Structural origins of the unusual thermal stability of amorphous Cu x Ge50−x Te50 (0 x 33.3)

Abstract

We have investigated the local atomic structures of several compositions of the amorphous phase of the system Cu x GeTe50 (), based on extended x-ray absorption fine-structure as well as anomalous x-ray scattering experiments, and discuss the unusual trend regarding their thermal stability as a function of the Cu content. At low concentrations (), Cu atoms tend to agglomerate in flat nanoclusters reminiscent of the crystalline phase of metallic Cu, leading to a more and more Ge-deficient Ge–Te host network structure with growing Cu content and an increasing thermal stability. At higher Cu concentrations (), Cu is incorporated into the network, leading to an overall weaker bonding situation which is associated with a decreasing thermal stability.