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

Extended x-ray-absorption fine-structure has been utilized to measure the c omposition dependence of the Ge-Ge and Ge-Si bond lengths in both crystalli ne and amorphous GexSi1-x alloys. Utilizing a new sample preparation techni que, transmission measurements were performed over greater ranges of photoe lectron momentum and composition and with lesser uncertainty than previousl y reported. As a consequence, the proposed increase in bond length as a fun ction of Ge composition has been unambiguously verified for the crystalline GexSi1-x alloys. For amorphous material, experimental results were also co nsistent with a bond length composition dependence and a phase-independent topological rigidity parameter. Though of greater uncertainty, the experime ntal values of Ge-Si bond length exhibited a lesser composition dependence than the Ge-Ge results. [S0163-1829(99)08339-3].