WorldWideScience

Sample records for amorphous hydrogenated silicon

  1. 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.

  2. NMR INVESTIGATIONS OF HYDROGENATED AMORPHOUS SILICON

    OpenAIRE

    J. Reimer

    1981-01-01

    A review is presented of the N.M.R. (Nuclear Magnetic Resonance) studies to date of hydrogenated amorphous silicon-hydrogen films. Structural features of proton N.M.R. lineshapes, dynamics of hydrogen containing defect sites, and the promise of quantitative determinations of local silicon-hydrogen bonding environments are discussed in detail. Finally, some comments are given on future directions for N.M.R. studies of hydrogenated thin films.

  3. Preparation of hydrogenated amorphous silicon tin alloys

    OpenAIRE

    Vergnat, M.; Marchal, G.; Piecuch, M.

    1987-01-01

    This paper describes a new method to obtain hydrogenated amorphous semiconductor alloys. The method is reactive co-evaporation. Silicon tin hydrogenated alloys are prepared under atomic hydrogen atmosphere. We discuss the influence of various parameters of preparation (hydrogen pressure, tungsten tube temperature, substrate temperature, annealing...) on electrical properties of samples.

  4. Stable Transistors in Hydrogenated Amorphous Silicon

    OpenAIRE

    J. M. Shannon

    2004-01-01

    Thin-film field-effect transistors in hydrogenated amorphous silicon are notoriously unstable due to the formation of silicon dangling bond trapping states in the accumulated channel region during operation. Here, we show that by using a source-gated transistor a major improvement in stability is obtained. This occurs because the electron quasi-Fermi level is pinned near the center of the band in the active source region of the device and strong accumulation of electrons is prevented. The use...

  5. Generation of correlated photons in hydrogenated amorphous-silicon waveguides

    OpenAIRE

    Clemmen, S.; Perret, A; Selvaraja, Shankar Kumar; Bogaerts, Wim; Van Thourhout, Dries; Baets, Roel; Emplit, Ph.; Massar, S.

    2011-01-01

    We report the first (to our knowledge) observation of correlated photon emission in hydrogenated amorphous- silicon waveguides. We compare this to photon generation in crystalline silicon waveguides with the same geome- try. In particular, we show that amorphous silicon has a higher nonlinearity and competes with crystalline silicon in spite of higher loss.

  6. Experimentally Constrained Molecular Relaxation: The case of hydrogenated amorphous silicon

    OpenAIRE

    Biswas, Parthapratim; Atta-Fynn, Raymond; Drabold, David A.

    2007-01-01

    We have extended our experimentally constrained molecular relaxation technique (P. Biswas {\\it et al}, Phys. Rev. B {\\bf 71} 54204 (2005)) to hydrogenated amorphous silicon: a 540-atom model with 7.4 % hydrogen and a 611-atom model with 22 % hydrogen were constructed. Starting from a random configuration, using physically relevant constraints, {\\it ab initio} interactions and the experimental static structure factor, we construct realistic models of hydrogenated amorphous silicon. Our models ...

  7. Laser annealing of hydrogen implanted amorphous silicon

    International Nuclear Information System (INIS)

    Amorphous silicon, prepared by silicon bombardment at energies of 200 to 250 keV, was implanted with 40 keV H2+ to peak concentrations up to 15 at .% and recrystallized in air by single 20 nsec pulses at 1.06 μm from a Nd:glass laser. Amorphous layer formation and recrystallization were verified using Raman spectroscopy and ion backscattering/channeling analysis

  8. Hydrogen, microstructure and defect density in hydrogenated amorphous silicon

    OpenAIRE

    Roca I Cabarrocas, Pere; Djebbour, Z.; Kleider, J.; Longeaud, C.; Mencaraglia, D.; Sib, J.; Bouizem, Y.; Thèye, M.; Sardin, G.; Stoquert, J.

    1992-01-01

    It is well established that by bonding with the dangling bonds of silicon, hydrogen reduces the density of states of amorphous silicon and renders this material suitable to electronic applications. For so-called “standard” a-Si : H films deposited by the RF glow discharge decomposition of silane at low deposition rates (≈1 Å/s) and over a large range of deposition temperatures, we observed the usual correlation between the hydrogen bonding and the defect density in the as-deposited material o...

  9. Hydrogenated amorphous silicon deposited by ion-beam sputtering

    Science.gov (United States)

    Lowe, V. E.; Henin, N.; Tu, C.-W.; Tavakolian, H.; Sites, J. R.

    1981-01-01

    Hydrogenated amorphous silicon films 1/2 to 1 micron thick were deposited on metal and glass substrates using ion-beam sputtering techniques. The 800 eV, 2 mA/sq cm beam was a mixture of argon and hydrogen ions. The argon sputtered silicon from a pure (7.6 cm) single crystal wafer, while the hydrogen combined with the sputtered material during the deposition. Hydrogen to argon pressure ratios and substrate temperatures were varied to minimize the defect state density in the amorphous silicon. Characterization was done by electrical resistivity, index of refraction and optical absorption of the films.

  10. Interaction of hydrogenated amorphous silicon films with transparent conductive films

    OpenAIRE

    Kitagawa, M.; Mori, K; Ishihara, S.; Ohno, M.; Hirao, T.; Yoshioka, Y.; Kohiki, S

    1983-01-01

    The effects of the deposition temperature on the interaction of the hydrogenated amorphous silicon films with indium-tin-oxide and tin-oxide films have been investigated in the temperature range 150-300 degrees C, using Auger electron spectroscopy, secondary ion mass spectrometry, and scanning electron microscopy. It was found that the constituent atoms such as indium and tin are detected in the thin amorphous silicon films deposited. Around the interface between the transparent conductive fi...

  11. Influence of microstructure and hydrogen concentration on amorphous silicon crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Budini, N., E-mail: nbudini@intec.unl.edu.a [Instituto de Desarrollo Tecnologico para la Industria Quimica, UNL-CONICET, Gueemes 3450, S3000GLN Santa Fe (Argentina); Rinaldi, P.A. [Instituto de Desarrollo Tecnologico para la Industria Quimica, UNL-CONICET, Gueemes 3450, S3000GLN Santa Fe (Argentina); Schmidt, J.A.; Arce, R.D.; Buitrago, R.H. [Instituto de Desarrollo Tecnologico para la Industria Quimica, UNL-CONICET, Gueemes 3450, S3000GLN Santa Fe (Argentina); Facultad de Ingenieria Quimica, UNL, Santiago del Estero 2829, S3000AOM Santa Fe (Argentina)

    2010-07-01

    Hydrogenated amorphous silicon samples were deposited on glass substrates at different temperatures by high frequency plasma-enhanced chemical vapor deposition. In this way, samples with different hydrogen concentrations and structures were obtained. The transition from an amorphous to a crystalline material, induced by a four-step thermal annealing sequence, has been followed. Effusion of hydrogen from the films plays an important role in the nucleation and growth mechanisms of crystalline silicon grains. Measurements of hydrogen concentrations, Raman scattering, X-ray diffraction and UV reflectance showed that an enhanced crystallization was obtained on samples deposited at lower substrate temperatures. A correlation between these measurements allows to analyze the evolution of structural properties of the samples. The presence of voids in the material, related to disorder in the amorphous matrix, results in a better quality of the resulting nanocrystalline silicon thin films.

  12. Influence of microstructure and hydrogen concentration on amorphous silicon crystallization

    International Nuclear Information System (INIS)

    Hydrogenated amorphous silicon samples were deposited on glass substrates at different temperatures by high frequency plasma-enhanced chemical vapor deposition. In this way, samples with different hydrogen concentrations and structures were obtained. The transition from an amorphous to a crystalline material, induced by a four-step thermal annealing sequence, has been followed. Effusion of hydrogen from the films plays an important role in the nucleation and growth mechanisms of crystalline silicon grains. Measurements of hydrogen concentrations, Raman scattering, X-ray diffraction and UV reflectance showed that an enhanced crystallization was obtained on samples deposited at lower substrate temperatures. A correlation between these measurements allows to analyze the evolution of structural properties of the samples. The presence of voids in the material, related to disorder in the amorphous matrix, results in a better quality of the resulting nanocrystalline silicon thin films.

  13. GHz-rate optical parametric amplifier in hydrogenated amorphous silicon

    International Nuclear Information System (INIS)

    We demonstrate optical parametric amplification operating at GHz-rates at telecommunications wavelengths using a hydrogenated amorphous silicon waveguide through the nonlinear optical process of four-wave mixing. We investigate how the parametric amplification scales with repetition rate. The ability to achieve amplification at GHz-repetition rates shows hydrogenated amorphous silicon’s potential for telecommunication applications and a GHz-rate optical parametric oscillator. (paper)

  14. Atomistic models of hydrogenated amorphous silicon nitride from first principles

    NARCIS (Netherlands)

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

    2010-01-01

    We present a theoretical study of hydrogenated amorphous silicon nitride (a-SiNx:H), with equal concentrations of Si and N atoms (x=1), for two considerably different densities (2.0 and 3.0 g/cm3). Densities and hydrogen concentration were chosen according to experimental data. Using first-principle

  15. Atomistic models of hydrogenated amorphous silicon nitride from first principles

    NARCIS (Netherlands)

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

    2010-01-01

    We present a theoretical study of hydrogenated amorphous silicon nitride (a-SiNx:H), with equal concentrations of Si and N atoms (x=1), for two considerably different densities (2.0 and 3.0 g/cm3). Densities and hydrogen concentration were chosen according to experimental data. Using first-principle

  16. Pyrolytic transformation from polydihydrosilane to hydrogenated amorphous silicon film

    International Nuclear Information System (INIS)

    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 Tp = 270 to 360 °C. The appearance of amorphous silicon phonon bands in Raman spectra for films prepared at Tp ≥ 330 °C suggests the construction of a three-dimensional amorphous silicon network. Films prepared at Tp ≥ 360 °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: ► We fabricate hydrogenated amorphous silicon (a-Si:H) films by a solution process. ► The a-Si:H films are prepared by pyrolytic transformation in polysilane solution. ► We investigate basic properties in relation to the pyrolysis temperature. ► Raman spectra, hydrogen content, and optical gap are similar to device-grade a-Si:H. ► Microstructure factor, spin density, and photoconductivity show poor quality.

  17. First-principles study of hydrogenated amorphous silicon

    NARCIS (Netherlands)

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

    2009-01-01

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

  18. 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.

  19. Pyrolytic transformation from polydihydrosilane to hydrogenated amorphous silicon film

    OpenAIRE

    Masuda, Takashi; Matsuki, Yasuo; Shimoda, Tatsuya

    2012-01-01

    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 S...

  20. Thermally stimulated H emission and diffusion in hydrogenated amorphous silicon

    OpenAIRE

    Abtew, T. A.; Inam, F.; Drabold, D. A.

    2006-01-01

    We report first principles ab initio density functional calculations of hydrogen dynam- ics in hydrogenated amorphous silicon. Thermal motion of the host Si atoms drives H diffusion, as we demonstrate by direct simulation and explain with simple models. Si-Si bond centers and Si ring centers are local energy minima as expected. We also describe a new mechanism for break- ing Si-H bonds to release free atomic H into the network: a fluctuation bond center detachment (FBCD) assisted diffusion. H...

  1. Hydrogen-free amorphous silicon with no tunneling states.

    Science.gov (United States)

    Liu, Xiao; Queen, Daniel R; Metcalf, Thomas H; Karel, Julie E; Hellman, Frances

    2014-07-11

    The ubiquitous low-energy excitations, known as two-level tunneling systems (TLSs), are one of the universal phenomena of amorphous solids. Low temperature elastic measurements show that e-beam amorphous silicon (a-Si) contains a variable density of TLSs which diminishes as the growth temperature reaches 400 °C. Structural analyses show that these a-Si films become denser and more structurally ordered. We conclude that the enhanced surface energetics at a high growth temperature improved the amorphous structural network of e-beam a-Si and removed TLSs. This work obviates the role hydrogen was previously thought to play in removing TLSs in the hydrogenated form of a-Si and suggests it is possible to prepare "perfect" amorphous solids with "crystal-like" properties for applications. PMID:25062205

  2. Study on stability of hydrogenated amorphous silicon films

    Institute of Scientific and Technical Information of China (English)

    Zhu Xiu-Hong; Chen Guang-Hua; Zhang Wen-Li; Ding Yi; Ma Zhan-Jie; Hu Yue-Hui; He Bin; Rong Yan-Dong

    2005-01-01

    Hydrogenated amorphous silicon (a-Si:H) films with high and same order of magnitude photosensitivity (~105) but different stability were prepared by using microwave electron cyclotron resonance chemical vapour deposition system under the different deposition conditions. It was proposed that there was no direct correlation between the photosensitivity and the hydrogen content (CH) as well as H-Si bonding configurations, but for the stability, they were the critical factors. The experimental results indicated that higher substrate temperature, hydrogen dilution ratio and lower deposition rate played an important role in improving the microstructure of a-Si:H films. We used hydrogen elimination model to explain our experimental results.

  3. 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.

  4. 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.

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

    Institute of Scientific and Technical Information of China (English)

    LIAO NaiMan; LI Wei; KUANG YueJun; JIANG YaDong; LI ShiBin; WU ZhiMing; QI KangCheng

    2009-01-01

    Hydrogenated amorphous silicon (a-Si:H) thin films were deposited by plasma-enhanced vapor depo-sition (PEOVD) 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 scat-tering spectra, ellipsometric transmittance spectra, and dark conductivity measurement, respectively. The results show that the increase in Tg leads to an improved ordering of amorphous network on the short and intermediate scales and an increase of both refractive index and absorption coefficient in a-Si:H thin films. It is indicated that the dark conductivity increases by two orders of magnitude when Tg is raised from room temperature (RT) to 433 K. The continuous ordering of amorphous network of a-Si:H thin films deposited at a higher Tg is the main cause for the increase of dark conductivity.

  6. 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.

  7. Deposition-induced defect profiles in amorphous hydrogenated silicon

    OpenAIRE

    Hata, N.; Wagner, S.; Roca i Cabarrocas, P.; Favre, M.

    2008-01-01

    The thickness dependence of the subgap optical absorption in plasma-deposited hydrogenated amorphous silicon is carefully studied by photothermal deflection spectroscopy. The deep-level defect concentration decays from the top surface into the bulk where it approaches the thermal equilibrium defect density. This defect profile is interpreted in terms of the annealing, during growth, of growth-induced surface defects. It is also shown that this defect profile is compatible with the known growt...

  8. First-principles study of hydrogenated amorphous silicon

    OpenAIRE

    Jarolimek, K.; de Groot, R. A.; de Wijs, G. A.; 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 of the cooling rate is examined. We prepared a total of five structures which compare well to experimental data obtained by neutron-scattering experiments. Two structures do not contain any struct...

  9. Atomistic models of hydrogenated amorphous silicon nitride from first principles

    OpenAIRE

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

    2010-01-01

    We present a theoretical study of hydrogenated amorphous silicon nitride (a-SiNx:H), with equal concentrations of Si and N atoms (x=1), for two considerably different densities (2.0 and 3.0 g/cm3). Densities and hydrogen concentration were chosen according to experimental data. Using first-principles molecular-dynamics within density-functional theory the models were generated by cooling from the liquid. Where both models have a short-range order resembling that of crystalline Si3N4 because o...

  10. INFRARED VIBRATIONAL SPECTRA OF CHLORINATED AND HYDROGENATED AMORPHOUS SILICON

    OpenAIRE

    Kalem, S; Chevallier, J.; Al Dallal, S.; Bourneix, J.

    1981-01-01

    The infrared spectra of chlorinated and hydrogenated amorphous silicon have been measured. In addition to the hydrogen induced bands at 2110, 1990, 885, 840 and 640 cm-1, we observe two new modes at 545 cm-1 (Si-Cl stretching) and 500 cm-1 ( Si TO modes induced by chlorine). Observation of the 545 cm-1 band proves that chlorine acts as a dangling bond terminator. Upon annealing, some of the Si-Cl groups transform into SiCl4 molecules (SiCl4 stretching at 615 cm-1). A good agreement is found b...

  11. 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

  12. 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.

  13. Elimination of residual stress in hydrogenated amorphous silicon films

    Energy Technology Data Exchange (ETDEWEB)

    Jones, P.L.; Korhonen, A.S.; Dimmey, L.J.; Cocks, F.H.; Pollock, J.T.A.

    1982-02-01

    Residual stresses were measured in hydrogenated amorphous silicon films produced by glow discharge decomposition of silane and deposited onto aluminium, Invar (36Ni-64Fe), copper and nickel substrates. The substrate temperatures were in the range 54-295/sup 0/C during deposition. For low deposition temperatures, all films irrespective of substrate exhibited compressive room temperature residual stresses ranging from -60 to -120 mPa. A major fraction of this residual stress is found to come from the intrinsic deposition stress, which has complex origins relating to deposition and substrate conditions. With aluminium substrates, increasing the deposition temperature increased the compressive residual stress, primarily because of the difference between the thermal expansion coefficients of silicon and aluminium. However, with Invar substrates, films deposited at 225/sup 0/C exhibited a zero residual stress at room temperature because of a balancing of the compressive intrinsic deposition stress with the tensile stress produced during cooling by the low thermal expansion of the Invar.

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

    OpenAIRE

    Jarmila Mullerova

    2006-01-01

    IR measurements were carried out on both amorphous and polycrystalline silicon samples deposited by PECVD on glass substrate. The transition from amorphous to polycrystalline phase was achieved by increasing dilution of silane plasma at the deposition process. The samples were found to be mixed phase materials. Commonly, infrared spectra of hydrogenated silicon thin films yield information about microstructure, hydrogen content and hydrogen bonding to silicon. In this paper, addit...

  15. Hydrogenated amorphous silicon thin film anode for proton conducting batteries

    Science.gov (United States)

    Meng, Tiejun; Young, Kwo; Beglau, David; Yan, Shuli; Zeng, Peng; Cheng, Mark Ming-Cheng

    2016-01-01

    Hydrogenated amorphous Si (a-Si:H) thin films deposited by chemical vapor deposition were used as anode in a non-conventional nickel metal hydride battery using a proton-conducting ionic liquid based non-aqueous electrolyte instead of alkaline solution for the first time, which showed a high specific discharge capacity of 1418 mAh g-1 for the 38th cycle and retained 707 mAh g-1 after 500 cycles. A maximum discharge capacity of 3635 mAh g-1 was obtained at a lower discharge rate, 510 mA g-1. This electrochemical discharge capacity is equivalent to about 3.8 hydrogen atoms stored in each silicon atom. Cyclic voltammogram showed an improved stability 300 mV below the hydrogen evolution potential. Both Raman spectroscopy and Fourier transform infrared spectroscopy studies showed no difference to the pre-existing covalent Si-H bond after electrochemical cycling and charging, indicating a non-covalent nature of the Si-H bonding contributing to the reversible hydrogen storage of the current material. Another a-Si:H thin film was prepared by an rf-sputtering deposition followed by an ex-situ hydrogenation, which showed a discharge capacity of 2377 mAh g-1.

  16. Role of amorphous silicon domains on Er3+ emission in the Er-doped hydrogenated amorphous silicon suboxide film

    Institute of Scientific and Technical Information of China (English)

    陈长勇; 陈维德; 李国华; 宋淑芳; 丁琨; 许振嘉

    2003-01-01

    An investigation on the correlation between amorphous Si (a-Si) domains and Er3+ emission in the Er-doped hydrogenated amorphous silicon suboxide (a-Si:O:H) film is presented. On one hand, a-Si domains provide sufficient carriers for Er3+ carrier-mediated excitation which has been proved to be the highest excitation path for Er3+ ion; on the other hand, hydrogen diffusion from a-Si domains to amorphous silicon oxide (a-SiOx) matrix during annealing has been found and this possibly decreases the number of nonradiative centres around Er3+ ions. This study provides a better understanding of the role of a-Si domains on Er3+ emission in a-Si:O:Hfilms.

  17. Role of amorphous silicon domains of Er3+ emission in the Er—doped hydrogenated amorphous silicon suboxide film

    Institute of Scientific and Technical Information of China (English)

    ChenChang-Yong; ChenWei-De; LeGuo-Hua; SongShu-Fang; DingKun; XuZhen-Jia

    2003-01-01

    An investigation on the correlation between amorphous Si(a-Si) domains and Er3+ emission in the Er-doped hydrogenated amorphous silicon suboxide (a-Si:O:H) film is presented. On one hand, a-Si domains provide sufficient carrlers for Er3+ carrier-mediated excitation which has been proved to be the highest excitation path for Er3+ ion; on the other hand, hydrogen diffusion from a-Si domains to amorphous silicon oxide (a-SiOx) matrix during annealing has been found and this possibly decreases the number of nonradiative centres around Er3+ ions. This study provides a better understanding of the role of a-Si domains on Er3+ emission in a-Si:O:H films.

  18. Optical determination of the mass density of amorphous and microcrystalline silicon layers with different hydrogen contents

    OpenAIRE

    Remeš, Z.; Vaněček, Milan; Torres, Pedro; Kroll, U.; Mahan, A. H.; Crandall, R. S.

    2008-01-01

    We have measured the density of amorphous and microcrystalline silicon films using an optical method. The mass density decreases with increasing hydrogen content, consistent with a hydrogenated di-vacancy model that fits the data for amorphous silicon. Material produced by hot wire assisted chemical vapour deposition, with low hydrogen content, has a higher density and is structurally different from glow discharge material with hydrogen content around 10 at.%. The lower density microcrystalli...

  19. Light-induced metastability in pure and hydrogenated amorphous silicon

    Science.gov (United States)

    Queen, D. R.; Liu, X.; Karel, J.; Wang, Q.; Crandall, R. S.; Metcalf, T. H.; Hellman, F.

    2015-10-01

    Light soaking is found to increase the specific heat C and internal friction Q-1 of pure (a-Si) and hydrogenated (a-Si:H) amorphous silicon. At the lowest temperatures, the increases in C and Q-1 are consistent with an increased density of two-level systems (TLS). The light-induced increase in C persists to room temperature. Neither the sound velocity nor shear modulus change with light soaking indicating that the Debye specific heat is unchanged which suggests that light soaking creates localized vibrational modes in addition to TLS. The increase can be reversibly added and removed by light soaking and annealing, respectively, suggesting that it is related to the Staebler-Wronski effect (SWE), even in a-Si without H, and involves a reversible nanoscale structural rearrangement that is facilitated by, but does not require, H to occur.

  20. 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, ...

  1. Optical limiting in hydrogenated amorphous silicon-selenium thin films

    Energy Technology Data Exchange (ETDEWEB)

    Manaa, Hacene, E-mail: hmanaa@gmail.co [Physics Department, Kuwait University, P.O. Box 5969, Safat 13060 (Kuwait); Al-Mulla, Abdullah; Al-Jamal, Noor [Physics Department, Kuwait University, P.O. Box 5969, Safat 13060 (Kuwait); Al-Dallal, Shawqi; Al-Alawi, Saleh [Physics Department, University of Bahrain, P.O. Box 32038 (Bahrain)

    2010-05-03

    Hydrogenated amorphous silicon-selenium alloy thin films grown by capacitively coupled radio-frequency glow-discharge are investigated. Nonlinear absorptive effects are evaluated with the help of open aperture z-scan technique in the 525 to 580 nm spectral range. The nonlinear absorption coefficient is found to be very large and reaching the value of 5.14 x 10{sup -3} cm/W at 525 nm. The origin of the optical nonlinearities is studied and found to be due mainly to two photon absorption in the case of pulsed excitation, whereas thermal effects are thought to be dominant when the sample is excited with a continuous wave laser. Optical limiting potentialities of the thin film are experimentally observed and their thresholds are found to be very low.

  2. Temperature dependence of hydrogenated amorphous silicon solar cell performances

    Science.gov (United States)

    Riesen, Y.; Stuckelberger, M.; Haug, F.-J.; Ballif, C.; Wyrsch, N.

    2016-01-01

    Thin-film hydrogenated amorphous silicon solar (a-Si:H) cells are known to have better temperature coefficients than crystalline silicon cells. To investigate whether a-Si:H cells that are optimized for standard conditions (STC) also have the highest energy yield, we measured the temperature and irradiance dependence of the maximum power output (Pmpp), the fill factor (FF), the short-circuit current density (Jsc), and the open-circuit voltage (Voc) for four series of cells fabricated with different deposition conditions. The parameters varied during plasma-enhanced chemical vapor deposition (PE-CVD) were the power and frequency of the PE-CVD generator, the hydrogen-to-silane dilution during deposition of the intrinsic absorber layer (i-layer), and the thicknesses of the a-Si:H i-layer and p-type hydrogenated amorphous silicon carbide layer. The results show that the temperature coefficient of the Voc generally varies linearly with the Voc value. The Jsc increases linearly with temperature mainly due to temperature-induced bandgap reduction and reduced recombination. The FF temperature dependence is not linear and reaches a maximum at temperatures between 15 °C and 80 °C. Numerical simulations show that this behavior is due to a more positive space-charge induced by the photogenerated holes in the p-layer and to a recombination decrease with temperature. Due to the FF(T) behavior, the Pmpp (T) curves also have a maximum, but at a lower temperature. Moreover, for most series, the cells with the highest power output at STC also have the best energy yield. However, the Pmpp (T) curves of two cells with different i-layer thicknesses cross each other in the operating cell temperature range, indicating that the cell with the highest power output could, for instance, have a lower energy yield than the other cell. A simple energy-yield simulation for the light-soaked and annealed states shows that for Neuchâtel (Switzerland) the best cell at STC also has the best energy

  3. High Pressure Chemical Vapor Deposition of Hydrogenated Amorphous Silicon Films and Solar Cells.

    Science.gov (United States)

    He, Rongrui; Day, Todd D; Sparks, Justin R; Sullivan, Nichole F; Badding, John V

    2016-07-01

    Thin films of hydrogenated amorphous silicon can be produced at MPa pressures from silane without the use of plasma at temperatures as low as 345 °C. High pressure chemical vapor deposition may open a new way to low cost deposition of amorphous silicon solar cells and other thin film structures over very large areas in very compact, simple reactors. PMID:27174318

  4. Excellent Silicon Surface Passivation Achieved by Industrial Inductively Coupled Plasma Deposited Hydrogenated Intrinsic Amorphous Silicon Suboxide

    Directory of Open Access Journals (Sweden)

    Jia Ge

    2014-01-01

    Full Text Available We present an alternative method of depositing a high-quality passivation film for heterojunction silicon wafer solar cells, in this paper. The deposition of hydrogenated intrinsic amorphous silicon suboxide is accomplished by decomposing hydrogen, silane, and carbon dioxide in an industrial remote inductively coupled plasma platform. Through the investigation on CO2 partial pressure and process temperature, excellent surface passivation quality and optical properties are achieved. It is found that the hydrogen content in the film is much higher than what is commonly reported in intrinsic amorphous silicon due to oxygen incorporation. The observed slow depletion of hydrogen with increasing temperature greatly enhances its process window as well. The effective lifetime of symmetrically passivated samples under the optimal condition exceeds 4.7 ms on planar n-type Czochralski silicon wafers with a resistivity of 1 Ωcm, which is equivalent to an effective surface recombination velocity of less than 1.7 cms−1 and an implied open-circuit voltage (Voc of 741 mV. A comparison with several high quality passivation schemes for solar cells reveals that the developed inductively coupled plasma deposited films show excellent passivation quality. The excellent optical property and resistance to degradation make it an excellent substitute for industrial heterojunction silicon solar cell production.

  5. 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.

  6. Fabrication of solution-processed hydrogenated amorphous silicon single junction solar cells

    OpenAIRE

    Masuda, Takashi; Sotani, Naoya; Hamada, Hiroki; Matsuki, Yasuo; Shimoda, Tatsuya

    2012-01-01

    Hydrogenated amorphous silicon solar cells were fabricated using solution-based processes. All silicon layers of the p-i-n junction were stacked by a spin-cast method using doped and non-doped polydihydrosilane solutions. Further, a hydrogen-radical treatment under vacuum conditions was employed to reduce spin density in the silicon films. Following this treatment, the electric properties of the silicon films were improved, and the power conversion efficiency of the solar cells was also incre...

  7. Structural and electrical properties of metastable defects in hydrogenated amorphous silicon

    NARCIS (Netherlands)

    Melskens, J.; Schnegg, A.; Baldansuren, A.; Lips, K.; Plokker, M.P.; Eijt, S.W.H.; Schut, H.; Fischer, M.; Zeman, M.; Smets, A.H.M.

    2015-01-01

    The structural and electrical properties of metastable defects in various types of hydrogenated amorphous silicon have been studied using a powerful combination of continuous wave electron-paramagnetic resonance spectroscopy, electron spin echo (ESE) decay measurements, and Doppler broadening positr

  8. Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

    OpenAIRE

    Roura Grabulosa, Pere; Farjas Silva, Jordi; Rath, Chandana; Serra-Miralles, J.; Bertrán Serra, Enric; Roca I Cabarrocas, Pere

    2006-01-01

    Differential scanning calorimetry (DSC) was used to study the dehydrogenation processes that take place in three hydrogenated amorphous silicon materials: nanoparticles, polymorphous silicon, and conventional device-quality amorphous silicon. Comparison of DSC thermograms with evolved gas analysis (EGA) has led to the identification of four dehydrogenation processes arising from polymeric chains (A), SiH groups at the surfaces of internal voids (A'), SiH groups at interfaces (B), and in the b...

  9. 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.

  10. 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. PMID:27227369

  11. 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.

  12. Electonic properties of hydrogenated amorphous silicon-germanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bullot, J.; Galin, M.; Gauthier, M. (Universite de Paris-Sud, Orsay (France)); Bourdon, B. (CIT-Alcatel Transmission, Marcoussis (France))

    1983-06-01

    The electronic properties of some binary hydrogenated amorphous silicon-germanium alloys a-Sisub(x)Gesub(1-x):H in the silicon rich region (x > 0.6) are investigated. Experimental evidence is presented of photo-induced effects similar to those described in Si:H (Staebler-Wronski effect). The electronic properties are then studied from the dual point of view of the germanium content dependence and of the photo and thermal histories of the films. The dark conductivity changes between the annealed state and the light-soaked state are interpreted in terms of the variation of the temperature coefficient of the Fermi level. The photoconductivity efficiency is shown to remain close to that of a-Si:H for 1 > x >= 0.9 and to strongly decrease when the germanium content is further increased: the photoresponse of the Sisub(0.62)Gesub(0.38) alloy is 10/sup 4/ times smaller than that of a-Si:H. This deterioration of the photoconductive properties is explained in terms of the increase of the density of gap states following Ge substitution. This conclusion is based on the study of the width of the exponential absorption edge and on the results of photoconductivity time response studies. The latter data are interpreted by means of the model of Rose of trapping and recombination kinetics and it is found that for x approximately 0.6 the density of states at 0.4-0.5 eV below the mobility edge is 7 x 10/sup 17/ eV/sup -1/ cm/sup -3/ as compared to 2.4 x 10/sup 16/ eV/sup -1/ cm/sup -3/ for x = 0.97.

  13. 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.

  14. 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.

  15. Dynamics of hydrogenated amorphous silicon flexural resonators for enhanced performance

    Science.gov (United States)

    Mouro, J.; Chu, V.; Conde, J. P.

    2016-04-01

    Hydrogenated amorphous silicon thin-film flexural resonators with sub-micron actuation gaps are fabricated by surface micromachining on glass substrates. Experimentally, the resonators are electrostatically actuated and their motion is optically detected. Three different configurations for the electrostatic excitation force are used to study the dynamics of the resonators. In the first case, a dc voltage (Vdc) is added to an ac voltage with variable excitation frequency (Vac(ω)) and harmonic, superharmonic, and subharmonic resonances of different orders are observed. The second case consists on mixing the dc voltage (Vdc) with an ac voltage applied at a fixed frequency of twice the natural frequency of the resonator (V(2ω0)). High-amplitude parametric resonance is excited at the natural frequency of the system, ω0. This configuration allows a separation between the frequencies of the excitation and the mechanical motion. Finally, in the third case, the dc voltage (Vdc) is combined with both ac voltages, Vac(ω) and V(2ω0), and parametric resonance is excited and emerges from the fundamental harmonic resonance peak. The single-degree-of-freedom equation of motion is modeled and discussed for each case. The nonlinearity inherent to the electrostatic force is responsible for modulating the spring constant of the system at different frequencies, giving rise to parametric resonance. These equations of motion are simulated in the time and frequency domains, providing a consistent explanation of the experimentally observed phenomena. A wide variety of possible resonance modes with different characteristics can be used advantageously in MEMS device design.

  16. In situ ultraviolet treatment in an Ar ambient upon p-type hydrogenated amorphous silicon-carbide windows of hydrogenated amorphous silicon based solar cells

    International Nuclear Information System (INIS)

    We proposed an in situ postdeposition ultraviolet treatment in an Ar ambient (UTA) to improve the p/i interface of amorphous silicon based solar cell. We have increased the conversion efficiency by ∼16% by improving the built-in potential and reducing recombination at the p/i interface. Through spectroscopic ellipsometry and Fourier-transform infrared measurements, it is concluded that the UTA process induces structural modification of the p-type hydrogenated amorphous silicon-carbide (p-a-SiC:H) window layer. An ultrathin p-a-SiC:H contamination layer formed during the UTA process acts as a buffer layer at the interface

  17. 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.

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

    Science.gov (United States)

    Fortmann, C. M.; Hegedus, S. S.

    1992-12-01

    Results and conclusions obtained during the investigation of amorphous silicon, 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.

  20. 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.

  1. Investigation of hydrogen plasma treatment for reducing defects in silicon quantum dot superlattice structure with amorphous silicon carbide matrix.

    Science.gov (United States)

    Yamada, Shigeru; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Konagai, Makoto

    2014-01-01

    We investigate the effects of hydrogen plasma treatment (HPT) on the properties of silicon quantum dot superlattice films. Hydrogen introduced in the films efficiently passivates silicon and carbon dangling bonds at a treatment temperature of approximately 400°C. The total dangling bond density decreases from 1.1 × 1019 cm-3 to 3.7 × 1017 cm-3, which is comparable to the defect density of typical hydrogenated amorphous silicon carbide films. A damaged layer is found to form on the surface by HPT; this layer can be easily removed by reactive ion etching. PMID:24521208

  2. Investigation of hydrogen plasma treatment for reducing defects in silicon quantum dot superlattice structure with amorphous silicon carbide matrix

    OpenAIRE

    Yamada, Shigeru; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; KONAGAI, MAKOTO

    2014-01-01

    We investigate the effects of hydrogen plasma treatment (HPT) on the properties of silicon quantum dot superlattice films. Hydrogen introduced in the films efficiently passivates silicon and carbon dangling bonds at a treatment temperature of approximately 400°C. The total dangling bond density decreases from 1.1 × 1019 cm-3 to 3.7 × 1017 cm-3, which is comparable to the defect density of typical hydrogenated amorphous silicon carbide films. A damaged layer is found to form on the surface by ...

  3. Hydrogenated amorphous silicon radiation detectors: Material parameters, radiation hardness, charge collection

    International Nuclear Information System (INIS)

    For nearly two decades now hydrogenated amorphous silicon has generated considerable interest for its potential use in various device applications namely, solar cells, electrolithography, large-area electronics etc. The development of efficient and economic solar cells has been on the forefront of this research. This interest in hydrogenated amorphous silicon has been motivated by the fact that amorphous silicon can be deposited over a large area at relatively low cost compared to crystalline silicon. Hydrogenated amorphous silicon, frequently abbreviated as a-Si:H, used in solar-cell applications is a micron or less thick. The basic device structure is a p-i-n diode where the i layer is the active layer for radiation to interact. This is so because intrinsic a-Si:H has superior electrical properties in comparison to doped a-Si:H which serves the purpose of forming a potential barrier on either end of the i layer. The research presented in this dissertation was undertaken to study the properties of a-Si:H for radiation detection applications in physics and medicine

  4. Nonlinear properties of and nonlinear processing in hydrogenated amorphous silicon waveguides

    DEFF Research Database (Denmark)

    Kuyken, B.; Ji, Hua; Clemmen, S.;

    2011-01-01

    We propose hydrogenated amorphous silicon nanowires as a platform for nonlinear optics in the telecommunication wavelength range. Extraction of the nonlinear parameter of these photonic nanowires reveals a figure of merit larger than 2. It is observed that the nonlinear optical properties of these...

  5. 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

  6. 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...

  7. 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.

  8. CORRELATION BETWEEN ELECTRICAL AND VIBRATIONAL PROPERTIES OF CHLORINATED AND HYDROGENATED AMORPHOUS SILICON PREPARED BY GLOW DISCHARGE

    OpenAIRE

    Al Dallal, S.; Chevallier, J.; Kalem, S; Bourneix, J.

    1982-01-01

    Electrical conductivity and infrared transmission measurements have been carried out on chlorinated and hydrogenated amorphous silicon films prepared by glow discharge. Upon increasing the plasma power, we observed a change of transport mechanism, accompanied by an evolution of hydrogen and chlorine related bands. From this correlation between the transport and the infrared data we suggest that the evolution of SiCl2 species with the plasma power is mainly responsible for the change in bandga...

  9. Structural, hydrogen bonding and in situ studies of the effect of hydrogen dilution on the passivation by amorphous silicon of n-type crystalline (100) silicon surfaces

    OpenAIRE

    Meddeb, H.; Bearda, T.; Abdelraheem, Y.; Ezzaouia, H.; Gordon, I.; Szlufcik, J.; Poortmans, Jef

    2015-01-01

    Hydrogenated amorphous silicon (a-Si : H) layers deposited by chemical vapour deposition provide an attractive route to achieve high-performance crystalline silicon (c-Si) solar cells due to their deposition at low temperatures and their superior passivation quality. Hydrogen certainly plays an additional crucial role by passivating the dangling bonds, and thus improving the electrical and optical properties. In this work, we present the variation of the effective lifetime with the hydrogen d...

  10. Microstructural tuning of polycrystalline silicon films from hydrogen diluted amorphous silicon films by AIC

    Energy Technology Data Exchange (ETDEWEB)

    Prathap, P.; Tuzun, O.; Roques, S.; Schmitt, S.; Slaoui, A. [InESS, CNRS-UdS, Strasbourg Cedex-2 (France); Maurice, C. [SMS Centre, UMR CNRS 5146, Ecole des Mines de Saint Etienne, 158 Cours Fauriel, 42023 Saint Etienne Cedex 2 (France)

    2011-03-15

    In the present study, the effect of hydrogen dilution in amorphous silicon on its crystallization kinetics and defect distribution using AIC has been studied. The a -Si films were deposited at different ratios of H{sub 2}/(H{sub 2}+SiH{sub 4}) using plasma enhanced chemical vapour deposition (ECR-PECVD) on glass-ceramic substrates. The thicknesses of aluminium and a -Si:H films were 0.20 {mu}m and 0. 37 {mu}m, respectively. The bi-layer structures were annealed in a tube furnace at 475 C for 8 hours in a nitrogen atmosphere. The results indicated that as the hydrogen dilution for a -Si:H films increased from 0% to 85%, the AIC grown poly-Si films were more stressed compressively, while the Raman peak broadened from 6.7 cm{sup -1} to 8.6 cm{sup -1}. It was found that the initiation of crystallization temperature as well as microstructure of poly-Si films was dramatically influenced by the hydrogen content in precursor a -Si films. The distribution of microstructural defects analysed by Electron Back Scattering Diffraction (EBSD) method indicated that frequency of low angle grain boundaries (LAGB) were more at higher hydrogen dilution ratios while coincident site lattice boundaries (CSL) of first order ({sigma}3), second order ({sigma}9) and third order ({sigma}27) were less sensitive to the hydrogen dilutions/content (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

    Science.gov (United States)

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

    2002-10-01

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

  12. The Interplay of Quantum Confinement and Hydrogenation in Amorphous Silicon Quantum Dots

    OpenAIRE

    Askari, Sadegh; Svrcek, Vladmir; Maguire, Paul; Mariotti, Davide

    2015-01-01

    Hydrogenation in amorphous silicon quantum dots (QDs) has a dramatic impact on the corresponding optical properties and band energy structure, leading to a quantum‐confined composite material with unique characteristics. The synthesis of a‐Si:H QDs is demonstrated with an atmospheric‐pressure plasma process, which allows for accurate control of a highly chemically reactive non‐equilibrium environment with temperatures well below the crystallization temperature of Si QDs.

  13. The Interplay of Quantum Confinement and Hydrogenation in Amorphous Silicon Quantum Dots.

    Science.gov (United States)

    Askari, Sadegh; Svrcek, Vladmir; Maguire, Paul; Mariotti, Davide

    2015-12-22

    Hydrogenation in amorphous silicon quantum dots (QDs) has a dramatic impact on the corresponding optical properties and band energy structure, leading to a quantum-confined composite material with unique characteristics. The synthesis of a-Si:H QDs is demonstrated with an atmospheric-pressure plasma process, which allows for accurate control of a highly chemically reactive non-equilibrium environment with temperatures well below the crystallization temperature of Si QDs. PMID:26523743

  14. The boron-tailing myth in hydrogenated amorphous silicon solar cells

    OpenAIRE

    Stuckelberger, M.; Park, B.-S.; Bugnon, G.; Despeisse, M; Schüttauf, J.-W.; Haug, F.-J.; Ballif, C.

    2015-01-01

    The boron-tailing effect in hydrogenated amorphous silicon (a-Si:H) solar cells describes the reduced charge collection specifically in the blue part of the spectrum for absorber layers deposited above a critical temperature. This effect limits the device performance of state-of-the art solar cells: For enhanced current density (reduced bandgap), the deposition temperature should be as high as possible, but boron tailing gets detrimental above 200°C. To investigate this limitation and to show...

  15. Optical Waveform Sampling of a 320 Gbit/s Serial Data Signal using a Hydrogenated Amorphous Silicon Waveguide

    DEFF Research Database (Denmark)

    Ji, Hua; Hu, Hao; Pu, Minhao;

    2011-01-01

    We propose using a hydrogenated amorphous silicon waveguide for ultra-high-speed serial data waveform sampling. 320 Gbit/s serial optical data sampling is experimentally demonstrated with +12 dB intrinsic four wave mixing conversion efficiency.......We propose using a hydrogenated amorphous silicon waveguide for ultra-high-speed serial data waveform sampling. 320 Gbit/s serial optical data sampling is experimentally demonstrated with +12 dB intrinsic four wave mixing conversion efficiency....

  16. 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.

  17. Properties of hydrogenated amorphous silicon (a-Si:H) deposited using a microwave Ecr plasma

    International Nuclear Information System (INIS)

    Hydrogenated amorphous silicon (a-Si:H) films have been widely applied to semiconductor devices, such as thin film transistors, solar cells and photosensitive devices. In this work, the first Si-H-Cl alloys (obtained at the National Institute for Nuclear Research of Mexico) were formed by a microwave electron cyclotron resonance (Ecr) plasma CVD method. Gaseous mixtures of silicon tetrachloride (Si Cl4), hydrogen and argon were used. The Ecr plasma was generated by microwaves at 2.45 GHz and a magnetic field of 670 G was applied to maintain the discharge after resonance condition (occurring at 875 G). Si and Cl contents were analyzed by Rutherford Backscattering Spectrometry (RBS). It was found that, increasing proportion of Si Cl4 in the mixture or decreasing pressure, the silicon and chlorine percentages decrease. Optical gaps were obtained by spectrophotometry. Decreasing temperature, optical gap values increase from 1.4 to 1.5 eV. (Author)

  18. Hydrogen reverses the clustering tendency of carbon in amorphous silicon oxycarbide

    OpenAIRE

    Hepeng Ding; Demkowicz, Michael J.

    2015-01-01

    Amorphous silicon oxycarbide (SiOC) is of great technological interest. However, its atomic-level structure is not well understood. Using density functional theory calculations, we show that the clustering tendency of C atoms in SiOC is extremely sensitive to hydrogen (H): without H, the C-C interaction is attractive, leading to enrichment of aggregated SiC[subscript 4] tetrahedral units; with hydrogen, the C-C interaction is repulsive, leading to enrichment of randomly distributed SiCO[subsc...

  19. Fabrication And Determination Of Coefficient Absorption Of Hydrogenated Amorphous Silicon By Direct Evaporation Method

    International Nuclear Information System (INIS)

    Fabrication and characterization of hydrogenated amorphous silicon produced by direct evaporation method have been done. The experiment was carried out at pressure conditions of 2 x 10-5 torr, RF frequency of 13.56 MHz, hydrogen gas flow of 0,8 1/minute, electrode distance of 2.48 cm. voltage electrode of 700 volt and evaporation time 1.45 minute. Using UV-VIS spectrophotometer, it is found that at wavelength of 359 nm, the absorbance degree of material that was by direct hydrogenated method was 0,886. This means that more hydrogen are absorbed by direct method While, if the hydrogenation is carried out by means of indirect method, the degree of absorbance at the wavelength of 359 nm is 0,103. From this result, it can be concluded that the direct methods is better than indirect method

  20. Radiative processes of amorphization and hydrogenation in monocrystalline silicon

    CERN Document Server

    Dovbnya, A N; Dyomin, V S

    2001-01-01

    The processes described will form the H-concentration at the required depth of Si semiconductor due spin splitting of Si:H compounds with the intensive electron beams and processes of the photo stimulation of the volume diffusion. This will provide a continuous migration of hydrogen into the bulk material.

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

    OpenAIRE

    Despeisse, M; Anelli, G.; Jarron, P.; Kaplon, J; Moraes, D.; A. Nardulli(Institute for Particle Physics, ETH Zurich, Zurich, Switzerland); Powolny, F; Wyrsch, N

    2008-01-01

    Radiation detectors based on the deposition of a 10 to 30 μm 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 c...

  2. Hydrogen-induced rupture of strained Si─O bonds in amorphous silicon dioxide

    OpenAIRE

    El-Sayed, Al-Moatasem; Watkins, Matthew B.; Grasser, Tibor; Afanas'ev, Valery; Shluger, Alexander L

    2015-01-01

    Using ab initio modeling we demonstrate that H atoms can break strained Si─O bonds in continuous amorphous silicon dioxide (a-SiO(2)) networks, resulting in a new defect consisting of a threefold-coordinated Si atom with an unpaired electron facing a hydroxyl group, adding to the density of dangling bond defects, such as E' centers. The energy barriers to form this defect from interstitial H atoms range between 0.5 and 1.3 eV. This discovery of unexpected reactivity of atomic hydrogen may hav...

  3. 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.

  4. 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. PMID:26716230

  5. Friction and wear of plasma-deposited amorphous hydrogenated films on silicon nitride

    Science.gov (United States)

    Miyoshi, Kazuhisa

    1991-01-01

    An investigation was conducted to examine the friction and wear behavior of amorphous hydrogenated carbon (a-C:H) films in sliding contact with silicon nitride pins in both dry nitrogen and humid air environments. Amorphous hydrogenated carbon films approximately 0.06 micron thick were deposited on silicon nitride flat substrates by using the 30 kHz ac glow discharge of a planar plasma reactor. The results indicate that an increase in plasma deposition power gives an increase in film density and hardness. The high-density a-C:H films deposited behaved tribologically much like bulk diamond. In the dry nitrogen environment, a tribochemical reaction produced a substance, probably a hydrocarbon-rich layer, that decreased the coefficient of friction. In the humid air environment, tribochemical interactions drastically reduced the wear life of a-C:H films and water vapor greatly increased the friction. Even in humid air, effective lubrication is possible with vacuum-annealed a-C:H films. The vacuum-annealed high-density a-C:H film formed an outermost superficial graphitic layer, which behaved like graphite, on the bulk a-C:H film. Like graphite, the annealed a-C:H film with the superficial graphitic layer showed low friction when adsorbed water vapor was present.

  6. 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.

  7. Hydrogen reverses the clustering tendency of carbon in amorphous silicon oxycarbide.

    Science.gov (United States)

    Ding, Hepeng; Demkowicz, Michael J

    2015-01-01

    Amorphous silicon oxycarbide (SiOC) is of great technological interest. However, its atomic-level structure is not well understood. Using density functional theory calculations, we show that the clustering tendency of C atoms in SiOC is extremely sensitive to hydrogen (H): without H, the C-C interaction is attractive, leading to enrichment of aggregated SiC4 tetrahedral units; with hydrogen, the C-C interaction is repulsive, leading to enrichment of randomly distributed SiCO3 tetrahedral units. Our results suggest that conflicting experimental characterizations of C distributions may be due to differing amounts of H present in the samples investigated. Our work also opens a path for tailoring the properties of SiOC by using the total H content to control the C distribution. PMID:26269200

  8. Visible Absorption Properties of Retinoic Acid Controlled on Hydrogenated Amorphous Silicon Thin Film

    Science.gov (United States)

    Tsujiuchi, Yutaka; Masumoto, Hiroshi; Goto, Takashi

    2008-02-01

    Langmuir-Blodgett (LB) films of retinoic acid and LB films of retinoic acid mixed with a peptide that contains an alanine-lysine-valine (AKV) amino acid sequence deposited on a hydrogenated amorphous silicon (a-Si:H) film prepared by electron cyclotron resonance (ECR) plasma sputtering were fabricated, and their light absorption spectrums were compared. A specific visible light absorption at approximately 500 nm occurred in a film that had a film thickness of more than 80 nm and a hydrogen concentration of more than 20% in the sputtering process gas. Mixing the AKV sequence peptide with retinoic acid caused a 6 nm blueshift, from 363 to 357 nm, of the absorption maximum of the composite LB film on a SiO2 substrate. Using the same peptide, a large 30 nm blueshift, from 500 to 470 nm, was induced in the composite LB film on the a-Si:H film.

  9. From amorphous to microcrystalline silicon films prepared by hydrogen dilution using the VHF (70 MHz) GD technique

    OpenAIRE

    Kroll, U.; Meier, Johannes; Torres, Pedro; Pohl, J.; Shah, Arvind

    2008-01-01

    The amorphous and microcrystalline silicon films have been prepared by hydrogen dilution from pure silane to silane concentrations ≥1.25%. At silane concentrations of less than 10%, a transition from the amorphous phase to the microcrystalline phase can be observed. X-ray diffraction spectroscopy indicates a preferential growth of the crystallites in the [220] direction. Additionally, the transition into the microcrystalline regime is accompanied by a shrinking of the optical gap, a reduction...

  10. Synchrotron radiation photoemission study of metal overlayers on hydrogenated amorphous silicon at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Pi, J.

    1990-09-21

    In this dissertation, metals deposited on a hydrogenated amorphous silicon (a-Si:H) film at room temperature are studied. The purpose of this work is mainly understanding the electronic properties of the interface, using high-resolution synchrotron radiation photoemission techniques as a probe. Atomic hydrogen plays an important role in passivating dangling bonds of a-Si:H films, thus reducing the gap-state distribution. In addition, singly bonded hydrogen also reduces states at the top of the valence band which are now replaced by deeper Si-H bonding states. The interface is formed by evaporating metal on an a-Si:H film in successive accumulations at room temperature. Au, Ag, and Cr were chosen as the deposited metals. Undoped films were used as substrates. Since some unique features can be found in a-Si:H, such as surface enrichment of hydrogen diffused from the bulk and instability of the free surface, we do not expect the metals/a-Si:H interface to behave exactly as its crystalline counterpart. Metal deposits, at low coverages, are found to gather preferentially around regions deficient in hydrogen. As the thickness is increased, some Si atoms in those regions are likely to leave their sites to intermix with metal overlayers like Au and Cr. 129 refs., 30 figs.

  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. 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.

  13. 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

  14. Estimation of the impact of electrostatic discharge on density of states in hydrogenated amorphous silicon thin-film transistors

    NARCIS (Netherlands)

    Tosic Golo, Natasa; Wal, van der Siebrigje; Kuper, F.G.; Mouthaan, A.J.

    2002-01-01

    The objective of this letter is to give an estimation of the impact of an electrostatic discharge (ESD) stress on the density of states (DOS) within the energy gap of hydrogenated amorphous silicon (a-Si:H) thin-film transistors. ESD stresses were applied by means of a transmission line model tester

  15. 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.

  16. Broadband, stable and highly coherent supercontinuum generation at telecommunication wavelengths in an hydrogenated amorphous silicon waveguide

    CERN Document Server

    Leo, F; Kuyken, B; Roelkens, G; Gorza, S -P

    2014-01-01

    Hydrogenated amorphous silicon (a:Si-H) has recently been recognized as a highly nonlinear CMOS compatible photonic platform. We experimentally demonstrate the generation of a supercontinuum (SC) spanning over 500 nm in a-Si:H photonic wire waveguide at telecommunication wavelengths using femtosecond input pulse with energy lower than 5 pJ. Numerical modeling of pulse propagation in the waveguide, based on the experimentally characterized dispersion profile, shows that the supercontinuum is the result of soliton fission and dispersive wave generation. It is demonstrated that the SC is highly coherent and that the waveguides do not suffer from material degradation under femtosecond pulse illumination. Finally, a direct comparison of SC generation in c-Si and a-Si:H waveguides confirms the higher performances of a-Si:H over c-Si for broadband low power SC generation at telecommunication wavelengths.

  17. Acoustically induced optical second harmonic generation in hydrogenated amorphous silicon films

    CERN Document Server

    Ebothe, J; Cabarrocas, P R I; Godet, C; Equer, B

    2003-01-01

    Acoustically induced second harmonic generation (AISHG) in hydrogenated amorphous silicon (a-Si : H) films of different morphology has been observed. We have found that with increasing acoustical power, the optical SHG of Gd : YAB laser light (lambda = 2.03 mu m) increases and reaches its maximum value at an acoustical power density of about 2.10 W cm sup - sup 2. With decreasing temperature, the AISHG signal strongly increases below 48 K and correlates well with the temperature behaviour of differential scanning calorimetry indicating near-surface temperature phase transition. The AISHG maxima were observed at acoustical frequencies of 10-11, 14-16, 20-22 and 23-26 kHz. The independently performed measurements of the acoustically induced IR spectra have shown that the origin of the observed phenomenon is the acoustically induced electron-phonon anharmonicity in samples of different morphology.

  18. Electroless chemical grafting of nitrophenyl groups on n-doped hydrogenated amorphous silicon surfaces.

    Science.gov (United States)

    Kim, Chulki; Oh, Kiwon; Han, Seunghee; Kim, Kyungkon; Kim, Il Won; Kim, Heesuk

    2014-08-01

    The direct spontaneous grafting of 4-nitrophenyl molecules onto n-doped hydrogenated amorphous silicon (a-Si:H) surfaces without external ultraviolet, thermal, or electrochemical energy was invegtigated. Clean n-doped a-Si:H thin films were dipped in a solution of 4-nitrobenzenediazonium salts (PNBD) in acetonitrile. After the modified surfaces were rinsed, they were analyzed qualitatively and quantitatively by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS and AFM results show that the reaction of an n-doped a-Si:H thin film with PNBD self-terminates without polymerization, after 5 h, and the surface number density of 4-nitrophenyl molecules is 4.2 x 10(15)/cm2. These results demonstrate that the spontaneous grafting of nitrophenyl layers onto n-doped a-Si:H thin films is an attractive pathway toward forming interfaces between a-Si:H and organic layers under ambient conditions. PMID:25936109

  19. Hydrogen-induced rupture of strained Si─O bonds in amorphous silicon dioxide.

    Science.gov (United States)

    El-Sayed, Al-Moatasem; Watkins, Matthew B; Grasser, Tibor; Afanas'ev, Valery V; Shluger, Alexander L

    2015-03-20

    Using ab initio modeling we demonstrate that H atoms can break strained Si─O bonds in continuous amorphous silicon dioxide (a-SiO(2)) networks, resulting in a new defect consisting of a threefold-coordinated Si atom with an unpaired electron facing a hydroxyl group, adding to the density of dangling bond defects, such as E' centers. The energy barriers to form this defect from interstitial H atoms range between 0.5 and 1.3 eV. This discovery of unexpected reactivity of atomic hydrogen may have significant implications for our understanding of processes in silica glass and nanoscaled silica, e.g., in porous low-permittivity insulators, and strained variants of a-SiO(2). PMID:25839289

  20. AFM and STM investigations of hydrogenated amorphous silicon: topography and barrier heights

    Energy Technology Data Exchange (ETDEWEB)

    Herion, J. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Schicht- und Ionentechnik; Szot, K. [Silesian Univ., Katowice (Poland); Barzen, S. [Colorado Univ., Boulder, CO (United States). Joint Inst. for Laboratory Astrophysics; Siebke, F. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Schicht- und Ionentechnik; Teske, M. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Grenzflaechenforschung und Vakuumphysik

    1997-05-01

    As-grown films of hydrogenated amorphous silicon (a-Si : H, highly phosphorous-doped) were investigated by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Hills up to 10 nm in height and 10 to 20 nm in diameter have been observed by AFM. By using STM in a new high-sensitivity mode, (1) atomically smooth areas (roughness about 0.3 A rms) which occur at the top of the hills, (2) subnanometer structures several A in height which cover large parts of the surface have been identified. Simultaneous measurements of the local apparent barrier heights (LABH) show a clear correlation to the topography. Areas showing subnanometer structures have always low LABHs while the highest values of the LABH occur on the smooth areas. (orig.). With 5 figs.

  1. Anomalous interaction of longitudinal electric field with hydrogenated amorphous silicon films

    OpenAIRE

    Zhang, J.; Gecevičius, M.; Beresna, M; Kazanskii, A.G.; Kazansky, P. G.

    2013-01-01

    Cylindrically polarized beams produced by femtosecond laser written S-waveplate are used to modify amorphous silicon films. Paradoxically, no crystallization is observed in the maximum of longitudinal electric field despite the strongest light intensity

  2. Development of X-ray/gamma-ray imaging system based on hydrogenated amorphous silicon/crystalline silicon heterojunction strip detector

    International Nuclear Information System (INIS)

    A high-energy X-ray/gamma-ray imaging system based on a hydrogenated amorphous silicon (a-Si : H)/crystalline silicon (c-Si) heterojunction strip detector was developed. The imaging system will be applied in nondestructive testing of concrete structures. We fabricated 50-channel heterojunction strip detectors with a 1 mm pitch on 500 μm thick p-type silicon wafers. The average leakage current was 2.9 nA per channel at 120 V reverse bias. Energy resolutions of 2.8 keV FWHM at 59.5 keV and 2.9 keV FWHM at 122 keV were obtained at 18degC. The position sensitivity of the strip detector was measured by edge-on irradiation with a 137Cs gamma-ray source. Edge-on gamma-ray imaging of a tungsten object using the prototype was performed. A module consisting of 20 stacked silicon strip detectors is being constructed. (author)

  3. 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...

  4. 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.

  5. Understanding the hydrogen and oxygen gas pressure dependence of the tribological properties of silicon oxide-doped hydrogenated amorphous carbon coatings

    OpenAIRE

    Koshigan, KD; Mangolini, F; McClimon, JB; Vacher, B.; Bec, S; Carpick, RW; Fontaine, J

    2015-01-01

    Silicon oxide-doped hydrogenated amorphous carbons (a–C:H:Si:O) are amorphous thin films used as solid lubricants in a range of commercial applications, thanks to its increased stability in extreme environments, relative to amorphous hydrogenated carbons (a–C:H). This work aims to develop a fundamental understanding of the environmental impact on the tribology of a–C:H:Si:O. Upon sliding an a–C:H:Si:O film against a steel counterbody, two friction regimes develop: high friction in high vacuum...

  6. Growth of hydrogenated amorphous silicon (a-Si:H) on patterned substrates for increased mechanical stability

    International Nuclear Information System (INIS)

    Residual stress in hydrogenated amorphous silicon (a-Si:H) film, which causes substrate bending and delamination, is studied. The internal stress can be reduced by controlling deposition parameters, but it is known to produce a trade-off between stress and electronic quality. Selective area deposition, in which the deposition area is reduced by making islands, reduced the stress when the lateral dimension of the islands becomes comparable to the film thickness. The overall stress is reduced by approximately 40% when the lateral dimension is decreased to 40 μm, but the adhesion was not improved much. However, substrates having a 2-dimensional array of inversed pyramids of 200 μm in lateral dimension produced overall stress 3 ∼ 4 times lower than that on the normal substrates. Such substrates were prepared by anisotropic etching of silicon wafers. The inversed pyramid structure also has other advantages including minimized delamination and increased effective thickness. Computer simulation confirmed that the overall stress can be reduced by deposition on the pyramidal structure

  7. [The Influence of Deposition Pressure on the Properties of Hydrogenated Amorphous Silicon Thin Films].

    Science.gov (United States)

    Yuan, Jun-bao; Yang, Wen; Chen, Xiao-bo; Yang, Pei-zhi; Song, Zhao-ning

    2016-02-01

    Hydrogenated amorphous silicon (a-Si:H) thin films on soda-lime glass substrates were deposited by plasma enhanced chemical vapor deposition (PECVD) using disilane and hydrogen as source gases. To study the influence of deposition pressure on the deposition rate, optical band gap and structure factor, a surface profilometer, an ultraviolet-visible spectrometer, a Fourier transform infrared (FTIR) spectrometer and a scanning electron microscopy (SEM) were used to characterize the deposited thin films. It is found that the deposition rate firstly increased and then decreased and the optical band gap monotonically decreased with the increasing deposition pressure. Moreover, the formation of SiH bond was preferable to the formation of SH₂ or SiH₃ bond when the deposition pressure was less than 210 Pa, while it was opposite when the deposition pressure is higher than 210 Pa. Finally, the deposition pressure in the range of 110~210 Pa was found to be more suitable for the preparation of high quality a-Si:H thin films. PMID:27209724

  8. Microstructure factor and mechanical and electronic properties of hydrogenated amorphous and nanocrystalline silicon thin-films for microelectromechanical systems applications

    Energy Technology Data Exchange (ETDEWEB)

    Mouro, J.; Gualdino, A.; Chu, V. [Instituto de Engenharia de Sistemas e Computadores – Microsistemas e Nanotecnologias (INESC-MN) and IN – Institute of Nanoscience and Nanotechnology, 1000-029 Lisbon (Portugal); Conde, J. P. [Instituto de Engenharia de Sistemas e Computadores – Microsistemas e Nanotecnologias (INESC-MN) and IN – Institute of Nanoscience and Nanotechnology, 1000-029 Lisbon (Portugal); Department of Bioengineering, Instituto Superior Técnico (IST), 1049-001 Lisbon (Portugal)

    2013-11-14

    Thin-film silicon allows the fabrication of MEMS devices at low processing temperatures, compatible with monolithic integration in advanced electronic circuits, on large-area, low-cost, and flexible substrates. The most relevant thin-film properties for applications as MEMS structural layers are the deposition rate, electrical conductivity, and mechanical stress. In this work, n{sup +}-type doped hydrogenated amorphous and nanocrystalline silicon thin-films were deposited by RF-PECVD, and the influence of the hydrogen dilution in the reactive mixture, the RF-power coupled to the plasma, the substrate temperature, and the deposition pressure on the structural, electrical, and mechanical properties of the films was studied. Three different types of silicon films were identified, corresponding to three internal structures: (i) porous amorphous silicon, deposited at high rates and presenting tensile mechanical stress and low electrical conductivity, (ii) dense amorphous silicon, deposited at intermediate rates and presenting compressive mechanical stress and higher values of electrical conductivity, and (iii) nanocrystalline silicon, deposited at very low rates and presenting the highest compressive mechanical stress and electrical conductivity. These results show the combinations of electromechanical material properties available in silicon thin-films and thus allow the optimized selection of a thin silicon film for a given MEMS application. Four representative silicon thin-films were chosen to be used as structural material of electrostatically actuated MEMS microresonators fabricated by surface micromachining. The effect of the mechanical stress of the structural layer was observed to have a great impact on the device resonance frequency, quality factor, and actuation force.

  9. Flexible Electronics: High Pressure Chemical Vapor Deposition of Hydrogenated Amorphous Silicon Films and Solar Cells (Adv. Mater. 28/2016).

    Science.gov (United States)

    He, Rongrui; Day, Todd D; Sparks, Justin R; Sullivan, Nichole F; Badding, John V

    2016-07-01

    On page 5939, J. V. Badding and co-workers describe the unrolling of a flexible hydrogenated amorphous silicon solar cell, deposited by high-pressure chemical vapor deposition. The high-pressure deposition process is represented by the molecules of silane infiltrating the small voids between the rolled up substrate, facilitating plasma-free deposition over a very large area. The high-pressure approach is expected to also find application for 3D nanoarchitectures. PMID:27442970

  10. Enhanced Photoelectrical Response of Hydrogenated Amorphous Silicon Single-Nanowire Solar Cells by Front-Opening Crescent Design

    OpenAIRE

    Yang, Zhenhai; Cao, Guoyang; Shang, Aixue; Lei, Dang Yuan; Zhang, Cheng; Gao, Pingqi; Ye, Jichun; Li, Xiaofeng

    2016-01-01

    We report an approach for substantially enhancing the light-trapping and photoconversion efficiency of hydrogenated amorphous silicon (a-Si:H) single-nanowire solar cells (SNSCs) by engineering the cross section of the nanowire from circular into a front-opening crescent shape. The proposed SNSCs show a broadband and highly tunable optical absorption compared to the conventional circular counterparts under both transverse electric and transverse magnetic incidences, enabling an enhancement ra...

  11. 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.

  12. 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.

  13. Hydrogenated Amorphous Silicon Germanium Active Layer for Top Cell of a Multi Junction Cell Structure.

    Science.gov (United States)

    Cho, Jaehyun; Iftiquar, S M; Kim, Minbum; Park, Jinjoo; Jung, Junhee; Kim, Jiwoong; Yi, Junsin

    2016-05-01

    Intrinsic hydrogenated amorphous silicon-germanium (a-SiGe:H) alloy is generally used in the bottom cell because of its low band gap. The a-SiGe:H has a higher photo conductivity in comparison to the a-Si:H; thus, it is expected that the a-SiGe:H can show better short circuit current density than that of the a-Si:H based solar cell. Therefore, we optimized a-SiGe:H active layer that can be a suitable choice for the front cell of a multi junction.solar cell. Furthermore, we carried out a comparative study of the solar cells that have a-SiGe:H and a-Si:H as respective active layers. The a-SiGe:H based solar cells show higher short circuit current density, while the a-Si:H based cells show higheropen circuit voltage. The current-voltage characteristics of these cells are as follows: (a) V(oc) = 770 mV, J(sc) = 15.0 mA/cm2, FF = 64.5%, and η = 7.47% for a-SiGe:H based cell; and (b) V(oc) = 826 mV, J(sc) = 13.63 mA/cm2, FF = 72.0%, and η = 8.1% for a-Si:H based cell. PMID:27483837

  14. Morphological characteristics and optical properties of hydrogenated amorphous silicon thin films

    Science.gov (United States)

    Tang, Haihua; Liu, Shuang; Zhou, Xiang; Liu, Yunfei; Chen, Dejun; Liu, Yong; Zhong, Zhiyong

    2016-05-01

    Hydrogenated amorphous silicon (a-Si:H) thin films were prepared by radio frequency (RF) plasma enhanced chemical vapor deposition (RF-PECVD) technique with silane (SiH4) as reactive gas. The influence of process parameters on the morphological characteristics and optical properties of a-Si:H thin films were systematically investigated. When the RF power density was taken as the only variable, it firstly improves the smoothness of the surface with increasing the RF power density below the value of 0.17 W/cm2, and then exhibits an obvious degradation at further power density. The refractive index, extinction coefficient, optical energy gap initially increase and reach a maximum at 0.17 W/cm2, followed by a significant decrease with further RF power density. When the RF power density was taken as the only variable, the surface of a-Si:H thin films become smoother by increasing the reaction pressure in the investigated range (from 50 Pa to 140 Pa), and the refractive index, extinction coefficient, optical energy gap increase with increasing of reaction pressure. The effect of RF power density and the reaction pressure on the morphological characteristics and optical properties of a-Si:H thin films was obtained, contributing to the further studies of the performance and applications of a-Si:H thin films.

  15. The boron-tailing myth in hydrogenated amorphous silicon solar cells

    Science.gov (United States)

    Stuckelberger, M.; Park, B.-S.; Bugnon, G.; Despeisse, M.; Schüttauf, J.-W.; Haug, F.-J.; Ballif, C.

    2015-11-01

    The boron-tailing effect in hydrogenated amorphous silicon (a-Si:H) solar cells describes the reduced charge collection specifically in the blue part of the spectrum for absorber layers deposited above a critical temperature. This effect limits the device performance of state-of-the art solar cells: For enhanced current density (reduced bandgap), the deposition temperature should be as high as possible, but boron tailing gets detrimental above 200 °C. To investigate this limitation and to show potential paths to overcome it, we deposited high-efficiency a-Si:H solar cells, varying the deposition temperatures of the p-type and the intrinsic absorber (i) layers between 150 and 250 °C. Using secondary ion mass spectroscopy, we study dedicated stacks of i-p-i layers deposited at different temperatures. This allows us to track boron diffusion at the p-i and i-p interfaces as they occur in the p-i-n and n-i-p configurations of a-Si:H solar cells for different deposition conditions. Finally, we prove step-by-step that the common explanation for boron tailing—boron diffusion from the p layer into the i layer leading to enhanced recombination—is not generally true and propose an alternative explanation for the experimentally observed drop in the external quantum efficiency at short wavelengths.

  16. Hydrogenated amorphous silicon sensors based on thin film on ASIC technology

    CERN Document Server

    Despeisse, M; Anelli, G; Jarron, P; Kaplon, J; Rusack, R; Saramad, S; Wyrsch, N

    2006-01-01

    The performance and limitations of a novel detector technology based on the deposition of a thin-film sensor on top of processed integrated circuits have been studied. Hydrogenated amorphous silicon (a-Si:H) films have been deposited on top of CMOS circuits developed for these studies and the resulting "thin-film on ASIC" (TFA) detectors are presented. The leakage current of the a-Si:H sensor at high reverse biases turns out to be an important parameter limiting the performance of a TFA detector. Its detailed study and the pixel segmentation of the detector are presented. High internal electric fields (in the order of 10/sup 4/-10/sup 5/ V/cm) can be built in the a-Si:H sensor and overcome the low mobility of electrons and holes in a-Si:H. Signal induction by generated carrier motion and speed in the a-Si:H sensor have been studied with a 660 nm pulsed laser on a TFA detector based on an ASIC integrating 5 ns peaking time pre- amplifiers. The measurement set-up also permits to study the depletion of the senso...

  17. The boron-tailing myth in hydrogenated amorphous silicon solar cells

    International Nuclear Information System (INIS)

    The boron-tailing effect in hydrogenated amorphous silicon (a-Si:H) solar cells describes the reduced charge collection specifically in the blue part of the spectrum for absorber layers deposited above a critical temperature. This effect limits the device performance of state-of-the art solar cells: For enhanced current density (reduced bandgap), the deposition temperature should be as high as possible, but boron tailing gets detrimental above 200 °C. To investigate this limitation and to show potential paths to overcome it, we deposited high-efficiency a-Si:H solar cells, varying the deposition temperatures of the p-type and the intrinsic absorber (i) layers between 150 and 250 °C. Using secondary ion mass spectroscopy, we study dedicated stacks of i-p-i layers deposited at different temperatures. This allows us to track boron diffusion at the p-i and i-p interfaces as they occur in the p-i-n and n-i-p configurations of a-Si:H solar cells for different deposition conditions. Finally, we prove step-by-step that the common explanation for boron tailing—boron diffusion from the p layer into the i layer leading to enhanced recombination—is not generally true and propose an alternative explanation for the experimentally observed drop in the external quantum efficiency at short wavelengths

  18. The boron-tailing myth in hydrogenated amorphous silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Stuckelberger, M., E-mail: michael.stuckelberger@alumni.ethz.ch; Bugnon, G.; Despeisse, M.; Schüttauf, J.-W.; Haug, F.-J.; Ballif, C. [Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin-Film Electronics Laboratory, Rue de la Maladière 71, CH-2000 Neuchâtel (Switzerland); Park, B.-S. [SIMS Services, Evans Analytical Group, 810 Kifer Road, Sunnyvale, California 94086 (United States)

    2015-11-16

    The boron-tailing effect in hydrogenated amorphous silicon (a-Si:H) solar cells describes the reduced charge collection specifically in the blue part of the spectrum for absorber layers deposited above a critical temperature. This effect limits the device performance of state-of-the art solar cells: For enhanced current density (reduced bandgap), the deposition temperature should be as high as possible, but boron tailing gets detrimental above 200 °C. To investigate this limitation and to show potential paths to overcome it, we deposited high-efficiency a-Si:H solar cells, varying the deposition temperatures of the p-type and the intrinsic absorber (i) layers between 150 and 250 °C. Using secondary ion mass spectroscopy, we study dedicated stacks of i-p-i layers deposited at different temperatures. This allows us to track boron diffusion at the p-i and i-p interfaces as they occur in the p-i-n and n-i-p configurations of a-Si:H solar cells for different deposition conditions. Finally, we prove step-by-step that the common explanation for boron tailing—boron diffusion from the p layer into the i layer leading to enhanced recombination—is not generally true and propose an alternative explanation for the experimentally observed drop in the external quantum efficiency at short wavelengths.

  19. 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.

  20. Solar Hydrogen Production by Amorphous Silicon Photocathodes Coated with a Magnetron Sputter Deposited Mo2C Catalyst.

    Science.gov (United States)

    Morales-Guio, Carlos G; Thorwarth, Kerstin; Niesen, Bjoern; Liardet, Laurent; Patscheider, Jörg; Ballif, Christophe; Hu, Xile

    2015-06-10

    Coupling of Earth-abundant hydrogen evolution catalysts to photoabsorbers is crucial for the production of hydrogen fuel using sunlight. In this work, we demonstrate the use of magnetron sputtering to deposit Mo2C as an efficient hydrogen evolution reaction catalyst onto surface-protected amorphous silicon (a-Si) photoabsorbers. The a-Si/Mo2C photocathode evolves hydrogen under simulated solar illumination in strongly acidic and alkaline electrolytes. Onsets of photocurrents are observed at potentials as positive as 0.85 V vs RHE. Under AM 1.5G (1 sun) illumination, the photocathodes reach current densities of -11.2 mA cm(-2) at the reversible hydrogen potential in 0.1 M H2SO4 and 1.0 M KOH. The high photovoltage and low-cost of the Mo2C/a-Si assembly make it a promising photocathode for solar hydrogen production.

  1. Development of radiation detectors based on hydrogenated amorphous silicon and its alloys

    International Nuclear Information System (INIS)

    Hydrogenated amorphous silicon and related materials have been applied to radiation detectors, utilizing their good radiation resistance and the feasibility of making deposits over a large area at low cost. Effects of deposition parameters on various material properties of a-Si:H have been studied to produce a material satisfying the requirements for specific detection application. Thick(-∼50 μm), device quality a-Si:H p-i-n diodes for direct detection of minimum ionizing particles have been prepared with low internal stress by a combination of low temperature growth, He-dilution of silane, and post annealing. The structure of the new film contained voids and tiny crystalline inclusions and was different from the one observed in conventional a-Si:H. Deposition on patterned substrates was attempted as an alternative to controlling deposition parameters to minimize substrate bending and delamination of thick a-Si:H films. Growth on an inversed-pyramid pattern reduced the substrate bending by a factor of 3∼4 for the same thickness film. Thin (0.1 ∼ 0.2 μm) films of a-Si:H and a-SiC:H have been applied to microstrip gas chambers to control gain instabilities due to charges on the substrate. Light sensitivity of the a-Si:H sheet resistance was minimized and the surface resistivity was successfully' controlled in the range of 1012 ∼ 1017 Ω/□ by carbon alloying and boron doping. Performance of the detectors with boron-doped a-Si:C:H layers was comparable to that of electronic-conducting glass. Hydrogen dilution of silane has been explored to improve electrical transport properties of a-Si:H material for high speed photo-detectors and TFT applications

  2. The Synthesis and Structural Properties of Crystalline Silicon Quantum Dots upon Thermal Annealing of Hydrogenated Amorphous Si-Rich Silicon Carbide Films

    Science.gov (United States)

    Wen, Guozhi; Zeng, Xiangbin; Li, Xianghu

    2016-08-01

    Silicon quantum dots (QDs) embedded in non-stoichiometric hydrogenated silicon carbide (SiC:H) thin films have been successfully synthesized by plasma-enhanced chemical vapor deposition and post-annealing. The chemical composition analyses have been carried out by x-ray photoelectron spectroscopy (XPS). The bonding configurations have been deduced from Fourier transform infrared absorption measurements (FTIR). The evolution of microstructure with temperature has been characterized by glancing incident x-ray diffraction (XRD) and Raman diffraction spectroscopy. XPS and FTIR show that it is in Si-rich feature and there are a few hydrogenated silicon clusters in the as-grown sample. XRD and Raman diffraction spectroscopy show that it is in amorphous for the as-grown sample, while crystalline silicon QDs have been synthesized in the 900°C annealed sample. Silicon atoms precipitation from the SiC matrix or silicon phase transition from amorphous SiC is enhanced with annealing temperature increase. The average sizes of silicon QDs are about 5.1 nm and 5.6 nm, the number densities are as high as 1.7 × 1012 cm-2 and 3.2 × 1012 cm-2, and the crystalline volume fractions are about 58.3% and 61.3% for the 900°C and 1050°C annealed samples, respectively. These structural properties analyses provide an understanding about the synthesis of silicon QDs upon thermal annealing for applications in next generation optoelectronic and photovoltaic devices.

  3. Reduction of tail state on boron doped hydrogenated amorphous silicon oxide films prepared at high hydrogen dilution.

    Science.gov (United States)

    Park, Jinjoo; Iftiquar, S M; Lee, Sunwha; Park, Hyeongsik; Shin, Chonghoon; Jung, Junhee; Lee, Youn-Jung; Balaji, Nagarajan; Yi, Junsin

    2013-12-01

    In this report, we have investigated on the defect state of diborane (B2H6) doped wide bandgap hydrogenated amorphous silicon oxide (p-type a-SiO:H) films prepared using silane (SiH4), hydrogen (H2) and nitrous oxide (N2O) in a radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) system with different hydrogen dilutions. The films prepared with higher hydrogen dilution show lower Urbach energy (Eu), lower microstructure (R*), lower short and medium range disorder (omegaTO, Gamma(TO), I(TA)/I(TO), I(LA)/I(TO)), higher dark conductivity (sigma d) and higher refractive index (n) with high optical gap (Eg). Eu decreases from 248 meV to 153 meV, and R* decreases from 0.46 to 0.26, Raman peak omegaTO-TO mode position shifts from 480.24 to 483.28, GammaTO-full width half maximum of omegaTO decreases from 78.16 to 63.87, I(TA)/I(TO)-the ratio of integrated area of TA and TO mode decreases from 0.624 to 0.474, I(LA)/I(TO)-the ratio of integrated area of LA and TO mode deceases from 0.272 to 0.151, sigma d increases from 4.6 x 10(-7) S/cm to 1.1 x 10(-6) S/cm, n increases from 3.70 to 3.86. Reduced Nd, Eu and R* at wide Eg indicates that the films are more useful for solar cell window layer. Applying this layer to a single junction solar cell shows open circuit voltage (Voc) = 0.80 V, short circuit current density (Jsc) = 16.3 mA/cm2, fill factor (FF) = 72%, efficiency (eta) = 9.4%. PMID:24266147

  4. High spatial resolution radiation detectors based on hydrogenated amorphous silicon and scintillator

    International Nuclear Information System (INIS)

    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 micros. 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

  5. Amorphous silicon based betavoltaic devices

    OpenAIRE

    Wyrsch, N; Riesen, Y.; Franco, A; S. Dunand; Kind, H.; Schneider, S.; Ballif, C.

    2013-01-01

    Hydrogenated amorphous silicon betavoltaic devices are studied both by simulation and experimentally. Devices exhibiting a power density of 0.1 μW/cm2 upon Tritium exposure were fabricated. However, a significant degradation of the performance is taking place, especially during the first hours of the exposure. The degradation behavior differs from sample to sample as well as from published results in the literature. Comparisons with degradation from beta particles suggest an effect of tritium...

  6. High Kerr nonlinearity hydrogenated amorphous silicon nanowires with low two photon absorption and high optical stability

    CERN Document Server

    Grillet, C; Monat, C; Grosse, P; Bakir, B Ben; Menezo, S; Fedeli, J M; Moss, David J

    2014-01-01

    We demonstrate optically stable amorphous silicon nanowires with both high nonlinear figure of merit (FOM) of ~5 and high nonlinearity Re({\\gamma}) = 1200W-1m-1. We observe no degradation in these parameters over the entire course of our experiments including systematic study under operation at 2 W coupled peak power (i.e. ~2GW/cm2) over timescales of at least an hour.

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

    Energy Technology Data Exchange (ETDEWEB)

    Woerdenweber, Jan

    2011-09-26

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

  8. THE ELECTRONIC STRUCTURE OF A MODEL DEFECT IN HYDROGENATED AMORPHOUS SILICON

    OpenAIRE

    DiVincenzo, D.; Bernholc, J.; Brodsky, M.

    1981-01-01

    We calculate the electronic properties of a model defect for hydrogen in hydrogenated amorphous Si. Our model is a vacancy in crystal Si with four H's satisfying the dangling bonds. Using a Green's function technique, we find the change in the density of states caused by the defect, as well as the local density of states for the Si-H bond and surrounding bonds. From several approaches, we extract information on band edge localization. Each approach gives a mobility edge of order tenths of an ...

  9. Charge deep-level transient spectroscopy study of high-energy-electron-beam-irradiated hydrogenated amorphous silicon

    OpenAIRE

    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 defect-state density increased. A similar trend is observed for a-Si:H which has been subjected to light soaking, but in that case the majority of defect states are created around midgap, whereas ...

  10. Solid-phase Crystallization of Hydrogenated Amorphous Silicon on Glass Substrates

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Amorphous silicon films prepared by PECVD on glass substrate have been crystallized by conventional furnace annealing and rapid thermal annealing(RTA), respectively. From the Raman spectra, X-ray diffraction and scanning electron microscope, it is found that the grain size is crystallized at 850℃ in both techniques. The thin film made by RTA is smooth and of perfect structure, the thin film annealed by FA has a highly structural disorder. An average grain size of about 30nm is obtained by both techniques.

  11. 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.

  12. Effect of the hydrogen dilution on the local microstructure in hydrogenated amorphous silicon films deposited by radiofrequency magnetron sputtering

    Science.gov (United States)

    Daouahi, M.; Zellama, K.; Bouchriha, H.; Elkaïm, P.

    2000-06-01

    The nature of the hydrogen bonding and content and their influence on the film microstructure have been investigated in detail, as a function of the H2 dilution and the residual pressure, in hydrogenated amorphous silicon (a-Si:H) films prepared by radiofrequency (rf) magnetron sputtering at a common substrate temperature (sim 250 °C) and pressure (5× 10^{-4} torr) and high rates (11-15 Å/s). H2 percentages in the gas phase mixture (Ar + % H2) of 5, 10, 15 and 20% have been introduced during growth. For the 20% of H2, two different pressures of 5× 10^{-4} and 50× 10^{-4} torr were used. A combination of infrared absorption, optical transmission and elastic recoil detection analysis experiments have been carried out to fully characterize the samples in their as-deposited state. The results clearly indicate that for H2 percentage equal to or lower than 15% , the total bonded H content in the films increases as the H2 percentage increases, and then reaches a saturation value or even decreases for higher H2 percentage. Moreover, the microstructure is also found to be deeply affected by the H2 dilution and pressure. In particular, for high H2 percentage (20% ) and high pressure (50× 10^{-4} torr), unbounded H as well as polyhydride (Si-H2)_n chains, possibly located in structural inhomogeneities such as voids, are also present in the films in addition to the isolated monohydride Si-H and polyhydride Si-H2 complexes. As a result, a reduction of the compactness of the film structure associated with a decrease of the refractive index n is observed. The optical gap is found to be rather controlled by the total bonded hydrogen content. The lowest proportion of isolated polyhydride Si-H2 complexes and the highest density are observed for films deposited with 10% of H2 in the gas phase and a pressure of 5× 10^{-4} torr.

  13. The effect of amorphous silicon surface hydrogenation on morphology, wettability and its implication on the adsorption of proteins

    Science.gov (United States)

    Filali, Larbi; Brahmi, Yamina; Sib, Jamal Dine; Bouhekka, Ahmed; Benlakehal, Djamel; Bouizem, Yahya; Kebab, Aissa; Chahed, Larbi

    2016-10-01

    We study the effect of amorphous silicon (a-Si) surface hydrogenation on Bovine Serum Albumin (BSA) adsorption. A set of (a-Si) films was prepared by radio frequency magnetron sputtering (RFMS) and after deposition; they were treated in molecular hydrogen ambient at different pressures (1-3 Pa). Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy and spectroscopic ellipsometry (SE) were used to study the hydrogenation effect and BSA adsorption. Atomic force microscopy (AFM) was used to evaluate morphological changes caused by hydrogenation. The wettability of the films was measured using contact angle measurement, and in the case of the hydrogenated surfaces, it was found to be driven by surface roughness. FTIR-ATR spectroscopy and SE measurements show that proteins had the strongest affinity toward the surfaces with the highest hydrogen content and their secondary structure was affected by a significant decrease of the α-helix component (-27%) compared with the proteins adsorbed on the un-treated surface, which had a predominantly α-helix (45%) structure. The adsorbed protein layer was found to be densely packed with a large thickness (30.9 nm) on the hydrogen-rich surfaces. The most important result is that the surface hydrogen content was the dominant factor, compared to wettability and morphology, for protein adsorption.

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

    Directory of Open Access Journals (Sweden)

    F. Urbain

    2014-01-01

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

  15. 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.)

  16. Study and characterization of an integrated circuit-deposited hydrogenated amorphous silicon sensor for the detection of particles and radiations

    International Nuclear Information System (INIS)

    Next generation experiments at the European laboratory of particle physics (CERN) require particle detector alternatives to actual silicon detectors. This thesis presents a novel detector technology, which is based on the deposition of a hydrogenated amorphous silicon sensor on top of an integrated circuit. Performance and limitations of this technology have been assessed for the first time in this thesis in the context of particle detectors. Specific integrated circuits have been designed and the detector segmentation, the interface sensor-chip and the sensor leakage current have been studied in details. The signal induced by the track of an ionizing particle in the sensor has been characterized and results on the signal speed, amplitude and on the sensor resistance to radiation are presented. The results are promising regarding the use of this novel technology for radiation detection, though limitations have been shown for particle physics application. (author)

  17. Characterization of 13 and 30 mum thick hydrogenated amorphous silicon diodes deposited over CMOS integrated circuits for particle detection application

    CERN Document Server

    Despeisse, M; Commichau, S C; Dissertori, G; Garrigos, A; Jarron, P; Miazza, C; Moraes, D; Shah, A; Wyrsch, N; Viertel, Gert M

    2004-01-01

    We present the experimental results obtained with a novel monolithic silicon pixel detector which consists in depositing a n-i-p hydrogenated amorphous silicon (a-Si:H) diode straight above the readout ASIC (this technology is called Thin Film on ASIC, TFA). The characterization has been performed on 13 and 30mum thick a-Si:H films deposited on top of an ASIC containing a linear array of high- speed low-noise transimpedance amplifiers designed in a 0.25mum CMOS technology. Experimental results presented have been obtained with a 600nm pulsed laser. The results of charge collection efficiency and charge collection speed of these structures are discussed.

  18. Amorphous silicon based particle detectors

    OpenAIRE

    Wyrsch, N; Franco, A; Riesen, Y.; Despeisse, M; S. Dunand; Powolny, F; Jarron, P.; Ballif, C.

    2012-01-01

    Radiation hard monolithic particle sensors can be fabricated by a vertical integration of amorphous silicon particle sensors on top of CMOS readout chip. Two types of such particle sensors are presented here using either thick diodes or microchannel plates. The first type based on amorphous silicon diodes exhibits high spatial resolution due to the short lateral carrier collection. Combination of an amorphous silicon thick diode with microstrip detector geometries permits to achieve micromete...

  19. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yong Liu

    2002-05-31

    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 H{sub 2}, 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 reduced

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

    NARCIS (Netherlands)

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

    2012-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Wight, Daniel Nilsen

    2008-07-01

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

  3. Annealing Kinetic Model Using Fast and Slow Metastable Defects for Hydrogenated-Amorphous-Silicon-Based Solar Cells

    Directory of Open Access Journals (Sweden)

    Seung Yeop Myong

    2007-01-01

    Full Text Available The two-component kinetic model employing “fast” and “slow” metastable defects for the annealing behaviors in pin-type hydrogenated-amorphous-silicon- (a-Si:H- based solar cells is simulated using a normalized fill factor. Reported annealing data on pin-type a-Si:H-based solar cells are revisited and fitted using the model to confirm its validity. It is verified that the two-component model is suitable for fitting the various experimental phenomena. In addition, the activation energy for annealing of the solar cells depends on the definition of the recovery time. From the thermally activated and high electric field annealing behaviors, the plausible microscopic mechanism on the defect removal process is discussed.

  4. Enhanced Photoelectrical Response of Hydrogenated Amorphous Silicon Single-Nanowire Solar Cells by Front-Opening Crescent Design.

    Science.gov (United States)

    Yang, Zhenhai; Cao, Guoyang; Shang, Aixue; Lei, Dang Yuan; Zhang, Cheng; Gao, Pingqi; Ye, Jichun; Li, Xiaofeng

    2016-12-01

    We report an approach for substantially enhancing the light-trapping and photoconversion efficiency of hydrogenated amorphous silicon (a-Si:H) single-nanowire solar cells (SNSCs) by engineering the cross section of the nanowire from circular into a front-opening crescent shape. The proposed SNSCs show a broadband and highly tunable optical absorption compared to the conventional circular counterparts under both transverse electric and transverse magnetic incidences, enabling an enhancement ratio of over 40 % in both the photocurrent density and the photoconversion efficiency in a-Si:H SNSCs with a diameter of 200 nm. We further show that the superior performance can be well maintained under a wide range of incident angle and is robust to the blunt crescent edges. PMID:27129685

  5. Enhanced Photoelectrical Response of Hydrogenated Amorphous Silicon Single-Nanowire Solar Cells by Front-Opening Crescent Design

    Science.gov (United States)

    Yang, Zhenhai; Cao, Guoyang; Shang, Aixue; Lei, Dang Yuan; Zhang, Cheng; Gao, Pingqi; Ye, Jichun; Li, Xiaofeng

    2016-04-01

    We report an approach for substantially enhancing the light-trapping and photoconversion efficiency of hydrogenated amorphous silicon (a-Si:H) single-nanowire solar cells (SNSCs) by engineering the cross section of the nanowire from circular into a front-opening crescent shape. The proposed SNSCs show a broadband and highly tunable optical absorption compared to the conventional circular counterparts under both transverse electric and transverse magnetic incidences, enabling an enhancement ratio of over 40 % in both the photocurrent density and the photoconversion efficiency in a-Si:H SNSCs with a diameter of 200 nm. We further show that the superior performance can be well maintained under a wide range of incident angle and is robust to the blunt crescent edges.

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

    Science.gov (United States)

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

    2016-06-01

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

  7. 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

  8. Simulation in Amorphous Silicon and Amorphous Silicon Carbide Pin Diodes

    OpenAIRE

    Gonçalves, Dora; Fernandes, Miguel; Louro, Paula; Fantoni, Alessandro; Vieira, Manuela

    2014-01-01

    Part 21: Electronics: Devices International audience Photodiodes are devices used as image sensors, reactive to polychromatic light and subsequently color detecting, and they are also used in optical communication applications. To improve these devices performance it is essential to study and control their characteristics, in fact their capacitance and spectral and transient responses. This study considers two types of diodes, an amorphous silicon pin and an amorphous silicon carbide pi...

  9. Effect of the hydrogen flow rate on the structural and optical properties of hydrogenated amorphous silicon thin films prepared by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ben Amor, Sana; Dimassi, Wissem; Ali Tebai, Mohamed; Ezzaouia, Hatem [Photovoltaic Laboratory Research and Technology Centre of Energy, Borj-Cedria Science and Technology Park, BP 95, 2050 Hammam-Lif (Tunisia)

    2012-10-15

    Hydrogenated amorphous silicon (a-Si:H) thin films were deposited from pure silane (SiH{sub 4}) and hydrogen (H{sub 2}) gas mixture by plasma enhanced chemical vapor deposition (PECVD) method at low temperature (400 C) using high rf power (60 W). The structural and optical properties of these films are systematically investigated as a function of the flow rate of hydrogen (F{sub H2}).The surface morphology is analyzed by atomic force microscopy (AFM). The characterization of these films with low angle X-ray diffraction revealed that the crystallite size in the films tends to decrease with increase in (F{sub H2}). The Fourier transform infrared (FTIR) spectroscopic analysis showed that at low values of (F{sub H2}),the hydrogen bonding in Si:H films shifts from di-hydrogen (Si-H{sub 2}) and (Si-H{sub 2})n complexes to the mono-hydrogen (Si-H) bonding configuration. Finally, for these optimized conditions, the deposition rate decreases with increasing (F{sub H2}). (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Hydrogenated amorphous silicon oxide containing a microcrystalline silicon phase and usage as an intermediate reflector in thin-film silicon solar cells

    OpenAIRE

    Lambertz, A.; Grundler, T.; F. Finger

    2011-01-01

    To further improve the stability of amorphous/microcrystalline silicon (a-Si:H/mu c-Si:H) tandem solar cells, it is important to reduce the thickness of the a-Si: H top cell. This can be achieved by introduction of an intermediate reflector between the a-Si: H top and the mu c-Si: H bottom cell which reflects light back into the a-Si: H cell and thus, increases its photocurrent at possibly reduced thickness. Microcrystalline silicon oxide (mu c-SiOx:H) is used for this purpose and the trade-o...

  11. Plasma Deposition of Amorphous Silicon

    Science.gov (United States)

    Calcote, H. F.

    1982-01-01

    Strongly adhering films of silicon are deposited directly on such materials as Pyrex and Vycor (or equivalent materials) and aluminum by a non-equilibrium plasma jet. Amorphous silicon films are formed by decomposition of silicon tetrachloride or trichlorosilane in the plasma. Plasma-jet technique can also be used to deposit an adherent silicon film on aluminum from silane and to dope such films with phosphorus. Ability to deposit silicon films on such readily available, inexpensive substrates could eventually lead to lower cost photovoltaic cells.

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

    Science.gov (United States)

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

    2016-01-01

    Dielectric nanosphere arrays are considered as promising light-trapping designs with the capability of transforming the freely propagated sunlight into guided modes. This kinds of designs are especially beneficial to the ultrathin hydrogenated amorphous silicon (a-Si:H) solar cells due to the advantages of using lossless material and easily scalable assembly. In this paper, we demonstrate numerically that the front-sided integration of high-index subwavelength titanium dioxide (TiO2) nanosphere arrays can significantly enhance the light absorption in 100 nm-thick a-Si:H thin films and thus the power conversion efficiencies (PCEs) of related solar cells. The main reason behind is firmly attributed to the strong scattering effect excited by TiO2 nanospheres in the whole waveband, which contributes to coupling the light into a-Si:H layer via two typical ways: 1) in the short-waveband, the forward scattering of TiO2 nanospheres excite the Mie resonance, which focuses the light into the surface of the a-Si:H layer and thus provides a leaky channel; 2) in the long-waveband, the transverse waveguided modes caused by powerful scattering effectively couple the light into almost the whole active layer. Moreover, the finite-element simulations demonstrate that photocurrent density (Jph) can be up to 15.01 mA/cm(2), which is 48.76% higher than that of flat system. PMID:27455911

  13. Surface passivation of crystalline silicon by Cat-CVD amorphous and nanocrystalline thin silicon films

    OpenAIRE

    Voz Sánchez, Cristóbal; Martin, I.; Orpella, A.; Puigdollers i González, Joaquim; Vetter, M.; Alcubilla González, Ramón; Soler Vilamitjana, David; Fonrodona Turon, Marta; Bertomeu i Balagueró, Joan; Andreu i Batallé, Jordi

    2003-01-01

    In this work, we study the electronic surface passivation of crystalline silicon with intrinsic thin silicon films deposited by Catalytic CVD. The contactless method used to determine the effective surface recombination velocity was the quasi-steady-state photoconductance technique. Hydrogenated amorphous and nanocrystalline silicon films were evaluated as passivating layers on n- and p-type float zone silicon wafers. The best results were obtained with amorphous silicon films, which allowed ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-01

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

  15. Amorphous silicon for thin-film transistors

    OpenAIRE

    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 addressable image sensor arrays, due to a new technology of low-cost, Iow-temperature processing overlarge areas. ... Zie: Abstract

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-10-04

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

  17. PHYSICAL PROPERTIES OF AMORPHOUS CVD SILICON

    OpenAIRE

    Hirose, M.

    1981-01-01

    Amorphous silicon produced from the chemical vapor decomposition of silane at ~600 °C offers a pure silicon network containing no bonded-hydrogen and involving native defects of the order of 1 x 1019 cm-3. Doped phosphorus or boron atoms in the CVD a-Si interact with the defects to reduce the gap states and the spin density as well. The mechanism of the defect compensation has been interpreted in terms of complex-defect formation through the reaction between three-fold dopant atoms and divaca...

  18. 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.

  19. Structure and Optical Properties of Silicon Nanocrystals Embedded in Amorphous Silicon Thin Films Obtained by PECVD

    OpenAIRE

    Monroy, B. M.; Aduljay Remolina Millán; García-Sánchez, M. F.; Ponce, A.; Picquart, M.; Santana, G.

    2011-01-01

    Silicon nanocrystals embedded in amorphous silicon matrix were obtained by plasma enhanced chemical vapor deposition using dichlorosilane as silicon precursor. The RF power and dichlorosilane to hydrogen flow rate ratio were varied to obtain different crystalline fractions and average sizes of silicon nanocrystals. High-resolution transmission electron microscopy images and RAMAN measurements confirmed the existence of nanocrystals embedded in the amorphous matrix with average sizes between 2...

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

    Science.gov (United States)

    Oh, Kyonghwan; Kwon, Oh-Kyong

    2012-03-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-01-15

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

  2. Amorphous silicon crystalline silicon heterojunction solar cells

    CERN Document Server

    Fahrner, Wolfgang Rainer

    2013-01-01

    Amorphous Silicon/Crystalline Silicon Solar Cells deals with some typical properties of heterojunction solar cells, such as their history, the properties and the challenges of the cells, some important measurement tools, some simulation programs and a brief survey of the state of the art, aiming to provide an initial framework in this field and serve as a ready reference for all those interested in the subject. This book helps to ""fill in the blanks"" on heterojunction solar cells. Readers will receive a comprehensive overview of the principles, structures, processing techniques and the curre

  3. 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.

  4. PHOTOEMISSION STUDIES OF THE TRANSITION FROM AMORPHOUS TO MICROCRYSTALLINE SILICON

    OpenAIRE

    Richter, H.; Ley, L.

    1981-01-01

    We have studied a series of samples spanning the range from purely amorphous to microcrystalline silicon prepared by chemical transport in a hydrogen plasma or by sputtering in a H2/Ar mixture. The first order Raman spectra show a superposition of amorphous and crystalline contribution, showing some features of wurtzite-silicon. The electronic density of states, as deduced from X-ray photoelectron-spectroscopy, shows a gradual change from microcrystalline structure for samples prepared by che...

  5. 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.

  6. Characterization of 13 and 30 $\\mu$m thick hydrogenated amorphous silicon diodes deposited over CMOS integrated circuits for particle detection application

    CERN Document Server

    Despeisse, M; Commichau, S C; Dissertori, G; Garrigos, A; Jarron, P; Miazza, C; Moraes, D; Shah, A; Viertel, G; Wyrsch, N; 10.1016/j.nima.2003.11.022

    2004-01-01

    We present the experimental results obtained with a novel monolithic silicon pixel detector which consists in depositing an n-i-p hydrogenated amorphous silicon (a-Si:H) diode straight above the readout ASIC (this technology is called thin film on ASIC, TFA). The characterization has been performed on 13 and 30 mu m thick a-Si:H films deposited on top of an ASIC containing a linear array of high- speed low-noise transimpedance amplifiers designed in a 0.25 mu m CMOS technology. Experimental results presented have been obtained with a 600 nm pulsed laser. The results of charge collection efficiency and charge collection speed of these structures are discussed.

  7. Amorphous-silicon cell reliability testing

    Science.gov (United States)

    Lathrop, J. W.

    1985-01-01

    The work on reliability testing of solar cells is discussed. Results are given on initial temperature and humidity tests of amorphous silicon devices. Calibration and measurement procedures for amorphous and crystalline cells are given. Temperature stress levels are diagrammed.

  8. Radiation resistance studies of amorphous silicon films

    Science.gov (United States)

    Woodyard, James R.; Payson, J. Scott

    1989-01-01

    Hydrogenated amorphous silicon thin films were irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15 cm(-2). The films were characterized using photothermal deflection spectroscopy and photoconductivity measurements. The investigations show that the radiation introduces sub-band-gap states 1.35 eV below the conduction band and the states increase supralinearly with fluence. Photoconductivity measurements suggest the density of states above the Fermi energy is not changing drastically with fluence.

  9. On the Effect of the Amorphous Silicon Microstructure on the Grain Size of Solid Phase Crystallized Polycrystalline Silicon

    NARCIS (Netherlands)

    Sharma, K.; Branca, A.; Illiberi, A.; Tichelaar, F. D.; Creatore, M.; M. C. M. van de Sanden,

    2011-01-01

    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

  10. Rapid Annealing Of Amorphous Hydrogenated Carbon

    Science.gov (United States)

    Alterovitz, Samuel A.; Pouch, John J.; Warner, Joseph D.

    1989-01-01

    Report describes experiments to determine effects of rapid annealing on films of amorphous hydrogenated carbon. Study represents first efforts to provide information for applications of a-C:H films where rapid thermal processing required. Major finding, annealing causes abrupt increase in absorption and concomitant decrease in optical band gap. Most of change occurs during first 20 s, continues during longer annealing times. Extend of change increases with annealing temperature. Researchers hypothesize abrupt initial change caused by loss of hydrogen, while gradual subsequent change due to polymerization of remaining carbon into crystallites or sheets of graphite. Optical band gaps of unannealed specimens on silicon substrates lower than those of specimens on quartz substrates.

  11. Towards upconversion for amorphous silicon solar cells

    NARCIS (Netherlands)

    de Wild, J.; Meijerink, A.; Rath, J.K.; van Sark, W.G.J.H.M.; Schropp, R.E.I.

    2010-01-01

    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 β-NaYF4:Yb3+(18%) Er3+(2%) at the back of an amorphous silicon solar cell in com

  12. Data supporting the role of electric field and electrode material on the improvement of the ageing effects in hydrogenated amorphous silicon solar cells

    Science.gov (United States)

    Scuto, Andrea; Valenti, Luca; Pierro, Silvio; Foti, Marina; Gerardi, Cosimo; Battaglia, Anna; Lombardo, Salvatore

    2015-01-01

    Hydrogenated amorphous Si (a­Si:H) solar cells are strongly affected by the well known Staebler–Wronski effect. This is a worsening of solar cell performances under light soaking which results in a substantial loss of cell power conversion efficiency compared to time zero performance. It is believed not to be an extrinsic effect, but rather a basic phenomenon related to the nature of a­Si:H and to the stability and motion of H­related species in the a­Si:H lattice. This work has been designed in support of the research article entitled “Role of electric field and electrode material on the improvement of the ageing effects in hydrogenated amorphous silicon solar cells” in Solar Energy Materials & Solar Cells (Scuto et al. [1]), which discusses an electrical method based on reverse bias stress to improve the solar cell parameters, and in particular the effect of temperature, electric field intensity and illumination level as a function of the stress time. Here we provide a further set of the obtained experimental data results. PMID:26966715

  13. Data supporting the role of electric field and electrode material on the improvement of the ageing effects in hydrogenated amorphous silicon solar cells

    Directory of Open Access Journals (Sweden)

    Andrea Scuto

    2015-09-01

    Full Text Available Hydrogenated amorphous Si (a­Si:H solar cells are strongly affected by the well known Staebler–Wronski effect. This is a worsening of solar cell performances under light soaking which results in a substantial loss of cell power conversion efficiency compared to time zero performance. It is believed not to be an extrinsic effect, but rather a basic phenomenon related to the nature of a­Si:H and to the stability and motion of H­related species in the a­Si:H lattice. This work has been designed in support of the research article entitled “Role of electric field and electrode material on the improvement of the ageing effects in hydrogenated amorphous silicon solar cells” in Solar Energy Materials & Solar Cells (Scuto et al. [1], which discusses an electrical method based on reverse bias stress to improve the solar cell parameters, and in particular the effect of temperature, electric field intensity and illumination level as a function of the stress time. Here we provide a further set of the obtained experimental data results.

  14. Influence of the absorber layer thickness and rod length on the performance of three-dimensional nanorods thin film hydrogenated amorphous silicon solar cells

    Science.gov (United States)

    Ho, Chung-I.; Liang, Wei-Chieh; Yeh, Dan-Ju; Su, Vin-Cent; Yang, Po-Chuan; Chen, Shih-Yen; Yang, Tsai-Ting; Lee, Jeng-Han; Kuan, Chieh-Hsiung; Cheng, I.-Chun; Lee, Si-Chen

    2013-04-01

    Performance of substrate-configured hydrogenated amorphous silicon solar cells based on ZnO nanorod arrays prepared by hydrothermal method has been investigated. The light harvest ability of three-dimensional nanorods solar cells is a compromise between the absorber layer thickness and the nanorods geometry. By optimizing the intrinsic a-Si:H absorber layer thickness from 75 to 250 nm and varying the length of the nanorods from 600 to 1800 nm, the highest energy conversion efficiency of 6.07% is obtained for the nanorods solar cell having thin absorber layer thickness of 200 nm with the rod length of 600 nm. This represents up to 28% enhanced efficiency compared to the conventional flat reference cell with similar absorber layer thickness.

  15. Investigation of the Stability and 1.0 MeV Proton Radiation Resistance of Commercially Produced Hydrogenated Amorphous Silicon Alloy Solar Cells

    Science.gov (United States)

    Lord, Kenneth R., II; Walters, Michael R.; Woodyard, James R.

    1994-01-01

    The radiation resistance of commercial solar cells fabricated from hydrogenated amorphous silicon alloys is reported. A number of different device structures were irradiated with 1.0 MeV protons. The cells were insensitive to proton fluences below 1E12 sq cm. The parameters of the irradiated cells were restored with annealing at 200 C. The annealing time was dependent on proton fluence. Annealing devices for one hour restores cell parameters for fluences below 1E14 sq cm fluences above 1E14 sq cm require longer annealing times. A parametric fitting model was used to characterize current mechanisms observed In dark I-V measurements. The current mechanism were explored with irradiation fluence, and voltage and light soaking times. The thermal generation current density and quality factor increased with proton fluence. Device simulation shows the degradation in cell characteristics may be explained by the reduction of the electric field in the intrinsic layer.

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

    Institute of Scientific and Technical Information of China (English)

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

    2005-01-01

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

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

    Science.gov (United States)

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

    2011-03-01

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

  18. Investigation of Sb diffusion in amorphous silicon

    OpenAIRE

    Csik, A.; Langer, G A; Erdelyi, G.; Beke, D. L.; Erdelyi, Z.; Vad, K.

    2009-01-01

    Amorphous silicon materials and its alloys become extensively used in some technical applications involving large area of the microelectronic and optoelectronic devices. However, the amorphous-crystalline transition, segregation and diffusion processes still have numerous unanswered questions. In this work we study the Sb diffusion into an amorphous Si film by means of Secondary Neutral Mass Spectrometry (SNMS). Amorphous Si/Si1-xSbx/Si tri-layer samples with 5 at% antimony concentration were...

  19. Tests Of Amorphous-Silicon Photovoltaic Modules

    Science.gov (United States)

    Ross, Ronald G., Jr.

    1988-01-01

    Progress in identification of strengths and weaknesses of amorphous-silicon technology detailed. Report describes achievements in testing reliability of solar-power modules made of amorphous-silicon photovoltaic cells. Based on investigation of modules made by U.S. manufacturers. Modules subjected to field tests, to accelerated-aging tests in laboratory, and to standard sequence of qualification tests developed for modules of crystalline-silicon cells.

  20. A first principles analysis of the effect of hydrogen concentration in hydrogenated amorphous silicon on the formation of strained Si-Si bonds and the optical and mobility gaps

    Energy Technology Data Exchange (ETDEWEB)

    Legesse, Merid; Nolan, Michael, E-mail: Michael.nolan@tyndall.ie; Fagas, Giorgos, E-mail: Georgios.fagas@tyndall.ie [Tyndall National Institute, University College Cork, Lee Maltings, Dyke Parade, Cork (Ireland)

    2014-05-28

    In this paper, we use a model of hydrogenated amorphous silicon generated from molecular dynamics with density functional theory calculations to examine how the atomic geometry and the optical and mobility gaps are influenced by mild hydrogen oversaturation. The optical and mobility gaps show a volcano curve as the hydrogen content varies from undersaturation to mild oversaturation, with largest gaps obtained at the saturation hydrogen concentration. At the same time, mid-gap states associated with dangling bonds and strained Si-Si bonds disappear at saturation but reappear at mild oversaturation, which is consistent with the evolution of optical gap. The distribution of Si-Si bond distances provides the key to the change in electronic properties. In the undersaturation regime, the new electronic states in the gap arise from the presence of dangling bonds and strained Si-Si bonds, which are longer than the equilibrium Si-Si distance. Increasing hydrogen concentration up to saturation reduces the strained bonds and removes dangling bonds. In the case of mild oversaturation, the mid-gap states arise exclusively from an increase in the density of strained Si-Si bonds. Analysis of our structure shows that the extra hydrogen atoms form a bridge between neighbouring silicon atoms, thus increasing the Si-Si distance and increasing disorder in the sample.

  1. Study on excimer laser irradiation for controlled dehydrogenation and crystallization of boron doped hydrogenated amorphous/nanocrystalline silicon multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Gontad, F., E-mail: fran_gontad@yahoo.es [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Conde, J.C. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Filonovich, S.; Cerqueira, M.F.; Alpuim, P. [Department of Physics, University of Minho, Campus de Azurém, 4800-058 Guimarães (Portugal); Chiussi, S. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain)

    2013-06-01

    We report on the excimer laser annealing (ELA) induced temperature gradients, allowing controlled crystallization and dehydrogenation of boron-doped a-Si:H/nc-Si:H multilayers. Depth of the dehydrogenation and crystallization process has been studied numerically and experimentally, showing that temperatures below the monohydride decomposition can be used and that significant changes of the doping profile can be avoided. Calculation of temperature profiles has been achieved through numerical modeling of the heat conduction differential equation. Increase in the amount of nano-crystals, but not in their size, has been demonstrated by Raman spectroscopy. Effective dehydrogenation and shape of the boron profile have been studied by time of flight secondary ion mass spectroscopy. The relatively low temperature threshold for dehydrogenation, below the monohydride decomposition temperature, has been attributed to both, the large hydrogen content of the original films and the partial crystallization during the ELA process. The results of this study show that UV-laser irradiation is an effective tool to improve crystallinity and dopant activation in p{sup +}-nc-Si:H films without damaging the substrate. - Highlights: • An efficient dehydrogenation is possible through excimer laser annealing. • 140 mJ/cm{sup 2} is enough for dehydrogenation without significant changes in doping profile. • Fluences up to 300 mJ/cm{sup 2} promote partial crystallization of the amorphous structures.

  2. Development of a very fast spectral response measurement system for analysis of hydrogenated amorphous silicon solar cells and modules

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, J.A., E-mail: jose.rodriguez@tsolar.eu [Dept. Technology, Development and Innovation, T-Solar Global S.A., Parque Tecnologico de Galicia, Avda. de Vigo 5, E-32900 San Cibrao das Vinas (Ourense) (Spain); Fortes, M. [Departamento de Electronica e Computacion, Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain); Alberte, C.; Vetter, M.; Andreu, J. [Dept. Technology, Development and Innovation, T-Solar Global S.A., Parque Tecnologico de Galicia, Avda. de Vigo 5, E-32900 San Cibrao das Vinas (Ourense) (Spain)

    2013-01-01

    Highlights: Black-Right-Pointing-Pointer Spectral response equipment for measuring a-Si:H solar cells in a few seconds. Black-Right-Pointing-Pointer Equipment based on 16 LEDs with simultaneous illumination of the solar cell. Black-Right-Pointing-Pointer The current generated by each LED is analyzed by a Fast Fourier Transform. Black-Right-Pointing-Pointer Cheap equipment without lock-in technology for the current measurement. Black-Right-Pointing-Pointer Measurement error vs. conventional measurement less than 1% in J{sub sc}. - Abstract: An important requirement for a very fast spectral response measurement system is the simultaneous illumination of the solar cell at multiple well defined wavelengths. Nowadays this can be done by means of light emitting diodes (LEDs) available for a multitude of wavelengths. For the purpose to measure the spectral response (SR) of amorphous silicon solar cells a detailed characterization of LEDs emitting in the wavelength range from 300 nm to 800 nm was performed. In the here developed equipment the LED illumination is modulated in the frequency range from 100 Hz to 200 Hz and the current generated by each LED is analyzed by a Fast Fourier Transform (FFT) to determine the current component corresponding to each wavelength. The equipment provides a signal to noise ratio of 2-4 orders of magnitude for individual wavelengths resulting in a precise measurement of the SR over the whole wavelength range. The difference of the short circuit current determined from the SR is less than 1% in comparison to a conventional system with monochromator.

  3. Studies of pure and nitrogen-incorporated hydrogenated amorphous carbon thin films and their possible application for amorphous silicon solar cells

    International Nuclear Information System (INIS)

    Hydrogenated amorphous carbon (a-C:H) and nitrogen-incorporated a-C:H (a-C:N:H) thin films were deposited using radio frequency-plasma-enhanced chemical vapor deposition technique and studied for their electrical, optical, and nano-mechanical properties. Introduction of nitrogen and increase of self bias enhanced the conductivity of a-C:H and a-C:N:H films, whereas current-voltage measurement reveals heterojunction formation due to their rectifying behavior. The bandgap of these films was changed over wide range from 1.9 eV to 3.45 eV by varying self bias and the nitrogen incorporation. Further, activation energy was correlated with the electronic structure of a-C:H and a-C:N:H films, and conductivity was discussed as a function of bandgap. Moreover, a-C:N:H films exhibited high hardness and elastic modulus, with maximum values as 42 GPa and 430 GPa, respectively, at -100 V. Observed fascinating electrical, optical, and nano-mechanical properties made it a material of great utility in the development of optoelectronic devices, such as solar cells. In addition, we also performed simulation study for an a-Si:H solar cell, considering a-C:H and C:N:H as window layers, and compared their performance with the a-Si:H solar cell having a-SiC:H as window layer. We also proposed several structures for the development of a near full-spectrum solar cell. Moreover, due to high hardness, a-C:N:H films can be used as a protective and encapsulate layer on solar cells, especially in n-i-p configuration on metal substrate. Nevertheless, a-C:H and a-C:N:H as a window layer can avoid the use of additional hard and protective coating and, hence, minimize the cost of the product.

  4. Multi-resonant silver nano-disk patterned thin film hydrogenated amorphous silicon solar cells for Staebler-Wronski effect compensation

    CERN Document Server

    Vora, Ankit; Pearce, Joshua M; Bergstrom, Paul L; Güney, Durdu Ö

    2014-01-01

    We study polarization independent improved light trapping in commercial thin film hydrogenated amorphous silicon (a-Si:H) solar photovoltaic cells using a three-dimensional silver array of multi-resonant nano-disk structures embedded in a silicon nitride anti-reflection coating (ARC) to enhance optical absorption in the intrinsic layer (i-a-Si:H) for the visible spectrum for any polarization angle. Predicted total optical enhancement (OE) in absorption in the i-a-Si:H for AM-1.5 solar spectrum is 18.51% as compared to the reference, and producing a 19.65% improvement in short-circuit current density (JSC) over 11.7 mA/cm2 for a reference cell. The JSC in the nano-disk patterned solar cell (NDPSC) was found to be higher than the commercial reference structure for any incident angle. The NDPSC has a multi-resonant optical response for the visible spectrum and the associated mechanism for OE in i-a-Si:H layer is excitation of Fabry-Perot resonance facilitated by surface plasmon resonances. The detrimental Staebl...

  5. Surface orientation effects in crystalline-amorphous silicon interfaces

    OpenAIRE

    Nolan, Michael; Legesse, Merid; Fagas, Giorgos

    2012-01-01

    In this paper we present the results of empirical potential and density functional theory (DFT) studies of models of interfaces between amorphous silicon (a-Si) or hydrogenated amorphous Si (a-Si:H) and crystalline Si (c-Si) on three unreconstructed silicon surfaces, namely (100), (110) and (111). In preparing models of a-Si on c-Si, melting simulations are run with classical molecular dynamics (MD) at 3000 K for 10 ps to melt part of the crystalline surface and the structure is quenched to 3...

  6. Raman Amplifier Based on Amorphous Silicon Nanoparticles

    OpenAIRE

    M.A. Ferrara; Rendina, I.; S. N. Basu; Dal Negro, L.; Sirleto, L.

    2012-01-01

    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 la...

  7. Electrical Characterization of Amorphous Silicon Nitride Passivation Layers for Crystalline Silicon Solar Cells

    OpenAIRE

    Helland, Susanne

    2011-01-01

    High quality surface passivation is important for the reduction of recombination losses in solar cells. In this work, the passivation properties of amorphous hydrogenated silicon nitride for crystalline silicon solar cells were investigated, using electrical characterization, lifetime measurements and spectroscopic ellipsometry. Thin films of varying composition were deposited on p-type monocrystalline silicon wafers by plasma enhanced chemical vapor deposition (PECVD). Highest quality surfac...

  8. Electron tunnelling into amorphous germanium and silicon.

    Science.gov (United States)

    Smith, C. W.; Clark, A. H.

    1972-01-01

    Measurements of tunnel conductance versus bias, capacitance versus bias, and internal photoemission were made in the systems aluminum-oxide-amorphous germanium and aluminium-oxide-amorphous silicon. A function was extracted which expresses the deviation of these systems from the aluminium-oxide-aluminium system.

  9. Study of hydrogenated amorphous silicon devices under intense electric field: application to nuclear detection; Etude de dispositifs electroniques en silicium amorphe hydrogene sous fort champ electrique: application a la detection nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Ilie, A. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Direction des Technologies Avancees]|[Paris-11 Univ., 91 - Orsay (France)

    1996-12-31

    The goal of this work was the study, development and optimization of hydrogenated amorphous silicon (a-Si:H) devices for use in detection of ionizing radiation. Thick p-i-n devices, capable of withstanding large electric fields (up to 10{sup 6} V/cm) with small currents (nA/cm{sup 2}), were developed. To decrease fabrication time, films were made using the `He diluted` PECVD process and compared to standard a-Si:H films. Aspects connected to specific detector applications as well as to the fundamental physics of a-Si:H were considered: the internal electric field technique, in which the depletion charge was measured as a function of the applied bias voltage; study of the leakage current of p-i-n devices permitted us to demonstrate different regimes: depletion, field-enhanced thermal generation and electronic injection across the p layer. The effect of the electric field on the thermal generation of the carriers was studied considering the Poole-Frenkel and tunneling mechanisms. A model was developed taking under consideration the statistics of the correlated states and electron-phonon coupling. The results suggest that mechanisms not included in the `standard model` of a Si:h need to be considered, such as defect relaxation, a filed-dependent mobility edge etc...; a new metastable phenomenon, induced by prolonged exposure to a strong electric field, was observed and studied. It is characterized by marked decrease of the leakage current and the detector noise, and increase in the breakdown voltage, as well as an improvement of carrier collection efficiency. This forming process appears to be principally due to an activation of the dopants in the p layer; finally, the capacity of thick p-i-n a Si:H devices to detect ionizing radiation has been evaluated. We show that it is possible, with 20-50 micron thick p-i-n devices, to detect the full spectrum of alpha and beta particles. With an appropriate converter, neutron detection then becomes possible. (author). 137 refs.

  10. The U.S. and Japanese amorphous silicon technology programs A comparison

    Science.gov (United States)

    Shimada, K.

    1984-01-01

    The U.S. Department of Energy/Solar Energy Research Institute Amorphous Silicon (a-Si) Solar Cell Program performs R&D on thin-film hydrogenated amorphous silicon for eventual development of stable amorphous silicon cells with 12 percent efficiency by 1988. The Amorphous Silicon Solar Cell Program in Japan is sponsored by the Sunshine Project to develop an alternate energy technology. While the objectives of both programs are to eventually develop a-Si photovoltaic modules and arrays that would produce electricity to compete with utility electricity cost, the U.S. program approach is research oriented and the Japanese is development oriented.

  11. Atomic-scale disproportionation in amorphous silicon monoxide.

    Science.gov (United States)

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. PMID:27172815

  12. Atomic-scale disproportionation in amorphous silicon monoxide

    Science.gov (United States)

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-05-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material.

  13. The influence of charge effect on the growth of hydrogenated amorphous silicon by the hot-wire chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Q.; Nelson, B.P.; Iwaniczko, E.; Mahan, A.H.; Crandall, R.S.; Benner, J. [National Renewable Energy Lab., Golden, CO (United States)

    1998-09-01

    The authors observe at lower substrate temperatures that the scatter in the dark conductivity on hydrogenated amorphous silicon (a-Si:H) films grown on insulating substrates (e.g., Corning 7059 glass) by the hot-wire chemical vapor deposition technique (HWCVD) can be five orders of magnitude or more. This is especially true at deposition temperatures below 350 C. However, when the authors grow the same materials on substrates with a conductive grid, virtually all of their films have acceptable dark conductivity (< 5 {times} 10{sup {minus}10} S/cm) at all deposition temperatures below 425 C. This is in contrast to only about 20% of the materials grown in this same temperature range on insulating substrates having an acceptable dark conductivity. The authors estimated an average energy of 5 eV electrons reaching the growing surface in vacuum, and did additional experiments to see the influence of both the electron flux and the energy of the electrons on the film growth. Although these effects do not seem to be important for growing a-Si:H by HWCVD on conductive substrates, they help better understand the important parameters for a-Si:H growth, and thus, to optimize these parameters in other applications of HWCVD technology.

  14. Amorphous silicon detectors in positron emission tomography

    International Nuclear Information System (INIS)

    The physics of the detection process is studied and the performances of different Positron Emission Tomography (PET) system are evaluated by theoretical calculation and/or Monte Carlo Simulation (using the EGS code) in this paper, whose table of contents can be summarized as follows: a brief introduction to amorphous silicon detectors and some useful equation is presented; a Tantalum/Amorphous Silicon PET project is studied and the efficiency of the systems is studied by Monte Carlo Simulation; two similar CsI/Amorphous Silicon PET projects are presented and their efficiency and spatial resolution are studied by Monte Carlo Simulation, light yield and time characteristics of the scintillation light are discussed for different scintillators; some experimental result on light yield measurements are presented; a Xenon/Amorphous Silicon PET is presented, the physical mechanism of scintillation in Xenon is explained, a theoretical estimation of total light yield in Xenon and the resulting efficiency is discussed altogether with some consideration of the time resolution of the system; the amorphous silicon integrated electronics is presented, total noise and time resolution are evaluated in each of our applications; the merit parameters ε2τ's are evaluated and compared with other PET systems and conclusions are drawn; and a complete reference list for Xenon scintillation light physics and its applications is presented altogether with the listing of the developed simulation programs

  15. Amorphous silicon detectors in positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Conti, M. (Istituto Nazionale di Fisica Nucleare, Pisa (Italy) Lawrence Berkeley Lab., CA (USA)); Perez-Mendez, V. (Lawrence Berkeley Lab., CA (USA))

    1989-12-01

    The physics of the detection process is studied and the performances of different Positron Emission Tomography (PET) system are evaluated by theoretical calculation and/or Monte Carlo Simulation (using the EGS code) in this paper, whose table of contents can be summarized as follows: a brief introduction to amorphous silicon detectors and some useful equation is presented; a Tantalum/Amorphous Silicon PET project is studied and the efficiency of the systems is studied by Monte Carlo Simulation; two similar CsI/Amorphous Silicon PET projects are presented and their efficiency and spatial resolution are studied by Monte Carlo Simulation, light yield and time characteristics of the scintillation light are discussed for different scintillators; some experimental result on light yield measurements are presented; a Xenon/Amorphous Silicon PET is presented, the physical mechanism of scintillation in Xenon is explained, a theoretical estimation of total light yield in Xenon and the resulting efficiency is discussed altogether with some consideration of the time resolution of the system; the amorphous silicon integrated electronics is presented, total noise and time resolution are evaluated in each of our applications; the merit parameters {epsilon}{sup 2}{tau}'s are evaluated and compared with other PET systems and conclusions are drawn; and a complete reference list for Xenon scintillation light physics and its applications is presented altogether with the listing of the developed simulation programs.

  16. Transverse and longitudinal vibrations in amorphous silicon

    Science.gov (United States)

    Beltukov, Y. M.; Fusco, C.; Tanguy, A.; Parshin, D. A.

    2015-12-01

    We show that harmonic vibrations in amorphous silicon can be decomposed to transverse and longitudinal components in all frequency range even in the absence of the well defined wave vector q. For this purpose we define the transverse component of the eigenvector with given ω as a component, which does not change the volumes of Voronoi cells around atoms. The longitudinal component is the remaining orthogonal component. We have found the longitudinal and transverse components of the vibrational density of states for numerical model of amorphous silicon. The vibrations are mostly transverse below 7 THz and above 15 THz. In the frequency interval in between the vibrations have a longitudinal nature. Just this sudden transformation of vibrations at 7 THz from almost transverse to almost longitudinal ones explains the prominent peak in the diffusivity of the amorphous silicon just above 7 THz.

  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. DEFECTS IN AMORPHOUS CHALCOGENIDES AND SILICON

    OpenAIRE

    Adler, D.

    1981-01-01

    Our comprehension of the physical properties of amorphous semiconductors has improved considerably over the past few years, but many puzzles remain. From our present perspective, the major features of chalcogenide glasses appear to be well understood, and some of the fine points which have arisen recently have been explained within the same general model. On the other hand, there are a grear number of unresolved mysteries with regard to amorphous silicon-based alloys. In this paper, the valen...

  19. Atomic-scale disproportionation in amorphous silicon monoxide

    OpenAIRE

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphou...

  20. Electronic Structure of Dangling Bonds in Amorphous Silicon Studied via a Density-Matrix Functional Method

    OpenAIRE

    Hennig, R. G.; Fedders, P. A.; Carlsson, A. E.

    2002-01-01

    A structural model of hydrogenated amorphous silicon containing an isolated dangling bond is used to investigate the effects of electron interactions on the electronic level splittings, localization of charge and spin, and fluctuations in charge and spin. These properties are calculated with a recently developed density-matrix correlation-energy functional applied to a generalized Anderson Hamiltonian, consisting of tight-binding one-electron terms parametrizing hydrogenated amorphous silicon...

  1. Neutron irradiation induced amorphization of silicon carbide

    International Nuclear Information System (INIS)

    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 x 1025 n/m2. 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 (-10.8%), elastic modulus as measured using a nanoindentation technique (-45%), hardness as measured by nanoindentation (-45%), and standard Vickers hardness (-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

  2. 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.

  3. Hydrogen Bonding in Hydrogenated Amorphous Germanium

    Institute of Scientific and Technical Information of China (English)

    M.S.Abo-Ghazala; S. Al Hazmy

    2004-01-01

    Thin films of hydrogenated amorphous germanium (a-Ge:H) were prepared by radio frequency glow discharge deposition at various substrate temperatures. The hydrogen distribution and bonding structure in a-Ge:H were discussed based on infrared absorption data. The correlation between infrared absorption spectra and hydrogen effusion measurements was used to determine the proportionality constant for each vibration mode of the Ge-H bonds. The results reveal that the bending mode appearing at 835 cm?1 is associated with the Ge-H2 (dihydride) groups on the internal surfaces of voids. While 1880 cm?1 is assigned to vibrations of Ge-H (monohydride) groups in the bulk, the 2000 cm?1 stretching mode is attributed to Ge-H and Ge-H2 bonds located on the surfaces of voids. For films associated with bending modes in the infrared spectra, the proportionality constant values of the stretching modes near 1880 and 2000 cm?1 are found to be lower than those of films which had no corresponding bending modes.

  4. Simulation studies on the effect of a buffer layer on the external parameters of hydrogenated amorphous silicon –– solar cells

    Indian Academy of Sciences (India)

    K Rajeev Kumar; M Zeman

    2008-10-01

    Device modeling of –– junction amorphous silicon solar cells has been carried out using the amorphous semiconductor analysis (ASA) simulation programme. The aim of the study was to explain the role of a buffer layer in between the - and -layers of the –– solar cell on the external parameters such as dark current density and open circuit voltage. Investigations based on the simulation of dark – characteristics revealed that as the buffer layer thickness increases the dark current for a given voltage decreases.

  5. Ground state structures and properties of small hydrogenated silicon clusters

    Indian Academy of Sciences (India)

    R Prasad

    2003-01-01

    We present results for ground state structures and properties of small hydrogenated silicon clusters using the Car–Parrinello molecular dynamics with simulated annealing. We discuss the nature of bonding of hydrogen in these clusters. We find that hydrogen can form a bridge like Si–H–Si bond connecting two silicon atoms. We find that in the case of a compact and closed silicon cluster hydrogen bonds to the silicon cluster from outside. To understand the structural evolutions and properties of silicon cluster due to hydrogenation, we have studied the cohesive energy and first excited electronic level gap of clusters as a function of hydrogenation. We find that first excited electronic level gap of Si and SiH fluctuates as function of size and this may provide a first principle basis for the short-range potential fluctuations in hydrogenated amorphous silicon. The stability of hydrogenated silicon clusters is also discussed.

  6. Free-carrier contribution to all-optical switching in Mie-resonant hydrogenated amorphous silicon nanodisks

    Science.gov (United States)

    Vabishchevich, Polina P.; Shorokhov, Alexander S.; Shcherbakov, Maxim R.; Fedyanin, Andrey A.

    2016-03-01

    Conventionally, all-optical switching devices made out from bulk silicon and other semiconductors are limited by free-carrier relaxation time which spans from picoseconds to microseconds. In this work, we discuss the possibility to suppress the undesired long free-carrier relaxation in subwavelength dielectric nanostructures exhibiting localized magnetic Mie resonances. Numerical calculations show the unsymmetrical modification of the transmittance spectra of the nanodisks due the free carriers photo-injection. Such a spectral dependance allows to control temporal response of the nanostructure by varying the laser pulse spectum.

  7. Amorphous Silicon: Flexible Backplane and Display Application

    Science.gov (United States)

    Sarma, Kalluri R.

    Advances in the science and technology of hydrogenated amorphous silicon (a-Si:H, also referred to as a-Si) and the associated devices including thin-film transistors (TFT) during the past three decades have had a profound impact on the development and commercialization of major applications such as thin-film solar cells, digital image scanners and X-ray imagers and active matrix liquid crystal displays (AMLCDs). Particularly, during approximately the past 15 years, a-Si TFT-based flat panel AMLCDs have been a huge commercial success. a-Si TFT-LCD has enabled the note book PCs, and is now rapidly replacing the venerable CRT in the desktop monitor and home TV applications. a-Si TFT-LCD is now the dominant technology in use for applications ranging from small displays such as in mobile phones to large displays such as in home TV, as well-specialized applications such as industrial and avionics displays.

  8. 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.

  9. Study and characterization of an integrated circuit-deposited hydrogenated amorphous silicon sensor for the detection of particles and radiations; Etude et caracterisation d'un capteur en silicium amorphe hydrogene depose sur circuit integre pour la detection de particules et de rayonnements

    Energy Technology Data Exchange (ETDEWEB)

    Despeisse, M

    2006-03-15

    Next generation experiments at the European laboratory of particle physics (CERN) require particle detector alternatives to actual silicon detectors. This thesis presents a novel detector technology, which is based on the deposition of a hydrogenated amorphous silicon sensor on top of an integrated circuit. Performance and limitations of this technology have been assessed for the first time in this thesis in the context of particle detectors. Specific integrated circuits have been designed and the detector segmentation, the interface sensor-chip and the sensor leakage current have been studied in details. The signal induced by the track of an ionizing particle in the sensor has been characterized and results on the signal speed, amplitude and on the sensor resistance to radiation are presented. The results are promising regarding the use of this novel technology for radiation detection, though limitations have been shown for particle physics application. (author)

  10. Amorphous silicon based large format uncooled FPA microbolometer technology

    Science.gov (United States)

    Schimert, T.; Brady, J.; Fagan, T.; Taylor, M.; McCardel, W.; Gooch, R.; Ajmera, S.; Hanson, C.; Syllaios, A. J.

    2008-04-01

    This paper presents recent developments in next generation microbolometer Focal Plane Array (FPA) technology at L-3 Communications Infrared Products (L-3 CIP). Infrared detector technology at L-3 CIP is based on hydrogenated amorphous silicon (a-Si:H) and amorphous silicon germanium(a-SiGe:H). Large format high performance, fast, and compact IR FPAs are enabled by a low thermal mass pixel design; favorable material properties; an advanced ROIC design; and wafer level packaging. Currently at L-3 CIP, 17 micron pixel FPA array technology including 320x240, 640 x 480 and 1024 x768 arrays is under development. Applications of these FPAs range from low power microsensors to high resolution near-megapixel imager systems.

  11. Spherical silicon photonic microcavities: From amorphous to polycrystalline

    Science.gov (United States)

    Fenollosa, R.; Garín, M.; Meseguer, F.

    2016-06-01

    Shaping silicon as a spherical object is not an obvious task, especially when the object size is in the micrometer range. This has the important consequence of transforming bare silicon material in a microcavity, so it is able to confine light efficiently. Here, we have explored the inside volume of such microcavities, both in their amorphous and in their polycrystalline versions. The synthesis method, which is based on chemical vapor deposition, causes amorphous microspheres to have a high content of hydrogen that produces an onionlike distributed porous core when the microspheres are crystallized by a fast annealing regime. This substantially influences the resonant modes. However, a slow crystallization regime does not yield pores, and produces higher-quality-factor resonances that could be fitted to the Mie theory. This allows the establishment of a procedure for obtaining size calibration standards with relative errors of the order of 0.1%.

  12. Temperature-dependent minority carrier lifetime of crystalline silicon wafers passivated by high quality amorphous silicon oxide

    Science.gov (United States)

    Inaba, Masahiro; Todoroki, Soichiro; Nakada, Kazuyoshi; Miyajima, Shinsuke

    2016-04-01

    We investigated the effects of annealing on the temperature-dependent minority carrier lifetime of a crystalline silicon wafer passivated by hydrogenated amorphous silicon oxide. The annealing significantly affects the lifetime and its temperature dependence. Our device simulations clearly indicate that valence band offset significantly affects the temperature dependence. We also found a slight increase in the interface defect density after annealing.

  13. RF sputtering for controlling dihydride and monohydride bond densities in amorphous silicon hydride

    Science.gov (United States)

    Jeffery, F.R.; Shanks, H.R.

    1980-08-26

    A process is described for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicone 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 solicone hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

  14. 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

  15. Self-Diffusion in Amorphous Silicon.

    Science.gov (United States)

    Strauß, Florian; Dörrer, Lars; Geue, Thomas; Stahn, Jochen; Koutsioubas, Alexandros; Mattauch, Stefan; Schmidt, Harald

    2016-01-15

    The present Letter reports on self-diffusion in amorphous silicon. Experiments were done on ^{29}Si/^{nat}Si heterostructures using neutron reflectometry and secondary ion mass spectrometry. The diffusivities follow the Arrhenius law in the temperature range between 550 and 700 °C with an activation energy of (4.4±0.3)  eV. In comparison with single crystalline silicon the diffusivities are tremendously higher by 5 orders of magnitude at about 700 °C, which can be interpreted as the consequence of a high diffusion entropy. PMID:26824552

  16. Amorphous metallic films in silicon metallization systems

    Science.gov (United States)

    So, F.; Kolawa, E.; Nicolet, M. A.

    1985-01-01

    Diffusion barrier research was focussed on lowering the chemical reactivity of amorphous thin films on silicon. An additional area of concern is the reaction with metal overlays such as aluminum, silver, and gold. Gold was included to allow for technology transfer to gallium arsenide PV cells. Amorphous tungsten nitride films have shown much promise. Stability to annealing temperatures of 700, 800, and 550 C were achieved for overlays of silver, gold, and aluminum, respectively. The lower results for aluminum were not surprising because there is an eutectic that can form at a lower temperature. It seems that titanium and zirconium will remove the nitrogen from a tungsten nitride amorphous film and render it unstable. Other variables of research interest were substrate bias and base pressure during sputtering.

  17. Transverse and longitudinal vibrations in amorphous silicon

    OpenAIRE

    Beltukov, Y. M.; De Fusco, C; Tanguy, A.; Parshin, D. A.

    2015-01-01

    We show that harmonic vibrations in amorphous silicon can be decomposed to transverse and longitudinal components in all frequency range even in the absence of the well defined wave vector ${\\bf q}$. For this purpose we define the transverse component of the eigenvector with given $\\omega$ as a component, which does not change the volumes of Voronoi cells around atoms. The longitudinal component is the remaining orthogonal component. We have found the longitudinal and transverse components of...

  18. Polymeric amorphous carbon as p-type window within amorphous silicon solar cells

    NARCIS (Netherlands)

    Khan, R.U.A.; Silva, S.R.P.; Van Swaaij, R.A.C.M.M.

    2003-01-01

    Amorphous carbon (a-C) has been shown to be intrinsically p-type, and polymeric a-C (PAC) possesses a wide Tauc band gap of 2.6 eV. We have replaced the p-type amorphous silicon carbide layer of a standard amorphous silicon solar cell with an intrinsic ultrathin layer of PAC. The thickness of the p

  19. 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.

  20. 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)

  1. The influence of post-deposition annealing upon amorphous silicon/crystalline silicon heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Mikolášek, Miroslav, E-mail: miroslav.mikolasek@stuba.sk [Slovak University of Technology, Faculty of Electrical Engineering and Information Technology, Ilkovičova 3, 812 19 Bratislava (Slovakia); Nemec, Michal; Kováč, Jaroslav [Slovak University of Technology, Faculty of Electrical Engineering and Information Technology, Ilkovičova 3, 812 19 Bratislava (Slovakia); Foti, Marina; Gerardi, Cosimo [IMS-R and D, STMicroelectronics, Stradale Primosole, 50, 95121 Catania (Italy); Mannino, Giovanni; Valenti, Luca; Lombardo, Salvatore [CNR-IMM, Zona Industriale, Ottava Strada, 5, 95121 Catania (Italy)

    2014-11-15

    Highlights: • We studied the impact of the thermal annealing on the silicon heterojunction solar cells. • Compared were samples deposited by ICP-CVD and PE-CVD methods. • Annealing up to 250 °C improves output performance of both solar cells. • Annealing above 250 °C increases defect states density at the interface and in the amorphous emitter. • Samples deposited by ICP-CVD shows better resistance against annealing. - Abstract: This paper presents a comparative study of the influence of post-deposition annealing on amorphous silicon/crystalline silicon heterojunction solar cells deposited by ICP-CVD and PE-CVD techniques. Two major effects on the solar cell efficiency occur caused by thermal annealing. The first effect is a slight improvement of the performance on annealing up to 250 °C. The second effect, for annealing temperatures above 250 °C, reveals deterioration of the solar cell performance. It is suggested that both effects are related to thermally activated diffusion of hydrogen. For low annealing temperatures, diffusion of weakly bonded hydrogen allows to passivate the defects in the amorphous emitter and at the heterointerface. In the high temperature annealing region, outdiffusion of hydrogen is assumed to be responsible for an increase of defect states in the structures. The results indicate a better stability after high temperature treatment for the sample prepared by ICP-CVD technology.

  2. Modelling the light induced metastable effects in amorphous silicon

    OpenAIRE

    Munyeme, G.; Chinyama, G.K.; Zeman, M.; R. E. I. Schropp; Weg, W

    2008-01-01

    We present results of computer simulations of the light induced degradation of amorphous silicon solar cells. It is now well established that when amorphous silicon is illuminated the density of dangling bond states increases. Dangling bond states produce amphoteric electronic mid-gap states which act as efficient charge trapping and recombination centres. The increase in dangling bond states causes a decrease in the performance of amorphous silicon solar cells. To show this effect, a modelli...

  3. Structure and Optical Properties of Silicon Nanocrystals Embedded in Amorphous Silicon Thin Films Obtained by PECVD

    Directory of Open Access Journals (Sweden)

    B. M. Monroy

    2011-01-01

    Full Text Available Silicon nanocrystals embedded in amorphous silicon matrix were obtained by plasma enhanced chemical vapor deposition using dichlorosilane as silicon precursor. The RF power and dichlorosilane to hydrogen flow rate ratio were varied to obtain different crystalline fractions and average sizes of silicon nanocrystals. High-resolution transmission electron microscopy images and RAMAN measurements confirmed the existence of nanocrystals embedded in the amorphous matrix with average sizes between 2 and 6 nm. Different crystalline fractions (from 12% to 54% can be achieved in these films by regulating the selected growth parameters. The global optical constants of the films were obtained by UV-visible transmittance measurements. Effective band gap variations from 1.78 to 2.3 eV were confirmed by Tauc plot method. Absorption coefficients higher than standard amorphous silicon were obtained in these thin films for specific growth parameters. The relationship between the optical properties is discussed in terms of the different internal nanostructures of the samples.

  4. 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.%.

  5. 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...

  6. Amorphous silicon oxide window layers for high-efficiency silicon heterojunction solar cells

    OpenAIRE

    Seif, Johannes Peter; Descoeudres, Antoine; Filipic, Miha; Smole, Franc; Topic, Marko; Holman, Zachary Charles; De Wolf, Stefaan; Ballif, Christophe

    2014-01-01

    In amorphous/crystalline silicon heterojunction solar cells, optical losses can be mitigated by replacing the amorphous silicon films by wider bandgap amorphous silicon oxide layers. In this article, we use stacks of intrinsic amorphous silicon and amorphous silicon oxide as front intrinsic buffer layers and show that this increases the short-circuit current density by up to 0.43 mA/cm2 due to less reflection and a higher transparency at short wavelengths. Additionally, high open-circuit volt...

  7. Effect of hydrogen on the microstructure of silicon carbide

    International Nuclear Information System (INIS)

    The effect of hydrogenation on the microstructure of a pressureless sintered silicon carbide was studied. Samples which were annealed in a 40:60 mole % H2:Ar atmosphere at 14000C for 50 hours were microstructurally compared with unannealed samples and samples that had been annealed in a similar manner but using an argon atmosphere. The results were also compared with microstructural results obtained from in situ studies using both hydrogen and argon atmospheres. These results were compared with a thermodynamic model which was constructed using a free energy minimization technique. The observed effects of hydrogenation were surface decarburization and amorphization throughout the silicon carbide material. Other observations include the thermally induced growth of microcrystalline silicon and accelerated amorphization around the silicon microcrystals in samples used in hydrogen in situ studies. An analysis of the microstructure of the reference material was also performed

  8. 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.

  9. Endurance Tests Of Amorphous-Silicon Photovoltaic Modules

    Science.gov (United States)

    Ross, Ronald G., Jr.; Sugimura, Russell S.

    1989-01-01

    Failure mechanisms in high-power service studied. Report discusses factors affecting endurance of amorphous-silicon solar cells. Based on field tests and accelerated aging of photovoltaic modules. Concludes that aggressive research needed if amorphous-silicon modules to attain 10-year life - value U.S. Department of Energy established as goal for photovoltaic modules in commercial energy-generating plants.

  10. Modelling the light induced metastable effects in amorphous silicon

    NARCIS (Netherlands)

    Munyeme, G.; Chinyama, G.K.; Zeman, M.; Schropp, R.E.I.; van der Weg, W.

    2008-01-01

    We present results of computer simulations of the light induced degradation of amorphous silicon solar cells. It is now well established that when amorphous silicon is illuminated the density of dangling bond states increases. Dangling bond states produce amphoteric electronic mid-gap states which a

  11. A STUDY OF TIN IMPURITY ATOMS IN AMORPHOUS SILICON

    OpenAIRE

    Rabchanova, Tatiana

    2013-01-01

    Using the Mössbauer spectroscopy method for the 119 Sn isotope the state of tin impurity atoms in amorphous a-Si silicon is studied. The electrical and optical properties of tin doped films of thermally spray-coated amorphous silicon have been studied. It is shown that in contrast to the crystalline silicon where tin is an electrically inactive substitution impurity, in vacuum deposited amorphous silicon it produces an acceptor band near the valence band and a fraction of the tin atoms become...

  12. 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.

  13. Amorphous Silicon Display Backplanes on Plastic Substrates

    Science.gov (United States)

    Striakhilev, Denis; Nathan, Arokia; Vygranenko, Yuri; Servati, Peyman; Lee, Czang-Ho; Sazonov, Andrei

    2006-12-01

    Amorphous silicon (a-Si) thin-film transistor (TFT) backplanes are very promising for active-matrix organic light-emitting diode displays (AMOLEDs) on plastic. The technology benefits from a large manufacturing base, simple fabrication process, and low production cost. The concern lies in the instability of the TFTs threshold voltage (VT) and its low device mobility. Although VT-instability can be compensated by means of advanced multi-transistor pixel circuits, the lifetime of the display is still dependent on the TFT process quality and bias conditions. A-Si TFTs with field-effect mobility of 1.1 cm2/V · s and pixel driver circuits have been fabricated on plastic substrates at 150 °C. The circuits are characterized in terms of current drive capability and long-term stability of operation. The results demonstrate sufficient and stable current delivery and the ability of the backplane on plastic to meet AMOLED requirements.

  14. Size modulation of nanocrystalline silicon embedded in amorphous silicon oxide by Cat-CVD

    International Nuclear Information System (INIS)

    Different issues related to controlling size of nanocrystalline silicon (nc-Si) embedded in hydrogenated amorphous silicon oxide (a-SiOx:H) deposited by catalytic chemical vapor deposition (Cat-CVD) have been reported. Films were deposited using tantalum (Ta) and tungsten (W) filaments and it is observed that films deposited using tantalum filament resulted in good control on the properties. The parameters which can affect the size of nc-Si domains have been studied which include hydrogen flow rate, catalyst and substrate temperatures. The deposited samples are characterized by X-ray diffraction, HRTEM and micro-Raman spectroscopy, for determining the size of the deposited nc-Si. The crystallite formation starts for Ta-catalyst around the temperature of 1700 oC.

  15. Advantages of N-Type Hydrogenated Microcrystalline Silicon Oxide Films for Micromorph Silicon Solar Cells

    OpenAIRE

    Amornrat Limmanee; Songkiate Kittisontirak; Sorapong Inthisang; Taweewat Krajangsang; Jaran Sritharathikhun; Kobsak Sriprapha

    2013-01-01

    We report on the development and application of n-type hydrogenated microcrystalline silicon oxide films (n μc-SiO:H) in hydrogenated amorphous silicon oxide/hydrogenated microcrystalline silicon (a-SiO:H/μc-Si:H) micromorph solar cells. The n μc-SiO:H films with high optical bandgap and low refractive index could be obtained when a ratio of carbon dioxide (CO2) to silane (SiH4) flow rate was raised; however, a trade-off against electrical property was observed. We applied the n μc-SiO:H film...

  16. Nano structures of amorphous silicon: localization and energy gap

    Directory of Open Access Journals (Sweden)

    Z Nourbakhsh

    2013-10-01

    Full Text Available Renewable energy research has created a push for new materials; one of the most attractive material in this field is quantum confined hybrid silicon nano-structures (nc-Si:H embedded in hydrogenated amorphous silicon (a-Si:H. The essential step for this investigation is studying a-Si and its ability to produce quantum confinement (QC in nc-Si: H. Increasing the gap of a-Si system causes solar cell efficiency to increase. By computational calculations based on Density Functional Theory (DFT, we calculated a special localization factor, [G Allan et al., Phys. Rev. B 57 (1997 6933.], for the states close to HOMO and LUMO in a-Si, and found most weak-bond Si atoms. By removing these silicon atoms and passivating the system with hydrogen, we were able to increase the gap in the a-Si system. As more than 8% hydrogenate was not experimentally available, we removed about 2% of the most localized Si atoms in the almost tetrahedral a-Si system. After removing localized Si atoms in the system with 1000 Si atoms, and adding 8% H, the gap increased about 0.24 eV. Variation of the gap as a function of hydrogen percentage was in good agreement with the Tight –Binding results, but about 2 times more than its experimental value. This might come from the fact that in the experimental conditions, it does not have the chance to remove the most localized states. However, by improving the experimental conditions and technology, this value can be improved.

  17. Growth mechanisms and characterization of hydrogenated amorphous-silicon-alloy films. Final subcontract report, 15 February 1991--14 April 1994

    Energy Technology Data Exchange (ETDEWEB)

    Gallagher, A.; Tanenbaum, D.; Laracuente, A.; Kalra, P. [National Inst. of Standards and Technology, Boulder, CO (United States)

    1994-07-01

    This report describes work performed to better understand the atomic-scale structure of glow-discharge-produced a-Si:H, a-Ge:H, and a-Si:Ge:H films; its effect on film quality; and its dependence on deposition discharge conditions. Hydrogenated a-Si films are from a silane rf discharge onto atomically flat crystal Si and GaAs substrates. The substrates are then transferred in a scanning tunneling microscope, where the atomic-scale surface morphology is measured. The films were deposited using device-quality deposition conditions; IR absorption, {sigma}{sub L}, and {sigma}{sub D} indicate high-quality intrinsic films. From the thickness dependence of the surface morphology, we determined that the films initially conform smoothly to an atomically flat Si or GaAs substrate, but as the thickness increases the roughness steadily increases to approximately 10% of the length of the scanned region. The surface of 100--400-nm-thick films is highly inhomogeneous, with steep hills and canyons in some areas and large atomically smooth regions in others. These unexpectedly large surface irregularities indicate severe and often connected void structures in the growing film, as well as relatively limited-range surface diffusion of the incorporating SiH{sub 3} radicals. On the other hand, large atomically flat surface were occasionally found, indicating the possibility of growing a homogeneous and compact amorphous film if appropriate growth conditions could be discovered.

  18. 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)

  19. Rare-earth Doped Amorphous Silicon Microdisk and Microstadium Resonators with Emission at 1550nm

    CERN Document Server

    Figueira, D S L

    2007-01-01

    Microdisks and microstadium resonators were fabricated on erbium doped amorphous hydrogenated silicon (a-Si:H) layers sandwiched in air and native SiO2 on Si substrates. Annealing condition is optimized to allow large emission at 1550 nm for samples with erbium concentrations as high as 1.02x10^20 atoms/cm3. Near field scanning optical microscopy shows evidences of the simultaneous presence of bow-tie and diamond scars. These modes indicate the high quality of the resonators and the potentiality for achieving amorphous silicon microcavity lasers.

  20. Radiation Resistance Studies of Amorphous Silicon Alloy Photovoltaic Materials

    Science.gov (United States)

    Woodyard, James R.

    1994-01-01

    The radiation resistance of commercial solar cells fabricated from hydrogenated amorphous silicon alloys was investigated. A number of different device structures were irradiated with 1.0 MeV protons. The cells were insensitive to proton fluences below 1E12 sq cm. The parameters of the irradiated cells were restored with annealing at 200 C. The annealing time was dependent on proton fluence. Annealing devices for one hour restores cell parameters for fluences below lE14 sq cm require longer annealing times. A parametric fitting model was used to characterize current mechanisms observed in dark I-V measurements. The current mechanisms were explored with irradiation fluence, and voltage and light soaking times. The thermal generation current density and quality factor increased with proton fluence. Device simulation shows the degradation in cell characteristics may be explained by the reduction of the electric field in the intrinsic layer.

  1. Laser annealing of amorphous silicon core optical fibers

    OpenAIRE

    Healy, N; Mailis, S.; Day, T. D.; Sazio, P.J.A.; Badding, J. V.; A.C. Peacock

    2012-01-01

    Laser annealing of an optical fiber with an amorphous silicon core is demonstrated. The annealing process produces a fiber that has a highly crystalline core, whilst reducing the optical transmission losses by ~3 orders of magnitude.

  2. 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.

  3. Thermal properties of amorphous/crystalline silicon superlattices.

    Science.gov (United States)

    France-Lanord, Arthur; Merabia, Samy; Albaret, Tristan; Lacroix, David; Termentzidis, Konstantinos

    2014-09-01

    Thermal transport properties of crystalline/amorphous silicon superlattices using molecular dynamics are investigated. We show that the cross-plane conductivity of the superlattices is very low and close to the conductivity of bulk amorphous silicon even for amorphous layers as thin as ≃ 6 Å. The cross-plane thermal conductivity weakly increases with temperature which is associated with a decrease of the Kapitza resistance with temperature at the crystalline/amorphous interface. This property is further investigated considering the spatial analysis of the phonon density of states in domains close to the interface. Interestingly, the crystalline/amorphous superlattices are shown to display large thermal anisotropy, according to the characteristic sizes of elaborated structures. These last results suggest that the thermal conductivity of crystalline/amorphous superlattices can be phonon engineered, providing new directions for nanostructured thermoelectrics and anisotropic materials in thermal transport. PMID:25105883

  4. Growth characteristics of amorphous-layer-free nanocrystalline silicon films fabricated by very high frequency PECVD at 250 ℃

    Institute of Scientific and Technical Information of China (English)

    Guo Yan-Qing; Huang Rui; Song Jie; Wang Xiang; Song Chao; Zhang Yi-Xiong

    2012-01-01

    Amorphous-layer-free nanocrystalline silicon films were prepared by a very high frequency plasma enhanced chemical vapor deposition (PECVD) technique using hydrogen-diluted SiH4 at 250 ℃.The dependence of the crystallinity of the film on the hydrogen dilution ratio and the film thickness was investigated.Raman spectra show that the thickness of the initial amorphous incubation layer on silicon oxide gradually decreases with increasing hydrogen dilution ratio.High-resolution transmission electron microscopy reveals that the initial amorphous incubation layer can be completely eliminated at a hydrogen dilution ratio of 98%,which is lower than that needed for the growth of amorphous-layer-free nanocrystalline silicon using an excitation frequency of 13.56 MHz.More studies on the microstructure evolution of the initial amorphous incubation layer with hydrogen dilution ratios were performed using Fourier-transform infrared spectroscopy.It is suggested that the high hydrogen dilution,as well as the higher plasma excitation frequency,plays an important role in the formation of amorphous-layer-free nanocrystalline silicon films.

  5. Crystallization of amorphous silicon thin films deposited by PECVD on nickel-metalized porous silicon

    OpenAIRE

    Ben Slama, Sonia; Hajji, Messaoud; Ezzaouia, Hatem

    2012-01-01

    Porous silicon layers were elaborated by electrochemical etching of heavily doped p-type silicon substrates. Metallization of porous silicon was carried out by immersion of substrates in diluted aqueous solution of nickel. Amorphous silicon thin films were deposited by plasma-enhanced chemical vapor deposition on metalized porous layers. Deposited amorphous thin films were crystallized under vacuum at 750°C. Obtained results from structural, optical, and electrical characterizations show that...

  6. 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.

  7. Structural,Optical and Electrical Properties of Hydrogen-Doped Amorphous GaAs Thin Films

    Institute of Scientific and Technical Information of China (English)

    YAO Yan-Ping; LIU Chun-Ling; QIAO Zhong-Liang; LI Mei; GAO Xin; BO Bao-Xue

    2008-01-01

    @@ Amorphous GaAs films are deposited on substrates of quartz glass and silicon by rf magnetron sputtering technique in different gas ambient.First,the amorphous structure of the prepared samples is identified by x-ray diffraction.Second,analysis by radial distribution function and pair correlation function method is established to characterize the microstructure of the samples.Then,the content and bond type of hydrogen are analysed using Fourier transform infrared absorption spectroscopy.

  8. Flexible Protocrystalline Silicon Solar Cells with Amorphous Buffer Layer

    Science.gov (United States)

    Ishikawa, Yasuaki; Schubert, Markus B.

    2006-09-01

    A low deposition temperature of 110 °C is mandatory for directly growing amorphous-silicon-based solar cells on plastic foil. The optimum absorber material at this low temperature is protocrystalline, i.e., right at the transition between amorphous and crystalline silicon. Polyethylene terephtalate foil of 50 μm thickness form the substrate of our flexible p-i-n single-junction cells. We discuss three peculiar processing techniques for achieving the maximum photovoltaic conversion efficiency of flexible low-temperature solar cells. First, we employ an optimized microcrystalline silicon p-type window layer; second, we use protocrystalline silicon for the i-layer; third, we insert an undoped amorphous silicon buffer layer at the p/i interface. The best flexible cells attain power conversion efficiencies of up to 4.9%.

  9. 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

  10. Anharmonic Decay of Vibrational States in Amorphous Silicon

    OpenAIRE

    Fabian, Jaroslav; Allen, Philip B.

    1996-01-01

    Anharmonic decay rates are calculated for a realistic atomic model of amorphous silicon. The results show that the vibrational states decay on picosecond timescales and follow the two-mode density of states, similar to crystalline silicon, but somewhat faster. Surprisingly little change occurs for localized states. These results disagree with a recent experiment.

  11. Polymeric amorphous carbon as p-type window within amorphous silicon solar cells

    OpenAIRE

    Khan, R U A; Silva, S. R. P.; Van Swaaij, R.A.C.M.M.

    2003-01-01

    Amorphous carbon (a-C) has been shown to be intrinsically p-type, and polymeric a-C (PAC) possesses a wide Tauc band gap of 2.6 eV. We have replaced the p-type amorphous silicon carbide layer of a standard amorphous silicon solar cell with an intrinsic ultrathin layer of PAC. The thickness of the p layer had to be reduced from 9 to 2.5 nm in order to ensure sufficient conduction through the PAC film. Although the resulting external parameters suggest a decrease in the device efficiency from 9...

  12. Preparation and Characterization of Amorphous Silicon Oxide Nanowires

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Large-scale amorphous silicon nanowires (SiNWs) with a diameter about 100 nm and a length of dozens of micrometers on silicon wafers were synthesized by thermal evaporation of silicon monoxide (SiO).Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations show that the silicon nanowires are smooth.Selected area electron diffraction (SAED) shows that the silicon nanowires are amorphous and energy-dispersive X-ray spectroscopy (EDS) indicates that the nanowires have the composition of Si and O elements in an atomic ratio of 1:2, their composition approximates that of SiO2.SiO is considered to be used as a Si sources to produce SiNWs.We conclude that the growth mechanism is closely related to the defect structure and silicon monoxide followed by growth through an oxide-assisted vapor-solid reaction.

  13. 后退火增强氢化非晶硅钝化效果的研究∗%Investigation of p ost-annealing enhancement effect of passivation quality of hydrogenated amorphous silicon

    Institute of Scientific and Technical Information of China (English)

    陈剑辉; 杨静; 沈艳娇; 李锋; 陈静伟; 刘海旭; 许颖; 麦耀华

    2015-01-01

    The excellent surface passivation scheme for suppression of surface recombination is a basic prerequisite to obtain high efficiency solar cells. Particularly, the HIT (heterojunction with intrinsic thin-layer) solar cell, which possesses an abrupt discontinuity of the crystal network at an interface between the crystalline silicon (c-Si) surface and the hydrogenated amorphous silicon (a-Si:H) thin film, usually causes a large density of defects in the bandgap due to a high density of dangling bonds, so it is very important for high energy conversion efficiency to obtain millisecond (ms) range of minority carrier lifetime (i. e. >2 ms). The a-Si:H, due to its excellent passivation properties obtained at low deposition temperatures and also mature processing, is still the best candidate materials for silicon HIT solar cell. Deposition of a transparent conductive oxide (TCO), such as indium tin oxide (ITO), has to be used to improve the carrier transport, since the lateral conductivity of a-Si:H is very poor. Usually, ITO is deposited by magnetron sputtering, but damage of a-Si:H layers by sputtering-induced ion bombardment inevitably occurs, thus triggering the serious degradation of the minority carrier lifetime, i. e., a loss in wafer passivation. Fortunately, this damage can be often recovered by some post-annealing. In this paper, however, the situation is different, and it is found that the minority carrier lifetime of ITO/a-Si:H/c-Si/a-Si:H heterojunction has been drastically enhanced by post-annealing after sputtering ITO on a-Si:H/c-Si/a-Si:H heterojunction (from 1.7 ms to 4.0 ms), not just recovering. It is very important to investigate how post-annealing enhances the lifetime and its physics nature. Combining the two experimental ways of HF treatment and vacuum annealing, three possible reasons for this enhancement effect (the field effect at the ITO/a-Si:H interface, the surface reaction-layer resulting from annealing in air, and the optimization of a

  14. Electrical characteristics of amorphous iron-tungsten contacts on silicon

    OpenAIRE

    Finetti, M.; Pan, E. T-S.; Suni, I.; Nicolet, M-A.

    1983-01-01

    The electrical characteristics of amorphous Fe-W contacts have been determined on both p-type and n-type silicon. The amorphous films were obtained by cosputtering from a composite target. Contact resistivities, pc=1×10^−7 and pc=2.8×10^−6, were measured on n+ and p+ silicon, respectively. These values remain constant after thermal treatment up to at least 500°C. A barrier height, φBn=0.61 V, was measured on n-type silicon.

  15. Electrical characteristics of amorphous iron-tungsten contacts on silicon

    Science.gov (United States)

    Finetti, M.; Pan, E. T.-S.; Nicolet, M.-A.; Suni, I.

    1983-01-01

    The electrical characteristics of amorphous Fe-W contacts have been determined on both p-type and n-type silicon. The amorphous films were obtained by cosputtering from a composite target. Contact resistivities of 1 x 10 to the -7th and 2.8 x 10 to the -6th were measured on n(+) and p(+) silicon, respectively. These values remain constant after thermal treatment up to at least 500 C. A barrier height of 0.61 V was measured on n-type silicon.

  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. CURRENT PATH IN AMORPHOUS-SILICON FIELD EFFECT TRANSISTORS

    OpenAIRE

    M. MATSUMURA; Kuno, S.; Uchida, Y.

    1981-01-01

    On-resistance of amorphous-silicon field effect transistors with staggered electrodes was investigated. It was found that dependences of the on-resistance on geometrical parameters were classified into two groups. The origin was attributed to the residual resistance between the n+ electrode and the channel which was formed at the silicon-silicon dioxide interface. The resistance was analyzed by taking space charge effect into account, and we found that it changes in accordance with sample pre...

  18. 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}.

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

    Science.gov (United States)

    Wan, Yimao; Yan, Di; Bullock, James; Zhang, Xinyu; Cuevas, Andres

    2015-12-01

    A sub-nm hydrogenated amorphous silicon (a-Si:H) film capped with silicon nitride (SiNx) 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 SiNx stack, recombination current density J0 values of 9, 11, 47, and 87 fA/cm2 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 J0 on n-type 10 Ω.cm wafers is further reduced to 2.5 ± 0.5 fA/cm2 when the a-Si:H film thickness exceeds 2.5 nm. The passivation by the sub-nm a-Si:H/SiNx stack is thermally stable at 400 °C in N2 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/SiNx 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.

  20. Amorphous and microcrystalline silicon films grown at low temperatures by radio-frequency and hot-wire chemical vapor deposition

    OpenAIRE

    Alpuim, P.; Chu, Virginia; Conde, João Pedro

    1999-01-01

    The effect of hydrogen dilution on the optical, transport, and structural properties of amorphous and microcrystalline silicon thin films deposited by hot-wire (HW) chemical vapor deposition and radio-frequency (rf) plasma-enhanced chemical vapor deposition using substrate temperatures (T-sub) of 100 and 25 degrees C is reported. Microcrystalline silicon (mu c-Si:H) is obtained using HW with a large crystalline fraction and a crystallite size of similar to 30 nm for hydrogen dilutions above 8...

  1. 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.

  2. 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%.

  3. Mechanism of Germanium-Induced Perimeter Crystallization of Amorphous Silicon

    OpenAIRE

    Hakim, M. M. A.; Ashburn, P.

    2007-01-01

    We report a study aimed at highlighting the mechanism of a new amorphous silicon crystallization phenomenon that originates from the perimeter of a germanium layer during low-temperature annealing (500°C). Results are reported on doped and undoped amorphous silicon films, with thicknesses in the range 40–200 nm, annealed at a temperature of 500 or 550°C. A comparison is made of crystallization arising from Ge and SiGe layers and the role of damage from a high-dose fluorine implant is investig...

  4. Potential of amorphous and microcrystalline silicon solar cells

    OpenAIRE

    Meier, Johannes; Spitznagel, J.; Kroll, U.; Bucher, C.; Faÿ Sylvie; Moriarty, T.; Shah, Arvind

    2008-01-01

    Low pressure chemical vapour deposition (LP-CVD) ZnO as front transparent conductive oxide (TCO), developed at IMT, has excellent light-trapping properties for a-Si:H p-i-n single-junction and ‘micromorph’ (amorphous/microcrystalline silicon) tandem solar cells. A stabilized record efficiency of 9.47% has independently been confirmed by NREL for an amorphous silicon single-junction p-i-n cell (~1 cm2) deposited on LP-CVD ZnO coated glass. Micromorph tandem cells with an initial efficiency of ...

  5. Optimization design of hydrogenated amorphous silicon germanium thin film solar cell with graded band gap profile%渐变带隙氢化非晶硅锗薄膜太阳能电池的优化设计

    Institute of Scientific and Technical Information of China (English)

    柯少颖; 王茺; 潘涛; 何鹏; 杨杰; 杨宇

    2014-01-01

    The simulation program AMPS-1D (analysis of microelectronic and photonic structures) employed to simulate and compare the performances of hydrogenated amorphous silicon germanium (a-SiGe : H) thin film solar cell with and without band gap grading at a radiation of AM1.5G (100 mW/cm2) and room temperature by introducing energy band engineering. The simulation results show that the efficiency of the solar cell with band gap grading is 0.477%higher than that without band gap grading due to the higher open circuit voltage (Voc) and better fill factor (F F ). Subsequently, a-SiGe : H thin film solar cells with three different window layers such as hydrogenated amorphous silicon (a-Si : H), hydrogenated amorphous silicon carbide (a-SiC:H) and hydrogenated nanocrystalline silicon (nc-Si:H) are simulated, respectively. The numeric calculation results indicate that the fermi level EF of the a-SiGe:H thin film solar cell crosses the valence band when nc-Si:H window layer is employed in the simulation. This will improve the conductivity and the open circuit voltage of the solar cell. In addition, the electric field at front contact interface is reduced due to the lower contact barrier height. This may be more beneficial to the carrier collection by front contact. On the other hand, thanks to the wider band-gap difference between the window layer and the intrinsic layer, a potential barrier is built at the valence-band p/i interface due to the band offset. This will hinder the hole migration and collection. Thus, an nc-Si:H buffer layer, which can relax the valence-band offset and be more beneficial to the carrier migration and collection, is introduced at p/i interface. Finally, the optimum conversion efficiency of the a-SiGe:H thin film solar cell with graded band gap is achieved to be 9.104%.%利用一维微电子-光电子结构分析软件(AMPS-1D)在AM1.5G (100 mW/cm2)、室温条件下模拟和比较了有、无渐变带隙氢化非晶硅锗(a-SiGe:H)薄膜太阳能

  6. Laser direct writing of oxide structures on hydrogen-passivated silicon surfaces

    OpenAIRE

    Müllenborn, Matthias; Birkelund, Karen; Grey, Francois; Madsen, Steen

    1996-01-01

    A focused laser beam has been used to induce oxidation of hydrogen-passivated silicon. The scanning laser beam removes the hydrogen passivation locally from the silicon surface, which immediately oxidizes in air. The process has been studied as a function of power density and excitation wavelength on amorphous and crystalline silicon surfaces in order to determine the depassivation mechanism. The minimum linewidth achieved is about 450 nm using writing speeds of up to 100 mm/s. The process is...

  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. Stable, highly nonlinear amorphous silicon nanowires with very low nonlinear absorption

    CERN Document Server

    Carletti, Luca; Grossec, Phillipe; Ben-Bakir, Badhise; Menezoc, Sylvie; Fedelic, Jean-Marc; Moss, David J; Monat, Christelle

    2014-01-01

    The nonlinear characteristics of hydrogenated amorphous silicon nanowires are experimentally demonstrated. A high nonlinear refractive index, n2=1.19 x 10-17 m2/W, combined with a low two-photon absorption, 0.14 x 10-11 m/W, resulted in a high nonlinear FOM of 5.5. Furthermore, systematic studies over hours of operational time under 2.2W of pulse peak power revealed no degradation of the optical response.

  9. Preparation and Characterisation of Amorphous-silicon Photovoltaic Devices Having Microcrystalline Emitters

    International Nuclear Information System (INIS)

    The present work summarises the essential aspects of the research carried out so far at CIEMAT on amorphous-silicon solar cells. The experience accumulated on the preparation and characterisation of amorphous and microcrystalline silicon has allowed to start from intrinsic (absorbent) and p- and n-type (emitters) materials not only having excellent optoelectronic properties, but enjoying certain technological advantages with respect to those developed by other groups. Among these are absorbent-layer growth rates between 5 and 10 times as fast as conventional ones and microcrystalline emitters prepared without using hydrogen. The preparation of amorphous-silicon cells has required the solution of a number of problems, such as those related to pinholes, edge leak currents and diffusion of metals into the semiconductor. Once such constraints have been overcome, it has been demonstrated not only that the amorphous-silicon technology developed at CIEMAT is valid for making solar cells, but also that the quality of the semiconductor material is good for the application according to the partial results obtained. The development of thin-film laser-scribing technology is considered essential. Additionally it has been concluded that cross contamination, originated by the fact of using a single-chamber reactor, is the basic factor limiting the quality of the cells developed at CIEMAT. The present research activity is highly focused on the solution of this problem. (Author)23 refs

  10. 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.

  11. Inter-Electrode Separation Induced Amorphous-to-Nanocrystalline Transition of Hydrogenated Silicon Prepared by Capacitively Coupled RF PE-CVD Technique

    Directory of Open Access Journals (Sweden)

    S.W. Gosavi

    2011-01-01

    Full Text Available Role of inter-electrode spacing in capacitively coupled radio frequency plasma enhanced chemical vapor deposition deposition (PE-CVD system was studied. The influence of inter-electrode separation on the structural, optical and electrical properties of the deposited films was carefully invesigated keeping all other deposition parameters constant. The results indicate that the film growth rate critically depends up on the plasma chemistry/gas phase chemistry altered by variation of inter-electrode separation. Structure and optical properties are strongly influenced by inter-electrode separation. The nanocrystallization in the material was observed for smaller inter-electrode separation, whereas higher inter-electrode separation favors amorphous structure of the deposited material. The band gap of the material was found to decrease from ~2 eV to 1.8 eV when inter-electrode separation was varied from 15 mm to 40 mm.

  12. Nanoindentation-induced amorphization in silicon carbide

    Science.gov (United States)

    Szlufarska, Izabela; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2004-07-01

    The nanoindentation-induced amorphization in SiC is studied using molecular dynamics simulations. The load-displacement response shows an elastic shoulder followed by a plastic regime consisting of a series of load drops. Analyses of bond angles, local pressure, and shear stress, and shortest-path rings show that these drops are related to dislocation activities under the indenter. We show that amorphization is driven by coalescence of dislocation loops and that there is a strong correlation between load-displacement response and ring distribution.

  13. Photocurrent images of amorphous-silicon solar-cell modules

    Science.gov (United States)

    Kim, Q.; Shumka, A.; Trask, J.

    1985-01-01

    Results obtained in applying the unique characteristics of the solar cell laser scanner to investigate the defects and quality of amorphous silicon cells are presented. It is concluded that solar cell laser scanners can be effectively used to nondestructively test not only active defects but also the cell quality and integrity of electrical contacts.

  14. Long-term stability of amorphous-silicon modules

    Science.gov (United States)

    Ross, R. G., Jr.

    1986-01-01

    The Jet Propulsion Laboratory (JPL) program of developing qualification tests necessary for amorphous silicon modules, including appropriate accelerated environmental tests reveal degradation due to illumination. Data were given which showed the results of temperature-controlled field tests and accelerated tests in an environmental chamber.

  15. Integral bypass diodes in an amorphous silicon alloy photovoltaic module

    Science.gov (United States)

    Hanak, J. J.; Flaisher, H.

    1991-01-01

    Thin-film, tandem-junction, amorphous silicon (a-Si) photovoltaic modules were constructed in which a part of the a-Si alloy cell material is used to form bypass protection diodes. This integral design circumvents the need for incorporating external, conventional diodes, thus simplifying the manufacturing process and reducing module weight.

  16. 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.

  17. Amorphous silicon carbide coatings for extreme ultraviolet optics

    Science.gov (United States)

    Kortright, J. B.; Windt, David L.

    1988-01-01

    Amorphous silicon carbide films formed by sputtering techniques are shown to have high reflectance in the extreme ultraviolet spectral region. X-ray scattering verifies that the atomic arrangements in these films are amorphous, while Auger electron spectroscopy and Rutherford backscattering spectroscopy show that the films have composition close to stoichiometric SiC, although slightly C-rich, with low impurity levels. Reflectance vs incidence angle measurements from 24 to 1216 A were used to derive optical constants of this material, which are presented here. Additionally, the measured extreme ultraviolet efficiency of a diffraction grating overcoated with sputtered amorphous silicon carbide is presented, demonstrating the feasibility of using these films as coatings for EUV optics.

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

    International Nuclear Information System (INIS)

    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 cm2 aperture area on the graphite substrate. The optical properties of the SiNx/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 SiNx/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. • SiNx/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

  19. Heat-Induced Agglomeration of Amorphous Silicon Nanoparticles Toward the Formation of Silicon Thin Film.

    Science.gov (United States)

    Jang, Bo Yun; Kim, Ja Young; Seo, Gyeongju; Shin, Chae-Ho; Ko, Chang Hyun

    2016-01-01

    The thermal behavior of silicon nanoparticles (Si NPs) was investigated for the preparation of silicon thin film using a solution process. TEM analysis of Si NPs, synthesized by inductively coupled plasma, revealed that the micro-structure of the Si NPs was amorphous and that the Si NPs had melted and merged at a comparatively low temperature (~750 °C) considering bulk melting temperature of silicon (1414 °C). A silicon ink solution was prepared by dispersing amorphous Si NPs in propylene glycol (PG). It was then coated onto a silicon wafer and a quartz plate to form a thin film. These films were annealed in a vacuum or in an N₂ environment to increase their film density. N2 annealing at 800 °C and 1000 °C induced the crystallization of the amorphous thin film. An elemental analysis by the SIMS depth profile showed that N₂annealing at 1000 °C for 180 min drastically reduced the concentrations of carbon and oxygen inside the silicon thin film. These results indicate that silicon ink prepared using amorphous Si NPs in PG can serve as a proper means of preparing silicon thin film via solution process. PMID:27398566

  20. 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. A ...

  1. The Urbach focus and optical properties of amorphous hydrogenated SiC thin films

    Science.gov (United States)

    Guerra, J. A.; Angulo, J. R.; Gomez, S.; Llamoza, J.; Montañez, L. M.; Tejada, A.; Töfflinger, J. A.; Winnacker, A.; Weingärtner, R.

    2016-05-01

    We report on the optical bandgap engineering of sputtered hydrogenated amorphous silicon carbide (a-SiC:H) thin films under different hydrogen dilution conditions during the deposition process and after post-deposition annealing treatments. The Tauc-gap and Urbach energy are calculated from ultraviolet-visible optical transmittance measurements. Additionally, the effect of the thermal annealing temperature on the hydrogen out-diffusion is assessed through infra-red absorption spectroscopy. A new model for the optical absorption of amorphous semiconductors is presented and employed to determine the bandgap as well as the Urbach energy from a single fit of the absorption coefficient. This model allowed the discrimination of the Urbach tail from the Tauc region without any external bias. Finally, the effect of the hydrogen dilution on the band-edge and the Urbach focus is discussed.

  2. 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.

  3. 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.

  4. Plasma Deposition of Doped Amorphous Silicon

    Science.gov (United States)

    Calcote, H. F.

    1985-01-01

    Pair of reports present further experimental details of investigation of plasma deposition of films of phosphorous-doped amosphous silicon. Probe measurements of electrical resistance of deposited films indicated films not uniform. In general, it appeared that resistance decreased with film thickness.

  5. Kirchhoff?s generalised law applied to amorphous silicon / crystalline silicon heterostructures

    OpenAIRE

    Brüggemann, Rudolf

    2009-01-01

    Abstract The electro- and photoluminescence spectra of amorphous silicon / crystalline silicon heterostructures and solar cells are determined by emission from the crystalline-silicon layer and are computed with Kirchhoff?s generalised law. The interface defect density strongly influences the luminescence yield which may be used to monitor the interface quality. Based on a comparison between numerical and analytically determined spectra, the temperature dependence of experimental e...

  6. Spectral selectivity constraints in fluorescence detection of biomolecules using amorphous silicon based detectors

    Energy Technology Data Exchange (ETDEWEB)

    Conde, J.P. [INESC Microsistemas e Nanotecnologias and IN- Institute of Nanoscience and Nanotechnology, Rua Alves Redol 9, 1000-029 Lisbon (Portugal); Department of Chemical and Biological Engineering, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1000-049 Lisbon (Portugal); Joskowiak, A.; Pimentel, A.; Santos, M.; Chu, V. [INESC Microsistemas e Nanotecnologias and IN- Institute of Nanoscience and Nanotechnology, Rua Alves Redol 9, 1000-029 Lisbon (Portugal); Lipovsek, B.; Krc, J.; Topic, M. [Laboratory of Photovoltaics and Optoelectronics, Faculty of Electrical Engineering, University of Ljubljana, Trzaska 25, 1000 Ljubljana (Slovenia); Pereira, A.T. [INESC Microsistemas e Nanotecnologias and IN- Institute of Nanoscience and Nanotechnology, Rua Alves Redol 9, 1000-029 Lisbon (Portugal); IBB-Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1000-049 Lisbon (Portugal); Prazeres, D.M.F. [Department of Chemical and Biological Engineering, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1000-049 Lisbon (Portugal); IBB-Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1000-049 Lisbon (Portugal)

    2010-04-15

    A microdevice based on a thin-film hydrogenated amorphous silicon (a -Si:H) p-i-n photodiode is used to quantify the density of DNA oligonucleotides labelled with a fluorophore and the density of E. coli cells expressing GFP (green fluorescent protein) by fluorescence. An absorption filter is integrated in the device which filters the excitation light and transmits the emitted light to the photodetector. This filter is an amorphous silicon carbon (a-SiC:H) alloy in which the bandgap can be selected according to the excitation and emission wavelengths of the fluorophores used by varying the carbon content of the film. Control of the thickness of the a-SiC:H film allows the modulation of the transmission ratio between the excitation wavelength and the emission wavelength. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. 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.……

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-02

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

  10. A delta-doped amorphous silicon thin-film transistor with high mobility and stability

    International Nuclear Information System (INIS)

    Ultrathin doped layers, known as delta-doped layers, were introduced within the intrinsic amorphous silicon (a-Si) active layer to fabricate hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with enhanced field-effect mobility. The performance of the delta-doped a-Si:H TFTs depended on the phosphine (PH3) flow rate and the distance from the n+ a-Si to the delta-doping layer. The delta-doped a-Si:H TFTs fabricated using a commercial manufacturing process exhibited an enhanced field-effect mobility of approximately ∼0.23 cm2/Vs (compared to a conventional a-Si:H TFT with 0.15 cm2/Vs) and a desirable stability under a bias-temperature stress test.

  11. Correlation between SiH2/SiH and light-induced degradation of p-i-n hydrogenated amorphous silicon solar cells

    Science.gov (United States)

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

    2016-07-01

    We have measured the hydrogen content ratio I SiH2/I SiH associated with Si-H2 and Si-H bonds in p-i-n (PIN) a-Si:H solar cells by Raman spectroscopy. With decreasing I SiH2/I SiH, the efficiency, short-circuit current density, open-circuit voltage, and fill factor of PIN a-Si:H solar cells after light soaking tend to increase. Namely, I SiH2/I SiH correlates well with light-induced degradation of the cells. While a single I-layer has a low I SiH2/I SiH of 0.03-0.09, a PIN cell has I SiH2/I SiH = 0.18 because many Si-H2 bonds exist in the P-layer and at the P/I interface of the PIN solar cells. To realize PIN solar cells with higher stability, we must suppress Si-H2 bond formation in the P-layer and at the P/I interface.

  12. 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.

  13. Electrochemical degradation of amorphous-silicon photovoltaic modules

    Science.gov (United States)

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

    1985-01-01

    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.

  14. Photo stability Assessment in Amorphous-Silicon Solar Cells

    International Nuclear Information System (INIS)

    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 characterisation in well established conditions. This method is suitable for all 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

  15. 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%.

  16. 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.

  17. 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.

  18. Corrosion In Amorphous-Silicon Solar Cells And Modules

    Science.gov (United States)

    Mon, Gordon R.; Wen, Liang-Chi; Ross, Ronald G., Jr.

    1988-01-01

    Paper reports on corrosion in amorphous-silicon solar cells and modules. Based on field and laboratory tests, discusses causes of corrosion, ways of mitigating effects, and consequences for modules already in field. Suggests sealing of edges as way of reducing entry of moisture. Cell-free perimeters or sacrificial electrodes suggested to mitigate effects of sorbed moisture. Development of truly watertight module proves to be more cost-effective than attempting to mitigate effects of moisture.

  19. Crystallization of amorphous silicon induced by mechanical shear deformations

    OpenAIRE

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

    2011-01-01

    We have investigated the response of amorphous silicon (a-Si), in particular crystallization, to external mechanical shear deformations using classical molecular dynamics (MD) simulations and the empirical Environment Dependent Inter-atomic Potential (EDIP) [Phys. Rev. B 56, 8542 (1997)]. In agreement with previous results we find that, at low shear velocity and low temperature, shear deformations increase disorder and defect density. At high temperatures, however, the deformations are found ...

  20. Structure of amorphous silicon alloy films: Annual subcontract report, January 15, 1988--January 14, 1989

    Energy Technology Data Exchange (ETDEWEB)

    Norberg, R.E.; Fedders, P.A.

    1989-06-01

    The principal objective of this research program has been to improve the understanding at the microscopic level of amorphous silicon-germanium-alloy films deposited under various conditions to assist researchers to produce higher quality films. The method has been a joint theoretical and experimental approach to the correlation of NMR, ESR, and other characterizations, especially relating to rearrangements of hydrogen. Deuteron magnetic resonance reveals the presence of (and changes in) tightly bonded hydrogen (deuterium), weakly bonded hydrogen, molecular hydrogen, and rotating silyl groups. Microvoids are investigated via observation of para D/sub 2/ for which /Delta/M/sub J/ transitions are frozen out. Solid echoes reveal HD and ortho D/sub 2/ trapped as singles in the semiconductor matrix. Theoretical calculations show dangling bonds to be more likely than floating bonds. 23 refs., 11 figs.

  1. Recombination of atomic oxygen and hydrogen on amorphous carbon

    International Nuclear Information System (INIS)

    Deposit buildup and fuel entrapment due to amorphous carbon are relevant issues in fusion devices with carbon based plasma facing components. Neutral atomic species play a significant role – atomic hydrogen facilitates the formation of amorphous carbon while atomic oxygen could be used to remove carbon deposits. The kinetics of either reaction depends on the density of neutral species, which in turn is influenced by recombination on the vessel walls. In this work, we measured the probability of heterogeneous recombination of atomic hydrogen and oxygen on amorphous carbon deposits. The recombination coefficients were determined by observing density profiles of atomic species in a closed side-arm of a plasma vessel with amorphous carbon deposit-lined walls. Density profiles were measured with fiber optics catalytic probes. The source of atomic species was inductively coupled radiofrequency plasma. The measured recombination coefficient values were of the order of 10−3 for both species

  2. Transition metal oxide window layer in thin film amorphous silicon solar cells

    International Nuclear Information System (INIS)

    Pin-type hydrogenated amorphous silicon solar cells have been fabricated by replacing state of the art silicon based window layer with more transparent transition metal oxide (TMO) materials. Three kinds of TMOs: vanadium oxide, tungsten oxide, and molybdenum oxide (MoOx) were comparatively investigated to reveal the design principles of metal oxide window layers. It was found that MoOx exhibited the best performance due to its higher work function property compared to other materials. In addition, the band alignment between MoOx and amorphous Si controls the series resistance, which was verified through compositional variation of MoOx thin films. The design principles of TMO window layer in amorphous Si solar cells are summarized as follows: A wide optical bandgap larger than 3.0 eV, a high work function larger than 5.2 eV, and a band alignment condition rendering efficient hole collection from amorphous Si absorber layer. - Highlights: • High work function metal oxides can potentially replace the conventional p-a-SiC. • V2Ox, WOx, and MoOx are comparatively investigated in this study. • MoOx is the most relevant material due to its highest work function. • Slightly oxygen deficient MoOx exhibited performance enhancement at x = 2.9

  3. ELECTRICAL PROPERTIES AND PHOTOLUMINESCENCE OF AMORPHOUS SILICON

    OpenAIRE

    Liao, X.; Kong, G.; X. Yang; Wang, P.; Chao, Y.; Chen, Z.; Liu, C

    1981-01-01

    The temperature dependence of conductivity, photoluminescence and ion-implantation doping effect of glow discharge (GD) and low pressure CVD a-Si films have been investigated. Post-hydrogenation significantly reduces the gap state density of LPCVD a-Si. Phosphorus and boron ion-implantation show that LPCVD a-Si has a higher doping efficiency than GD samples, reaching a maximum R.T. conductivity of 0.3 Ω-1 cm-1. Two peaks were observed in the luminescence spectrum of GD a-Si films and the orig...

  4. Laser direct writing of oxide structures on hydrogen-passivated silicon surfaces

    DEFF Research Database (Denmark)

    Müllenborn, Matthias; Birkelund, Karen; Grey, Francois;

    1996-01-01

    on amorphous and crystalline silicon surfaces in order to determine the depassivation mechanism. The minimum linewidth achieved is about 450 nm using writing speeds of up to 100 mm/s. The process is fully compatible with local oxidation of silicon by scanning probe lithography. Wafer-scale patterns can......A focused laser beam has been used to induce oxidation of hydrogen-passivated silicon. The scanning laser beam removes the hydrogen passivation locally from the silicon surface, which immediately oxidizes in air. The process has been studied as a function of power density and excitation wavelength...

  5. 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.

  6. 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.

  7. Integrated Amorphous Silicon p-i-n Temperature Sensor for CMOS Photonics

    Directory of Open Access Journals (Sweden)

    Sandro Rao

    2016-01-01

    Full Text Available Hydrogenated amorphous silicon (a-Si:H shows interesting optoelectronic and technological properties that make it suitable for the fabrication of passive and active micro-photonic devices, compatible moreover with standard microelectronic devices on a microchip. A temperature sensor based on a hydrogenated amorphous silicon p-i-n diode integrated in an optical waveguide for silicon photonics applications is presented here. The linear dependence of the voltage drop across the forward-biased diode on temperature, in a range from 30 °C up to 170 °C, has been used for thermal sensing. A high sensitivity of 11.9 mV/°C in the bias current range of 34–40 nA has been measured. The proposed device is particularly suitable for the continuous temperature monitoring of CMOS-compatible photonic integrated circuits, where the behavior of the on-chip active and passive devices are strongly dependent on their operating temperature.

  8. Flexible amorphous silicon PIN diode x-ray detectors

    Science.gov (United States)

    Marrs, Michael; Bawolek, Edward; Smith, Joseph T.; Raupp, Gregory B.; Morton, David

    2013-05-01

    A low temperature amorphous silicon (a-Si) thin film transistor (TFT) and amorphous silicon PIN photodiode technology for flexible passive pixel detector arrays has been developed using active matrix display technology. The flexible detector arrays can be conformed to non-planar surfaces with the potential to detect x-rays or other radiation with an appropriate conversion layer. The thin, lightweight, and robust backplanes may enable the use of highly portable x-ray detectors for use in the battlefield or in remote locations. We have fabricated detector arrays up to 200 millimeters along the diagonal on a Gen II (370 mm x 470 mm rectangular substrate) using plasma enhanced chemical vapor deposition (PECVD) a-Si as the active layer and PECVD silicon nitride (SiN) as the gate dielectric and passivation. The a-Si based TFTs exhibited an effective saturation mobility of 0.7 cm2/V-s, which is adequate for most sensing applications. The PIN diode material was fabricated using a low stress amorphous silicon (a-Si) PECVD process. The PIN diode dark current was 1.7 pA/mm2, the diode ideality factor was 1.36, and the diode fill factor was 0.73. We report on the critical steps in the evolution of the backplane process from qualification of the low temperature (180°C) TFT and PIN diode process on the 150 mm pilot line, the transfer of the process to flexible plastic substrates, and finally a discussion and demonstration of the scale-up to the Gen II (370 x 470 mm) panel scale pilot line.

  9. 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.

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

    International Nuclear Information System (INIS)

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

  11. 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).

  12. Magnetism of hydrogen-irradiated silicon carbide

    International Nuclear Information System (INIS)

    Spin-polarized density functional theory is used to study two-hydrogen defect complexes in silicon carbide. We find that the magnetism depends on the distances of the two hydrogen atoms. Magnetism appears when the two hydrogen defects are distant from each other, and magnetism cancels out if they are close to each other. The critical distance between the two hydrogen defects is determined.

  13. 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

  14. 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.

  15. 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.

  16. Ultralight amorphous silicon alloy photovoltaic modules for space applications

    Science.gov (United States)

    Hanak, J. J.; Chen, Englade; Fulton, C.; Myatt, A.; Woodyard, J. R.

    1987-01-01

    Ultralight and ultrathin, flexible, rollup monolithic PV modules have been developed consisting of multijunction, amorphous silicon alloys for either terrestrial or aerospace applications. The rate of progress in increasing conversion efficiency of stable multijunction and multigap PV cells indicates that arrays of these modules can be available for NASA's high power systems in the 1990's. Because of the extremely light module weight and the highly automated process of manufacture, the monolithic a-Si alloy arrays are expected to be strongly competitive with other systems for use in NASA's space station or in other large aerospace applications.

  17. Radiation damage and annealing of amorphous silicon solar cells

    Science.gov (United States)

    Byvik, C. E.; Slemp, W. S.; Smith, B. T.; Buoncristiani, A. M.

    1984-01-01

    Amorphous silicon solar cells were irradiated with 1 MeV electrons at the Space Environmental Effects Laboratory of the NASA Langley Research Center. The cells accumulated a total fluence of 10 to the 14th, 10 to the 15th, and 10 to the 16th electrons per square centimeter and exhibited increasing degradation with each irradiation. This degradation was tracked by evaluating the I-V curves for AM0 illumination and the relative spectral response. The observed radiation damage was reversed following an anneal of the cells under vacuum at 200 C for 2 hours.

  18. Two-Level Systems in Evaporated Amorphous Silicon

    OpenAIRE

    Queen, D. R.; Liu, X.; Karel, J.; Jacks, H. C.; Metcalf, T. H.; Hellman, F.

    2015-01-01

    In $e$-beam evaporated amorphous silicon ($a$-Si), the densities of two-level systems (TLS), $n_{0}$ and $\\overline{P}$, determined from specific heat $C$ and internal friction $Q^{-1}$ measurements, respectively, have been shown to vary by over three orders of magnitude. Here we show that $n_{0}$ and $\\overline{P}$ are proportional to each other with a constant of proportionality that is consistent with the measurement time dependence proposed by Black and Halperin and does not require the i...

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

    OpenAIRE

    Wenjie Zhang; Bin Hao; Nianping Li

    2014-01-01

    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 consis...

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

    Institute of Scientific and Technical Information of China (English)

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

    2007-01-01

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

  1. Lithium concentration dependent structure and mechanics of amorphous silicon

    Science.gov (United States)

    Sitinamaluwa, H. S.; Wang, M. C.; Will, G.; Senadeera, W.; Zhang, S.; Yan, C.

    2016-06-01

    A better understanding of lithium-silicon alloying mechanisms and associated mechanical behavior is essential for the design of Si-based electrodes for Li-ion batteries. Unfortunately, the relationship between the dynamic mechanical response and microstructure evolution during lithiation and delithiation has not been well understood. We use molecular dynamic simulations to investigate lithiated amorphous silicon with a focus to the evolution of its microstructure, phase composition, and stress generation. The results show that the formation of LixSi alloy phase is via different mechanisms, depending on Li concentration. In these alloy phases, the increase in Li concentration results in reduction of modulus of elasticity and fracture strength but increase in ductility in tension. For a LixSi system with uniform Li distribution, volume change induced stress is well below the fracture strength in tension.

  2. Evolution of charge emission for amorphous silicon FETs exposed to radiation

    International Nuclear Information System (INIS)

    Large area flat panel radiation imagers are currently based on hydrogenated amorphous silicon (α-Si:H) devices. For extended use in medical applications and most industrial applications the properties of the panels can be altered by the high dose the panels experience. One characteristic of these panels is a dark offset due to emission of charge from deep trap states (detrapping currents) of the α-Si:H FETs. We report on a method of isolating the contribution of channel and contact (source/drain) silicon in a standard inverted gate FET to the total charge emission current and directly measure the time evolution of both. Additionally, we investigate changes in the charge emission coming from FETs on the imager panel as a function of radiation dose up to 15 Mrad (150 kGy) absorbed in the α-Si:H of the FETs

  3. Electrical Characterization of Amorphous Silicon MIS-Based Structures for HIT Solar Cell Applications.

    Science.gov (United States)

    García, Héctor; Castán, Helena; Dueñas, Salvador; Bailón, Luis; García-Hernansanz, Rodrigo; Olea, Javier; Del Prado, Álvaro; Mártil, Ignacio

    2016-12-01

    A complete electrical characterization of hydrogenated amorphous silicon layers (a-Si:H) deposited on crystalline silicon (c-Si) substrates by electron cyclotron resonance chemical vapor deposition (ECR-CVD) was carried out. These structures are of interest for photovoltaic applications. Different growth temperatures between 30 and 200 °C were used. A rapid thermal annealing in forming gas atmosphere at 200 °C during 10 min was applied after the metallization process. The evolution of interfacial state density with the deposition temperature indicates a better interface passivation at higher growth temperatures. However, in these cases, an important contribution of slow states is detected as well. Thus, using intermediate growth temperatures (100-150 °C) might be the best choice. PMID:27423876

  4. Electron transport in W-containing amorphous carbon-silicon diamond-like nanocomposites

    International Nuclear Information System (INIS)

    The electron transport in amorphous hydrogenated carbon-silicon diamond-like nanocomposite films containing tungsten over the concentration range 12-40 at.% was studied in the temperature range 80-400 K. The films were deposited onto polycrystalline substrates, placed on the RF-biased substrate holder, by the combination of two methods: PECVD of siloxane vapours in the stimulated dc discharge and dc magnetron sputtering of tungsten target. The experimental dependences of the conductivity on the temperature are well fitted by the power-law dependences over the entire temperature range. The results obtained are discussed in terms of the model of inelastic tunnelling of the electrons in amorphous dielectrics. The average number of localized states (n) in the conducting channels between metal clusters calculated in the framework of this model is characterized by the non-monotonic dependence on the tungsten concentration in the films. The qualitative explanation of the results on the basis of host carbon-silicon matrix structural modifications is proposed. The evolution of the carbon-silicon matrix microstructure by the increase in the tungsten concentration is confirmed by the Raman spectroscopy data

  5. Electrical characteristics of amorphous molybdenum-nickel contacts to silicon

    Science.gov (United States)

    Kung, K. T.-Y.; Nicolet, M.-A.; Suni, I.

    1984-01-01

    The electrical characteristics of sputtered, amorphous Mo-Ni contacts have been measured on both p- and n-type Si, as functions of composition (30, 54, and 58 at. percent Mo). The contact resistivity on both p(+) and n(+) Si is in the 0.00000 ohm sq cm range. The barrier height for as-deposited samples varies between phi-bp = 0.47-0.42 V on p-type Si and between phi-bn = 0.63-0.68 V on n-type Si, as the composition of the amorphous layer goes from Ni-rich to Mo-rich. The sum phi-bp + phi-bn always equals 1.12 V, within experimental error. After thermal treatment at 500 C for 1/2 h, the contact resistivity changes by a factor of two or less, while the barrier height changes by at most approximately 0.05 V. In light of these results, the amorphous Mo-Ni film makes good ohmic contacts to silicon.

  6. Theory of structural transformation in lithiated amorphous silicon.

    Science.gov (United States)

    Cubuk, Ekin D; Kaxiras, Efthimios

    2014-07-01

    Determining structural transformations in amorphous solids is challenging due to the paucity of structural signatures. The effect of the transitions on the properties of the solid can be significant and important for applications. Moreover, such transitions may not be discernible in the behavior of the total energy or the volume of the solid as a function of the variables that identify its phases. These issues arise in the context of lithiation of amorphous silicon (a-Si), a promising anode material for high-energy density batteries based on lithium ions. Recent experiments suggest the surprising result that the lithiation of a-Si is a two-phase process. Here, we present first-principles calculations of the structure of a-Si at different lithiation levels. Through a detailed analysis of the short and medium-range properties of the amorphous network, using Voronoi-Delaunay methods and ring statistics, we show that a-LixSi has a fundamentally different structure below and above a lithiation level corresponding to x ∼ 2. PMID:24911996

  7. 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

  8. Advantages of N-Type Hydrogenated Microcrystalline Silicon Oxide Films for Micromorph Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Amornrat Limmanee

    2013-01-01

    Full Text Available We report on the development and application of n-type hydrogenated microcrystalline silicon oxide films (n μc-SiO:H in hydrogenated amorphous silicon oxide/hydrogenated microcrystalline silicon (a-SiO:H/μc-Si:H micromorph solar cells. The n μc-SiO:H films with high optical bandgap and low refractive index could be obtained when a ratio of carbon dioxide (CO2 to silane (SiH4 flow rate was raised; however, a trade-off against electrical property was observed. We applied the n μc-SiO:H films in the top a-SiO:H cell and investigated the changes in cell performance with respect to the electrical and optical properties of the films. It was found that all photovoltaic parameters of the micromorph silicon solar cells using the n top μc-SiO:H layer enhanced with increasing the CO2/SiH4 ratio up to 0.23, where the highest initial cell efficiency of 10.7% was achieved. The enhancement of the open circuit voltage (Voc was likely to be due to a reduction of reverse bias at subcell connection—n top/p bottom interface—and a better tunnel recombination junction contributed to the improvement in the fill factor (FF. Furthermore, the quantum efficiency (QE results also have demonstrated intermediate-reflector function of the n μc-SiO:H films.

  9. Enhanced Multiple Exciton Generation in Amorphous Silicon Nanoparticles

    OpenAIRE

    Kryjevski, Andrei; Kilin, Dmitri

    2014-01-01

    Multiple exciton generation (MEG) in nanometer-sized hydrogen-passivated silicon nanowires (NWs), and quasi two-dimensional nanofilms strongly depends on the degree of the core structural disorder as shown by the many-body perturbation theory (MBPT) calculations based on the density functional theory (DFT) simulations. Working to the second order in the electron-photon coupling and in the screened Coulomb interaction we calculate quantum efficiency (QE), the average number of excitons created...

  10. First principles simulation of amorphous silicon bulk, interfaces, and nanowires for photovoltaics

    OpenAIRE

    Belayneh, Merid Legesse

    2015-01-01

    Amorphous silicon has become the material of choice for many technologies, with major applications in large area electronics: displays, image sensing and thin film photovoltaic cells. This technology development has occurred because amorphous silicon is a thin film semiconductor that can be deposited on large, low cost substrates using low temperature. In this thesis, classical molecular dynamics and first principles DFT calculations have been performed to generate structural models of amorph...

  11. Optical near-field lithography on hydrogen-passivated silicon surfaces

    DEFF Research Database (Denmark)

    Madsen, Steen; Müllenborn, Matthias; Birkelund, Karen;

    1996-01-01

    optical near field, were observed after etching in potassium hydroxide. The uncoated fibers can also induce oxidation without light exposure, in a manner similar to an atomic force microscope, and linewidths of 50 nm have been achieved this way. (C) 1996 American Institute of Physics.......We report on a novel lithography technique for patterning of hydrogen-passivated amorphous silicon surfaces. A reflection mode scanning near-field optical microscope with uncoated fiber probes has been used to locally oxidize a thin amorphous silicon layer. Lines of 110 nm in width, induced by the...

  12. 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.

  13. Micro-cutting of silicon implanted with hydrogen and post-implantation thermal treatment

    Science.gov (United States)

    Jelenković, Emil V.; To, Suet; Sundaravel, B.; Xiao, Gaobo; Huang, Hu

    2016-07-01

    It was reported that non-amorphizing implantation by hydrogen has a potential in improving silicon machining. Post-implantation high-temperature treatment will affect implantation-induced damage, which can have impact on silicon machining. In this article, a relation of a thermal annealing of hydrogen implanted in silicon to micro-cutting experiment is investigated. Hydrogen ions were implanted into 4″ silicon wafers with 175 keV, 150 keV, 125 keV and doses of 2 × 1016 cm-2, 2 × 1016 cm-2 and 3 × 1016 cm-2, respectively. In this way, low hydrogen atom-low defect concentration was created in the region less than ~0.8 μm deep and high hydrogen atom-high defect concentration was obtained at silicon depth of ~0.8-1.5 μm. The post-implantation annealing was carried out at 300 and 400 °C in nitrogen for 1 h. Physical and electrical properties of implanted and annealed samples were characterized by secondary ion mass spectroscopy (SIMS), X-ray diffraction (XRD), Rutherford backscattering (RBS) and nanoindentation. Plunge cutting experiment was carried out in and silicon crystal direction. The critical depth of cut and cutting force were monitored and found to be influenced by the annealing. The limits of hydrogen implantation annealing contribution to the cutting characteristics of silicon are discussed in light of implantation process and redistribution of hydrogen and defects generation during annealing process.

  14. Thermally induced recrystallization of textured hydrogenated nanocrystalline silicon

    Science.gov (United States)

    Fugallo, Giorgia; Mattoni, Alessandro

    2014-01-01

    By an analysis of the local crystallinity based on model potential molecular dynamics simulations we investigated the effect of dissolved hydrogen on the thermally induced recrystallization of nanocrystalline silicon. By using the Kolmogorov-Johnson-Mehl-Avrami theory to analyze the atomistic data, we find that the recrystallization rate decreases exponentially with the hydrogen contamination. At low concentration, the kinetics is moderately affected by the H atoms that tend to migrate to the boundaries increasing their effective interface. At higher H content, we find an increasing number of SimHn hydrides that affect the crystalline order of the material and severely impede recrystallization. The analysis based on crystallinity is supported by the atomic scale study of the recrystallization mechanism, here identified as an inverted bond-switching process, and by the ability of hydrates to pin the amorphous-crystalline boundaries.

  15. Atomistic simulations of material damping in amorphous silicon nanoresonators

    Science.gov (United States)

    Mukherjee, Sankha; Song, Jun; Vengallatore, Srikar

    2016-06-01

    Atomistic simulations using molecular dynamics (MD) are emerging as a valuable tool for exploring dissipation and material damping in nanomechanical resonators. In this study, we used isothermal MD to simulate the dynamics of the longitudinal-mode oscillations of an amorphous silicon nanoresonator as a function of frequency (2 GHz–50 GHz) and temperature (15 K–300 K). Damping was characterized by computing the loss tangent with an estimated uncertainty of 7%. The dissipation spectrum displays a sharp peak at 50 K and a broad peak at around 160 K. Damping is a weak function of frequency at room temperature, and the loss tangent has a remarkably high value of ~0.01. In contrast, at low temperatures (15 K), the loss tangent increases monotonically from 4× {{10}-4} to 4× {{10}-3} as the frequency increases from 2 GHz to 50 GHz. The mechanisms of dissipation are discussed.

  16. Rapid Thermal annealing of silicon layers amorphized by ion implantation

    International Nuclear Information System (INIS)

    The recrystallization behavior and the supression mechanisms of the residual defects of silicon layers amorphized by ion implantation, were investigated. The samples were annealed with the aid of a rapid thermal annealing (RTA) system at temperature range from 850 to 12000C, and annealing time up to 120 s. Random and aligned Rutherford backscattering spectroscopy were used to analyse the samples. Similarities in the recrystallization behavior for layers implanted with ions of the same chemical groups such as As or Sb; Ge, Sn or Pb, In or Ga, are observed. The results show that the effective supression of resisual defects of the recrystallired layers is vinculated to the redistribution of impurities via thermal diffusion. (author)

  17. Roughening transition in nanoporous hydrogenated amorphous germanium: Roughness correlation to film stress

    Science.gov (United States)

    Carroll, M. S.; Verley, J. C.; Sheng, J. J.; Banks, J.

    2007-03-01

    Hydrogenated amorphous germanium (a-Ge:H) is a material of interest for optoelectronic applications such as solar cells and radiation detectors because of the material's potential to extend the wavelength sensitivity of hydrogenated amorphous silicon (a-Si:H). An increase in porosity is observed in amorphous germanium compared to a-Si :H, and this increase in porosity has been correlated with a degradation of the electrical performance. Improved understanding of the mechanisms of porous formation in a-Ge :H films is therefore desirable in order to better control it. In this paper we describe a correlation between film stress and surface roughness, which evolves with increasing thickness of a-Ge :H. A roughening transition from planar two-dimensional growth to three-dimensional growth at a critical thickness less than 800Å results in a network of needlelike nanotrench cavities which stretch from the transition thickness to the surface in films up to 4000Å thick. Surface roughness measurements by atomic force microscope and transmission electron microscopy indicate that the transition is abrupt and that the roughness increases linearly after the transition thickness. The roughening transition thickness is, furthermore, found to correlate with the maxima of the integrated compressive stress. The compressive stress is reduced after this transition thickness due to the incorporation of nanovoids into the film that introduce tensile stress as the islands coalesce together. The roughening transition behavior is similar to that found in a general class of Volmer-Weber mode thin film deposition (e.g., Cu, Ag, and nonhydrogenated amorphous silicon), which offers additional insight into the underlying mechanisms of the stress and roughening in these a-Ge :H films. The suppression of the roughening transition by changing the kinetics of the deposition rates (e.g., slowing the deposition rate with a weak sputtering bias) is also observed and discussed.

  18. 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.

  19. Excellent crystalline silicon surface passivation by amorphous silicon irrespective of the technique used for chemical vapor deposition

    OpenAIRE

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

    2011-01-01

    Crystalline silicon surface passivation by amorphous silicon deposited by three different chemical vapor deposition (CVD) techniques at low (T ∼ 130 °C) temperatures is compared. For all three techniques, surface recombination velocities (SRVs) are reduced by two orders of magnitude after prolonged thermal annealing at 200 °C. This reduction correlates with a decreased dangling bond density at the amorphous-crystalline interface, indicating that dangling bond saturation is the predominant mec...

  20. Pulsed Excimer (KrF) Laser Melting of Amorphous and Crystalline Silicon Layers

    OpenAIRE

    Walthuis, A.; Stritzker, B.; White, C. W.; J. Narayan; Aziz, Michael

    1985-01-01

    We have investigated depth of melting as a function of pulse energy density in amorphous and crystalline silicon layers. The melting threshold for KrF laser pulses (lambda=0.249 µm, tau=24×10−9 s) in amorphous (7660-Å-thick) and crystalline silicon layers were determined to be 0.16±0.02 and 0.75±0.05 J cm−2, respectively. The formation of fine- and large-polycrystalline regions was clearly identified in the amorphous silicon layers for energy densities below that needed for complete annealing...

  1. Heteroatom-doped hydrogenated amorphous carbons, a-C:H:X 'Volatile' silicon, sulphur and nitrogen depletion, blue photoluminescence, diffuse interstellar bands and ferro-magnetic carbon grain connections (Research Note)

    CERN Document Server

    Jones, A P

    2014-01-01

    Context. Hydrogenated amorphous carbons, a-C:H, can incorporate a variety of heteroatoms, which can lead to interesting effects. Aims. To investigate the doping of interstellar a-C:H grains with, principally, Si, O, N and S atoms within the astrophysical context. Methods. A search of the literature on doped a-C:H reveals a number of interesting phenomena of relevance to astrophysics. Results. X dopants in a-C:H:X materials can affect the sp3/sp2 ratio (X = Si, O and N), lead to blue photoluminescence (undoped or X = N), induce ferromagnetic-like behaviour (X = N and S) or simply be incorporated (depleted) into the structure (X = Si, O, N and S). Si and N atoms could also incorporate into fullerenes, possibly forming colour-centres that could mimic diffuse interstellar bands. Conclusions. Doped a-C:H grains could explain several dust-related conundrums, such as: 'volatile' Si in photo-dissociation regions, S and N depletion in molecular clouds, blue luminescence, some diffuse interstellar bands and ferromagnet...

  2. Growth, characterisation and electronic applications of amorphous hydrogenated carbon

    CERN Document Server

    Paul, S

    2000-01-01

    temperature on GaAs, has been studied and concluded to be satisfactory on the basis of good adherence and low leakage currents. Such a structure was motivated by the applicability in Metal Insulator Semiconductor Field Effect Transistors (MISFET). My thesis proposes solutions to a number of riddles associated with the material, hydrogenated amorphous carbon, (a-C:H). This material has lately generated interest in the electronic engineering community, owing to some remarkable properties. The characterisation of amorphous carbon films, grown by radio frequency plasma enhanced chemical vapour deposition has been reported. The coexistence of multiple phases in the same a-C:H film manifests itself in the inconsistent electrical behaviour of different parts of the film, thus rendering it difficult to predict the nature of films. For the first time, in this thesis, a reliable prediction of Schottky contact formation on a-C:H films is reported. A novel and simple development on a Scanning Electron Microscope, configu...

  3. Development of thin film amorphous silicon oxide/microcrystalline silicon double-junction solar cells and their temperature dependence

    Energy Technology Data Exchange (ETDEWEB)

    Sriprapha, K.; Piromjit, C.; Limmanee, A.; Sritharathikhun, J. [Institute of Solar Energy Technology Development (SOLARTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Phahonyothin Road, Klong 1, Klong Luang, Pathumthani 12120 (Thailand)

    2011-01-15

    We have developed thin film silicon double-junction solar cells by using micromorph structure. Wide bandgap hydrogenated amorphous silicon oxide (a-SiO:H) film was used as an absorber layer of top cell in order to obtain solar cells with high open circuit voltage (V{sub oc}), which are attractive for the use in high temperature environment. All p, i and n layers were deposited on transparent conductive oxide (TCO) coated glass substrate by a 60 MHz-very-high-frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique. The p-i-n-p-i-n double-junction solar cells were fabricated by varying the CO{sub 2} and H{sub 2} flow rate of i top layer in order to obtain the wide bandgap with good quality material, which deposited near the phase boundary between a-SiO:H and hydrogenated microcrystalline silicon oxide ({mu}c-SiO:H), where the high V{sub oc} can be expected. The typical a-SiO:H/{mu}c-Si:H solar cell showed the highest initial cell efficiency of 10.5%. The temperature coefficient (TC) of solar cells indicated that the values of TC for conversion efficiency ({eta}) of the double-junction solar cells were inversely proportional to the initial V{sub oc}, which corresponds to the bandgap of the top cells. The TC for {eta} of typical a-SiO:H/{mu}c-Si:H was -0.32%/ C, lower than the value of conventional a-Si:H/{mu}c-Si:H solar cell. Both the a-SiO:H/{mu}c-Si:H solar cell and the conventional solar cell showed the same light induced degradation ratio of about 20%. We concluded that the solar cells using wide bandgap a-SiO:H film in the top cells are promising for the use in high temperature regions. (author)

  4. 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.)

  5. Excellent crystalline silicon surface passivation by amorphous silicon irrespective of the technique used for chemical vapor deposition

    NARCIS (Netherlands)

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

    2011-01-01

    Crystalline silicon surface passivation by amorphous silicon deposited by three different chemical vapor deposition (CVD) techniques at low (T ∼ 130 °C) temperatures is compared. For all three techniques, surface recombination velocities (SRVs) are reduced by two orders of magnitude after prolonged

  6. 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

  7. Nonlinear Optical Functions in Crystalline and Amorphous Silicon-on-Insulator Nanowires

    DEFF Research Database (Denmark)

    Baets, R.; Kuyken, B.; Liu, X.;

    2012-01-01

    Silicon-on-Insulator nanowires provide an excellent platform for nonlinear optical functions in spite of the two-photon absorption at telecom wavelengths. Work on both crystalline and amorphous silicon nanowires is reviewed, in the wavelength range of 1.5 to 2.5 µm.......Silicon-on-Insulator nanowires provide an excellent platform for nonlinear optical functions in spite of the two-photon absorption at telecom wavelengths. Work on both crystalline and amorphous silicon nanowires is reviewed, in the wavelength range of 1.5 to 2.5 µm....

  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. Accuracy and long-term stability of amorphous-silicon measurements

    Science.gov (United States)

    Mueller, R.

    1986-01-01

    The measurement system requirements to obtain accurate electrical performance measurements of amorphous silicon cells and modules were described. The progress achieved in modifying the Jet Propulsion Laboratory (JPL) system toward that objective were reviewed.

  10. 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.).

  11. 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.

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

    OpenAIRE

    Černý, R.; A. Kalbáč

    2000-01-01

    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 ...

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

    OpenAIRE

    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 solar cells and the role of dangling bond states in mediating or driving the degradation mechanism. The approach taken in this study has enabled has to examine how light induced degradation is aff...

  14. Label-Free Direct Electronic Detection of Biomolecules with Amorphous Silicon Nanostructures

    OpenAIRE

    Lund, John; Mehta, Ranjana; Parviz, Babak A.

    2006-01-01

    We present the fabrication and characterization of a nano-scale sensor made of amorphous silicon for the label-free, electronic detection of three classes of biologically important molecules: ions, oligonucleotides, and proteins. The sensor structure has an active element which is a 50 nm wide amorphous silicon semicircle and has a total footprint of less than 4 μm2. We demonstrate the functionalization of the sensor with receptor molecules and the electronic detection of three targets: H+ io...

  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. Evaluation of Bonding Orbitals in Amorphous Silicon by Means of the Chemical Pseudopotential Method

    OpenAIRE

    Grado Caffaro, M. A.; Grado Caffaro, M.

    1994-01-01

    The chemical pseudopotential method has been used by a number of workers in order to study the valence bands of amorphous tetrahedrally bonded semiconductors. However, various problems related to this method are unsolved. In this paper, a theoretical formulation tending to clarify some of these. problems is presented. This formulation concerns bonding orbitals and is valid, in principle, for amorphous silicon.

  17. Quantitative assessment of molecular dynamics-grown amorphous silicon and germanium films on silicon (111)

    Science.gov (United States)

    Käshammer, Peter; Borgardt, Nikolai I.; Seibt, Michael; Sinno, Talid

    2016-09-01

    Molecular dynamics based on the empirical Tersoff potential was used to simulate the deposition of amorphous silicon and germanium on silicon(111) at various deposition rates and temperatures. The resulting films were analyzed quantitatively by comparing one-dimensional atomic density profiles to experimental measurements. It is found that the simulations are able to capture well the structural features of the deposited films, which exhibit a gradual loss of crystalline order over several monolayers. A simple mechanistic model is used to demonstrate that the simulation temperature may be used to effectively accelerate the surface relaxation processes during deposition, leading to films that are consistent with experimental samples grown at deposition rates many orders-of-magnitude slower than possible in a molecular dynamics simulation.

  18. Role of hydrogen plasma pretreatment in improving passivation of the silicon surface for solar cells applications.

    Science.gov (United States)

    Wang, Fengyou; Zhang, Xiaodan; Wang, Liguo; Jiang, Yanjian; Wei, Changchun; Sun, Jian; Zhao, Ying

    2014-09-10

    We have investigated the role of hydrogen plasma pretreatment in promoting silicon surface passivation, in particular examining its effects on modifying the microstructure of the subsequently deposited thin hydrogenated amorphous silicon (a-Si:H) passivation film. We demonstrate that pretreating the silicon surface with hydrogen plasma for 40 s improves the homogeneity and compactness of the a-Si:H film by enhancing precursor diffusion and thus increasing the minority carrier lifetime (τ(eff)). However, excessive pretreatment also increases the density of dangling bond defects on the surface due to etching effects of the hydrogen plasma. By varying the duration of hydrogen plasma pretreatment in fabricating silicon heterojunction solar cells based on textured substrates, we also demonstrate that, although the performance of the solar cells shows a similar tendency to that of the τ(eff) on polished wafers, the optimal duration is prolonged owing to the differences in the surface morphology of the substrates. These results suggest that the hydrogen plasma condition must be carefully regulated to achieve the optimal level of surface atomic hydrogen coverage and avoid the generation of defects on the silicon wafer. PMID:25141300

  19. 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.

  20. Power change in amorphous silicon technology by low temperature annealing

    Directory of Open Access Journals (Sweden)

    Mittal Ankit

    2015-01-01

    Full Text Available Amorphous silicon (a-Si is one of the best established thin-film solar-cell technologies. Despite its long history of research, it still has many critical issues because of its defect rich material and its susceptibility to degrade under light also called as Staebler-Wronski effect (SWE. This leads to an increase in the defect density of a-Si, but as a metastable effect it can be completely healed at temperatures above 170 °C. Our study is focused on investigating the behavior of annealing of different a-Si modules under low temperature conditions below 80 °C indicated by successive change of module power. These conditions reflect the environmental temperature impact of the modules in the field, or integrated in buildings as well. The power changes were followed by STC power rating and investigation of module-power evolution under low irradiance conditions at 50 W/m2. Our samples were recovered close to their initial state of power, reaching as high as 99% from its degraded value. This shows the influence of low temperature annealing and light on metastable module behavior in a-Si thin-film modules.

  1. 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...

  2. Deployable aerospace PV array based on amorphous silicon alloys

    Science.gov (United States)

    Hanak, Joseph J.; Walter, Lee; Dobias, David; Flaisher, Harvey

    1989-01-01

    The development of the first commercial, ultralight, flexible, deployable, PV array for aerospace applications is discussed. It is based on thin-film, amorphous silicon alloy, multijunction, solar cells deposited on a thin metal or polymer by a proprietary, roll-to-roll process. The array generates over 200 W at AM0 and is made of 20 giant cells, each 54 cm x 29 cm (1566 sq cm in area). Each cell is protected with bypass diodes. Fully encapsulated array blanket and the deployment mechanism weigh about 800 and 500 g, respectively. These data yield power per area ratio of over 60 W/sq m specific power of over 250 W/kg (4 kg/kW) for the blanket and 154 W/kg (6.5 kg/kW) for the power system. When stowed, the array is rolled up to a diameter of 7 cm and a length of 1.11 m. It is deployed quickly to its full area of 2.92 m x 1.11 m, for instant power. Potential applications include power for lightweight space vehicles, high altitude balloons, remotely piloted and tethered vehicles. These developments signal the dawning of a new age of lightweight, deployable, low-cost space arrays in the range from tens to tens of thousands of watts for near-term applications and the feasibility of multi-100 kW to MW arrays for future needs.

  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. 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.

  5. Hydrogen adsorption on hexagonal silicon nanotubes

    OpenAIRE

    Ryou, Junga; Hong, Suklyun; Kim, Gunn

    2009-01-01

    We present a first-principles study of geometrical structure and energetics of hydrogen adsorbed on hexagonal single-walled silicon nanotubes (SiNTs). The adsorption behaviors of hydrogen molecules in SiNTs are investigated. The binding energies for the most stable physisorbed configurations are calculated to be less than 0.1 eV. The energy barriers are also investigated for dissociation of H2 molecules. Finally, we consider encapsulation of H2 molecules in SiNTs. The possibility of SiNTs as ...

  6. Effect of structural variations in amorphous silicon based single and multi-junction solar cells from numerical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kabir, M.I. [Department of Electrical, Electronic and System Engineering, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600 (Malaysia); Ibrahim, Zahari; Sopian, Kamaruzzaman [Solar Energy Research Institute, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600 (Malaysia); Amin, Nowshad [Department of Electrical, Electronic and System Engineering, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600 (Malaysia); Solar Energy Research Institute, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600 (Malaysia); Center of Excellence for Research in Engineering Materials (CEREM), College of Engineering, King Saud University, Riyadh 11421 (Saudi Arabia)

    2010-09-15

    In this paper, single and multi-junction solar cells based on hydrogenated amorphous silicon (a-Si:H) and its alloy amorphous silicon carbide (a-SiC:H) are analyzed using one dimensional simulator AMPS-1D (Analysis of Microelectronic and Photonic Structures). Effects of thickness and doping concentration of different layers as well as the operating temperature on cell efficiency have been investigated with a view to find a more efficient and stable cell. For the single junction cell, the maximum efficiency of 19.62% has been achieved for a thickness of 500 nm of i-layer, which further improved to 20.8% after the optimization of the doping concentration. In case of double junction cell, the highest efficiency of 20.19% was found for top i-layer thickness of 700 nm after optimizing the bottom cell parameters. For the triple junction cell, parameters of the bottom cell and middle cell were optimized and the maximum efficiency of 21.89% was found with the top i-layer thickness of 600 nm. As regards the operating temperature, the double junction and the triple junction tandem cells showed better stability, with temperature gradient of 0.17% and 0.18%/C, respectively, than the single junction cell of 0.23%/C. The overall investigation on amorphous silicon solar cells as done here gives potential parametric suggestion that may lead to the fabrication of the high efficiency and stabilized a-Si thin film solar cells. (author)

  7. Study of an Amorphous Silicon Oxide Buffer Layer for p-Type Microcrystalline Silicon Oxide/n-Type Crystalline Silicon Heterojunction Solar Cells and Their Temperature Dependence

    Directory of Open Access Journals (Sweden)

    Taweewat Krajangsang

    2014-01-01

    Full Text Available Intrinsic hydrogenated amorphous silicon oxide (i-a-SiO:H films were used as front and rear buffer layers in crystalline silicon heterojunction (c-Si-HJ solar cells. The surface passivity and effective lifetime of these i-a-SiO:H films on an n-type silicon wafer were improved by increasing the CO2/SiH4 ratios in the films. Using i-a-SiO:H as the front and rear buffer layers in c-Si-HJ solar cells was investigated. The front i-a-SiO:H buffer layer thickness and the CO2/SiH4 ratio influenced the open-circuit voltage (Voc, fill factor (FF, and temperature coefficient (TC of the c-Si-HJ solar cells. The highest total area efficiency obtained was 18.5% (Voc=700 mV, Jsc=33.5 mA/cm2, and FF=0.79. The TC normalized for this c-Si-HJ solar cell efficiency was −0.301%/°C.

  8. A hybrid solar cell fabricated using amorphous silicon and a fullerene derivative.

    Science.gov (United States)

    Yun, Myoung Hee; Jang, Ji Hoon; Kim, Kyung Min; Song, Hee-eun; Lee, Jeong Chul; Kim, Jin Young

    2013-12-01

    Hybrid solar cells, based on organic and inorganic semiconductors, are a promising way to enhance the efficiency of solar cells because they make better use of the solar spectrum and are straightforward to fabricate. We report on a new hybrid solar cell comprised of hydrogenated amorphous silicon (a-Si:H), [6,6]-phenyl-C71-butyric acid methyl ester ([71]PCBM), and poly-3,4-ethylenedioxythiophene poly styrenesulfonate (PEDOT:PSS). The properties of these PEDOT:PSS/a-Si:H/[71]PCBM devices were studied as a function of the thickness of the a-Si:H layer. It was observed that the open circuit voltage and the short circuit current density of the device depended on the thickness of the a-Si:H layer. Under simulated one sun AM 1.5 global illumination (100 mW cm(-2)), a power conversion efficiency of 2.84% was achieved in a device comprised of a 274 nm-thick layer of a-Si:H; this is the best performance achieved to date for a hybrid solar cell made of amorphous Si and organic materials. PMID:24149894

  9. Extended defects in hydrogen-implanted (111) silicon wafer treated by high temperature annealing process

    Institute of Scientific and Technical Information of China (English)

    XIAO Qinghua; TU Hailing

    2004-01-01

    High resolution transmission electron microscopy (HRTEM) has been used to investigate the extended defects induced by the interaction between hydrogen and silicon during the high temperature annealing process in the hydrogen-implanted (111) silicon wafer. It has been found that the high temperature annealing process, like the low temperature annealing process, leads to the formation of cracks. However, beneath the cracks induced by high temperature annealing, there appear many additional dislocations. Some amorphous bands have also been observed. In addition, a string of cavities, which are truncated octahedral in shape and surrounded by {111} and {100 } lattice planes, have been revealed. These cavities, some of which have amorphous inner walls, are arrayed parallel to the top surface. Between cavities, there normally appears a dislocation band.

  10. EFFECTS OF ARGON ON THE PROPERTIES OF RF SPUTTERED AMORPHOUS SILICON

    OpenAIRE

    Shao-Qi, Peng; Qai, Yu; Xian, Zhang; Jing, Ye

    1981-01-01

    The Effects of argon on the properties of rf sputtered amorphous silicon film have been investigated. As the sputtering argon pressure is increased from 2 to 20 mTorr, the content of argon in the amorphous silicon film increases apparently (Argon/Silicon : from 10-2 to 5 x 10-2). The other properties measured as a function of argon pressure PAr show that as the PAr is increased, the photoconductivity, resistivity (300K), conductivity activation energy and optical gap increase also, while the ...

  11. Fabrication of amorphous silicon nanoribbons by atomic force microscope tip induced local oxidation for thin film device applications

    OpenAIRE

    Pichon, Laurent; Rogel, Regis; Demami, Fouad

    2010-01-01

    WOS International audience We demonstrate the feasibility of induced local oxidation of amorphous silicon by atomic force microscopy. The resulting local oxide is used as mask for the elaboration of thin film silicon resistor. A thin amorphous silicon layer deposited on a glass substrate is locally oxidized following narrow continuous lines. The corresponding oxide line is then used as mask during plasma etching of the amorphous layer leading to the formation of nanoribbon. Such amorpho...

  12. Palladium Implanted Silicon Carbide for Hydrogen Sensing

    Science.gov (United States)

    Muntele, C. I.; Ila, D.; Zimmerman, R. L.; Muntele, L.; Poker, D. B.; Hensley, D. K.; Larkin, David (Technical Monitor)

    2001-01-01

    Silicon carbide is intended for use in fabrication of high-temperature, efficient hydrogen sensors. Traditionally, when a palladium coating is applied on the exposed surface of SiC, the chemical reaction between palladium and hydrogen produces a detectable change in the surface chemical potential. We have produced both a palladium coated SiC as well as a palladium, ion implanted SiC sensor. The palladium implantation was done at 500 C into the Si face of 6H, N-type SiC at various energies, and at various fluences. Then, we measured the hydrogen sensitivity response of each fabricated sensor by exposing them to hydrogen while monitoring the current flow across the p-n junction(s), with respect to time. The sensitivity of each sensor was measured at temperatures between 27 and 300 C. The response of the SiC sensors produced by Pd implantation has revealed a completely different behaviour than the SiC sensors produced by Pd deposition. In the Pd-deposited SiC sensors as well as in the ones reported in the literature, the current rises in the presence of hydrogen at room temperature as well as at elevated temperatures. In the case of Pd-implanted SiC sensors, the current decreases in the presence of hydrogen whenever the temperature is raised above 100 C. We will present the details and conclusions from the results obtained during this meeting.

  13. Plasmonic effects in ultrathin amorphous silicon solar cells: performance improvements with Ag nanoparticles on the front, the back, and both.

    Science.gov (United States)

    Winans, Joshua D; Hungerford, Chanse; Shome, Krishanu; Rothberg, Lewis J; Fauchet, Philippe M

    2015-02-01

    Thin-film hydrogenated amorphous silicon (a-Si:H) solar cells that are free-standing over a 2x2 mm area have been fabricated with thicknesses of 150 nm, 100 nm, and 60 nm. Silver nanoparticles (NPs) created on the front and/or back surfaces of the solar cells led to improvement in performance measures such as current density, overall efficiency, and external quantum efficiency. The effect of changing silver nanoparticle size and incident light angle was tested. Finite-Difference Time-Domain simulations are presented as a way to understand the experimental results as well as guide future research efforts. PMID:25836257

  14. Comparative anomalous small-angle X-ray scattering study of hotwire and plasma grown amorphous silicon-germanium alloys

    OpenAIRE

    Goerigk, G.; Williamson, D. L.

    2001-01-01

    The nanostructure of hydrogenated amorphous silicon-germanium alloys, a-Si1-xGex:H, prepared by the hotwire deposition technique (x=0.06-0.79) and by the plasma enhanced chemical vapor deposition technique (x=0 and 0.50) was analyzed by anomalous small-angle x-ray scattering experiments. For all alloys with x >0 the Ge component was found to be inhomogeneously distributed with correlation lengths of about 1 nm. A systematic increase of the separated scattering was found due to the increasing ...

  15. Fiber Optic Excitation of Silicon Microspheres in Amorphous and Crystalline Fluids

    Science.gov (United States)

    Yılmaz, Huzeyfe; Yılmaz, Hasan; Sharif Murib, Mohammed; Serpengüzel, Ali

    2016-03-01

    This study investigates the optical resonance spectra of free-standing monolithic single crystal silicon microspheres immersed in various amorphous fluids, such as air, water, ethylene glycol, and 4-Cyano-4'-pentylbiphenyl nematic liquid crystal. For the various amorphous fluids, morphology-dependent resonances with quality factors on the order of 105 are observed at 1428 nm. The mode spacing is always on the order of 0.23 nm. The immersion in various amorphous fluids affects the spectral response of the silicon microsphere and heralds this technique for use in novel optofluidics applications. Even though the nematic liquid crystal is a highly birefringent, scattering, and high-index optical medium, morphology-dependent resonances with quality factors on the order of 105 are observed at 1300 nm in the elastic scattering spectra of the silicon microsphere, realizing a liquid-crystal-on-silicon geometry. The relative refractive index and the size parameter of the silicon microsphere are the parameters that affect the resonance structure. The more 4-Cyano-4'-pentylbiphenyl interacting with the silicon microsphere, the lower the quality factor of the resonances is. The more 4-Cyano-4'-pentylbiphenyl is interacting with the silicon microsphere, the lower the mode spacing Δλ of the resonances is. The silicon microspheres wetted with nematic liquid crystal can be used for optically addressed liquid-crystal-on-silicon displays, light valve applications, or reconfigurable optical networks.

  16. Amorphous-silicon module hot-spot testing

    Science.gov (United States)

    Gonzalez, C. C.

    1985-01-01

    Hot spot heating occurs when cell short-circuit current is lower than string operating current. Amorphous cell hot spot are tested to develop the techniques required for performing reverse bias testing of amorphous cells. Also, to quantify the response of amorphous cells to reverse biasing. Guidelines are developed from testing for reducing hot spot susceptibility of amorphous modules and to develop a qualification test for hot spot testing of amorphous modules. It is concluded that amorphous cells undergo hot spot heating similarly to crystalline cells. Comparison of results obtained with submodules versus actual modules indicate heating levels lower in actual modules. Module design must address hot spot testing and hot spot qualification test conducted on modules showed no instabilities and minor cell erosion.

  17. Formation of amorphous silicon by light ion damage

    International Nuclear Information System (INIS)

    Amorphization by implantation of boron ions (which is the lightest element generally used in I.C. fabrication processes) has been systematically studied for various temperatures, various voltages and various dose rates. Based on theoretical considerations and experimental results, a new amorphization model for light and intermediate mass ion damage is proposed consisting of two stages. The role of interstitial type point defects or clusters in amorphization is emphasized. Due to the higher mobility of interstitials out-diffusion to the surface particularly during amorphization with low energy can be significant. From a review of the idealized amorphous structure, diinterstitial-divacancy pairs are suggested to be the embryos of amorphous zones formed during room temperature implantation. The stacking fault loops found in specimens implanted with boron at room temperature are considered to be the origin of secondary defects formed during annealing

  18. Three-dimensional atomic mapping of hydrogenated polymorphous silicon solar cells

    Science.gov (United States)

    Chen, Wanghua; Pareige, Philippe; Roca i Cabarrocas, Pere

    2016-06-01

    Hydrogenated polymorphous silicon (pm-Si:H) is a nanostructured material consisting of silicon nanocrystals embedded in an amorphous silicon matrix. Its use as the intrinsic layer in thin film p-i-n solar cells has led to good cell properties in terms of stability and efficiency. Here, we have been able to assess directly the concentration and distribution of nanocrystals and impurities (dopants) in p-i-n solar cells, by using femtosecond laser-assisted atom probe tomography (APT). An effective sample preparation method for APT characterization is developed. Based on the difference in atomic density between hydrogenated amorphous and crystalline silicon, we are able to distinguish the nanocrystals from the amorphous matrix by using APT. Moreover, thanks to the three-dimensional reconstruction, we demonstrate that Si nanocrystals are homogeneously distributed in the entire intrinsic layer of the solar cell. The influence of the process pressure on the incorporation of nanocrystals and their distribution is also investigated. Thanks to APT we could determine crystalline fractions as low as 4.2% in the pm-Si:H films, which is very difficult to determine by standard techniques, such as X-ray diffraction, Raman spectroscopy, and spectroscopic ellipsometry. Moreover, we also demonstrate a sharp p/i interface in our solar cells.

  19. Surface morphology, cohesive and adhesive properties of amorphous hydrogenated carbon nanocomposite films

    International Nuclear Information System (INIS)

    In this work, amorphous hydrogenated carbon (a-C:H), SiOx containing a-C:H (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) thin films were deposited on chromium thin film coated glass using a closed drift ion beam source. Acetylene gas, hexamethyldisiloxane and hydrogen or 20% nitrogen/hydrogen mixture were used as precursors. Resulting hydrogenated carbon thin film surface morphology as well as their cohesive and adhesive properties were studied using progressive loading scratch tests followed by optical microscopy analysis. Surface analysis was also performed using atomic force microscopy via topography, surface morphology parameter, height distribution histogram and bearing ratio curve based hybrid parameter measurements. The a-C:H/SiOx and a-C:H:N/SiOx thin films showed better mechanical strength as compared to the conventional a-C:H films. X-ray photoelectron spectroscopy was used to determine the chemical composition of these films. It showed increased amounts of silicon and absence of terminal oxygenated carbon bonds in a-C:H:N/SiOx thin film which was attributed to its improved mechanical properties.

  20. Memory effect under pressure in low density amorphous silicon

    OpenAIRE

    Garg, Nandini; Pandey, K. K.; K. V. Shanavas; Betty, C. A.; Sharma, Surinder M

    2010-01-01

    Our investigations on porous Si show that on increase of pressure it undergoes crystalline phase transitions instead of pressure induced amorphization - claimed earlier, and the amorphous phase appears only on release of pressure. This amorphous phase, when subjected to higher pressures, transforms reversibly to a higher coordinated primitive hexagonal phase showing a kind of memory effect which may be the only example of its kind in the elemental solids. First principles calculations and the...

  1. Amorphous silicon oxide layers for surface passivation and contacting of heterostructure solar cells of amorphous and crystalline silicon; Amorphe Siliziumoxidschichten zur Oberflaechenpassivierung und Kontaktierung von Heterostruktur-Solarzellen aus amorphen und kristallinem Silizium

    Energy Technology Data Exchange (ETDEWEB)

    Einsele, Florian

    2010-02-05

    Atomic hydrogen plays a dominant role in the passivation of crystalline silicon surfaces by layers of amorphous silicon. In order to research into this role, this thesis presents the method of hydrogen effusion from thin amorphous films of silicon (a-Si:H) and silicon oxide (a-SiO{sub x}:H). The oxygen concentration of the sub-stoichiometric a-SiO{sub x}:H films ranges up to 10 at.-%. The effusion experiment yields information about the content and thermal stability of hydrogen and about the microstructure of the films. A mathematical description of the diffusion process of atomic hydrogen yields an analytical expression of the effusion rate R{sub E} depending on the linearly increasing temperature in the experiment. Fitting of the calculated effusion rates R{sub E} to measured effusion spectra yields the diffusion coefficient of atomic hydrogen in a-SiO{sub x}:H. With increasing oxygen concentration, the diffusion coefficient of hydrogen in the a-SiO{sub x}:H films decreases. This is attributed to an increasing Si-H bond energy due to back bonded oxygen, resulting in a higher stability of hydrogen in the films. This result is confirmed by an increasing thermal stability of the p-type c-Si passivation with a-SiO{sub x}:H of increasing oxygen concentrations up to 5 at.-%. The passivation reaches very low recombination velocities of S < 10 cm/s at the interface. However, for higher oxygen concentrations up to 10 at.-%, the passivation quality decreases significantly. Here, infrared spectroscopy of Si-H vibrational modes and hydrogen effusion show an increase of hydrogen-rich interconnected voids in the films. This microstructure results in a high amount of molecular hydrogen (H{sub 2}) in the layers, which is not suitable for the saturation of c-Si interface defects. Annealing of the films at temperatures around 400 C leads to a release of H{sub 2} from the voids, as a result of which Si-Si bonds in the material reconstruct. Subsequently, hydrogen migration in the

  2. Rapid thermal annealing of Amorphous Hydrogenated Carbon (a-C:H) films

    Science.gov (United States)

    Alterovitz, Samuel A.; Pouch, John J.; Warner, Joseph D.

    1987-01-01

    Amorphous hydrogenated carbon (a-C:H) films were deposited on silicon and quartz substrates by a 30 kHz plasma discharge technique using methane. Rapid thermal processing of the films was accomplished in nitrogen gas using tungsten halogen light. The rapid thermal processing was done at several fixed temperatures (up to 600 C), as a function of time (up to 1800 sec). The films were characterized by optical absorption and by ellipsometry in the near UV and the visible. The bandgap, estimated from extrapolation of the linear part of a Tauc plot, decreases both with the annealing temperature and the annealing time, with the temperature dependence being the dominating factor. The density of states parameter increases up to 25 percent and the refractive index changes up to 20 percent with temperature increase. Possible explanations of the mechanisms involved in these processes are discussed.

  3. Reaction of amorphous Ni-W and Ni-N-W films with substrate silicon

    Science.gov (United States)

    Zhu, M. F.; Suni, I.; Nicolet, M.-A.; Sands, T.

    1984-01-01

    Wiley et al. (1982) have studied sputtered amorphous films of Nb-Ni, Mo-Ni, Si-W, and Si-Mo. Kung et al. (1984) have found that amorphous Ni-Mo films as diffusion barriers between multilayer metallizations on silicon demonstrate good electrical and thermal stability. In the present investigation, the Ni-W system was selected because it is similar to the Ni-Mo system. However, W has a higher silicide formation temperature than Mo. Attention is given to aspects of sample preparation, sample characterization, the interaction between amorphous Ni-W films and Si, the crystallization of amorphous Ni(36)W(64) films on SiO2, amorphous Ni-N-W films, silicide formation and phase separation, and the crystallization of amorphous Ni(36)W(64) and Ni(30)N(21)W(49) layers.

  4. Hydrogenation of Silicon Tetrachloride in Microwave Plasma

    Institute of Scientific and Technical Information of China (English)

    卢振西; 张伟刚

    2014-01-01

    This study investigated the hydrogenation of silicon tetrachloride (SiCl4) in microwave plasma. A new launcher of argon (Ar) and hydrogen (H2) plasma was introduced to produce a non-thermodynamic equilibrium ac-tivation plasma. The plasma state exhibited a characteristic temperature related to the equilibrium constant, which was termed“Reactive Temperature”in this study. Thus, the hydrogenation of SiCl4 in the plasma could easily be handled with high conversion ratio and very high selectivity to trichlorosilane (SiHCl3). The effects of SiCl4/Ar and H2/Ar ratios on the conversion were also investigated using a mathematical model developed to determine the op-timum experimental parameters. The highest hydrogenation conversion ratio was produced at a H2/SiCl4 molar ratio of 1, with mixtures of SiCl4 and H2 to Ar molar ratio of 1.2 to 1.4. In this plasma, the special system pressure and incident power were required for the highest energy efficiency of hydrogenating SiCl4, while the optimum system pressure varies from 26.6 to 40 kPa depending on input power, and the optimum feed gas (H2 and SiCl4) molar en-ergy input was about 350 kJ·mol-1.

  5. Influence of the deposition parameters on the transition region of hydrogenated silicon films growth

    Institute of Scientific and Technical Information of China (English)

    Lei Qing-Song; Wu Zhi-Meng; Geng Xin-Hua; Zhao Ying; Xi Jian-Ping

    2005-01-01

    Hydrogenated microcrystalline and amorphous silicon thin films were prepared by very high frequency plasmaenhanced chemical vapour deposition (VHF PECVD) by using a mixture of silane and hydrogen as source gas. The influence of deposition parameters on the transition region of hydrogenated silicon films growth was investigated by varying the silane concentration (SC), plasma power (Pw), working pressure (P), and substrate temperature (Ts).Results suggest that SC and Ts are the most critical factors that affect the film structure transition from microcrystalline to amorphous phase. A narrow region in the range of SC and Ts, in which the rapid phase transition takes place, was identified. It was found that at lower P or higher Pw, the transition region is shifted to larger SC. In addition, the dark conductivity and photoconductivity decrease with SC and show sharp changes in the transition region. It proposed that the transition process and the transition region are determined by the competition between the etching effect of atomic hydrogen and the growth of amorphous phase.

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

    Science.gov (United States)

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

    2016-10-01

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

  7. 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.

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

    International Nuclear Information System (INIS)

    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 (Voc) of 0.87, 0.90 V, short circuit current densities (Jsc) of 14.2, 15.36 mA/cm2 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 (di) 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 di while the Voc and fill factor, decreases steadily. However, maximum cell efficiency can be obtained when di = 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 Jsc and red response of the external quantum efficiency to 16.6 mA/cm2 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 • Jsc increases and Voc decreases with the increase in i-layer thickness. • Observed optimized thickness of i-layer as 400 nm • Jsc improved from 15.4 mA/cm2 to 16.6 mA/cm2 due to the light trapping. • Efficiency (η) improved from 9.7% to 10.6% due to better red response of the EQE

  9. Shrinking of silicon nanocrystals embedded in an amorphous silicon oxide matrix during rapid thermal annealing in a forming gas atmosphere

    Science.gov (United States)

    van Sebille, M.; Fusi, A.; Xie, L.; Ali, H.; van Swaaij, R. A. C. M. M.; Leifer, K.; Zeman, M.

    2016-09-01

    We report the effect of hydrogen on the crystallization process of silicon nanocrystals embedded in a silicon oxide matrix. We show that hydrogen gas during annealing leads to a lower sub-band gap absorption, indicating passivation of defects created during annealing. Samples annealed in pure nitrogen show expected trends according to crystallization theory. Samples annealed in forming gas, however, deviate from this trend. Their crystallinity decreases for increased annealing time. Furthermore, we observe a decrease in the mean nanocrystal size and the size distribution broadens, indicating that hydrogen causes a size reduction of the silicon nanocrystals.

  10. 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

  11. 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.

  12. 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

  13. Programmable SERS active substrates for chemical and biosensing applications using amorphous/crystalline hybrid silicon nanomaterial

    OpenAIRE

    Jeffery Alexander Powell; Krishnan Venkatakrishnan; Bo Tan

    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 plu...

  14. Electrical properties of amorphous chalcogenide/silicon heterojunctions modified by ion implantation

    OpenAIRE

    Fedorenko, Yanina G.; Hughes, Mark A.; Colaux, Julien L.; Jeynes, C.; Gwilliam, Russell M.; Homewood, Kevin P.; Yao, Jin; Hewak, Dan W.; Lee, Tae-Hoon; Elliott, Stephen R; Gholipour, B.; Curry, Richard J.

    2014-01-01

    Doping of amorphous chalcogenide films of rather dissimilar bonding type and resistivity, namely, Ga-La-S, GeTe, and Ge-Sb-Te by means of ion implantation of bismuth is considered. To characterize defects induced by ion-beam implantation space-charge-limited conduction and capacitance-voltage characteristics of amorphous chalcogenide/silicon heterojunctions are investigated. It is shown that ion implantation introduces substantial defect densities in the films and their interfaces with silico...

  15. Direct simulation of ion beam induced stressing and amorphization of silicon

    OpenAIRE

    Beardmore, Keith M.; Gronbech-Jensen, Niels

    1999-01-01

    Using molecular dynamics (MD) simulation, we investigate the mechanical response of silicon to high dose ion-irradiation. We employ a realistic and efficient model to directly simulate ion beam induced amorphization. Structural properties of the amorphized sample are compared with experimental data and results of other simulation studies. We find the behavior of the irradiated material is related to the rate at which it can relax. Depending upon the ability to deform, we observe either the ge...

  16. 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.

  17. Light-induced Voc increase and decrease in high-efficiency amorphous silicon solar cells

    OpenAIRE

    Stuckelberger, Michael; Riesen, Yannick Samuel; Despeisse, Matthieu; Schüttauf, Jan-Willem Alexander; Haug, Franz-Josef; Ballif, Christophe

    2014-01-01

    High-efficiency amorphous silicon (a-Si:H) solar cells were deposited with different thicknesses of the p-type amorphous silicon carbide layer on substrates of varying roughness. We observed a light-induced open-circuit voltage (Voc) increase upon light soaking for thin p-layers, but a decrease for thick p-layers. Further, the Voc increase is enhanced with increasing substrate roughness. After correction of the p-layer thickness for the increased surface area of rough substrates, we can exclu...

  18. 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.

  19. 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.

  20. Preparation and Characterisation of Amorphous-silicon Photovoltaic Devices Having Microcrystalline Emitters; Preparacion y Caracterizacion de Dispositivos Fotovoltaicos de Silicio Amorfo con Emisiones Microcristalinos

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, M. T.; Gandia, J. J.; Carabe, J. [CIEMAT. Madrid (Spain)

    1999-11-01

    The present work summarises the essential aspects of the research carried out so far at CIEMAT on amorphous-silicon solar cells. The experience accumulated on the preparation and characterisation of amorphous and microcrystalline silicon has allowed to start from intrinsic (absorbent) and p-and n-type (emitters) materials not only having excellent optoelectronic properties, but enjoying certain technological advantages with respect to those developed by other groups. Among these are absorbent-layer growth rates between 5 and 10 times as fast as conventional ones and microcrystalline emitters prepared without using hydrogen. The preparation of amorphous-silicon cells has required the solution of a number of problems, such as those related to pinholes, edge leak currents and diffusion of metals into the semiconductor. Once such constraints have been overcome, it has been demonstrated not only that the amorphous-silicon technology developed at CIEMAT is valid for making solar cells, but also that the quality of the semiconductor material is good for the application according to the partial results obtained. The development of thin-film laser-scribing technology is considered essential. Additionally it has been concluded that cross contamination, originated by the fact of using a single-chamber reactor, is the basic factor limiting the quality of the cells developed at CIEMAT. The present research activity is highly focused on the solution of this problem. (Author)

  1. Computational Evaluation of Amorphous Carbon Coating for Durable Silicon Anodes for Lithium-Ion Batteries

    OpenAIRE

    Jeongwoon Hwang; Jisoon Ihm; Kwang-Ryeol Lee; Seungchul Kim

    2015-01-01

    We investigate the structural, mechanical, and electronic properties of graphite-like amorphous carbon coating on bulky silicon to examine whether it can improve the durability of the silicon anodes of lithium-ion batteries using molecular dynamics simulations and ab-initio electronic structure calculations. Structural models of carbon coating are constructed using molecular dynamics simulations of atomic carbon deposition with low incident energies (1–16 eV). As the incident energy decrease...

  2. 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.)

  3. Field Emission from Amorphous carbon Nitride Films Deposited on silicon Tip Arrays

    Institute of Scientific and Technical Information of China (English)

    李俊杰; 郑伟涛; 孙龙; 卞海蛟; 金曾孙; 赵海峰; 宋航; 孟松鹤; 赫晓东; 韩杰才

    2003-01-01

    Amorphous carbon nitride films (a-CNx) were deposited on silicon tip arrays by rf magnetron sputtering in pure nitrogen atmosphere. The field emission property of carbon nitride films on Si tips was compared with that of carbon nitride on silicon wafer. The results show that field emission property of carbon nitride films deposited on silicon tips can be improved significantly in contrast with that on wafer. It can be explained that field emission is sensitive to the local curvature and geometry, thus silicon tips can effectively promote field emission property of a-CNx films. In addition, the films deposited on silicon tips have a smaller effective work function ( F = 0.024 eV)of electron field emission than that on silicon wafer ( F = 0.060 e V), which indicates a significant enhancement of the ability of electron field emission from a-CNx films.

  4. Thermal post-deposition treatment effects on nanocrystalline hydrogenated silicon prepared by PECVD under different hydrogen flow rates

    Science.gov (United States)

    Amor, Sana Ben; Meddeb, Hosny; Daik, Ridha; Othman, Afef Ben; Slama, Sonia Ben; Dimassi, Wissem; Ezzaouia, Hatem

    2016-01-01

    In this paper, hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited on mono-crystalline silicon substrate by plasma enhanced chemical vapor deposition (PECVD) under different hydrogen flow rates followed by a thermal treatment in an infrared furnace at different temperature ranging from 300 to 900 °C. The investigated structural, morphological and optoelectronic properties of samples were found to be strongly dependent on the annealing temperature. Raman spectroscopy revealed that nc-Si:H films contain crystalline, amorphous and mixed structures as well. We find that post-deposition thermal treatment may lead to a tendency for structural improvement and a decrease of the disorder in the film network at moderate temperature under 500 °C. As for annealing at higher temperature up to 900 °C induces the recrystallization of the film which is correlated with the grain size and volume fraction in the layer. We demonstrate that high annealing temperature can lead to a decrease of silicon-hydrogen bonds corresponding to a reduction of the amorphous matrix in the layer promoting the formation of covalent Si-Si bonds. The effusion of the hydrogen from the grown film leads to increase its density and therefore induces a decrease in the thickness of the layer. For post-deposition thermal treatment in temperature range under 700 °C, the post-deposition anneal seems to be crucial for obtaining good passivation quality as expressed by a minority carrier lifetime of 17 μs, as it allows a significant reduction in defect states at the layer/substrate interface. While for a temperature higher than 900 °C, the lifetime reduction is obtained because of hydrogen effusion phenomenon, thus a tendency for crystallization in the grown film.

  5. Charging/discharging behavior and mechanism of silicon quantum dots embedded in amorphous silicon carbide films

    International Nuclear Information System (INIS)

    The charging/discharging behavior of Si quantum dots (QDs) embedded in amorphous silicon carbide (a-SiCx) was investigated based on the Al/insulating layer/Si QDs embedded in a-SiCx/SiO2/p-Si (metal-insulator-quantum dots-oxide-silicon) multilayer structure by capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. Transmission electron microscopy and Raman scattering spectroscopy measurements reveal the microstructure and distribution of Si QDs. The occurrence and shift of conductance peaks indicate the carrier transfer and the charging/discharging behavior of Si QDs. The multilayer structure shows a large memory window of 5.2 eV at ±8 V sweeping voltage. Analysis of the C-V and G-V results allows a quantification of the Coulomb charging energy and the trapped charge density associated with the charging/discharging behavior. It is found that the memory window is related to the size effect, and Si QDs with large size or low Coulomb charging energy can trap two or more electrons by changing the charging voltage. Meanwhile, the estimated lower potential barrier height between Si QD and a-SiCx, and the lower Coulomb charging energy of Si QDs could enhance the charging and discharging effect of Si QDs and lead to an enlarged memory window. Further studies of the charging/discharging mechanism of Si QDs embedded in a-SiCx can promote the application of Si QDs in low-power consumption semiconductor memory devices

  6. Comparison of amorphous silicon absorber materials: Light-induced degradation and solar cell efficiency

    Science.gov (United States)

    Stuckelberger, M.; Despeisse, M.; Bugnon, G.; Schüttauf, J.-W.; Haug, F.-J.; Ballif, C.

    2013-10-01

    Several amorphous silicon (a-Si:H) deposition conditions have been reported to produce films that degrade least under light soaking when incorporated into a-Si:H solar cells. However, a systematic comparison of these a-Si:H materials has never been presented. In the present study, different plasma-enhanced chemical vapor deposition conditions, yielding standard low-pressure VHF a-Si:H, protocrystalline, polymorphous, and high-pressure RF a-Si:H materials, are compared with respect to their optical properties and their behavior when incorporated into single-junction solar cells. A wide deposition parameter space has been explored in the same deposition system varying hydrogen dilution, deposition pressure, temperature, frequency, and power. From the physics of layer growth, to layer properties, to solar cell performance and light-induced degradation, a consistent picture of a-Si:H materials that are currently used for a-Si:H solar cells emerges. The applications of these materials in single-junction, tandem, and triple-junction solar cells are discussed, as well as their deposition compatibility with rough substrates, taking into account aspects of voltage, current, and charge collection. In sum, this contributes to answering the question, "Which material is best for which type of solar cell?"

  7. Adjustable optical response of amorphous silicon nanowires integrated with thin films.

    Science.gov (United States)

    Dhindsa, Navneet; Walia, Jaspreet; Pathirane, Minoli; Khodadad, Iman; Wong, William S; Saini, Simarjeet Singh

    2016-04-01

    We experimentally demonstrate a new optical platform by integrating hydrogenated amorphous silicon nanowire arrays with thin films deposited on transparent substrates like glass. A 535 nm thick thin film is anisotropically etched to fabricate vertical nanowire arrays of 100 nm diameter arranged in a square lattice. Adjusting the nanowire length, and consequently the thin film thickness permits the optical properties of this configuration to be tuned for either transmission filter response or enhanced broadband absorption. Vivid structural colors are also achieved in reflection and transmission. The optical properties of the platform are investigated for three different etch depths. Transmission filter response is achieved for a configuration with nanowires on glass without any thin film. Alternatively, integrating thin film with nanowires increases the absorption efficiency by ∼97% compared to the thin film starting layer and by ∼78% over nanowires on glass. The ability to tune the optical response of this material in this fashion makes it a promising platform for high performance photovoltaics, photodetectors and sensors. PMID:26906427

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

    International Nuclear Information System (INIS)

    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. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  9. 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.

  10. 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)

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Amorphous silicon research. Annual subcontract report, October 1, 1994--September 30, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Arya, R R; Bennett, M; Bradley, D [and others

    1996-02-01

    The major effort in this program is to develop cost-effective processes which satisfy efficiency, yield, and material usage criteria for mass production of amorphous silicon-based multijunction modules. New and improved processes were developed for the component cells and a more robust rear contact was developed for better long term stability.

  18. 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

  19. The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

    Science.gov (United States)

    Nordell, Bradley J.; Karki, Sudarshan; Nguyen, Thuong D.; Rulis, Paul; Caruso, A. N.; Purohit, Sudhaunshu S.; Li, Han; King, Sean W.; Dutta, Dhanadeep; Gidley, David; Lanford, William A.; Paquette, Michelle M.

    2015-07-01

    observed in amorphous hydrogenated silicon (a-Si:H), which suggests parallels between the influence of hydrogenation on their material properties and possible avenues for optimization. Finally, an increase in electrical resistivity with increasing H at <35 at. % H concentration is explained, not by disorder as in a-Si:H, but rather by a lower rate of hopping associated with a lower density of sites, assuming a variable range hopping mechanism interpreted in the framework of percolation theory.

  20. A preliminary investigation into hybrid photovoltaic cells with organic phthalocyanines and amorphous silicon heterojunction

    International Nuclear Information System (INIS)

    Hybrid photovoltaic cells take the advantages of silicon in charge carrier separation and transport and organic dyes in strong complementary light absorption. Photovoltaic responses from a set of hybrid solar cells based on amorphous silicon and phthalocyanine dyes of double- or triple-layer heterojunction structures were investigated, which were found to have thickness dependence with the organic active layers. It was found that the photocurrent contributions from organic layers are limited, although they are strong light absorbers. The main photocurrent contributions are from the silicon counterpart. (paper)

  1. 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.

  2. Effect of a-Si:H interface buffer layer on the performance of hydrogenated amorphous silicon germanium thin film solar cell%非晶硅界面缓冲层对非晶硅锗电池性能的影响

    Institute of Scientific and Technical Information of China (English)

    刘伯飞; 白立沙; 张德坤; 魏长春; 孙建; 侯国付; 赵颖; 张晓丹

    2013-01-01

    In the light of the open circuit voltage and fill factor reduction resulting from band gap discontinuities and high defect densities at interfaces when more germanium is mixed into the intrinsic layer of hydrogenated amorphous silicon germanium solar cell, the insertion of a-Si:H buffer layer with proper band gap into PI interface not only mitigates band gap discontinuities and interface recombination, but also improves the electric field distribution by reducing the defect densities at PI interface, thus the collection efficiency of a-SiGe:H solar cell is enhanced. By inserting a-Si:H buffer layer into IN interface and designing band gap profile along the a-SiGe:H intrinsic layer further, the 8.72%conversion efficiency of single junction a-SiGe:H solar cell is achieved when only Al back reflector is added as back contact.%针对非晶硅锗电池本征层高锗含量时界面带隙失配以及高界面缺陷密度造成电池开路电压和填充因子下降的问题,通过在PI界面插入具有合适带隙的非晶硅缓冲层,不仅有效缓和了带隙失配,降低界面复合,同时也通过降低界面缺陷密度改善内建电场分布,从而提高了电池的收集效率.进一步引入IN界面缓冲层以及对非晶硅锗本征层进行能带梯度设计,在仅采用Al背电极时,单结非晶硅锗电池转换效率达8.72%.

  3. The role of oxide interlayers in back reflector configurations for amorphous silicon solar cells

    NARCIS (Netherlands)

    Demontis, V.; Sanna, C.; Melskens, J.; Santbergen, R.; Smets, A.H.M.; Damiano, A.; Zeman, M.

    2013-01-01

    Thin oxide interlayers are commonly added to the back reflector of thin-film silicon solar cells to increase their current. To gain more insight in the enhancement mechanism, we tested different back reflector designs consisting of aluminium-doped zinc oxide (ZnO:Al) and/or hydrogenated silicon oxid

  4. Molecular dynamics studies of the bonding properties of amorphous silicon nitride coatings on crystalline silicon

    OpenAIRE

    Butler, K.T.; Lamers, M.P.W.E.; Weeber, A. W.; Harding, J. H.

    2011-01-01

    In this paper we present molecular dynamics simulations of silicon nitride, both in bulk and as an interface to crystalline silicon. We investigate, in particular, the bonding structure of the silicon nitride and analyze the simulations to search for de- fective geometries which have been identified as potential charge carrier traps when silicon nitride forms an interface with silicon semiconductors. The simulations reveal how the bonding patterns in silicon nitride are dependent upon the sto...

  5. Oxidation of hydrogen-passivated silicon surfaces by scanning near-field optical lithography using uncoated and aluminum-coated fiber probes

    DEFF Research Database (Denmark)

    Madsen, Steen; Bozhevolnyi, Sergey I.; Birkelund, Karen;

    1997-01-01

    Optically induced oxidation of hydrogen-passivated silicon surfaces using a scanning near-field optical microscope was achieved with both uncoated and aluminum-coated fiber probes. Line scans on amorphous silicon using uncoated fiber probes display a three-peak profile after etching in potassium...... hydroxide. Numerical simulations of the electromagnetic field around the probe-sample interaction region are used to explain the experimental observations. With an aluminum-coated fiber probe, lines of 35 nm in width were transferred into the amorphous silicon layer. (C) 1997 American Institute of Physics....

  6. Amorphous silicon materials and solar cells - Progress and directions

    Science.gov (United States)

    Sabisky, E.; Mahan, H.; McMahon, T.

    In 1978, the U.S. Department of Energy initiated government sponsored research in amorphous materials and thin film solar cells. The program was subsequently transferred to the Solar Energy Research Institute for program management. The program grew into a major program for the development of high efficiency (greater than 10 percent), cost effective (15-40 cents per peak watt) thin film amorphous solar cells. The present international interest, the substantial progress made in the device area (2 percent PIN cell in 1976 to 10 percent PIN cell in 1982), and the marketing of the first consumer products using thin film solar cells are to a large ducts using thin film solar cells are to a large extent a consequence of this goal-oriented program.

  7. 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.

  8. An amorphous phase formation at palladium / silicon oxide (Pd/SiOx) interface through electron irradiation - electronic excitation process

    International Nuclear Information System (INIS)

    A Pd-Si amorphous phase was formed at a palladium/silicon oxide (Pd/SiOx) interface at room temperature by electron irradiation at acceleration voltages ranging between 25 kV and 200 kV. Solid-state amorphization was stimulated without the electron knock-on effects. The total dose required for the solid-state amorphization decreases with decreasing acceleration voltage. This is the first report on electron irradiation induced metallic amorphous formation caused by the electronic excitation at metal/silicon oxide interface

  9. H-plasma-assisted aluminum induced crystallization of amorphous silicon

    Institute of Scientific and Technical Information of China (English)

    Li Juan; Liu Ning; Luo Chong; Meng Zhiguo; Xiong Shaozhen; Hoi Sing Kwok

    2012-01-01

    A technique to improve and accelerate aluminum induced crystallization (AIC) by using hydrogen plasma is proposed.Raman spectroscopy and secondary ion mass spectrometry of crystallized poly-Si thin films show that hydrogen plasma radicals reduce the crystallization time of AIC.This technique shortens the annealing time from 10 to 4 h and increases the Hall mobility from 22.1 to 42.5 cm2/(V·s).The possible mechanism of AIC assisted by hydrogen radicals is also discussed.

  10. Hydrogen isotopic substitution experiments in nanostructured porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, W.D. [Facultad de Ciencias Exactas y Naturales y Agrimensura - (UNNE), Avenida Libertad 5500, 3400 Corrientes (Argentina); Koropecki, R.R. [INTEC (CONICET-UNL), Gueemes 3450, 3000 Santa Fe (Argentina)], E-mail: rkoro@intec.ceride.gov.ar; Arce, R.D. [INTEC (CONICET-UNL), Gueemes 3450, 3000 Santa Fe (Argentina); Busso, A. [Facultad de Ciencias Exactas y Naturales y Agrimensura - (UNNE), Avenida Libertad 5500, 3400 Corrientes (Argentina)

    2008-04-30

    Nanostructured porous silicon is usually prepared by electrochemical anodization of monocrystalline silicon using a fluorine-rich electrolyte. As a result of this process, the silicon atoms conserve their original crystalline location, and many of the dangling bonds appearing on the surface of the nanostructure are saturated by hydrogen coming from the electrolyte. This work presents an IR study of the effects produced by partial substitution of water in the electrolytic solution by deuterium oxide. The isotopic effects on the IR spectra are analyzed for the as-prepared samples and for the samples subjected to partial thermal effusion of hydrogen and deuterium. We demonstrate that, although deuterium is chemically indistinguishable from hydrogen, it presents a singular behaviour when used in porous silicon preparation. We found that deuterium preferentially bonds forming Si-DH groups. A possible explanation of the phenomenon is presented, based on the different diffusivities of hydrogen and deuterium.

  11. Anti-reflective nanoporous silicon for efficient hydrogen production

    Science.gov (United States)

    Oh, Jihun; Branz, Howard M

    2014-05-20

    Exemplary embodiments are disclosed of anti-reflective nanoporous silicon for efficient hydrogen production by photoelectrolysis of water. A nanoporous black Si is disclosed as an efficient photocathode for H.sub.2 production from water splitting half-reaction.

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

    Directory of Open Access Journals (Sweden)

    Rosari Saleh

    2002-04-01

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

  13. AuPd CATALYTIC NANOPARTICLE SIZE EFFECT ON THE FORMATION OF AMORPHOUS SILICON NANOWIRES

    Institute of Scientific and Technical Information of China (English)

    LIU ZU-QIN; SUN LIAN-FENG; TANG DONG-SHENG; ZHOU WEI-YA; LI YU-BAO; Zou XIAO-PING

    2000-01-01

    Amorphous silicon (a-Si) nanowires have been prepared on SiO2/Si substrates by AuPd nanoparticles / silane reaction method. Field-emission scanning electron microscopy and transmission electron microscopy were used to characterize the samples. The typical a-Si nanowires we obtained are of a uniform diameter about 20 nm and length up to several micrometers. The growth mechanism of the nanowires seems to be the vapor-liquid-solid mechanism. The catalytic particle size effect on the formation of the nanowires and the cause of forming amorphous state Si nanowires are discussed.

  14. 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.

  15. Amorphous nickel/cobalt tungsten sulfide electrocatalysts for high-efficiency hydrogen evolution reaction

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Amorphous nickel/cobalt tungsten sulfides were synthesized by a thermolytic process. • Amorphous NiWS and CoWS could realize hydrogen evolution efficiently. • Ni/Co promotion and annealing alter the porous structure and chemical bonding states. • Active sites on the surface of amorphous WSx are increased with Ni or Co doping. • Amorphous NiWS and CoWS have immense potentials in water splitting devices. - Abstract: The hydrogen evolution reaction (HER), an appealing solution for future energy supply, requires efficient and inexpensive electrocatalysts with abundant active surface sites. Although crystalline MoS2 and WS2 are promising candidates, their activity is dominated by edge sites. Amorphous tungsten sulfide prepared so far lacks the required active sites and its application has thus been hampered. In this work, nickel and cobalt incorporated amorphous tungsten sulfide synthesized by a thermolytic process is demonstrated to enhance the HER efficiency dramatically. The amorphous nickel tungsten sulfide (amorphous NiWS) annealed at 210 °C delivers the best HER performance in this system boasting a Tafel slope of 55 mV per decade and current density of 8.6 mA cm−2 at 250 mV overpotential in a sustained test for 24 h. The introduction of Ni or Co into the catalyst and subsequent thermal treatment alters the porous structure and chemical bonding states thereby increasing the density of active sites on the surface

  16. Thermodynamic model of hydrogen-induced silicon surface layer cleavage

    International Nuclear Information System (INIS)

    A thermodynamic model of hydrogen-induced silicon surface layer splitting with the help of a bonded silicon wafer is proposed in this article. Wafer splitting is the result of lateral growth of hydrogen blisters in the entire hydrogen-implanted region during annealing. The blister growth rate depends on the effective activation energies of both hydrogen complex dissociation and hydrogen diffusion. The hydrogen blister radius was studied as a function of annealing time, annealing temperature, and implantation dose. The critical radius was obtained according to the Griffith energy condition. The time required for wafer splitting at the cut temperature was calculated in accordance with the growth of hydrogen blisters. [copyright] 2001 American Institute of Physics

  17. Application of hydrogen-plasma technology for property modification of silicon and producing the silicon-based structures

    International Nuclear Information System (INIS)

    Effects of atomic hydrogen on the properties of Czochralski-grown single crystal silicon as well as polycrystalline shaped silicon have been investigated. It was established that the buried defect layers created by high-energy hydrogen or helium ion implantation act as a good getter centers for hydrogen atoms introduced in silicon in the process of hydrogen plasma hydrogenation. Atomic hydrogen was shown to be active as a catalyzer significantly enhancing the rate of thermal donors formation in p-type single crystal silicon. This effect can be used for n-p- and p-n-p-silicon based device structures producing

  18. Band offsets between amorphous La2Hf2O7 and silicon

    Institute of Scientific and Technical Information of China (English)

    CHENG Xuerui; WANG Yongqiang; QI Zeming; ZHANG Guobin; WANG Yuyin; SHAO Tao; ZHANG Wenhua

    2012-01-01

    Amorphous La2Hf2O7 films were grown on Si(100) by pulsed laser deposition method.The valence and conduction band offsets between amorphous La2Hf2O7 film and silicon were determined by using synchrotron radiation photoemission spectroscopy.The energy band gap of amorphous La2Hf2O7 film was measured from the energy-loss spectra of O 1s photoelectrons.The band gap of amorphous La2Hf2O7 film was determined to be 5.4±0.2 eV.The valence and the conduction-band offsets of amorphous La2Hf2O7 film to Si were obtained to be 2.7±0.2 and 1.6±0.2 eV,respectively.These results indicated that the amorphous La2Hf2O7 film could be one promising candidate for high-k gate dielectrics.

  19. Investigation of isochronal annealing on the optical properties of HWCVD amorphous silicon nitride deposited at low temperatures and low gas flow rates

    Science.gov (United States)

    Muller, T. F. G.; Jacobs, S.; Cummings, F. R.; Oliphant, C. J.; Malgas, G. F.; Arendse, C. J.

    2015-06-01

    Hydrogenated amorphous silicon nitride (a-SiNx:H) is used as anti-reflection coatings in commercial solar cells. A final firing step in the production of micro-crystalline silicon solar cells allows hydrogen effusion from the a-SiNx:H into the solar cell, and contributes to bulk passivation of the grain boundaries. In this study a-SiNx:H deposited in a hot-wire chemical vapour deposition (HWCVD) chamber with reduced gas flow rates and filament temperature compared to traditional deposition regimes, were annealed isochronally. The UV-visible reflection spectra of the annealed material were subjected to the Bruggeman Effective Medium Approximation (BEMA) treatment, in which a theoretical amorphous semiconductor was combined with particle inclusions due to the structural complexities of the material. The extraction of the optical functions and ensuing Wemple-DeDomenici analysis of the wavelength-dependent refractive index allowed for the correlation of the macroscopic optical properties with the changes in the local atomic bonding configuration, involving silicon, nitrogen and hydrogen.

  20. Atomistic Models of Amorphous Semiconductors

    NARCIS (Netherlands)

    Jarolimek, K.

    2011-01-01

    Crystalline silicon is probably the best studied material, widely used by the semiconductor industry. The subject of this thesis is an intriguing form of this element namely amorphous silicon. It can contain a varying amount of hydrogen and is denoted as a-Si:H. It completely lacks the neat long ran

  1. Preparation and Surface Analysis of a Fluorinated Amorphous Silicon for Photo-voltaic Device Application

    Science.gov (United States)

    McWhinney, Hylton G.; Burton, Dawn; Fogarty, Thomas N.

    1998-01-01

    Amorphous silicon films (a-Si:H) have been routinely deposited on a variety of substrates. Surface and interfacial studies were carried out with a PHI 5600 X-ray photo electron spectrometer. Co-deposition with fluorine yielded films having oxygen present as bulk oxide. The higher the fluorine content, the greater the amount of bulk oxygen observed. The presence of oxygen may be a contributing factor to inconsistent film properties of fluorine doped silicon materials, reported else where. A definite chemical interface between a layer containing fluorine and a layer made from pure silane has been delineated.

  2. 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.

  3. Carbon nanotube-amorphous silicon hybrid solar cell with improved conversion efficiency

    Science.gov (United States)

    Funde, Adinath M.; Nasibulin, Albert G.; Gufran Syed, Hashmi; Anisimov, Anton S.; Tsapenko, Alexey; Lund, Peter; Santos, J. D.; Torres, I.; Gandía, J. J.; Cárabe, J.; Rozenberg, A. D.; Levitsky, Igor A.

    2016-05-01

    We report a hybrid solar cell based on single walled carbon nanotubes (SWNTs) interfaced with amorphous silicon (a-Si). The high quality carbon nanotube network was dry transferred onto intrinsic a-Si forming Schottky junction for metallic SWNT bundles and heterojunctions for semiconducting SWNT bundles. The nanotube chemical doping and a-Si surface treatment minimized the hysteresis effect in current-voltage characteristics allowing an increase in the conversion efficiency to 1.5% under an air mass 1.5 solar spectrum simulator. We demonstrated that the thin SWNT film is able to replace a simultaneously p-doped a-Si layer and transparent conductive electrode in conventional amorphous silicon thin film photovoltaics.

  4. Measurement of the quantum efficiency of CsI, amorphous silicon and organometallic reflective photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Malamud, G. (LPNHE, Ecole Polytechnique, IN2P3-CNRS, 91128 Palaiseau (France)); Mine, P. (LPNHE, Ecole Polytechnique, IN2P3-CNRS, 91128 Palaiseau (France)); Vartsky, D. (LPNHE, Ecole Polytechnique, IN2P3-CNRS, 91128 Palaiseau (France)); Equer, B. (PICM, Ecole Polytechnique, CNRS (UPR258), 91128 Palaiseau (France)); Besson, P. (CE Saclay, DAPNIA/SED, 91191 Gif-sur-Yvette Cedex (France)); Bourgeois, P. (CE Saclay, DAPNIA/SED, 91191 Gif-sur-Yvette Cedex (France)); Breskin, A. (LPNHE, Ecole Polytechnique, IN2P3-CNRS, 91128 Palaiseau (France)); Chechik, R. (The Weizmann Institute of Science, 76100 Rehovot (Israel))

    1994-09-01

    We performed a systematic investigation of the quantum efficiency of some solid reflective photocathodes in the spectral range 140-240 nm. The measurements were made without gaseous amplification in vacuum and in methane. No significant difference was found among CsI photocathodes prepared by vacuum deposition at different institutes, either from powders or from crystals of different origins, and measured either in vacuum or in methane. Amorphous silicon photocathodes were prepared by the plasma enhanced chemical vapor deposition technique. We present the results for several doping conditions of amorphous silicon and for p-n junctions. Some organometallic photocathodes, containing iron or other transition metals (cerium), were evaporated and measured. Among them decamethylferrocene exhibits the highest quantum efficiency in the range 190-240 nm. ((orig.))

  5. 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.

  6. Carbon nanotube-amorphous silicon hybrid solar cell with improved conversion efficiency.

    Science.gov (United States)

    Funde, Adinath M; Nasibulin, Albert G; Syed, Hashmi Gufran; Anisimov, Anton S; Tsapenko, Alexey; Lund, Peter; Santos, J D; Torres, I; Gandía, J J; Cárabe, J; Rozenberg, A D; Levitsky, Igor A

    2016-05-01

    We report a hybrid solar cell based on single walled carbon nanotubes (SWNTs) interfaced with amorphous silicon (a-Si). The high quality carbon nanotube network was dry transferred onto intrinsic a-Si forming Schottky junction for metallic SWNT bundles and heterojunctions for semiconducting SWNT bundles. The nanotube chemical doping and a-Si surface treatment minimized the hysteresis effect in current-voltage characteristics allowing an increase in the conversion efficiency to 1.5% under an air mass 1.5 solar spectrum simulator. We demonstrated that the thin SWNT film is able to replace a simultaneously p-doped a-Si layer and transparent conductive electrode in conventional amorphous silicon thin film photovoltaics. PMID:27005494

  7. Amorphous and 'micromorph' silicon tandem cells with high open-circuit voltage

    Energy Technology Data Exchange (ETDEWEB)

    Loeffler, J.; Gordijn, A.; Stolk, R.L.; Li, H.; Rath, J.K.; Schropp, R.E.I. [Utrecht University (Netherlands). Debye Inst.

    2005-05-01

    For amorphous and 'micromorph' silicon multi-junction solar cells, we have developed tunnel recombination junctions consisting of two microcrystalline doped layers with a defect-rich interface. While the solar cells performed reasonably well under AM 1.5 light, we found in spectral response measurements that the first deposited cell of tandem structures in nip and pin configuration was apparently leaking under low light conditions. Insertion of a thin protection layer of n-type amorphous silicon solved this issue, and led to an increase in open-circuit voltage. Voltages as high as 1.76 V have been obtained for a-Si/a-Si pinpin tandem cells. (author)

  8. 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.

  9. 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.

  10. Characterization of amorphous hydrogenated carbon films deposited by MFPUMST at different ratios of mixed gases

    Indian Academy of Sciences (India)

    Haiyang Dai; Changyong Zhan; Hui Jiang; Ningkang Huang

    2012-12-01

    Amorphous hydrogenated carbon films (-C:H) on -type (100) silicon wafers were prepared with a middle frequency pulsed unbalanced magnetron sputtering technique (MFPUMST) at different ratios of methane–argon gases. The band characteristics, mechanical properties as well as refractive index were measured by Raman spectra, X-ray photoelectron spectroscopy (XPS), nano-indentation tests and spectroscopic ellipsometry. It is found that the 3 fraction increases with increasing Ar concentration in the range of 17–50%, and then decreases when Ar concentration exceeds 50%. The nano-indentation tests reveal that nano-hardness and elastic modulus of the films increase with increasing Ar concentration in the range of 17–50%, while decreases with increasing Ar concentration from 50% to 86%. The variations in the nano-hardness and the elastic modulus could be interpreted due to different 3 fractions in the prepared -C:H films. The variation of refractive index with wavelength have the same tendency for the -C:H films prepared at different Ar concentrations, they decrease with increasing wavelength from 600 to 1700 nm. For certain wavelengths within 600–1700 nm, refractive index has the highest value at the Ar concentration of 50%, and it is smaller at the Ar concentration of 86% than at 17%. The results given above indicate that ratio of mixed gases has a strong influence on bonding configuration and properties of -C:H films during deposition. The related mechanism is discussed in this paper.

  11. 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.

  12. Adopting a customer-focused team approach to amorphous silicon multijunction module R ampersand D

    International Nuclear Information System (INIS)

    Informed observers of energy markets now generally believe that photovoltaics (PV) will not significantly penetrate the utility bulk-power sector before price and performance approach $50/m2 for 15% efficient modules in flat-plate systems. Recent progress toward such ''utility grade'' modules using amorphous thin films has been slow. The important amorphous thin-film research issues have been well known for some years. These have not been promptly and conclusively addressed, at least in part, because of inadequate PV industry involvement in academic research. In view of this situation, the authors recently modified their research programs seeking to improve the efficiency of amorphous silicon PV research, conclusively address the key issues, and accelerate commercial introduction of utility-grade products. They began this by seeking ''customer'' (PV industry) specification of research priorities and forming mission-oriented teams to pursue the high-priority issues (customer requirements). This paper describes the process and results to date

  13. 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.

  14. Efficient nanorod-based amorphous silicon solar cells with advanced light trapping

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Vandentop, G.J.

    1990-07-01

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

  16. Highly Efficient Hybrid Polymer and Amorphous Silicon Multijunction Solar Cells with Effective Optical Management.

    Science.gov (United States)

    Tan, Hairen; Furlan, Alice; Li, Weiwei; Arapov, Kirill; Santbergen, Rudi; Wienk, Martijn M; Zeman, Miro; Smets, Arno H M; Janssen, René A J

    2016-03-16

    Highly efficient hybrid multijunction solar cells are constructed with a wide-bandgap amorphous silicon for the front subcell and a low-bandgap polymer for the back subcell. Power conversion efficiencies of 11.6% and 13.2% are achieved in tandem and triple-junction configurations, respectively. The high efficiencies are enabled by deploying effective optical management and by using photoactive materials with complementary absorption. PMID:26780260

  17. Failure analysis of thin-film amorphous-silicon solar-cell modules

    Science.gov (United States)

    Kim, Q.

    1984-01-01

    A failure analysis of thin film amorphous silicon solar cell modules was conducted. The purpose of this analysis is to provide information and data for appropriate corrective action that could result in improvements in product quality and reliability. Existing techniques were expanded in order to evaluate and characterize degradational performance of a-Si solar cells. Microscopic and macroscopic defects and flaws that significantly contribute to performance degradation were investigated.

  18. HEATING OF CRYSTALLINE AND AMORPHOUS SILICON BY C-SWITCHED LASER RADIATION

    OpenAIRE

    Meyer, J.; Bartoli, F.; Kruer, M.

    1980-01-01

    A theory for optical heating in semiconductors has been formulated in terms of the coupled diffusion equations for heat and excess carriers. Closed-form solutions for the region near the surface of the material have been obtained in the general case where the optical and transport parameters of the semiconductor are allowed to depend in an arbitrary way on temperature and laser-generated carrier density. The theory is applied here to heating of crystalline and amorphous silicon by Q-switched ...

  19. Activated mechanisms in amorphous silicon: an activation-relaxation-technique study

    OpenAIRE

    Mousseau, N.; Barkema, G. T.

    1999-01-01

    At low temperatures, dynamics in amorphous silicon occurs through a sequence of discrete activated events that locally reorganize the topological network. Using the activation-relaxation technique, a data base containing over 8000 such events is generated, and the events are analyzed with respect to their energy barrier and asymmetry, displacement and volume expansion/contraction. Special attention is paid to those events corresponding to diffusing coordination defects. The energetics is not ...

  20. Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon

    OpenAIRE

    Astakhov, O.; Carius, R.; F. Finger; Petrusenko, Y.; Borysenko, V.; Barankov, D.

    2009-01-01

    The influence of dangling-bond defects and the position of the Fermi level on the charge carrier transport properties in undoped and phosphorous doped thin-film silicon with structure compositions all the way from highly crystalline to amorphous is investigated. The dangling-bond density is varied reproducibly over several orders of magnitude by electron bombardment and subsequent annealing. The defects are investigated by electron-spin-resonance and photoconductivity spectroscopies. Comparin...

  1. Vibrational properties of amorphous silicon from tight-binding O(N) calculation

    OpenAIRE

    Biswas, Parthapratim

    2001-01-01

    We present an O(N) algorithm to study the vibrational properties of amorphous silicon within the framework of tight-binding approach. The dynamical matrix elements have been evaluated numerically in the harmonic approximation exploiting the short-range nature of the density matrix to calculate the vibrational density of states which is then compared with the same obtained from a standard O($N^4$) algorithm. For the purpose of illustration, an 1000-atom model is studied to calculate the locali...

  2. 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).

  3. Investigation of an amorphous silicon flat-panel detector for ion radiography

    OpenAIRE

    Telsemeyer, Julia

    2012-01-01

    Using heavy ions in radiotherapy offers a good potential for targeted radiation of tumors and the ability to spare healthy tissue. Their characteristic interaction with matter holds the potential to employ ions for high-contrast radiographic imaging at a decreased dose in comparison to conventional X-ray imaging; however, it lacks simple detectors suitable for this purpose. In this study the performance of an amorphous silicon flat-panel detector, originally designed for photon imaging, was i...

  4. 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.

  5. 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.

  6. Influence of screening effect on hydrogen passivation of hole silicon

    CERN Document Server

    Aleksandrov, O V

    2002-01-01

    The simulation of hole silicon passivation during hydrogen diffusion with account of hydrogen-acceptor pairs formation, internal electrical field and screening effect has been carried out. Screening by free carriers of hydrogen and acceptor ions results in shortening their interaction radii and slacking the concentration dependence of hydrogen diffusivity at high level of silicon doping. The consistency of simulated and experimental profiles of holes and hydrogen-acceptor pairs is reached in a broad band of doping levels from 4 x 10 sup 1 sup 4 to 1.2 x 10 sup 2 sup 0 cm sup - sup 3 at the pair binding energy of 0.70-0.79 eV while the radius of the Coulomb interaction of hydrogen and boron ions is equal to 35 A under low doping and decrease with increasing doping level

  7. Amorphous silicon image sensors for x-ray detection in NDT

    International Nuclear Information System (INIS)

    Acquiring radiographic images in a digital format offers significant advantages over film. Besides eliminating the need for chemical processing, a digital image can be easily stored for more convenient retrieval, transmitted to remote locations for interpretation, and image processed to provide enhanced interpretation and greater latitude in exposure. Amorphous silicon image sensors, developed by dpiX, a Xerox Company, offer an improved method of acquiring digital x-ray images. Amorphous silicon image sensor technology provides the opportunity to have large format size similar to x-ray film, high resolution, and a compact package for ease of use in NDT applications. This technology can also be used to replace x-ray image intensifier tubes to provide real-time fluoroscopic imaging for capturing time related events such as x-ray examination of objects on a conveyor belt. This paper presents a description of amorphous silicon image sensor technology and provides examples of the performance that can be achieved using a system that has an 8 x 10 inch x-ray image acquisition area and 127 micron pixels for 4 lp/mm resolution

  8. Light-induced changes in silicon nanocrystal based solar cells: Modification of silicon–hydrogen bonding on silicon nanocrystal surface under illumination

    Science.gov (United States)

    Kim, Ka-Hyun; Johnson, Erik V.; Cabarrocas, Pere Roca i.

    2016-07-01

    Hydrogenated polymorphous silicon (pm-Si:H) is a material consisting of a small volume fraction of nanocrystals embedded in an amorphous matrix. pm-Si:H solar cells demonstrate interesting initial degradation behaviors such as rapid initial change in photovoltaic parameters and self-healing after degradation during light-soaking. The precise dynamics of the light-induced degradation was studied in a series of light-soaking experiments under various illumination conditions such as AM1.5G and filtered 570 nm yellow light. Hydrogen effusion experiment before and after light-soaking further revealed that the initial degradation of pm-Si:H solar cells originate from the modification of silicon–hydrogen bonding on the surface of silicon nanocrystals in pm-Si:H.

  9. Hydrogen passivation of multi-crystalline silicon solar cells

    Institute of Scientific and Technical Information of China (English)

    胡志华; 廖显伯; 刘祖明; 夏朝凤; 陈庭金

    2003-01-01

    The effects of hydrogen passivation on multi-crystalline silicon (mc-Si) solar cells are reported in this paper.Hydrogen plasma was generated by means of ac glow discharge in a hydrogen atmosphere. Hydrogen passivation was carried out with three different groups of mc-Si solar cells after finishing contacts. The experimental results demonstrated that the photovoltaic performances of the solar cell samples have been improved after hydrogen plasma treatment, with a relative increase in conversion efficiency up to 10.6%. A calculation modelling has been performed to interpret the experimental results using the model for analysis of microelectronic and photonic structures developed at Pennsylvania State University.

  10. NATO Advanced Study Institute on Hydrogen in Disordered and Amorphous Solids

    CERN Document Server

    Bowman, Robert

    1986-01-01

    This is the second volume in the NATO ASI series dealing with the topic of hydrogen in solids. The first (V. B76, Metal Hydrides) appeared five years ago and focussed primarily on crystalline phases of hydrided metallic systems. In the intervening period, the amorphous solid state has become an area of intense research activity, encompassing both metallic and non-metallic, e.g. semiconducting, systems. At the same time the problem of storage of hydrogen, which motivated the first ASI, continues to be important. In the case of metallic systems, there were early indications that metallic glasses and disordered alloys may be more corrosion resistant, less susceptible to embrittlement by hydrogen and have a higher hydrogen mobility than ordered metals or intermetallics. All of these properties are desirable for hydrogen storage. Subsequent research has shown that thermodynamic instability is a severe problem in many amorphous metal hydrides. The present ASI has provided an appropriate forum to focus on these issu...

  11. Amorphous silicon thin films: The ultimate lightweight space solar cell

    Science.gov (United States)

    Vendura, G. J., Jr.; Kruer, M. A.; Schurig, H. H.; Bianchi, M. A.; Roth, J. A.

    1994-01-01

    Progress is reported with respect to the development of thin film amorphous (alpha-Si) terrestrial solar cells for space applications. Such devices promise to result in very lightweight, low cost, flexible arrays with superior end of life (EOL) performance. Each alpha-Si cell consists of a tandem arrangement of three very thin p-i-n junctions vapor deposited between film electrodes. The thickness of this entire stack is approximately 2.0 microns, resulting in a device of negligible weight, but one that must be mechanically supported for handling and fabrication into arrays. The stack is therefore presently deposited onto a large area (12 by 13 in), rigid, glass superstrate, 40 mil thick, and preliminary space qualification testing of modules so configured is underway. At the same time, a more advanced version is under development in which the thin film stack is transferred from the glass onto a thin (2.0 mil) polymer substrate to create large arrays that are truly flexible and significantly lighter than either the glassed alpha-Si version or present conventional crystalline technologies. In this paper the key processes for such effective transfer are described. In addition, both glassed (rigid) and unglassed (flexible) alpha-Si cells are studied when integrated with various advanced structures to form lightweight systems. EOL predictions are generated for the case of a 1000 W array in a standard, 10 year geosynchronous (GEO) orbit. Specific powers (W/kg), power densities (W/sq m) and total array costs ($/sq ft) are compared.

  12. 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.

  13. A Study of The Evolution of The Silicon Nanocrystallites in The Amorphous Silicon Carbide Under Argon Dilution of the Source Gases

    Directory of Open Access Journals (Sweden)

    A. Kole

    2011-01-01

    Full Text Available Structural evolution of the hydrogenated amorphous silicon carbide (a-SiC:H films deposited by rf-PECVD from a mixture of SiH4 and CH4 diluted in Ar shows that a smooth transition from amorphous to nanocrystalline phase occurs in the material by increasing the Ar dilution. The optical band gap (Eg decreases from 1.99 eV to 1.91 eV and the H-content (CH decreases from 14.32 at% to 5.29 at% by increasing the dilution from 94 % to 98 %. at 98 % Ar dilution, the material contains irregular shape Si nanocrystallites with sizes over 10 nm. Increasing the Ar dilution further to 98.4 % leads to a reduction of the size of the Si nanocrystals to regular shape Si quantum dots of size about 5 nm. The quantum confinement effect is apparent from the increase in the Eg value to 2.6 eV at 98.4 % Ar dilution. Formation of Si quantum dots may be explained by the etching of the nanocrystallites of Si by the energetic ion bombardment from the plasma.

  14. Hydrogen desorption from hydrogen fluoride and remote hydrogen plasma cleaned silicon carbide (0001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    King, Sean W., E-mail: sean.king@intel.com; Tanaka, Satoru; Davis, Robert F. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Nemanich, Robert J. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2015-09-15

    Due to the extreme chemical inertness of silicon carbide (SiC), in-situ thermal desorption is commonly utilized as a means to remove surface contamination prior to initiating critical semiconductor processing steps such as epitaxy, gate dielectric formation, and contact metallization. In-situ thermal desorption and silicon sublimation has also recently become a popular method for epitaxial growth of mono and few layer graphene. Accordingly, numerous thermal desorption experiments of various processed silicon carbide surfaces have been performed, but have ignored the presence of hydrogen, which is ubiquitous throughout semiconductor processing. In this regard, the authors have performed a combined temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) investigation of the desorption of molecular hydrogen (H{sub 2}) and various other oxygen, carbon, and fluorine related species from ex-situ aqueous hydrogen fluoride (HF) and in-situ remote hydrogen plasma cleaned 6H-SiC (0001) surfaces. Using XPS, the authors observed that temperatures on the order of 700–1000 °C are needed to fully desorb C-H, C-O and Si-O species from these surfaces. However, using TPD, the authors observed H{sub 2} desorption at both lower temperatures (200–550 °C) as well as higher temperatures (>700 °C). The low temperature H{sub 2} desorption was deconvoluted into multiple desorption states that, based on similarities to H{sub 2} desorption from Si (111), were attributed to silicon mono, di, and trihydride surface species as well as hydrogen trapped by subsurface defects, steps, or dopants. The higher temperature H{sub 2} desorption was similarly attributed to H{sub 2} evolved from surface O-H groups at ∼750 °C as well as the liberation of H{sub 2} during Si-O desorption at temperatures >800 °C. These results indicate that while ex-situ aqueous HF processed 6H-SiC (0001) surfaces annealed at <700 °C remain terminated by some surface C–O and

  15. 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 (

  16. Annealing characteristics of irradiated hydrogenated amorphous silicon solar cells

    Science.gov (United States)

    Payson, J. S.; Abdulaziz, S.; Li, Y.; Woodyard, J. R.

    1991-01-01

    It was shown that 1 MeV proton irradiation with fluences of 1.25E14 and 1.25E15/sq cm reduces the normalized I(sub SC) of a-Si:H solar cell. Solar cells recently fabricated showed superior radiation tolerance compared with cells fabricated four years ago; the improvement is probably due to the fact that the new cells are thinner and fabricated from improved materials. Room temperature annealing was observed for the first time in both new and old cells. New cells anneal at a faster rate than old cells for the same fluence. From the annealing work it is apparent that there are at least two types of defects and/or annealing mechanisms. One cell had improved I-V characteristics following irradiation as compared to the virgin cell. The work shows that the photothermal deflection spectroscopy (PDS) and annealing measurements may be used to predict the qualitative behavior of a-Si:H solar cells. It was anticipated that the modeling work will quantitatively link thin film measurements with solar cell properties. Quantitative predictions of the operation of a-Si:H solar cells in a space environment will require a knowledge of the defect creation mechanisms, defect structures, role of defects on degradation, and defect passivation and annealing mechanisms. The engineering data and knowledge base for justifying space flight testing of a-Si:H alloy based solar cells is being developed.

  17. The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

    Energy Technology Data Exchange (ETDEWEB)

    Nordell, Bradley J.; Karki, Sudarshan; Nguyen, Thuong D.; Rulis, Paul; Caruso, A. N.; Paquette, Michelle M., E-mail: paquettem@umkc.edu [Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States); Purohit, Sudhaunshu S. [Department of Chemistry, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States); Li, Han; King, Sean W. [Logic Technology Development, Intel Corporation, Hillsboro, Oregon 97124 (United States); Dutta, Dhanadeep; Gidley, David [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States); Lanford, William A. [Department of Physics, University at Albany, Albany, New York 12222 (United States)

    2015-07-21

    structural disorder. All of these correlations in a-B{sub x}C:H{sub y} are found to be very similar to those observed in amorphous hydrogenated silicon (a-Si:H), which suggests parallels between the influence of hydrogenation on their material properties and possible avenues for optimization. Finally, an increase in electrical resistivity with increasing H at <35 at. % H concentration is explained, not by disorder as in a-Si:H, but rather by a lower rate of hopping associated with a lower density of sites, assuming a variable range hopping mechanism interpreted in the framework of percolation theory.

  18. Understanding the amorphous-to-microcrystalline silicon transition in SiF{sub 4}/H{sub 2}/Ar gas mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Dornstetter, Jean-Christophe [TOTAL New Energies, 24 cours Michelet, 92069 Paris La Défense Cedex (France); LPICM-CNRS, Ecole Polytechnique, 91128 Palaiseau (France); Bruneau, Bastien; Bulkin, Pavel; Johnson, Erik V.; Roca i Cabarrocas, Pere [LPICM-CNRS, Ecole Polytechnique, 91128 Palaiseau (France)

    2014-06-21

    We report on the growth of microcrystalline silicon films from the dissociation of SiF{sub 4}/H{sub 2}/Ar gas mixtures. For this growth chemistry, the formation of HF molecules provides a clear signature of the amorphous to microcrystalline growth transition. Depositing films from silicon tetrafluoride requires the removal of F produced by SiF{sub 4} dissociation, and this removal is promoted by the addition of H{sub 2} which strongly reacts with F to form HF molecules. At low H{sub 2} flow rates, the films grow amorphous as all the available hydrogen is consumed to form HF. Above a critical flow rate, corresponding to the full removal of F, microcrystalline films are produced as there is an excess of atomic hydrogen in the plasma. A simple yet accurate phenomenological model is proposed to explain the SiF{sub 4}/H{sub 2} plasma chemistry in accordance with experimental data. This model provides some rules of thumb to achieve high deposition rates for microcrystalline silicon, namely, that increased RF power must be balanced by an increased H{sub 2} flow rate.

  19. Energy investments and production costs of amorphous silicon PV modules

    Energy Technology Data Exchange (ETDEWEB)

    Srinivas, K.S. (Neuchatel Univ., Inst. de Microtechnique, Neuchatel (Switzerland))

    1991-10-01

    Viability of large scale applications of photovoltaic technology will ultimately depend upon the economics of energy payback and production costs associated with it. For the potential options among the various PV technologies this aspect has been analysed to a considerable extent for crystalline silicon (mono- and poly-) modules. No systematic study, based on practical aspects of A-Si PV module production has yet been reported. In this study the energy investments and production costs of A-Si PV module production have been analysed based on factual data from two manufacturing units. Each process step involved in the manufacture of A-Si modules is analysed for the process electrical energy and the hidden energy content in the various materials associated with that step. Energy payback period and the production costs have been calculated on the basis of prevailing levels of conversion efficiency (5%) and production yield ([approx equal]80%). The report also covers salient features of A-Si technology, the current status of PV industry in respect of production, R+D and cost status of competing PV technologies. A review of earlier studies on energy investments and production costs of A-Si modules and a comparison of their findings with that of the present study are also discussed. Certain details which could not be included in the main text to maintain the continuity of thoughts, are presented as annexes. A short note on 'criteria for choice of technology for large scale PV production' and a brief description of the status of other thin-film technologies (CIS,CdTe) are included as Appendices at the end. figs., tabs., 18 refs.

  20. Photoluminescence of amorphous carbon films fabricated by layer-by-layer hydrogen plasma chemical annealing method

    Institute of Scientific and Technical Information of China (English)

    徐骏; 黄晓辉; 李伟; 王立; 陈坤基

    2002-01-01

    A method in which nanometre-thick film deposition was alternated with hydrogen plasma annealing (layer-by-layermethod) was applied to fabricate hydrogenated amorphous carbon films in a conventional plasma-enhanced chemicalvapour deposition system. It was found that the hydrogen plasma treatment could decrease the hydrogen concentrationin the films and change the sp2/sp3 ratio to some extent by chemical etching. Blue photoluminescence was observed atroom temperature, as a result of the reduction of sp2 clusters in the films.

  1. Hydrogen adsorption in metal-decorated silicon carbide nanotubes

    Science.gov (United States)

    Singh, Ram Sevak; Solanki, Ankit

    2016-09-01

    Hydrogen storage for fuel cell is an active area of research and appropriate materials with excellent hydrogen adsorption properties are highly demanded. Nanotubes, having high surface to volume ratio, are promising storage materials for hydrogen. Recently, silicon carbide nanotubes have been predicted as potential materials for future hydrogen storage application, and studies in this area are ongoing. Here, we report a systematic study on hydrogen adsorption properties in metal (Pt, Ni and Al) decorated silicon carbide nanotubes (SiCNTs) using first principles calculations based on density functional theory. The hydrogen adsorption properties are investigated by calculations of adsorption energy, electronic band structure, density of states (DOS) and Mulliken charge population analysis. Our findings show that hydrogen adsorptions on Pt, Ni and Al-decorated SiCNTs undergo spontaneous exothermic reactions with significant modulation of electronic structure of SiCNTs in all cases. Importantly, according to the Mulliken charge population analysis, dipole-dipole interaction causes chemisorptions of hydrogen in Pt, Ni and Al decorated SiCNTs with formation of chemical bonds. The study is a platform for the development of metal decorated SiCNTs for hydrogen adsorption or hydrogen storage application.

  2. 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.

  3. On the thermodynamically stable amorphous phase of polymer-derived silicon oxycarbide.

    Science.gov (United States)

    Yu, Liping; Raj, Rishi

    2015-01-01

    A model for the thermodynamic stability of amorphous silicon oxycarbide (SiCO) is presented. It builds upon the reasonably accepted model of SiCO which is conceived as a nanodomain network of graphene. The domains are expected to be filled with SiO2 molecules, while the interface with graphene is visualized to contain mixed bonds described as Si bonded to C as well as to O atoms. Normally these SiCO compositions would be expected to crystallize. Instead, calorimetric measurements have shown that the amorphous phase is thermodynamically stable. In this article we employ first-principles calculations to estimate how the interfacial energy of the graphene networks is favorably influenced by having mixed bonds attached to them. We analyze the ways in which this reduction in interfacial energy can stabilize the amorphous phase. The approach highlights how density functional theory computations can be combined with the classical analysis of phase transformations to explain the behavior of a complex material. In addition we discover a two-dimensional lattice structure, with the composition Si2C4O3 that is constructed from a single layer of graphene congruent with silicon and oxygen bonds on either side. PMID:26419962

  4. Low-mobility solar cells: a device physics primer with application to amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Schiff, E.A. [Syracuse University, New York (United States). Department of Physics

    2003-07-01

    The properties of pin solar cells based on photogeneration of charge carriers into low-mobility materials were calculated for two models. Ideal p- and n-type electrode layers were assumed in both cases. The first, elementary case involves only band mobilities and direct electron-hole recombination. An analytical approximation indicates that the power in thick cells rises as the 1/4 power of the lower band mobility, which reflects the buildup of space-charge under illumination. The approximation agrees well with computer simulation. The second model includes exponential bandtail trapping, which is commonly invoked to account for very low hole drift mobilities in amorphous silicon and other amorphous semiconductors. The two models have similar qualitative behavior. Predictions for the solar conversion efficiency of amorphous silicon-based cells that are limited by valence bandtail trapping are presented. The predictions account adequately for the efficiencies of present a-Si : H cells in their 'as-prepared' state (without light-soaking), and indicate the improvement that may be expected if hole drift mobilities (and valence bandtail widths) can be improved. (author)

  5. Controlling Ethylene Hydrogenation Reactivity on Pt13 Clusters by Varying the Stoichiometry of the Amorphous Silica Support.

    Science.gov (United States)

    Crampton, Andrew S; Rötzer, Marian D; Schweinberger, Florian F; Yoon, Bokwon; Landman, Uzi; Heiz, Ueli

    2016-07-25

    Ethylene hydrogenation was investigated on size-selected Pt13 clusters supported on three amorphous silica (a-SiO2 ) thin films with different stoichiometries. Activity measurements of the reaction at 300 K revealed that on a silicon-rich and a stoichiometric film, Pt13 exhibits a similar activity to that of Pt(111), in line with the known structure insensitivity of the reaction. On an oxygen-rich film, a threefold increased rate was measured. Pulsing ethylene at 400 K, then measuring the activity at 300 K, resulted in complete loss of activity on the silicon-rich surface compared to only marginal losses on the other surfaces. The measured reactivity trends correlate with charging characteristics of a Pt13 cluster on the SiO2 films, predicted through first-principle calculations. The results reveal that the stoichiometry-dependent charging by the support can be used to tune the selectivity of reaction pathways during a catalytic hydrogenation reaction. PMID:27356301

  6. Computational Evaluation of Amorphous Carbon Coating for Durable Silicon Anodes for Lithium-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Jeongwoon Hwang

    2015-10-01

    Full Text Available We investigate the structural, mechanical, and electronic properties of graphite-like amorphous carbon coating on bulky silicon to examine whether it can improve the durability of the silicon anodes of lithium-ion batteries using molecular dynamics simulations and ab-initio electronic structure calculations. Structural models of carbon coating are constructed using molecular dynamics simulations of atomic carbon deposition with low incident energies (1–16 eV. As the incident energy decreases, the ratio of sp2 carbons increases, that of sp3 decreases, and the carbon films become more porous. The films prepared with very low incident energy contain lithium-ion conducting channels. Also, those films are electrically conductive to supplement the poor conductivity of silicon and can restore their structure after large deformation to accommodate the volume change during the operations. As a result of this study, we suggest that graphite-like porous carbon coating on silicon will extend the lifetime of the silicon anodes of lithium-ion batteries.

  7. Molecular dynamics study of hydrogen isotopes migration in amorphous silica

    International Nuclear Information System (INIS)

    Fused silica is a material of interest due to its increasing number of applications in many different technology fields. In thermonuclear fusion it is a key component in a number of diagnostics of the Safety and Control Systems of the ITER machine as well as in the final focusing optics of lasers for NIF. Materials properties of interest (optical absorption, radioluminescence, mechanical properties, ...) are closely related to the presence of defects. These defects can be generated directly by irradiation or by the presence of impurities in the material. Hydrogen is an ubiquitous impurity in this material and, moreover in a fusion reactor environment this material will be exposed to energetic hydrogen isotopes. Hydrogen isotopes will be deposited also on the surface of the fused silica components coming from the reaction chamber. On the other hand, some experimental results show that radiation damage can be different depending on hydrogen content, indicating that a detailed knowledge of the hydrogen role in fused silica should be fully understood. In this work we present molecular dynamics simulations to study the effects of different hydrogen isotopes in this material and their interaction with the defects. The interatomic potential developed by Feuston and Garofallini will be used in these studies. The diffusion coefficients and mechanisms of H mobility in fused silica will be calculated and compared with those existing in the literature. (author)

  8. Modelling of the hydrogen effects on the morphogenesis of hydrogenated silicon nano-structures in a plasma reactor

    International Nuclear Information System (INIS)

    This work pursues the goal of understanding mechanisms related to the morphogenesis of hydrogenated silicon nano-structures in a plasma reactor through modeling techniques. Current technologies are first reviewed with an aim to understand the purpose behind their development. Then follows a summary of the possible studies which are useful in this particular context. The various techniques which make it possible to simulate the trajectories of atoms by molecular dynamics are discussed. The quantum methods of calculation of the interaction potential between chemical species are then developed, reaching the conclusion that only semi-empirical quantum methods are sufficiently fast to be able to implement an algorithm of quantum molecular dynamics on a reasonable timescale. From the tools introduced, a reflection on the nature of molecular metastable energetic states is presented for the theoretical case of the self-organized growth of a linear chain of atoms. This model - which consists of propagating the growth of a chain by the successive addition of the atom which least increases the electronic energy of the chain - shows that the Fermi level is a parameter essential to self organization during growth. This model also shows that the structure formed is not necessarily a total minimum energy structure. From all these numerical tools, the molecular growth of clusters can be simulated by using parameters from magnetohydrodynamic calculation results of plasma reactor modeling (concentrations of the species, interval between chemical reactions, energy of impact of the reagents...). The formation of silicon-hydrogen clusters is thus simulated by the successive capture of silane molecules. The structures formed in simulation at the operating temperatures of the plasma reactor predict the formation of spherical clusters constituting an amorphous silicon core covered by hydrogen. These structures are thus not in a state of minimum energy, contrary to certain experimental

  9. Large Size High Performance Transparent Amorphous Silicon Sensors for Laser Beam Position Detection and Monitoring

    International Nuclear Information System (INIS)

    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)

  10. Structural and Dynamic Properties of Amorphous Silicon:Tight-Binding Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    HUANG Shi-Ping; WANG Wen-Chuan

    2004-01-01

    @@ The tight-binding molecular dynamics simulation has been performed to study structural and dynamical properties of amorphous silicon. It is found that the radial distribution function and static structure factor are in good agreement with the experimental measurements. The bond order parameters Ql are sensitive to the structure change at different quenching rates. For the dynamical properties, we have calculated the vibration and electronic density of states. The simulation results show that the transverse acoustic is in good agreement with the experimental data, and the high frequency transverse optical (TO) peak shifts to the right of the experimental TO peak.

  11. The influence of confinements on the photon flux spectra in amorphous silicon quantum dots

    OpenAIRE

    ABDULRIDA, Moafak Cadim; and, Nidhal Moosa ABDUL-AMEER

    2012-01-01

    We have theoretically calculated the photon flux of radiative recombination in amorphous silicon quantum dots (a-SiQDs) at room temperature. These quantum dots have been ranged in their diameter 1 to 4 nm. The convolution of probability density function of deepest energy states of conduction PC(E) and valence PV(E) bands within the capture volume was adopted. The behavior of this function can be classified into four regions according to the quantum dot size. The effect of spatial an...

  12. Nanopatterned front contact for broadband absorption in ultra-thin amorphous silicon solar cells

    OpenAIRE

    Massiot, I.; Colin, Clément; Péré-Laperne, Nicolas; Roca I Cabarrocas, Pere; Sauvan, Christophe; Lalanne, Philippe; Pelouard, Jean-Luc; Collin, Stéphane

    2012-01-01

    International audience Broadband light trapping is numerically demonstrated in ultra-thin solar cells composed of a flat amorphous silicon absorber layer deposited on a silver mirror. A one-dimensional silver array is used to enhance light absorption in the visible spectral range with low polarization and angle dependencies. In addition, the metallic nanowires play the role of transparent electrodes. We predict a short-circuit current density of 14:6mA=cm2 for a solar cell with a 90 nm-thi...

  13. Elastic measurements of TLSs in amorphous silicon at mK temperatures

    Science.gov (United States)

    Fefferman, Andrew; Liu, Xiao; Metcalf, Thomas; Jernigan, Glenn; Collin, Eddy

    The low temperature properties of glass are distinct from those of crystals due to the presence of poorly understood low-energy excitations. These are usually thought to be atoms tunneling between nearby equilibria, forming tunneling two level systems (TLSs). Elastic measurements on amorphous silicon films deposited with e-beam evaporation showed that this material contains a variable density of TLSs that decreases as the growth temperature increases from 45 to 400 deg C. We will present an analysis of the elastic properties of these films down to the low mK range in the framework of the standard tunneling model

  14. On the thermodynamically stable amorphous phase of polymer-derived silicon oxycarbide

    OpenAIRE

    Liping Yu; Rishi Raj

    2015-01-01

    A model for the thermodynamic stability of amorphous silicon oxycarbide (SiCO) is presented. It builds upon the reasonably accepted model of SiCO which is conceived as a nanodomain network of graphene. The domains are expected to be filled with SiO2 molecules, while the interface with graphene is visualized to contain mixed bonds described as Si bonded to C as well as to O atoms. Normally these SiCO compositions would be expected to crystallize. Instead, calorimetric measurements have shown t...

  15. 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%.

  16. 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)

  17. 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.

  18. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyoung-Rae; Park, Jea-Gun [Hanyang University, Seoul (Korea, Republic of)

    2014-10-15

    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{sub 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{sub x} distributed on the a-IGZO surface reduced the adsorption and the desorption of H{sub 2}O and O{sub 2}. This process is applicable to the TFT manufacturing process with a variable sputtering target.

  20. Electrical behavior of multi-walled carbon nanotube network embedded in amorphous silicon nitride

    Directory of Open Access Journals (Sweden)

    Buiculescu Raluca

    2011-01-01

    Full Text Available Abstract The electrical behavior of multi-walled carbon nanotube network embedded in amorphous silicon nitride is studied by measuring the voltage and temperature dependences of the current. The microstructure of the network is investigated by cross-sectional transmission electron microscopy. The multi-walled carbon nanotube network has an uniform spatial extension in the silicon nitride matrix. The current-voltage and resistance-temperature characteristics are both linear, proving the metallic behavior of the network. The I-V curves present oscillations that are further analyzed by computing the conductance-voltage characteristics. The conductance presents minima and maxima that appear at the same voltage for both bias polarities, at both 20 and 298 K, and that are not periodic. These oscillations are interpreted as due to percolation processes. The voltage percolation thresholds are identified with the conductance minima.