Composition-dependent bond lengths in crystalline and amorphized GexSi1-x alloys

Extended x-ray-absorption fine-structure has been utilized to measure the composition dependence of the Ge-Ge and Ge-Si bond lengths in both crystalline and amorphous Ge_xSi_1-x alloys. Utilizing a new sample preparation technique, transmission measurements were performed over greater ranges of photoelectron momentum and composition and with lesser uncertainty than previously reported. As a consequence, the proposed increase in bond length as a function of Ge composition has been unambiguously verified for the crystalline Ge_xSi_1-x alloys. For amorphous material, experimental results were also consistent with a bond length composition dependence and a phase-independent topological rigidity parameter. Though of greater uncertainty, the experimental values of Ge-Si bond length exhibited a lesser composition dependence than the Ge-Ge results. © 1999 The American Physical Society.