Origin of the unusual reflectance and density contrasts in the phase-change material Cu2GeTe3

The recent demonstration of Cu2GeTe3 (CGT) as a potential phase-change material (PCM) for next-generation non-volatile memories represents a significant discovery. In contrast to widely studied PCMs, amorphous CGT is denser and more reflective than crystalline CGT, and the phase transition takes place to a tetrahedrally bonded crystal, a very different geometry to the octahedrally bonded cubic structures adopted by other PCMs. We have performed a computer-simulational study of CGT, investigating the atomic-level structure and physical properties of both phases. Our results lead to hypotheses to account for the higher amorphous-phase density and reflectivity, which may provide new design criteria for identifying novel PCMs. (C) 2013 AIP Publishing LLC.