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Abstract: A detailed microstructural analysis of amorphous silicon–germanium alloys with germanium fraction ranging from 0.1 to 0.5 is performed by means of a numerical modeling technique. By substituting Ge atoms for Si atoms in nanoporous paracrystalline network of amorphous silicon, several amorphous silicon–germanium structures have been generated then relaxed. The main aim of our work is to study the effect of compositional heterogeneities on the structural properties of amorphous silicon–germanium alloys in comparison with the standard case, that of a homogeneous random distribution of the atoms. In the present work we envisage the two-phase amorphous silicon–germanium model proposed by Goerigk and Williamson to interpret their anomalous small-angle X-ray scattering measurements; it consists on a mixture of Ge-rich and Ge-poor domains at the nanoscale. The microstructure of our structural models is analyzed by examining the macroscopic mass density, the X-ray diffraction intensity, the radial distribution functions, the bond lengths and the coordination numbers within the first coordination shell of Si and Ge atoms. [Copyright &y& Elsevier]

Abstract: A detailed microstructural analysis of amorphous silicon–germanium alloys with Ge fraction ranging from 0.1 to 0.5 is performed by means of a numerical modeling technique. By substituting Ge atoms for Si atoms in the nanoporous paracrystalline network of amorphous silicon, several amorphous silicon–germanium structures have been generated. Our main aim in the present work is to study the effect of compositional heterogeneities on the structural properties of amorphous silicon–germanium alloys in comparison with the standard case, that of a homogeneous random distribution of the atoms. We have limited ourselves here to the borderline case, that of segregation of Ge atoms at the nanoscale. The microstructure of our structural models is analyzed by examining the macroscopic mass density, the intensity of X-ray diffraction, the pair distribution functions, the bond lengths and the coordination numbers within the first coordination shell of Si and Ge atoms. Our structural models account for the experimentally derived mass densities regardless of the Ge distribution pattern. They also account for the intense small-angle X-ray scattering observed for some amorphous silicon–germanium samples. The short-range compositional disorder, reflected in the bond lengths and the coordination numbers within the first coordination shell of Ge atoms, is found to be very sensitive to how these atoms are arranged in the alloys. [Copyright &y& Elsevier]