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On Nanometer Ordering in thin Amorphous Hydrogenated Silicon  [cached]
Jarmila Mullerova,Veronika Vavrunkova,Pavol Sutta
Advances in Electrical and Electronic Engineering , 2008,
Abstract: We investigated thin films of amorphous hydrogenated silicon (a-Si:H) deposited by PECVD under increasingdilutions of silane plasma by hydrogen. We found out that under increasing additional hydrogen at the depositions, thin filmsobtain less hydrogen bonded to silicon. The optical band gap energies determined from UV Vis transmittance and reflectancespectra were found to be increasing function of the dilution. We deduce that optical band gaps expanse due to the decreasingdimensions of silicon nanocrystals. They were calculated to be of 2 – 4 nm which proves the medium-range order in a-Si:H.
Generation of correlated photons in hydrogenated amorphous-silicon waveguides  [PDF]
S. Clemmen,A. Perret,S. K. Selvaraja,W. Bogaerts,D. van Thourhout,R. Baets,Ph. Emplit,S. Massar
Physics , 2011,
Abstract: 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.
Study on stability of hydrogenated amorphous silicon films
Zhu Xiu-Hong,Chen Guang-Hu,Zhang Wen-Li,Ding Yi,Ma Zhan-Jie,Hu Yue-Hui,He Bin,Rong Yan-Dong,

中国物理 B , 2005,
Abstract: Hydrogenated amorphous silicon (a-Si:H) films with high and same order of magnitude photosensitivity (\sim 10^{5}) 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 (C_H}) 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.
Experimentally Constrained Molecular Relaxation: The case of hydrogenated amorphous silicon  [PDF]
Parthapratim Biswas,Raymond Atta-Fynn,David A. Drabold
Physics , 2007, DOI: 10.1103/PhysRevB.76.125210
Abstract: 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 confirm the presence of a high frequency localized band in the vibrational density of states due to Si-H vibration that has been observed in a recent vibrational transient grating measurements on plasma enhanced chemical vapor deposited films of hydrogenated amorphous silicon.
Network structure and dynamics of hydrogenated amorphous silicon  [PDF]
D. A. Drabold,T. A. Abtew,F. Inam,Y. Pan
Physics , 2007, DOI: 10.1016/j.jnoncrysol.2007.09.081
Abstract: In this paper we discuss the application of current it ab initio computer simulation techniques to hydrogenated amorphous silicon (a-Si:H). We begin by discussing thermal fluctuation in the number of coordination defects in the material, and its temperature dependence. We connect this to the ``fluctuating bond center detachment" mechanism for liberating H bonded to Si atoms. Next, from extended thermal MD simulation, we illustrate various mechanisms of H motion. The dynamics of the lattice is then linked to the electrons, and we point out that the squared electron-lattice coupling (and the thermally-induced mean square variation in electron energy eigenvalues) is robustly proportional to the localization of the conjugate state, if localization is measured with inverse participation ratio. Finally we discuss the Staebler-Wronski effect using these methods, and argue that a sophisticated local heating picture (based upon reasonable calculations of the electron-lattice coupling and molecular dynamic simulation) explains significant aspects of the phenomenon.
Study on Structural Stability of Hydrogenated Amorphous Germanium-Nitrogen Alloys
半导体学报 , 1997,
Abstract: Hydrogenated arnorphous silicon(a-Si:H) and its related alloys,such as a-SlN:H,a-SiC:H etc,have been widely studied for many years since the pioneering work of Spearand Le ComberL1:.However,hydrogenated amorphous germanium-nitrogen(a-GeN:H) alloy sareless understood compared with...
Relaxation and derelaxation of pure and hydrogenated amorphous silicon during thermal annealing experiments  [PDF]
F. Kail,J. Farjas,P. Roura,C. Secouard,O. Nos,J. Bertomeu,F. Alzina,P. Roca i Cabarrocas
Physics , 2010, DOI: 10.1063/1.3464961
Abstract: The structural relaxation of pure amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) materials, that occurs during thermal annealing experiments, has been analysed by Raman spectroscopy and differential scanning calorimetry. Unlike a-Si, the heat evolved from a-Si:H cannot be explained by relaxation of the Si-Si network strain, but it reveals a derelaxation of the bond angle strain. Since the state of relaxation after annealing is very similar for pure and hydrogenated materials, our results give strong experimental support to the predicted configurational gap between a-Si and crystalline silicon.
Structural modifications induced in hydrogenated amorphous Si/Ge multilayers by heat treatments  [PDF]
C. Frigeri,M. Serenyi,A. Csik,Z. Erdelyi,D. L. Beke,L. Nasi
Physics , 2009,
Abstract: A study is presented of the structural changes occurring as a function of the annealing conditions in hydrogenated amorphous Si/Ge multilayers prepared by sputtering. Annealing changes the structure of the as-deposited multilayer except for the less severe conditions here applied (150 oC, time<22 h). For higher temperatures and/or times, the modifications consist of layer intermixing and surface degradation in the shape of bumps and craters. They are argued to be due to the formation of H bubbles upon heating. Hydrogen should be mostly released from the amorphous Ge layers.
Thermally stimulated H emission and diffusion in hydrogenated amorphous silicon  [PDF]
T. A. Abtew,F. Inam,D. A. Drabold
Physics , 2006, DOI: 10.1209/0295-5075/79/36001
Abstract: 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 dynamics in a-Si:H is dominated by structural fluctuations intrinsic to the amorphous phase not present in the crystal.
Room temperature ferromagnetism in Cr-doped hydrogenated amorphous Si films  [PDF]
Jia-Hsien Yao,Hsiu-Hau Lin,Tsung-Shune Chin
Physics , 2009, DOI: 10.1063/1.2946662
Abstract: Ferromagnetism above room temperature was observed in Cr-doped hydrogenated amorphous silicon films deposited by rf magnetron-sputtering. Structure analysis reveals that films are amorphous without any detectable precipitates up to the solubility limit 16 atomic percentages of Cr. Experimental results suggest that hydrogenation has a dramatic influence on magnetic properties, electrical conductivity and carrier concentration in the thin films. Pronounced anomalous Hall effect and magnetization curve both suggest the origin of the ferromagnetism may arises from percolation of magnetic polarons.
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