Coexistence of tetrahedral and octahedral-like sites in amorphous phase change materials

TL;DR

This study uses ab-initio molecular dynamics to reveal that amorphous Ge2Sb2Te5 contains both tetrahedral and defective octahedral sites, shedding light on its atomic structure relevant for optical and memory applications.

Contribution

It provides the first detailed atomic-level insight into the coexistence of tetrahedral and octahedral-like sites in amorphous GST through first-principles simulations.

Findings

Approximately one-third of Ge atoms are tetrahedral.

Remaining Ge, Sb, Te atoms are in defective octahedral environments.

Supports the structural similarity between amorphous and crystalline GST.

Abstract

Chalcogenide alloys are materials of interest for optical recording and non-volatile memories. We perform ab-initio molecular dynamics simulations aiming at shading light onto the structure of amorphous Ge2Sb2Te5 (GST), the prototypical material in this class. First principles simulations show that amorphous GST obtained by quenching from the liquid phase displays two types of short range order. One third of Ge atoms are in a tetrahedral environment while the remaining Ge, Sb and Te atoms display a defective octahedral environment, reminiscent of cubic crystalline GST.