Selective detection of tetrahedral units in amorphous GeTe-based phase change alloys using Ge L3-edge x-ray absorption near-edge structure spectroscopy

Using Ge L₃-edge x-ray absorption near-edge structure (XANES) studies, we demonstrate a noticeable difference in local structure between amorphous and thermally crystallized GeTe-based phase change alloys. The pronounced change appears as a step-like feature at the absorption edge corresponding to a 2p → 5s (4d) electron transition. Comparison with ab initio XANES simulations suggest that the step-like feature is due to the presence of tetrahedrally coordinated Ge atoms in the as-deposited samples. The obtained results demonstrate that Ge L₃-edge XANES can be used as a structural probe for the existence of tetrahedral Ge sites in GeTe-based phase change alloys.