Artykuły w czasopismach: „Amorphous Silicon (a-Si:H)”

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FU, GUANG-SHENG, YAN-BIN YANG, WEI YU, WAN-BING LU, WEN-GE DING i LI HAN. "AMORPHOUS SILICON NANO-PARTICLES IN A-SiNx:H PREPARED BY HELICON WAVE PLASMA-ENHANCED CHEMICAL VAPOUR DEPOSITION". International Journal of Modern Physics B 19, nr 15n17 (10.07.2005): 2704–9. http://dx.doi.org/10.1142/s0217979205031560.

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Amorphous silicon nano-particles embedded in hydrogenated amorphous silicon nitride ( a - SiN x: H ) matrix have been prepared using an approach based on the deposition of Si -rich a - SiN x: H thin films by helicon wave plasma-enhanced chemical vapour deposition (HWP-CVD) technique, which has a characteristic of high plasma density at low working pressure. X-ray photoelectron spectroscopy analysis shows that the silicon atom bonds exist in the Si-Si and Si-N configurations and the amorphous silicon regions appear separately in the Si -rich a - SiN x: H films. The existence of amorphous silicon nano-particles without any post annealing in the a - SiN x: H random matrix is confirmed by the image of high-resolution transmission electron microscopy. Through infrared absorption analysis, the formation of the separated amorphous silicon nano-particles structure is closely correlated with the deposition parameters such as low working pressure and Ar dilution in the HWP-CVD process.

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Rath, Chandana, J. Farjas, P. Roura, F. Kail, P. Roca i Cabarrocas i E. Bertran. "Thermally Induced Structural Transformations on Polymorphous Silicon". Journal of Materials Research 20, nr 9 (wrzesień 2005): 2562–67. http://dx.doi.org/10.1557/jmr.2005.0322.

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Polymorphous Si is a nanostructured form of hydrogenated amorphous Si that contains a small fraction of Si nanocrystals or clusters. Its thermally induced transformations such as relaxation, dehydrogenation, and crystallization have been studied by calorimetry and evolved gas analysis as a complementary technique. The observed behavior has been compared to that of conventional hydrogenated amorphous Si and amorphous Si nanoparticles. In the temperature range of our experiments (650–700 °C), crystallization takes place at almost the same temperature in polymorphous and in amorphous Si. In contrast, dehydrogenation processes reflect the presence of different hydrogen states. The calorimetry and evolved gas analysis thermograms clearly show that polymorphous Si shares hydrogen states of both amorphous Si and Si nanoparticles. Finally, the total energy of the main Si–H group present in polymorphous Si has been quantified.

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CHEN, C. Y., W. D. CHEN, S. F. SONG i C. C. HSU. "CORRELATION BETWEEN Er3+ EMISSION AND THE MICROSTRUCTURE OF A-SiOx:H FILMS". International Journal of Modern Physics B 16, nr 28n29 (20.11.2002): 4246–49. http://dx.doi.org/10.1142/s0217979202015182.

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Photoluminescence (PL) from Er-implanted hydrogenated amorphous silicon suboxide ( a - SiO X : H 〈 Er 〉( x <2.0)) films was measured. Two luminescence bands with maxima at λ ≅ 750 nm and λ ≅ 1.54μ m, ascribed to the a - SiO x : H intrinsic emission and Er 3+ emission, were observed. Peak intensities of the two bands follow the same trend as a function of annealing temperature from 300 to 1000°C. Micro-Raman results indicate that the a - SiO x : H < Er > films are a mixture of two phases, an amorphous SiO x matrix and amorphous silicon (a-Si) domains embedded there in. FTIR spectra confirm that hydrogen effusion from a - SiO x : H < Er > films occurs during annealing. Hydrogen effusion leads to a reconstruction of the microstructure of a-Si domains, thus having a strong influence on Er 3+ emission. Our study emphasizes the role of a-Si domains on Er 3+ emission in a - SiO x : H < Er > films.

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Follstaedt, D. M., J. A. Knapp i S. M. Myers. "Mechanical properties of ion-implanted amorphous silicon". Journal of Materials Research 19, nr 1 (styczeń 2004): 338–46. http://dx.doi.org/10.1557/jmr.2004.19.1.338.

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We used nanoindentation coupled with finite element modeling to determine the mechanical properties of amorphous Si layers formed by self-ion implantation of crystalline Si at approximately 100 K. When the effects of the harder substrate on the response of the layers to indentation were accounted for, the amorphous phase was found to have a Young’s modulus of 136 ± 9 GPa and a hardness of 10.9 ± 0.9 GPa, which were 19% and 10% lower than the corresponding values for crystalline Si. The hardness agrees well with the pressure known to induce a phase transition in amorphous Si to the denser β–Sn-type structure of Si. This transition controls the yielding of amorphous Si under compressive stress during indentation, just as it does in crystalline Si. After annealing 1 h at 500 °C to relax the amorphous structure, the corresponding values increase slightly to 146 ± 9 GPa and 11.6 ± 1.0 GPa. Because hardness and elastic modulus are only moderately reduced with respect to crystalline Si, amorphous Si may be a useful alternative material for components in Si-based microelectromechanical systems if other improved properties are needed, such as increased fracture toughness.

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LIM, P. K., i W. K. TAM. "LOCAL VIBRATIONAL MODES AND THE OPTICAL ABSORPTION TAIL OF AMORPHOUS SILICON". International Journal of Modern Physics B 20, nr 25n27 (30.10.2006): 4261–66. http://dx.doi.org/10.1142/s0217979206041197.

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Local vibrational modes of Si - H is an important research area in recent years. Local vibrational modes of chemical bonds between Si atom and other impurity atoms such as H and O in amorphous silicon films produced by radio frequency sputtering were studied by means of Fourier transform infrared spectroscopy. The concentrations of Si - H , Si - O and Si - C in the sample were calculated. It was found that the concentration of Si - H bond varied significantly when the material was annealed at temperatures Ta >600 K and tended to zero for Ta >1000 K . The optical absorption edge was also found to depend strongly on the thermal history of the amorphous semiconductor. A strong correlation between the optical absorption coefficient and the concentration of Si - H was also observed.

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Wang, Sheng Zhao, Ying Peng Yin, Chun Juan Nan i Ming Ji Shi. "Influence of Substrate on μc-Si: H Thin Films". Key Engineering Materials 538 (styczeń 2013): 169–72. http://dx.doi.org/10.4028/www.scientific.net/kem.538.169.

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By PECVD deposition technology, we mainly investigated the influence of substrate on intrinsic amorphous/microcrystalline silicon thin film prepared at 300°C. We study the crystallization ratio, grain size of the silicon thin film specially. The results reveal that the crystallization ratio and grain size of the silicon thin film changed along with different substrates. The silicon thin film crystallization ratio and grain size changed sharply when using glass and stainless steel substrate. On this work we think ideal μc-Si:H can be obtained by using glass as substrate and in the suitable experimental conditions.

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Leila, Ayat, Meftah Afek, Idda Ahmed i Zebri Halima. "Analysis and Optimization of the Performance of Hydrogenated Amorphous Silicon Solar Cell". Journal of New Materials for Electrochemical Systems 24, nr 3 (30.09.2021): 151–58. http://dx.doi.org/10.14447/jnmes.v24i3.a02.

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As the name implies, hydrogenated amorphous silicon (a-Si: H) is composed of silicon atoms which are in a disordered configuration away from all Bravais lattices. The hydrogenated amorphous silicon was manufactured in 1969 where there was a renewed interest in non-hydrogenated amorphous silicon. The use of hydrogenated amorphous silicon as the active material in solar cells inefficient but cheap, is currently much studied. We have presented in this work, the results of the numerical simulation of a-Si: H solar cell by the wxAMPS (Analysis of Microelectronic and Photonic Structures) software and the results were compared with those found experimentally, we find a good agreement. For the efficiency there was a difference of 0.17%. We also study the influence of the thickness of a-Si: H intrinsic layer on the photovoltaic parameters of the solar cell. This allows considering the use of amorphous thinner layers for photovoltaic applications. The efficiency has a maximum value of 7.117 %, corresponding to a intrinsic layer thickness of 560 nm. The using a-Si:H alloys provide a good solution to enhance a-Si:H solar cell performance. The use of a-SiC:H as a p-type window layer in amorphous silicon solar cells is one of its primary photovoltaic applications. The wide band gap of p-a-SiC:H alloy used as window layer for minimizing the optical loss. To improve the efficiency of a-Si:H solar cell, we have study by simulation the performance of the (p) a-SiC:H/(i) a-Si:H/ (n) a-Si:H heterojunction solar cell. The effects of a-SiC:H window layer on the photovoltaic performance have been investigated, where the best initial conversion efficiency of 10.59%.

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Sun, Jia Xin, Bing Qing Zhou i Xin Gu. "Preparation and Spectrial Studies of Silicon Nitride Thin Films Containing Amorphous Silicon Quantum Dots". Solid State Phenomena 323 (30.08.2021): 48–55. http://dx.doi.org/10.4028/www.scientific.net/ssp.323.48.

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Silicon-rich silicon nitride thin films are prepared on P-type monocrystalline silicon wafer (100) and glass substrate by plasma chemical vapor deposition with reaction gas sources SiH4 and NH3. The deposited samples are thermally annealed from 600°C to 1000°C in an atmosphere furnace filled with high purity nitrogen. The annealing time is 60 minutes. Fourier transform infrared spectroscopy (FTIR) is carried out to investigate the bonding configurations in the films. The results show that the Si-H bond and N-H bond decrease with the increase of annealing temperature, and completely disappear at the annealing temperature of 900°C. But the Si-N bond is enhanced with the increase of annealing temperature, and the blue shift occurs, then Si content in the film increases. The Raman Spectra show that the amorphous Si Raman peak appears at 480 cm-1 in the film at 700°C. The Raman spectra of the films annealed at 1000 °C is fitted with two peaks, and a peak at 497 cm -1 is found, which indicated that the Si phase in the films changed from amorphous to crystalline with the increase of annealing temperature. The experiment also analyses the luminescence properties of the samples through PL spectrum, and it is found that there are five luminescence peaks in each sample under different annealing temperature. Based on the analysis of Raman spectrum and FTIR spectrum, the PL peak of amorphous silicon quantum dots appears at the wavelength range of 525-555nm, and the other four PL peaks are all from the defect state luminescence in the thin films, and the amorphous silicon quantum dot size is calculated according to the formula.

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Денисова, К. Н., А. С. Ильин, М. Н. Мартышов i А. С. Воронцов. "Влияние легирования на свойства аморфного гидрогенизированного кремния, облученного фемтосекундными лазерными импульсами". Физика твердого тела 60, nr 4 (2018): 637. http://dx.doi.org/10.21883/ftt.2018.04.45669.034.

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AbstractA comparative analysis of the effect of femtosecond laser irradiation on the structure and conductivity of undoped and boron-doped hydrogenated amorphous silicon ( a -Si: H) is performed. It is demonstrated that the process of nanocrystal formation in the amorphous matrix under femtosecond laser irradiation is initiated at lower laser energy densities in undoped a -Si: H samples. The differences in conductivity between undoped and doped a -Si: H samples vanish almost completely after irradiation with an energy density of 150–160 mJ/cm^2.

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Iwase, Yoshiaki, Teruaki Fuchigami, Yoji Horie, Yusuke Daiko, Sawao Honda i Yuji Iwamoto. "Formation and Thermal Behaviors of Ternary Silicon Oxycarbides derived from Silsesquioxane Derivatives". Materials 12, nr 10 (27.05.2019): 1721. http://dx.doi.org/10.3390/ma12101721.

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Silsesquioxane (SQ) derivatives possessing intramolecular H2C = CH- groups and Si-H groups were designed as precursors for ternary silicon oxycarbide (SiOC). By using R-Si(OMe)3, H-Si(OEt)3 and (H-Si(Me)2)2O as starting compounds, SQ derivatives of VH-SQ (R = vinyl) and St-H-SQ (R = stylyl) were successfully synthesized through the conventional sol-gel route. Simultaneous thermogravimetric and mass spectroscopic analyses up to 1000 °C revealed that in situ cross-linking via hydrosilylation and demethanation of VH-SQ suppressed the evolution of gaseous hydrocarbon species to afford amorphous SiOC having a composition close to the desired stoichiometric SiO2(1−x)Cx (x = ca. 0.3) with a high yield. The effect of carbon content on the phase separation and crystallization of the SQ-derived amorphous SiOC was studied by several spectroscopic analyses and TEM observation. The results were discussed aiming to develop a novel polymer-derived ceramics (PDCs) route for in situ formation of binary β-SiC-amorphous SiO2 nanocomposites with enhanced thermal and mechanical stability.

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Kato, Shinya, Yasuyoshi Kurokawa, Kazuhiro Gotoh i Tetsuo Soga. "Fabrication of a Silicon Nanowire Solar Cell on a Silicon-on-Insulator Substrate". Applied Sciences 9, nr 5 (26.02.2019): 818. http://dx.doi.org/10.3390/app9050818.

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This study proposes metal-assisted chemical etching (MAE) as a facile method to fabricate silicon nanowire (SiNW) array structures, with high optical confinement for thin crystalline silicon solar cells. Conventional SiNW arrays are generally fabricated on Si wafer substrates. However, tests on conventional SiNW-based solar cells cannot determine whether the photo-current is derived from SiNWs or from the Si wafer. Herein, SiNW arrays were fabricated on a silicon-on-insulator substrate with a 10-μm-thick silicon layer for measuring the photocurrent of the SiNW only. The 9 μm-long p-type SiNW arrays were applied to a solar cell structure fabricated using an n-type H-doped amorphous Si layer, thereby confirming the photovoltaic effect. However, the device exhibited a conversion efficiency of 0.0017% because of a low short-circuit current (Jsc) and a low open-circuit voltage (Voc). The low Jsc resulted from a high series resistance and high absorption loss from the amorphous Si layer, whereas the low Voc resulted from the high surface recombination velocity of the SiNW array structure. Therefore, reducing the surface recombination of SiNW-based solar cells can improve their conversion efficiency.

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Shim, Jae Hyun, Nam Hee Cho, Y. J. Kim, Chin Myung Whang, Won Seung Cho, Yeon Chul Yoo, J. G. Kim i Young Jae Kwon. "Nanostructural and Optical Features of nc-Si:H Thin Films Prepared by Plasma Enhanced Chemical Vapor Deposition Techniques". Materials Science Forum 510-511 (marzec 2006): 962–65. http://dx.doi.org/10.4028/www.scientific.net/msf.510-511.962.

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The nanostructural and optical features of hydrogenated nanocrystalline silicon (nc-Si:H) thin films, which were prepared by plasma enhanced chemical vapor deposition (PECVD), were investigated as a function of deposition conditions. It was found that the crystallite size varied with the relative fraction of Si-H3 bonds in the films, [ ] eger n n n H Si H Si int 3 1 3 / ] [ = = ∑ − − , which was sensitively related with the flow rate of SiH4 reaction gas. The silicon nanocrystallites in the films enlarged from ~2.0 to ~8.0 nm in their size with increasing gas flow rate, while the PL emission energy varied from 2.5 to 1.8 eV; the relative fractions of the Si-H3, Si-H2, and Si-H bonds in the amorphous matrix were also varied sensitively with the SiH4 flow rate. A model for the nanostructure of the nc-Si:H films was suggested to discribe the variations in the size and chemical bonds of the nanocrystallites as well as the amorphous matrix depending on the deposition conditions.

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KAPOOR, MANISH, i VIJAY A. SINGH. "A PHENOMENOLOGICAL STUDY OF THE Si–H INFRARED SPECTRA IN POROUS AND AMORPHOUS SILICON". Modern Physics Letters B 13, nr 20 (30.08.1999): 703–8. http://dx.doi.org/10.1142/s0217984999000889.

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It is observed that Si–H stretching mode vibrational spectra in porous silicon and in hydrogenated amorphous silicon: (i) is broad with a full width at half maxima of ≈20-40 cm -1; (ii) has a long low energy tail; and (iii) has a peak value shifted by 100 cm -1 from 2000 cm -1 (crystalline silicon case) to 2100 cm -1. We propose a simple phenomenological model to account for the above features. The model invokes a narrow distribution in the Si–H bond distances. The first feature namely the broadening can be satisfactorily explained. Although our model yields a low energy tail, it is not as pronounced as the experimental tail. Our model can be shown to be consistent with the third feature, namely the peak shift.

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Rella, C. W., M. van der Voort, A. V. Akimov, A. F. G. van der Meer i J. I. Dijkhuis. "Localization of the Si–H stretch vibration in amorphous silicon". Applied Physics Letters 75, nr 19 (8.11.1999): 2945–47. http://dx.doi.org/10.1063/1.125196.

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Chen, Lan Li, Jia Hui Yu, Sheng Zhao Wang i Ming Ji Shi. "Influence of Hydrogen Dilution on Microstructure of μc-Si: H Films". Key Engineering Materials 538 (styczeń 2013): 138–41. http://dx.doi.org/10.4028/www.scientific.net/kem.538.138.

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The influence of hydrogen dilution (D) on glass/stainless steel-based intrinsic amorphous/microcrystalline silicon thin film prepared was investigated by PECVD technology. The crystallization ratio and grain size of the silicon thin film at different hydrogen dilution is studied. The results reveal that the crystallization ratio and grain size of silicon thin film changed along with D. The crystallization ratio and grain size of the silicon thin film become larger when D is higher. However, the deposition rate is slow when the D value is too high. On this work, optimal μc-Si:H can be obtained at D of about 98% in the suitable experimental conditions.

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Cazako, Catheline, Karim Inal, Alain Burr, Frederic Georgi i Rodolphe Cauro. "Hypothetic impact of chemical bonding on the moisture resistance of amorphous SixNyHz by plasma-enhanced chemical vapor deposition". Metallurgical Research & Technology 115, nr 4 (2018): 406. http://dx.doi.org/10.1051/metal/2018072.

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The relationship between the microstructure of silicon nitride and its sensitivity to moisture was studied. The effectiveness of Si-H rich and N-H rich silicon nitride layers was measured under attack from water in vapor and liquid states. For water vapor attack, samples are exposed to vapor at 85 °C with a relative humidity of 85% during 1600 hours; for liquid water attack, samples are dipped in water at 60, 85 and 100 °C for 200 hours. The water resistance of the Si-H rich and N-H rich silicon nitride layers was evaluated by measuring: (i) the thickness of the silicon dioxide formed after their oxidation with water vapor, (ii) the rate of dissolution of the silicon nitride in liquid water and (iii) the corresponding activation of energy. This evaluation was performed by coupling spectroscopic ellipsometry, infra-red and X-ray photoelectron spectrometry analyses. The results revealed that for Si-H rich layer, 10 nm of silicon dioxide was formed during the water vapor attack; for liquid water attack, a high activation energy (0.88 eV) and a low dissolution rate were observed regardless of the water temperature. For N-H rich layers, approximatively 6–8 nm of silicon dioxide was formed and a low activation energy (0.64 eV) with a high dissolution rate were observed. All of these observations lead to the conclusion that the N-H rich layers could be less resistant to moisture because the isoelectronic relationship between Si2N-H and −H2O+ facilitated their deterioration in water. Moreover, a higher rate of nanoporosity for N-H rich layers than Si-H rich layer could complete this hypothesis.

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HAMMAM, M. "PREPARATION AND CHARACTERIZATION OF GRADED BANDGAP AMORPHOUS HYDROGENATED SILICON-SULFUR THIN FILMS". Modern Physics Letters B 06, nr 08 (10.04.1992): 469–75. http://dx.doi.org/10.1142/s0217984992000545.

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Compositionally graded hydrogenated amorphous silicon-sulfur alloys ( a-Si 1−x S x: H ) were grown by RF glow discharge decomposition of silane and hydrogen sulfide gases. Infrared spectra show clear evidence for the incorporation of sulfur in the form of Si-S bonds in the material. The graded bandgap films possess optical bandgaps ranging from 1.91 to 2.05 eV depending on the RF power. The compositionally graded layers display high photosensitivities indicating that they may be ideal candidates for use in amorphous silicon based tandem cells.

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Ponomarev, Ilia, i Peter Kroll. "29Si NMR Chemical Shifts in Crystalline and Amorphous Silicon Nitrides". Materials 11, nr 9 (7.09.2018): 1646. http://dx.doi.org/10.3390/ma11091646.

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We investigate 29Si nuclear magnetic resonance (NMR) chemical shifts, δiso, of silicon nitride. Our goal is to relate the local structure to the NMR signal and, thus, provide the means to extract more information from the experimental 29Si NMR spectra in this family of compounds. We apply structural modeling and the gauge-included projector augmented wave (GIPAW) method within density functional theory (DFT) calculations. Our models comprise known and hypothetical crystalline Si3N4, as well as amorphous Si3N4 structures. We find good agreement with available experimental 29Si NMR data for tetrahedral Si[4] and octahedral Si[6] in crystalline Si3N4, predict the chemical shift of a trigonal-bipyramidal Si[5] to be about −120 ppm, and quantify the impact of Si-N bond lengths on 29Si δiso. We show through computations that experimental 29Si NMR data indicates that silicon dicarbodiimide, Si(NCN)2 exhibits bent Si-N-C units with angles of about 143° in its structure. A detailed investigation of amorphous silicon nitride shows that an observed peak asymmetry relates to the proximity of a fifth N neighbor in non-bonding distance between 2.5 and 2.8 Å to Si. We reveal the impact of both Si-N(H)-Si bond angle and Si-N bond length on 29Si δiso in hydrogenated silicon nitride structure, silicon diimide Si(NH)2.

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KEFFOUS, AISSA, ABDELHAK CHERIET, YOUCEF BELKACEM, AMAR MANSERI, NOUREDDINE GABOUZE, MOHAMED KECHOUANE, AMER BRIGHET i in. "INVESTIGATION PROPERTIES OF a-Si1-xCx:H FILMS ELABORATED BY CO-SPUTTERING OF Si AND 6H-SiC". Modern Physics Letters B 24, nr 19 (30.07.2010): 2101–12. http://dx.doi.org/10.1142/s0217984910024262.

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Hydrogenated amorphous SiC films ( a - Si 1-x C x: H ) were prepared by DC magnetron sputtering technique on p type Si (100) and corning 9075 substrates at low temperature, by using 32 sprigs of silicon carbide (6 H - SiC ). The deposited film a - Si 1-x C x: H was realized under a mixture of argon and hydrogen gases. The ( a - Si 1-x C x: H ) films have been investigated by scanning electronic microscopy equipped with EDS system (SEM-EDS), X-rays diffraction (XRD), secondary ions mass spectrometry (SIMS), Fourier transform infrared spectroscopy (FTIR), UV-visible-IR spectrophotometry, and photoluminescence (PL). XRD results showed that the deposited film was amorphous with a structure of a - Si 0.81 C 0.19: H corresponding to 19 at.% carbon. The photoluminescence response of the samples was observed in the visible range at room temperature with two peaks centered at 463 nm (2.68 eV) and 542 nm (2.29 eV). The structural properties and the origin of the luminescence were discussed.

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Bugaev, Kirill O., Anastasia A. Zelenina i Vladimir A. Volodin. "Vibrational Spectroscopy of Chemical Species in Silicon and Silicon-Rich Nitride Thin Films". International Journal of Spectroscopy 2012 (2.10.2012): 1–5. http://dx.doi.org/10.1155/2012/281851.

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

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LEOY, C. C., EWH KAN, J. ARIANTO, W. K. CHOI, A. T. S. WEE i Y. J. LIU. "OXIDATION STUDY OF RF SPUTTERED AMORPHOUS AND POLYCRYSTALLINE SILICON GERMANIUM FILMS". International Journal of Modern Physics B 16, nr 28n29 (20.11.2002): 4224–27. http://dx.doi.org/10.1142/s0217979202015133.

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Oxidation study of rf sputtered amorphous and polycrystalline silicon germanium ( Si 1-x Ge x ) film which was conducted using infrared spectroscopy (FTIR). The oxidation results showed linear oxidation rate of amorphous Si 1-x Ge x and polycrystalline Si 1-x Ge x films in the dry oxygen ambient did not depend on the Ge concentration. We found that Ge nanocrystals were formed from mixed ( Si , Ge ) O 2 oxides when annealed in forming gas (10% H 2 + N 2) while pure N 2 showed formation of Ge clusters.

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Zamchiy, Alexandr, Evgeniy Baranov, Sergey Khmel i Marat Sharafutdinov. "Effect of annealing time on aluminum-induced crystallization of silicon suboxide thin films". EPJ Web of Conferences 196 (2019): 00039. http://dx.doi.org/10.1051/epjconf/201919600039.

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Polycrystalline silicon (poly-Si) thin films were obtained by aluminium induced crystallisation of amorphous silicon suboxide (a-SiOx, x = 0.22) via annealing of a-SiO0.22/Al bilayer structures at 550 °C for 4 - 30 h. The a-SiO0.22/Al thickness ratio was approximately 1. According optical microscopy measurements, the crystallized fraction reached the saturation value of 85% after annealing for 20 h. The further increase in the annealing time didn’t lead to an increase in this value. X-ray diffraction measurements revealed that the formed poly-Si had a strong Si (111) preferred orientation.

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Gat, E., M. A. El Khakani, M. Chaker, A. Jean, S. Boily, H. Pépin, J. C. Kieffer i in. "A study of the effect of composition on the microstructural evolution of a–SixC1−x: H PECVD films: IR absorption and XPS characterizations". Journal of Materials Research 7, nr 9 (wrzesień 1992): 2478–87. http://dx.doi.org/10.1557/jmr.1992.2478.

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Amorphous silicon carbide films (a–SixC1−x :H) deposited by the argon- or helium-diluted PECVD technique were studied as a function of their composition. Microstructural investigations were mainly achieved by means of FTIR and XPS techniques. Nuclear techniques were used to obtain precise information on the film hydrogen content. The Si–H IR-absorption band was deconvoluted in different monohydride and dihydride silicon environments. The existence of SiH2 bonds in the Si-rich composition was evidenced. From the analysis of the C–H and Si–H absorption bands it is shown that hydrogen atoms are preferentially bonded to carbon atoms. The deconvolution of the Si2p core level peak suggests that above a composition of x ∊ 0.5, the noncarburized (Si, Si, H) local environment contribution increases to the detriment of the hydrocarburized (Si, C, H) environments. From the evolution of the C1s peak, it can be deduced that there is a change in the carbon atom bonding states when the film composition is varied. These results are correlated and discussed in terms of the local bonding environments and their evolution with film composition.

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Son, Won-Ho, M. Siva Pratap Reddy i Sie-Young Choi. "Hydrogenated amorphous silicon thin film solar cell with buffer layer of DNA-CTMA biopolymer". Modern Physics Letters B 28, nr 13 (30.05.2014): 1450107. http://dx.doi.org/10.1142/s0217984914501073.

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The characteristics of nip-type a- Si : H thin film solar cells based on DNA-CTMA biopolymer was investigated. The DNA-CTMA was used as the buffer layer in nip-type a- Si : H solar cell. The E opt of the DNA-CTMA biopolymer was measured with UV-VIS spectrometer. The E opt of DNA-CTMA was determined as 3.96 eV by the plot of (Ahν)2 versus hν. All films of amorphous materials were deposited by PECVD method. The solar cell with a simple structure of glass/ITO/n-a- Si : H /i-a- Si : H /p-a- Si : H /DNA-CTMA/ Al was fabricated. The various values of V oc , J sc , FF , and conversion efficiency η were measured under 100 mW/cm2 (AM 1.5) solar simulator irradiation. Consequently, the resulting in solar cell showed an enhancement in conversion efficiency η compared to conventional nip-type a- Si : H solar cell without buffer layer of DNA-CTMA biopolymer.

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Kamaev, Gennadiy, Mikhail Efremov, Aleksandr Antonenko, Vladimir Volodin, Sofia Arzhannikova, Denis Marin i Andrey Gismatulin. "Creation of Nanoperiodical Multilayer Si/SiO2 Structures in Plasma-Chemical Reactor of Induction Type and Their Properties". Siberian Journal of Physics 6, nr 4 (1.12.2011): 107–14. http://dx.doi.org/10.54362/1818-7919-2011-6-4-107-114.

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Multilayer structures with extra-thin SiO2 and hydrogenated amorphous silicon (a-Si: H) layers were created and investigated. Structures were obtained using cycles of deposition of the films α-Si: H and their subsequent partial oxidation in oxygen plasma. Properties of the structures were investigated by electron microscopy, Raman spectroscopy, photoluminescence techniques and by measurements of their electrical characteristics

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Heyne, Markus H., Jean-François de Marneffe, Thomas Nuytten, Johan Meersschaut, Thierry Conard, Matty Caymax, Iuliana Radu, Annelies Delabie, Erik C. Neyts i Stefan De Gendt. "The conversion mechanism of amorphous silicon to stoichiometric WS2". Journal of Materials Chemistry C 6, nr 15 (2018): 4122–30. http://dx.doi.org/10.1039/c8tc00760h.

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Oheda, Hidetoshi. "Real-time modulation of Si-H vibration in hydrogenated amorphous silicon". Physical Review B 60, nr 24 (15.12.1999): 16531–42. http://dx.doi.org/10.1103/physrevb.60.16531.

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Gong, Dao Ren, Dong Sheng Li, Zhi Zhong Yuan i De Ren Yang. "Reaction of Iron with Amorphous Silicon and Crystal Silicon for the Fabrication of Iron Silicides". Defect and Diffusion Forum 272 (marzec 2008): 99–106. http://dx.doi.org/10.4028/www.scientific.net/ddf.272.99.

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Iron silicide films with two different structures were fabricated by electron beam evaporation (EBE) technique. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscope (SEM) were carried out to describe the characteristics and structures of the films. It was found that after annealing at 800oC for 5 h, the β-FeSi2 film formed in the sample with the structure of Si/Fe film on silicon substrate, while only FeSi film generated in the sample with the structure of Si/Fe/Si films on silicon substrate. It is considered that the different iron silicides may be due to the different reaction of iron with crystal silicon or amorphous silicon, which is related to diffusion of iron or silicon atoms.

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29

Zyubin, A. S., i S. A. Dembovsky. "Quantum chemical modelling of three-centre Si-H-Si bonds in amorphous hydrogenated silicon". Solid State Communications 87, nr 3 (lipiec 1993): 175–78. http://dx.doi.org/10.1016/0038-1098(93)90470-8.

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El Khakani, M. A., M. Chaker, A. Jean, S. Boily, J. C. Kieffer, M. E. O'Hern, M. F. Ravet i F. Rousseaux. "Hardness and Young's modulus of amorphous a-SiC thin films determined by nanoindentation and bulge tests". Journal of Materials Research 9, nr 1 (styczeń 1994): 96–103. http://dx.doi.org/10.1557/jmr.1994.0096.

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Due to its interesting mechanical properties, silicon carbide is an excellent material for many applications. In this paper, we report on the mechanical properties of amorphous hydrogenated or hydrogen-free silicon carbide thin films deposited by using different deposition techniques, namely plasma enhanced chemical vapor deposition (PECVD), laser ablation deposition (LAD), and triode sputtering deposition (TSD). a-SixC1−x: H PECVD, a-SiC LAD, and a-SiC TSD thin films and corresponding free-standing membranes were mechanically investigated by using nanoindentation and bulge techniques, respectively. Hardness (H), Young's modulus (E), and Poisson's ratio (v) of the studied silicon carbide thin films were determined. It is shown that for hydrogenated a-SixC1−x: H PECVD films, both hardness and Young's modulus are dependent on the film composition. The nearly stoichiometric a-SiC: H films present higher H and E values than the Si-rich a-SixC1−x: H films. For hydrogen-free a-SiC films, the hardness and Young's modulus were as high as about 30 GPa and 240 GPa, respectively. Hydrogen-free a-SiC films present both hardness and Young's modulus values higher by about 50% than those of hydrogenated a-SiC: H PECVD films. By using the FTIR absorption spectroscopy, we estimated the Si-C bond densities (NSiC) from the Si-C stretching absorption band (centered around 780 cm−1), and were thus able to correlate the observed mechanical behavior of a-SiC films to their microstructure. We indeed point out a constant-plus-linear variation of the hardness and Young's modulus upon the Si-C bond density, over the NSiC investigated range [(4–18) × 1022 bond · cm−3], regardless of the film composition or the deposition technique.

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31

Jo, Seungil, Hyunsoo Kim i Nae-Man Park. "Snow-Ice-Inspired Approach for Growth of Amorphous Silicon Nanotips". Nanomaterials 9, nr 5 (2.05.2019): 680. http://dx.doi.org/10.3390/nano9050680.

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The growth of one-dimensional nanostructures without a metal catalyst via a simple solution method is of considerable interest due to its practical applications. In this study, the growth of amorphous silicon (a-Si) nanotips was investigated using an aqueous solution dropped onto the Si substrate, followed by drying at room temperature or below for 24 h, resulting in the formation of a-Si nanotips on the Si substrate. Typically, the a-Si nanotips were up to 1.6 μm long, with average top and middle diameters of 30 and 80 nm, respectively, and contained no metal catalyst in their structure. The growth of a-Si nanotips can be explained in terms of the liquid–solid mechanism, where the supercritical Si solution (liquid) generated on the Si substrate (after reaction with the aqueous solution) promotes the nucleation of solid Si (acting as seeds) on the roughened surface, followed by surface diffusion of Si atoms along the side wall of the Si seeds. This is very similar to the phenomenon observed in the growth of snow ice crystals in nature. When photoexcited at 265 nm, the a-Si nanotips showed blue luminescence at around 435 nm (2.85 eV), indicating feasible applicability of the nanotips in optoelectronic functional devices.

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32

SHI, J., E. F. CHOR i W. K. CHOI. "ICP ETCHING OF RF SPUTTERED AND PECVD SILICON CARBIDE FILMS". International Journal of Modern Physics B 16, nr 06n07 (20.03.2002): 1067–71. http://dx.doi.org/10.1142/s0217979202010877.

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In this paper, we report the Inductive Coupled Plasma (ICP) etching of RF sputtered unhydrogenated amorphous silicon carbide film (a-Si0.5C0.5) , and plasma enhanced chemical vapour deposited (PECVD) hydrogenated amorphous silicon carbide films (a-Si0.3C0.7:H and a-Si0.7C0.3:H) , asprepared and annealed, using CF4/O2 chemistry. The etch rate of amorphous SiC is observed to be closely related to the hydrogen content. The mechanism of etching is studied by varying the RIE power, ICP power and pressure. It has been suggested that the removal of surface polymers (CFx) is a key factor in the etching process. In order to study the difference in etch rate between sputtered and PECVD SiC and the effects of changing Si/C ratio, IR spectra are used to reveal the bonds density in the samples.

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Talbi, Mourad, Nawel Mensia, Jassem Arfaoui i Abdelmajid Zairi. "Modelling of Novel Architecture of PV Generator Based on a-Si: H/c-Si Materials and Using Solar Tracker for Partial Shading". Light & Engineering, nr 05-2022 (październik 2022): 92–97. http://dx.doi.org/10.33383/2021-085.

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The purpose of this study is to investigate the shading effect on a novel architecture of photovoltaic generator (PVG) proposed in this paper. This architecture consists of three photovoltaic (PV) modules in series connected. Two of them consist of amorphous silicon cells in series connected. The third module consists of monocrystalline silicon cells in series connected. This architecture is conceived as a PV concentrator, where the two amorphous PV modules are located in the lower position, and the third one is located in the upper position precisely in the focus. The role of the upper module is to absorb the solar rays, which are reflected by the two other modules to gain the maximum of solar energy. This novel architecture is aimed at solving the problems existing with the architecture of tandem solar cells proposed in literature. Those problems are the mismatch between cells and the tunnel junction costs and fabrication. In this work, we use MATLAB/Simulink for modelling this architecture and studying its characteristics (I–V and P–V) in case of partial shading. Through this study, it was found that the maximum PV power is affected by the partial shading. To solve this problem, we have implemented in this work a solar tracker.

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Klaumünzer, S., M. Rammensee, S. Löffler, H. C. Neitzert i G. Saemann-Ischenko. "Cavity formation and plastic flow of a–Si: H during heavy ion bombardment". Journal of Materials Research 6, nr 10 (październik 1991): 2109–19. http://dx.doi.org/10.1557/jmr.1991.2109.

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Irradiation of unsupported samples of hydrogenated amorphous silicon below 100 K with 360-MeV Xe ions results in macroscopically visible changes in sample dimensions. These changes have two different causes. Formation and growth of cavities lead to an isotropic increase of the specimen dimensions and to a drastic decrease of the mass density. Simultaneously plastic flow occurs, which produces additional but anisotropic changes of the specimen dimensions. The dimensions perpendicular to the beam grow whereas the dimension parallel to the ion beam shrinks. Neither effect saturates in the investigated fluence range (Φt < 1014 Xe/cm2) and both are absent in crystalline silicon. The effects are most likely provoked by electronic excitations and/or ionizations in the wake of the fast ions. With respect to plastic flow, a–Si:H behaves like metallic and oxide glasses. Formation of cavities and their growth, however, seem to occur only in tetrahedrally coordinated solids.

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Лунев, Н. А., А. О. Замчий, Е. А. Баранов, И. Е. Меркулова, В. О. Константинов, И. В. Корольков, Е. А. Максимовский i В. А. Володин. "Золото-индуцированная кристаллизация тонких пленок аморфного субоксида кремния". Письма в журнал технической физики 47, nr 14 (2021): 35. http://dx.doi.org/10.21883/pjtf.2021.14.51185.18793.

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For the first time, polycrystalline silicon (poly-Si) was obtained as a result of the gold-induced crystallization of amorphous silicon suboxide (a-SiOx). It is shown that, during annealing of a sample with a “substrate/gold thin film/a-SiO0.2 thin film” structure at 335 ℃, poly-Si is formed in a bottom layer (on the substrate), while gold diffuses into the upper layer. With an increase in the temperature to 370 ℃, the mechanism of poly-Si formation remains unchanged, however, only the rate of the crystallization process increases. Apparently, the process of poly-Si formation proceeds through the formation of gold silicides, which almost completely decompose into crystalline phases of gold and silicon at 370 ℃ for 10 h.

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36

Nunomura, Shota, Takayoshi Tsutsumi, Kazuya Nakane, Aiko Sato, Isao Sakata i Masaru Hori. "Ion-induced interface defects in a-Si:H/c-Si heterojunction: possible roles and kinetics of hot mobile hydrogens". Japanese Journal of Applied Physics 61, nr 5 (1.05.2022): 056003. http://dx.doi.org/10.35848/1347-4065/ac5210.

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Abstract Interface defects in state-of-the-art semiconductors have a strong impact on device performance. These defects are often generated during device fabrication, in which a variety of plasma processing is used for deposition, etching and implantation. Here, we present the ion-induced defects in hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) heterojunction. The experiments of argon ion (Ar+) irradiation over an a-Si:H/c-Si stack are systematically performed. The results suggest that the defects are generated not only by the impact of Ar+ (i.e. well-known effects), but also by another unique effect associated with “hot” mobile hydrogens (H). The mobile H atoms generated near the a-Si:H surface by the impact of Ar+ diffuse deeper, and they generate the a-Si:H/c-Si interface defects such as dangling bonds. The diffusion length of mobile H is determined to be 2.7 ± 0.3 nm, which indicates efficient reactions of mobile H with weak bonds in an a-Si:H network structure.

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37

CHOI, W. K., C. C. LEOY i L. P. LEE. "INVESTIGATION ON OXIDE GROWTH MECHANISM OF PECVD SILICON CARBIDE FILMS". International Journal of Modern Physics B 16, nr 06n07 (20.03.2002): 1062–66. http://dx.doi.org/10.1142/s0217979202010865.

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The effect of the Si-C , Si-CH3 , C-Hn , Si-H and Si dangling bonds on the oxidation process was investigated by monitoring the changes of these bands as a function of oxidation temperature or duration using the infrared spectroscopy technique. We concluded that the activation energy obtained from the linear regime of the oxide growth is related to the C-Hn bonds. We suggested that most of the C-Hn bonds were bonded to Si with n = 3 , that gave rise to voids to facilitate the oxidation of amorphous silicon carbide films.

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38

Pérez, César B., i C. Reyes-Betanzo. "Stress Reduction of Amorphous Silicon Deposited by PECVD". MRS Proceedings 1812 (2016): 109–16. http://dx.doi.org/10.1557/opl.2016.26.

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ABSTRACTAmorphous silicon (α-Si) was deposited on glass substrates by PECVD at different deposition conditions in order to characterize the residual stress on the film. Subsequently, a thermal-annealing was applied for different times at 400 °C in a N2 atmosphere, aiming to reduce the stress in the films. The deposition power was between 15 and 30 W at 13.56 MHz, the pressure in the chamber was adjusted in a range from 600 to 900 mTorr, and the temperature was varied from 140 to 200 °C. The stress was determined by using the Stoney equation, measuring the curvature and thickness of the α-Si films with a stylus profilometer. A deposition rate between 7-24 nm/min was obtained, and the time for thermal-annealing needed to reduce the stress was reduced from 10 to 2-4 h, obtaining a minimum compressive stress of 17 MPa. With this value of stress, it was possible to use the α-Si as masking material for wet etching of glass during the manufacturing of microfluidic devices, in order to obtain microstructures in the glass with 150 μm in depth.

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39

Sidhu, L. S., T. Kosteski, N. P. Kherani, F. Gaspari, S. Zukotynski i W. Shmayda. "An Infrared and Luminescence Study of Tritiated Amorphous Silicon". MRS Proceedings 467 (1997). http://dx.doi.org/10.1557/proc-467-129.

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ABSTRACTTritium, has been incorporated into amorphous silicon. Infrared spectroscopy shows new infrared vibration modes due to silicon-tritium (Si-T) bonds in the amorphous silicon network. Si-T vibration frequencies are related to Si-H vibration frequencies by simple mass relationships. Inelastic collisions of β particles, produced as a result of tritium decay, with the amorphous silicon network results in the generation of electron-hob pairs. Radiative recombination of these carriers is observed. Dangling bonds associated with the tritium decay reduce luminescence efficiency.

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40

Scharff, R. Jason, i Shawn D. McGrane. "Si-H bond dynamics in hydrogenated amorphous silicon". Physical Review B 76, nr 5 (1.08.2007). http://dx.doi.org/10.1103/physrevb.76.054301.

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Branz, Howard M., i Eugene Iwaniczko. "Observation of Metastability in Amorphous Silicon Containing 0.1 at.% Hydrogen". MRS Proceedings 258 (1992). http://dx.doi.org/10.1557/proc-258-389.

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ABSTRACTWe observe reversible quenched-in metastability in the dark conductivity of extremely low-H-content amorphous silicon (a-Si). The sample is sputtered, P-implanted a-Si containing 0.1 at.% of H. Except for the high value of its equilibration temperature (T*), 355° ± 20°C, this metastability is similar to that observed in doped hydrogenated a-Si (a-Si:H). The ∼10 at.% H present in a-Si:H is not essential for a-Si metastability. After hydrogenation with about 10 at.% of H, T* falls to 175° ± 10°C. We propose that higher H content reduces T* by increasing Si network flexibility.

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42

Fujiwara, Hiroyuki, Michio Kondo i Akihisa Matsuda. "Effect of Strained Si-Si Bonds in Amorphous Silicon Incubation Layer on Microcrystalline Silicon Nucleation". MRS Proceedings 664 (2001). http://dx.doi.org/10.1557/proc-664-a1.2.

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ABSTRACTIn order to investigate microcrystalline silicon (μc-Si:H) nucleation from the hydrogenated amorphous silicon (a-Si:H) phase, we performed a H2-plasma treatment of a-Si:H layers deposited at different temperatures. In the H-treatment experiment, the formation process of an infrared peak at ∼1937 cm-1, assigned to SiHn (n=1∼2) complex, is studied, as the SiHn complex is proposed to be a precursor for the μc-Si:H nucleation. With increasing the a-Si:H deposition temperature, the total amount of the SiHn complex formed by the H treatment increased. Nucleation of μc-Si:H under high H2-dilution conditions showed a clear relationship with the SiHn complex formed by the H treatment. The SiHn complex formation process, in terms of strained Si-Si bond breaking by H, is discussed.

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43

Jiang, Lin, E. A. Schiff, F. Finger, P. Hapke, S. Koynov, R. Schwarz, N. Wyrsch, A. Shah, J. Yang i S. Guha. "Electroabsorption Spectra of Hydrogenated Amorphous and Microcrystalline Silicon". MRS Proceedings 467 (1997). http://dx.doi.org/10.1557/proc-467-295.

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ABSTRACTWe report on electroabsorption spectra for plasma deposited thin films of hydrogenated silicon ranging from amorphous (a-Si:H) to microcrystalline (μc-Si-H) structures. The EA spectrum of a-Si:H deposited from silane with low hydrogen dilution were consistent with previous works; material prepared with high hydrogen dilution showed a 0.07 eV blue shift of the spectrum and somewhat stronger electroabsorption. μc-Si-H specimens have a sharp peak at 1.19eV; the spectrum is blue shifted by 0.03 eV and is significantly stronger than electroabsorption reported in single crystal silicon. Spectral features which have no correspondence to single crystal silicon were also observed in μc-Si-H. Specimens deposited using “cyclic” deposition and chemical annealing had electroabsorption spectra with both the 1.19 eV, crystalline feature and a band peaking at 2.02 eV which we attribute to strongly hydrogenated a-Si:H. We discuss applications of electroabsorption to determining the crystal fraction of microcrystalline material and to determining grain size distributions.

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44

Biswas, R., B. C. Pan i V. Selvaraj. "Microcrystalline and Nanocrystalline Silicon: Simulation of Material Properties". MRS Proceedings 862 (2005). http://dx.doi.org/10.1557/proc-862-a24.3.

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AbstractWe have simulated nano-crystalline silicon and microcrystalline silicon structures with varying crystallite volume fractions, using molecular dynamics simulations. The crystallite regions reside in an amorphous matrix. We find the amorphous matrix is better ordered in nanocrystalline-Si than in the homogenous amorphous silicon networks, consistent with the observed higher stability of H-diluted films. There is a critical size above which the crystallites are stable and may grow. Sub-nm size crystallites in the protocrystalline phase are found to reduce the strain of the amorphous matrix. We simulated micro-crystalline silicon with a substantial crystallite volume fraction. Microcrystalline structures exhibit a crystalline core surrounded by an amorphous shell with similarities to silicon nanowires. We find a relatively uniform H distribution in the amorphous region and a crystal-amorphous phase boundary that is not welldefined.

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45

Li, Yupu, Shaw Wang, Xue-Feng Lin i Luncun Wei. "Characterization of Amorphous Silicon by Secondary Ion Mass Spectrometry". MRS Proceedings 862 (2005). http://dx.doi.org/10.1557/proc-862-a18.3.

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AbstractBased on various implanted standards, we have used SIMS (Secondary Ion Mass Spectrometry) to characterize amorphous Si thin films with high hydrogen content. SIMS and HFS (Hydrogen Forward Scattering) showed good agreement on the measured total H doses for H-implanted Si samples and the a-Si thin films. For the H-implanted Si samples, in the dose range of 2e15 atoms/cm2 to 2e17 atoms/cm2 (corresponding to peak H concentration from 0.32 at.% to 32 at.%), SIMS results showed that the calibration curve is a straight line. In other words, no correction for SIMS quantification is needed when moving from low to high hydrogen content samples. Analysis of P (Phosphorus) in a-Si thin films requires the use of high mass resolution magnetic sector SIMS to separate P and a mass interference from (30Si+H). Using a magnetic sector SIMS instrument, P-doped a-Si thin layers (˜ 50nm thick) were analyzed using 3keV O2 beam with oxygen leak for better depth resolution and improved detection limits. For the analysis of C, N, O in a-Si thin films (again approximately 50nm thick) the profiling energy typically needs to be lowered down to 3keV and the material needs to be sputtered at a high rate in order to reach real background levels. In this work, a-Si thin films were also analyzed using a 3keV Cs+ primary ion beam with (Cs2M)+ (M= C, N, O) detection for good depth resolution and detection limits.

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46

Biswas, R., Qiming Li, B. C. Pan i Y. Yoon. "Reactivity and Migration of Hydrogen in A-SI:H". MRS Proceedings 467 (1997). http://dx.doi.org/10.1557/proc-467-135.

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ABSTRACTTight-binding molecular dynamics calculations reveal a new mechanism for hydrogen diffusion in hydrogenated amorphous silicon. Hydrogen diffuses through the network by successively bonding with nearby silicon and breaking their Si-Si bonds. The diffusing hydrogen carries with it a newly created dangling bond. These intermediate transporting states are densely populated in the network and have lower energies than H at the center of stretched Si-Si bonds.

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47

Crandall, R. S., A. H. Mahan, E. Iwaniczko, K. M. Jones, X. Liu, B. E. White i R. O. Pohl. "New Results on the Microstructure of Amorphous Silicon as Observed by Internal Friction". MRS Proceedings 467 (1997). http://dx.doi.org/10.1557/proc-467-191.

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ABSTRACTWe have measured the low temperature internal friction (Q−1) of amorphous silicon (a-Si) films. Electron-beam evaporation leads to the well-known temperature-independent plateau common to all amorphous solids. For hydrogenated amorphous silicon (a-Si:H) with about 1 at.% H produced by hot wire chemical vapor deposition, however, the value of is over two hundred times smaller than for e-beam a-Si. This is the first observation of an amorphous solid without any significant low energy excitations. This finding offers the opportunity to study amorphous solids containing controlled densities of tunneling defects, and thus to explore their nature.

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48

Crandall, R. S., E. Iwaniczko, A. H. Mahan, X. Liu i R. O. Pohl. "Low Temperature Vibrational Properties of Amorphous Silicon". MRS Proceedings 507 (1998). http://dx.doi.org/10.1557/proc-507-585.

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ABSTRACTWe present internal friction and shear modulus measurements of amorphous silicon (a-Si) and germanium (a-Ge) films. The temperature independent plateau in internal friction below 10 K, common to all amorphous solids, also exists in these films. However, its magnitude which depends critically on the deposition method is smaller than found for all other amorphous solids. In particular, hydrogenated a-Si with about 1 at. % H prepared by hot-wire chemical-vapor-deposition leads to an internal friction nearly three orders of magnitude smaller than observed for all other amorphous solids. The internal friction increases after the hydrogen is removed by effusion.

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49

Choi, W. K., L. P. Lee i C. C. Leoy. "Oxidation study of hydrogenated amorphous silicon carbide films". MRS Proceedings 640 (2000). http://dx.doi.org/10.1557/proc-640-h5.15.

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ABSTRACTWe present results of an oxidation study of a-Si1−xCx:H films prepared by the plasma enhanced chemical vapor deposition of silane and acetylene. The composition (i.e. x) of the samples was determined by the flow rates of silane and acetylene. Oxidation was carried out at 400 to 850°C in dry oxygen ambient. The infrared (IR) spectra of the as-prepared films showed the intensity of the Si-C peak decreases and the Si-CH3 peak increases as x increases. The Si-H peak shifts to higher frequency as x increases. Note that the incorporation of CH3 radicals in a-Si1−xCx:H films has shown to introduce voids and increased the porosity of the films. The IR spectra of the oxidized samples showed clear Si-O stretching and rocking/wagging modes for all films. We suggest that the growth of oxide on a-Si1−xCx:H is a result of voids that facilitate the diffusion of oxidants into the film. We shown that the activation energy, obtained from the linear rate region of the oxide growth, was far less than the dissociation energies of the Si-Si, Si-C and Si-H bonds. We suggest that this could be due to the amorphous nature of the samples that caused the various chemical bonds to be weaker during oxidation.

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50

Sridhar, Nagarajan, D. D. L. Chung i W. A. Anderson. "Thermodynamics and Kinetics of Hydrogen Evolution in Hydrogenated Amorphous Silicon Films". MRS Proceedings 377 (1995). http://dx.doi.org/10.1557/proc-377-319.

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ABSTRACTThe enthalpy (endothermic) of hydrogen evolution from p-type (boron doped) amorphous silicon with 17 at. % H was 4.8, 10.3, 15.8 and 17.3 kJ/g, the evolution temperature was 585, 606, 625 and 644 °C and the entropy of evolution was 5.6, 11.7, 17.5 and 18.9 J/g.K at heating rates of 5, 10, 20 and 30 °C/min respectively. That the enthalpy and entropy increased with heating rate means that the evolution involves not only Si-H bond breaking, but also Si-Si bond breaking and other defect formation. The Si-Si bond breaking and defect formation were enhanced at high heating rates, which caused high rates of hydrogen evolution. For n-type (phosphorous-doped) and intrinsic amorphous silicon with 25 and 23 at. % H respectively, the enthalpy and entropy of hydrogen evolution were higher than the p-type case, due to severe defect formation resulting from the higher hydrogen content. The activation energy of hydrogen evolution was 1.38, 2.5 and 4 kJ/g for the p-type, intrinsic and n-type materials respectively. Crystallization which occurred at temperatures higher than hydrogen evolution, was delayed for the amorphous silicon film in a higher disordered state after hydrogen evolution, suggesting that hydrogen evolution influenced the crystallization process.

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