Local lattice distortion of Ge-dilute Ge-Si alloy: Multiple-scattering EXAFS study

Abstract

The local structure of a Ge{sub 0.006}Si{sub 0.994} thin film with dilute Ge impurity in a Si host has been studied by fluorescence x-ray absorption fine structure spectroscopy in the temperature region of 10-300 K using the multiple-scattering data analysis method. Contrary to the elongation of 0.029 A ring for the Ge-Si distance in the first shell, the Ge-Si interatomic distance in the second shell shows a contraction of about 0.013 A ring relative to the corresponding Si-Si distance in the Si host. This coincides with the theoretical result calculated using the formula proposed by Mousseau and Thorpe [Phys. Rev. B 46, 15887 (1992)] which includes both the bond-length mismatch and bond-angle deviation. It turns out that the contraction of the second-shell Ge-Si distance is due to the deviation of the Ge-Si-Si bond angle from the ideal tetrahedral angle. From the obtained Ge-Si distances within the first three shells, it is revealed that dilute Ge doped into a Si host can lead to local distortion rather than an average lattice change.