Structure of amorphous Cu$_2$GeTe$_3$ and a model for its fast phase-change mechanism

TL;DR

This paper investigates the atomic structure of amorphous Cu$_2$GeTe$_3$ using advanced x-ray techniques and modeling, proposing a new model for its rapid phase-change mechanism based on atomic movements and structural motifs.

Contribution

It combines experimental scattering data with reverse Monte Carlo modeling to elucidate the short- and intermediate-range order in amorphous Cu$_2$GeTe$_3$ and proposes a novel phase transition model.

Findings

Atoms move toward the center of 6-fold rings during phase change.

Formation of wrong bonds and broader ring distribution in amorphous phase.

Some crystal structural motifs are preserved in the amorphous state.

Abstract

The structure of amorphous Cu$_2$GeTe$_3$ is investigated by a combination of anomalous x-ray scattering and extended x-ray absorption fine structure experiments. The experimental data are analyzed with a reverse Monte Carlo modeling procedure, and interpreted in terms of the short- and intermediate-range order. Based on this information, a model for the phase transition in Cu$_2$GeTe$_3$ is proposed, in which atoms move toward the center of the 6-fold rings of the crystal structure, leading to the formation of wrong bonds and a broader distribution of ring structures, but also preserving some structural motifs of the crystal.