Structure and physical properties of paracrystalline atomistic models of amorphous silicon

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Date
2001Author
Voyles, P. M.
Zotov, N.
Nakhmanson, S. M.
Drabold, D. A.
Gibson, J. M.
Treacy, M. M. J.
Keblinski, P.
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We have examined the structure and physical properties of paracrystalline molecular dynamics
models of amorphous silicon. Simulations from these models show qualitative agreement with the
results of recent mesoscale fluctuation electron microscopy experiments on amorphous silicon and
germanium. Such agreement is not found in simulations from continuous random network models.
The paracrystalline models consist of topologically crystalline grains which are strongly strained and a disordered matrix between them. We present extensive structural and topological characterization of the medium range order present in the paracrystalline models and examine their physical properties, such as the vibrational density of states, Raman spectra, and electron density of states. We show by direct simulation that the ratio of the transverse acoustic mode to transverse optical mode intensities ITA /ITO in the vibrational density of states and the Raman spectrum can provide a measure of medium range order. In general, we conclude that the current paracrystalline
models are a good qualitative representation of the paracrystalline structures observed in the
experiment and thus provide guidelines toward understanding structure and properties of
medium-range-ordered structures of amorphous semiconductors as well as other amorphous
materials.
Subject
amorphous silicon
fluctuation electron microscopy
paracrystalline silicon
Permanent Link
http://digital.library.wisc.edu/1793/64416Type
Article
Citation
Journal of Applied Physics 90, 4437 (2001)