Atomic-scale structure of Si_xGe_1-x solid solutions

The atomic-scale structure of Czochralski-grown Si_xGe _1-x binary solid solutions was studied experimentally and theoretically. By extended x-ray absorption fine structure (XAFS) studies it is found that bulk SiGe is a random mixture and that the Ge-Ge, Ge-Si and Si-Si bond lengths maintain distinctly different lengths and vary in a linear fashion against the alloy composition across the whole composition range 0<_x<, in good agreement with expectations derived from the ab-inito electronic structure calculations. The result indicates that SiGe is a suitable model for a disorder material and that the bond lengths and bond angles are distorted with the composition.