XAFS Analysis of Crystal GeCu₂Te₃ Phase Change Material

The structure of crystal GeCu₂Te₃ was investigated by X-ray absorption fine structure (XAFS) measurement. We found that the Ge-Te interatomic distances obtained from XAFS are larger than those obtained from X-ray diffraction, and the Cu-Te distances are smaller. The averaged Ge-Te and Cu-Te distances obtained from XAFS are almost equal to the corresponding interatomic distances in amorphous GeCu₂Te₃. Therefore both crystal and amorphous GeCu₂Te₃ seem to be built up of the same local configurations of GeTe₄ and CuTe₄ tetrahedrons. This would be the reason why the phase change in GeCu₂Te₃ occurs very fast.