Molecular dynamics study of structural and dynamical properties of amorphous Si-Ge alloys

Abstract

Structural and dynamical properties of amorphous silicon-germanium $(a\ensuremath{-}{\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x})$ alloys have been examined by molecular dynamics simulations using the Tersoff interatomic potential. Amorphous networks were generated by rapid quenching from liquid ${\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x}$ alloys. Good agreement was obtained between the simulated and experimentally measured radial distribution functions and phonon densities of states, suggesting that the Tersoff potential is useful for analyzing the atomic configurations and vibrational properties of $a\ensuremath{-}{\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x}$ alloys. Local atomistic structures, such as topological and chemical short-range order states, were also examined in detail, and we compared them with experimental and theoretical results reported previously. On the basis of the results obtained here, we proposed that the bond length and bond angle around Ge atoms have more distortion than those around Si atoms in $a\ensuremath{-}{\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x}$ networks.