Short- and intermediate-range order in amorphous GeTe

We have investigated amorphous GeTe by anomalous X-ray scattering coupled with reverse Monte Carlo modeling. Experiments were conducted at the two K-absorption edges in order to determine differential structure factors for both elements. The results indicate that simple models like the 8 - N bonding rule cannot accurately rationalize the atomic structure. Te atoms are found to be over-coordinated with a mean coordination number of about 2.5. Moreover, evidence is given for a high level of intermediate-range order based on Ge, which has not been reported previously. This order has a pronounced effect on the ring statistics observed in the amorphous network, and thereby on the phase-change speed of GeTe. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim