was made by evaluating the frequency dependence of the capacitance via a new p i n junction model to obtain the density of states and the drift field in the i-layer for doping and light-soaking.

  13. Modified Mechanism of Eutectic Silicon in Al2O3/Al-Si Alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Al2O3/Al-Si alloy composite was manufactured by squeeze casting. The morphology of the eutectic silicon in the composite was observed by scanning electronic microscope (SEM), and the modified mechanism of eutectic silicon in the composite was approached. The alumina fiber in the composite can trigger twin during the growth of Al-Si eutectic and lead to the modification of eutectic silicon near the fiber.

  14. Comparison of Crevice Corrosion of Fe-Based Amorphous Metal and Crystalline Ni-Cr-Mo Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Shan, X; Ha, H; Payer, J H

    2008-07-24

    The crevice corrosion behaviors of an Fe-based bulk metallic glass alloy (SAM1651) and a Ni-Cr-Mo crystalline alloy (C-22) were studied in 4M NaCl at 100 C with cyclic potentiodynamic polarization and constant potential tests. The corrosion damage morphologies, corrosion products and the compositions of corroded surfaces of these two alloys were studied with optical 3D reconstruction, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Auger Electron Spectroscopy (AES). It was found that the Fe-based bulk metallic glass (amorphous alloy) SAM1651 had a more positive breakdown potential and repassivation potential than crystalline alloy C-22 in cyclic potentiodynamic polarization tests and required a more positive oxidizing potential to initiate crevice corrosion in constant potential test. Once crevice corrosion initiated, the corrosion propagation of C-22 was more localized near the crevice border compared to SAM1651, and SAM1651 repassivated more readily than C-22. The EDS results indicated that the corrosion products of both alloys contained high amount of O and were enriched in Mo and Cr. The AES results indicated that a Cr-rich oxide passive film was formed on the surfaces of both alloys, and both alloys were corroded congruently.

  15. Preparation of Plate Fe60Co8Zr10Mo5W2B15 Bulk Amorphous Alloy and Its Fracture Toughness

    Institute of Scientific and Technical Information of China (English)

    XIAO Huaxing; CHEN Guang

    2005-01-01

    With processes of arc melting, inductive melting and copper mold suction casting, a plate Fe-based bulk amorphous alloy Fe60Co8Zr10Mo5W2B15 with a thickness of 1mm was prepared. The surfaces and fractures of the cast bulk amorphous alloy were agleam and with typical metallic luster. The glass transition temperature(Tg), supercooled liquid region(△Tx)and reduced glass transition temperature(T rg)of the prepared Fe-based amorphous alloy are 884 K,63 K, and 0.611 respectively. The fracture toughness of the cast bulk amorphous alloy is at the level of 1.6 MPa·m1/2.

  16. Hydriding and dehydriding characteristics of nanocrystalline and amorphous Mg20-xLaxNi10(x=0-6) alloys prepared by melt-spinning

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yanghuan; ZHAO Dongliang; REN Huiping; GUO Shihai; WANG Qingchun; WANG Xinlin

    2009-01-01

    In order to improve the hydrogenation and dehydrogenation performances of the Mg2Ni-type alloys, Mg was partially substituted by La in the alloy, and melt spinning technology was used for the preparation of the Mg20-xLaxNi10 (x=0, 2, 4, 6) hydrogen storage alloys. The structures of the alloys were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). It was found that no amorphous phase formed in the as-spun La-free alloy, but the as-spun alloys containing La held a major amorphous phase. When La content x≤2, the major phase in the as-cast alloys was Mg2Ni phase, but with further increase of La content, the major phase of the as-cast alloys changed into LaNi5+LaMg3 phase. Thermal stability of the as-spun alloys was studied by differential scanning calorimetry (DSC), showing that spinning rate was a negligible factor on the crystallization temperature of the amor-phous phase. The hydrogen absorption and desorption kinetics of the as-cast and as-spun alloys were measured using an automatically con-trolled Sieverts apparatus, confirming that the hydrogen absorption and desorption capacities and kinetics of the as-cast alloys clearly in-creased with rising La content. For La content x=2, the as-spun alloy displayed optimal hydrogen desorption kinetics at 200 ℃.

  17. 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

  18. Study on Interface Structure and Bond Properties between Cemented Carbide and Tool Steel Blazing with amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    Bao Ming-dong; Xu Jin-fu; Xu Xue-bo; Zou Gui-sheng; Huang Geng-hua

    2004-01-01

    Cemented Carbide YG11C and Tool Steel Crl2MoV was blazed with Ni-base amorphous alloys, QG-1011,MBF-20 and MBF-75, using dynamics thermodynamics analogue testing machine Gleeble 1500D. The effects of brazing temperature, holding time and holding pressure on micro-structure and bond strength were investigated. Results showed that YG11C and Cr12MoV were all wetted well by these three Ni-base alloys, and the bond strength was as high as 220MPa,320MPa, 320MPa respectively. When the blazing temperature was at the point over the melting point 60-70℃ of Ni-base alloy, the holding time was about 2-10min, the suitable pressure was benefit for improving the brazing quality.Microanalysis showed Co in cemented carbide diffused into liquid brazing alloy and formed the Fe-Co solid .solution.

  19. Parametric Study of Amorphous High-Entropy Alloys formation from two New Perspectives: Atomic Radius Modification and Crystalline Structure of Alloying Elements

    Science.gov (United States)

    Hu, Q.; Guo, S.; Wang, J.M.; Yan, Y.H.; Chen, S.S.; Lu, D.P.; Liu, K.M.; Zou, J.Z.; Zeng, X.R.

    2017-01-01

    Chemical and topological parameters have been widely used for predicting the phase selection in high-entropy alloys (HEAs). Nevertheless, previous studies could be faulted due to the small number of available data points, the negligence of kinetic effects, and the insensitivity to small compositional changes. Here in this work, 92 TiZrHfM, TiZrHfMM, TiZrHfMMM (M = Fe, Cr, V, Nb, Al, Ag, Cu, Ni) HEAs were prepared by melt spinning, to build a reliable and sufficiently large material database to inspect the robustness of previously established parameters. Modification of atomic radii by considering the change of local electronic environment in alloys, was critically found out to be superior in distinguishing the formation of amorphous and crystalline alloys, when compared to using atomic radii of pure elements in topological parameters. Moreover, crystal structures of alloying element were found to play an important role in the amorphous phase formation, which was then attributed to how alloying hexagonal-close-packed elements and face-centered-cubic or body-centered-cubic elements can affect the mixing enthalpy. Findings from this work not only provide parametric studies for HEAs with new and important perspectives, but also reveal possibly a hidden connection among some important concepts in various fields. PMID:28051186

  20. Parametric Study of Amorphous High-Entropy Alloys formation from two New Perspectives: Atomic Radius Modification and Crystalline Structure of Alloying Elements.

    Science.gov (United States)

    Hu, Q; Guo, S; Wang, J M; Yan, Y H; Chen, S S; Lu, D P; Liu, K M; Zou, J Z; Zeng, X R

    2017-01-04

    Chemical and topological parameters have been widely used for predicting the phase selection in high-entropy alloys (HEAs). Nevertheless, previous studies could be faulted due to the small number of available data points, the negligence of kinetic effects, and the insensitivity to small compositional changes. Here in this work, 92 TiZrHfM, TiZrHfMM, TiZrHfMMM (M = Fe, Cr, V, Nb, Al, Ag, Cu, Ni) HEAs were prepared by melt spinning, to build a reliable and sufficiently large material database to inspect the robustness of previously established parameters. Modification of atomic radii by considering the change of local electronic environment in alloys, was critically found out to be superior in distinguishing the formation of amorphous and crystalline alloys, when compared to using atomic radii of pure elements in topological parameters. Moreover, crystal structures of alloying element were found to play an important role in the amorphous phase formation, which was then attributed to how alloying hexagonal-close-packed elements and face-centered-cubic or body-centered-cubic elements can affect the mixing enthalpy. Findings from this work not only provide parametric studies for HEAs with new and important perspectives, but also reveal possibly a hidden connection among some important concepts in various fields.

  1. 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...

  2. 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.

  3. Effect of crystallization on corrosion behavior of Fe40Ni38B18Mo4 amorphous alloy in 3.5% sodium chloride solution

    DEFF Research Database (Denmark)

    Wu, Y.F.; Chiang, Wen-Chi; Wu, J.K.

    2008-01-01

    After the crystallization of F40Ni38B18Mo4 amorphous alloy by vacuum annealing, the corrosion resistance of its crystalline state shows inferior to its amorphous state due to the local cell action between Ni phase and (Fe, Ni, Mo)(23)B-6 phase in matrix....

  4. Reversible amorphous-crystalline phase changes in a wide range of Se1-xTex alloys studied using ultrafast differential scanning calorimetry

    NARCIS (Netherlands)

    Vermeulen, Paul. A.; Momand, Jamo; Kooi, Bart J.

    2014-01-01

    The reversible amorphous-crystalline phase change in a chalcogenide material, specifically the Se1-xTex alloy, has been investigated for the first time using ultrafast differential scanning calorimetry. Heating rates and cooling rates up to 5000 K/s were used. Repeated reversible amorphous-crystalli

  5. Classical molecular dynamics and quantum abs-initio studies on lithium-intercalation in interconnected hollow spherical nano-spheres of amorphous Silicon

    DEFF Research Database (Denmark)

    Bhowmik, Arghya; Malik, R.; Prakash, S.;

    2016-01-01

    interconnected hollow nano-spheres of amorphous silicon have been found to exhibit high cyclability. The absence of fracture upon lithiation and the high cyclability has been attributed to reduction in intercalation stress due to hollow spherical geometry of the silicon nano-particles. The present work argues...

  6. Preparation and Cycling Performance of Iron or Iron Oxide Containing Amorphous Al-Li Alloys as Electrodes

    Directory of Open Access Journals (Sweden)

    Franziska Thoss

    2014-12-01

    Full Text Available Crystalline phase transitions cause volume changes, which entails a fast destroying of the electrode. Non-crystalline states may avoid this circumstance. Herein we present structural and electrochemical investigations of pre-lithiated, amorphous Al39Li43Fe13Si5-powders, to be used as electrode material for Li-ion batteries. Powders of master alloys with the compositions Al39Li43Fe13Si5 and Al39Li43Fe13Si5 + 5 mass-% FeO were prepared via ball milling and achieved amorphous/nanocrystalline states after 56 and 21.6 h, respectively. In contrast to their Li-free amorphous pendant Al78Fe13Si9, both powders showed specific capacities of about 400 and 700 Ah/kgAl, respectively, after the third cycle.

  7. Graded Index Silicon Geranium on Lattice Matched Silicon Geranium Semiconductor Alloy

    Science.gov (United States)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Elliott, James R., Jr. (Inventor); Stoakley, Diane M. (Inventor)

    2009-01-01

    A lattice matched silicon germanium (SiGe) semiconductive alloy is formed when a {111} crystal plane of a cubic diamond structure SiGe is grown on the {0001} C-plane of a single crystalline Al2O3 substrate such that a orientation of the cubic diamond structure SiGe is aligned with a orientation of the {0001} C-plane. A lattice match between the substrate and the SiGe is achieved by using a SiGe composition that is 0.7223 atomic percent silicon and 0.2777 atomic percent germanium. A layer of Si(1-x), ,Ge(x) is formed on the cubic diamond structure SiGe. The value of X (i) defines an atomic percent of germanium satisfying 0.2277

  8. Preparation and Characterization of Amorphous Layer on Aluminum Alloy Formed by Plasma Electrolytic Deposition (PED)

    Institute of Scientific and Technical Information of China (English)

    GUANYong-jun; XIAYuan

    2004-01-01

    In this investigation, protective layers were formed on aluminum substrate by Plasma Electrolytic Deposition (PED) using sodium silicate solution. The relation between the thickness of the layer and process time were studied. XRD, SEM, EDS were used to study the layer's structure, composition and micrograph. The results show that the deposited layers are amorphous and contain mainly oxygen, silicon, and aluminum. The possible formation mechanism of amorphous[Al-Si-O] layer was proposed: During discharge periods, Al2O3 phase of the passive film and SiO32- near the substrate surface are sintered into xSiO2(1-x)Al2O3 and then transformed into amorphous [Al-Si-O] phase.

  9. Electrochemical Impedance Spectroscopy study in micro-grain structured amorphous silicon anodes for lithium-ion batteries

    Science.gov (United States)

    Paloukis, Fotis; Elmasides, Costas; Farmakis, Filippos; Selinis, Petros; Neophytides, Stylianos G.; Georgoulas, Nikolaos

    2016-11-01

    In this paper, a study of the lithiation mechanism of micro-grain structured silicon anode is presented. Micro-grain amorphous silicon was deposited on special copper foil and it is shown that after several decades of galvanostatic cycles, it preserves its granular nature with minor degradation. In order to shed light on the lithiation mechanisms of the micro-grain silicon, Electrochemical Impedance Spectroscopy (EIS) was conducted on silicon half-cells at various State-of-Charge (SoC) and various discharging current values and the Solid-Electrolyte Interphase (SEI) RSEI and polarization resistance Rpol were determined. Results reveal that Rpol highly increases for cell voltages lower than 0.2 V and it strongly depends on the discharging C-rate. From X-ray Photoelectron Spectroscopy (XPS) measurements combined with surface sputtering, the existence of a LixSiyOz interlayer between SEI and silicon is confirmed, which is believed to play an important role to the lithium kinetics. Finally, combining our results, a lithiation mechanism of the micro-grain silicon anode is proposed.

  10. Investigation of carrier density and mobility in microcrystalline silicon alloys using Hall effect and thermopower measurements; Untersuchung der Ladungstraegerkonzentration und -beweglichkeit in mikrokristallinen Siliziumlegierungen mit Hall-Effekt und Thermokraft

    Energy Technology Data Exchange (ETDEWEB)

    Sellmer, Christian

    2012-08-31

    The electronic properties of amorphous and microcrystalline silicon layers in thin-film solar cells significantly affect the efficiency of solar cells. An important property of the individual layer is the electronic transport, which is described by the variables conductivity, photoconductivity, mobility, and carrier concentration. In the past, individual characterization methods were typically used to determine the electronic properties. Using the combination of Hall effect, conductivity, and thermoelectric power measurements additional variables can be derived, such as the effective density of states at the valence and conduction band edge, making a more detailed description of the material possible. To systematically study the electronic properties - in particular carrier mobility and carrier concentration - various series of silicon films are prepared for this work including microcrystalline silicon layers of different doping and crystallinity and a series of silicon films where the Fermi level is moved by irradiation with high energy electrons on one and the same sample. The results show that the transition from amorphous to microcrystalline transport is relatively abrupt. If the electron transport takes place in only amorphous regions, it is marked by the sign anomaly of the Hall effect. If a continuous crystalline path exists, the electronic properties are dominated by the crystalline volume fraction. The results of the measurements of silicon layers are compared with those of microcrystalline silicon carbide samples. Silicon carbide is especially interesting for future applications in thin-film solar cells due to high transparency and high conductivity. It is shown that the effective density of states at the valence and conduction band edge as a function of temperature in p- and n-type microcrystalline silicon and silicon carbide samples largely coincide with those of crystalline silicon or silicon carbide. A square root shaped profile of the density of

  11. Electrical and Magneto-Resistivity Measurements on Amorphous Copper-Titanium Alloys at Low Temperatures

    Science.gov (United States)

    Fan, Renyong

    1992-01-01

    The anomalous transport properties of highly disordered metallic glasses, which require corrections to the classical Boltzmann theory, are due to quantum interference effects of the scattered electron waves. These corrections provide new contributions to the resistivity: "weak localization" and "electron-electron interaction". To study these quantum interference effects, we have made the highest-precision measurements, so far, of the resistances of the amorphous rm Cu_{50}Ti_{50 } and rm Cu_{60}Ti _{40} ribbons at much lower temperatures than before (15mK 0.15K. In contrast, at the lowest temperatures, the magnetoresistances were dominated by weak localization with Zeeman splitting and Maki-Thompson superconducting fluctuations. For higher magnetic fields and lowest temperatures (B/T > 1 T/K), we find discrepancies between our data and the theoretical calculations. We found that most of the parameters of the theoretical fits to the data were similar for both rm Cu_{50}Ti_{50} and rm Cu_{60}Ti_ {40} alloys. The two important exceptions were the inelastic and spin-orbit lifetimes: their zero -field values were about an order of magnitude smaller than those from the magnetoresistances. Also the inelastic lifetimes tend to saturate for T<0.1K in non-zero magnetic fields. Finally, we were also able to estimate the expected superconducting transition temperatures of both rm Cu_{50}Ti_{50} and rm Cu_{60}Ti _{40} alloys: less than 15mK and 5mK, respectively. Our novel technique can, in principle, be used to make high precision resistance measurements down to 15mK on any ribbon or film-like high resistivity metal.

  12. Scanning transmission electron microscope analysis of amorphous-Si insertion layers prepared by catalytic chemical vapor deposition, causing low surface recombination velocities on crystalline silicon wafers

    OpenAIRE

    2012-01-01

    Microstructures of stacked silicon-nitride/amorphous-silicon/crystalline-silicon (SiN_x/a-Si/c-Si) layers prepared by catalytic chemical vapor deposition were investigated with scanning transmission electron microscopy to clarify the origin of the sensitive dependence of surface recombination velocities (SRVs) of the stacked structure on the thickness of the a-Si layer. Stacked structures with a-Si layers with thicknesses greater than 10 nm exhibit long effective carrier lifetimes, while thos...

  13. Accelerated kinetics of amorphous silicon using an on-the-fly off-lattice kinetic Monte-Carlo method

    Science.gov (United States)

    Joly, Jean-Francois; El-Mellouhi, Fedwa; Beland, Laurent Karim; Mousseau, Normand

    2011-03-01

    The time evolution of a series of well relaxed amorphous silicon models was simulated using the kinetic Activation-RelaxationTechnique (kART), an on-the-fly off-lattice kinetic Monte Carlo method. This novel algorithm uses the ART nouveau algorithm to generate activated events and links them with local topologies. It was shown to work well for crystals with few defects but this is the first time it is used to study an amorphous material. A parallel implementation allows us to increase the speed of the event generation phase. After each KMC step, new searches are initiated for each new topology encountered. Well relaxed amorphous silicon models of 1000 atoms described by a modified version of the empirical Stillinger-Weber potential were used as a starting point for the simulations. Initial results show that the method is faster by orders of magnitude compared to conventional MD simulations up to temperatures of 500 K. Vacancy-type defects were also introduced in this system and their stability and lifetimes are calculated.

  14. 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.

  15. Plasmonic enhancement of amorphous silicon solar photovoltaic cells with hexagonal silver arrays made with nanosphere lithography

    Science.gov (United States)

    Zhang, C.; Guney, D. O.; Pearce, J. M.

    2016-10-01

    Nanosphere lithography (NSL) provides an opportunity for a low-cost and scalable method to optically engineer solar photovoltaic (PV) cells. For PV applications, NSL is widely used in rear contact scenarios to excite surface plasmon polariton and/or high order diffractions, however, the top contact scenarios using NSL are rare. In this paper a systematic simulation study is conducted to determine the capability of achieving efficiency enhancement in hydrogenated amorphous silicon (a-Si:H) solar cells using NSL as a top contact plasmonic optical enhancer. The study focuses on triangular prism and sphere arrays as they are the most commonly and easily acquired through direct deposition or low-temperature annealing, respectively. For optical enhancement, a characteristic absorption profile is generated and analyzed to determine the effects of size, shape and spacing of plasmonic structures compared to an un-enhanced reference cell. The factors affecting NSL-enhanced PV performance include absorption, shielding effects, diffraction, and scattering. In the triangular prism array, parasitic absorption of the silver particles proves to be problematic, and although it can be alleviated by increasing the particle spacing, no useful enhancement was observed in the triangular prism arrays that were simulated. Sphere arrays, on the other hand, have broad scattering cross-sections that create useful scattering fields at several sizes and spacing intervals. For the simulated sphere arrays the highest enhancement found was 7.4%, which was fabricated with a 250 nm radius nanosphere and a 50 nm silver thickness, followed by annealing in inert gas. These results are promising and provide a path towards the commercialization of plasmonic a-Si:H solar cells using NSL fabrication techniques.

  16. The status of lightweight photovoltaic space array technology based on amorphous silicon solar cells

    Science.gov (United States)

    Hanak, Joseph J.; Kaschmitter, Jim

    1991-01-01

    Ultralight, flexible photovoltaic (PV) array of amorphous silicon (a-Si) was identified as a potential low cost power source for small satellites. A survey was conducted of the status of the a-Si PV array technology with respect to present and future performance, availability, cost, and risks. For existing, experimental array blankets made of commercial cell material, utilizing metal foil substrates, the Beginning of Life (BOL) performance at Air Mass Zero (AM0) and 35 C includes total power up to 200 W, power per area of 64 W/sq m and power per weight of 258 W/kg. Doubling of power per weight occurs when polyimide substrates are used. Estimated End of Life (EOL) power output after 10 years in a nominal low earth orbit would be 80 pct. of BOL, the degradation being due to largely light induced effects (-10 to -15 pct.) and in part (-5 pct.) to space radiation. Predictions for the year 1995 for flexible PV arrays, made on the basis of published results for rigid a-Si modules, indicate EOL power output per area and per weight of 105 W/sq m and 400 W/kg, respectively, while predictions for the late 1990s based on existing U.S. national PV program goals indicate EOL values of 157 W/sq m and 600 W/kg. Cost estimates by vendors for 200 W ultralight arrays in volume of over 1000 units range from $100/watt to $125/watt. Identified risks include the lack of flexible, space compatible encapsulant, the lack of space qualification effort, recent partial or full acquisitions of US manufacturers of a-Si cells by foreign firms, and the absence of a national commitment for a long range development program toward developing of this important power source for space.

  17. 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.

  18. Multidetector-row CT with a 64-row amorphous silicon flat panel detector

    Science.gov (United States)

    Shapiro, Edward G.; Colbeth, Richard E.; Daley, Earl T.; Job, Isaias D.; Mollov, Ivan P.; Mollov, Todor I.; Pavkovich, John M.; Roos, Pieter G.; Star-Lack, Josh M.; Tognina, Carlo A.

    2007-03-01

    A unique 64-row flat panel (FP) detector has been developed for sub-second multidetector-row CT (MDCT). The intent was to explore the image quality achievable with relatively inexpensive amorphous silicon (a-Si) compared to existing diagnostic scanners with discrete crystalline diode detectors. The FP MDCT system is a bench-top design that consists of three FP modules. Each module uses a 30 cm x 3.3 cm a-Si array with 576 x 64 photodiodes. The photodiodes are 0.52 mm x 0.52 mm, which allows for about twice the spatial resolution of most commercial MDCT scanners. The modules are arranged in an overlapping geometry, which is sufficient to provide a full-fan 48 cm diameter scan. Scans were obtained with various detachable scintillators, e.g. ceramic Gd IIO IIS, particle-in-binder Gd IIO IIS:Tb and columnar CsI:Tl. Scan quality was evaluated with a Catphan-500 performance phantom and anthropomorphic phantoms. The FP MDCT scans demonstrate nearly equivalent performance scans to a commercial 16-slice MDCT scanner at comparable 10 - 20 mGy/100mAs doses. Thus far, a high contrast resolution of 15 lp/cm and a low contrast resolution of 5 mm @ 0.3 % have been achieved on 1 second scans. Sub-second scans have been achieved with partial rotations. Since the future direction of MDCT appears to be in acquiring single organ coverage per scan, future efforts are planned for increasing the number of detector rows beyond the current 64- rows.

  19. Photothermal performance of an amorphous silicon photovoltaic panel integrated in a membrane structure

    Science.gov (United States)

    Zhao, Bing; Hu, Jianhui; Chen, Wujun; Qiu, Zhenyu; Zhou, Jinyu; Qu, Yegao; Ge, Binbin

    2016-10-01

    The amorphous silicon photovoltaic (a-Si PV) cells are widely used for electricity generation from solar energy. When the a-Si PV cells are integrated into building roofs, such as ETFE (ethylene-tetrafouoroethylene) cushions, the temperature characteristics are indispensible for evaluating the thermal performances of a-Si PV and its constructions. This temperature value is directly dependent on the solar irradiance, wind velocity, ambient temperature and installation form. This paper concerns the field experiments and numerical modeling on the temperature characteristics and temperature value of the a-Si PV integrated in a double-layer ETFE cushion structure. To this end, an experimental model composed of two a-Si PV cells and a double-layer ETFE cushion was developed, and the corresponding experiments were carried out under two typical weather conditions (summer sunny and summer cloudy). The theoretical thermal model was developed based on an energy balance equation taking the short wave radiation, long wave radiation, convection and generated power into account. The measured solar irradiance and air temperature were used as real weather conditions for the thermal model. The corresponding differential equation of the a-Si PV temperature varying with the solar irradiance and air temperature was solved by a newly developed program based on the numerical method. The measured results show that the influence of solar irradiance on the temperature is much more significant than the other parameters, and the maximum temperature variation under sunny conditions is greater than that under cloudy conditions. The comparative study between the experimental and numerical results shows the correct predictions of the a-Si PV temperature under the sunny and cloudy conditions. The maximum difference is 3.9 °C with the acceptable reasons of the solar irradiance fluctuation and the PV thermal response time. These findings will provide useful observations and explanations for

  20. Intrinsic stress mitigation via elastic softening during two-step electrochemical lithiation of amorphous silicon

    Science.gov (United States)

    Jia, Zheng; Li, Teng

    2016-06-01

    Recent experiments and first-principles calculations show the two-step lithiation of amorphous silicon (a-Si). In the first step, the lithiation progresses by the movement of a sharp phase boundary between a pristine a-Si phase and an intermediate L iη Si phase until the a-Si phase is fully consumed. Then the second step sets in without a visible interface, with the L iη Si phase continuously lithiating to a L i3.75 Si phase. This unique feature of lithiation is believed to have important consequences for mechanical durability of a-Si anodes in lithium ion batteries, however the mechanistic understanding of such consequences is still elusive so far. Here, we reveal an intrinsic stress mitigation mechanism due to elastic softening during two-step lithiation of a-Si, via chemo-mechanical modeling. We find that lithiation-induced elastic softening of a-Si leads to effective stress mitigation in the second step of lithiation. These mechanistic findings allow for the first time to quantitatively predict the critical size of an a-Si anode below which the anode becomes immune to lithiation-induced fracture, which is in good agreement with experimental observations. Further studies on lithiation kinetics suggest that the two-step lithiation also results in a lower stress-induced energy barrier for lithiation. The present study reveals the physical underpinnings of previously unexplained favorable lithiation kinetics and fracture behavior of a-Si anodes, and thus sheds light on quantitative design guidelines toward high-performance anodes for lithium ion batteries.