A zero density change phase change memory material: GeTe-O structural characteristics upon crystallisation

Xilin Zhou,Hao Zhang,Weiling Dong,Robert E Simpson

doi:10.1038/srep11150

Xilin Zhou, Hao Zhang + Show 2 more

Open Access

https://doi.org/10.1038/srep11150

Copy DOI

Abstract

Oxygen-doped germanium telluride phase change materials are proposed for high temperature applications. Up to 8 at.% oxygen is readily incorporated into GeTe, causing an increased crystallisation temperature and activation energy. The rhombohedral structure of the GeTe crystal is preserved in the oxygen doped films. For higher oxygen concentrations the material is found to phase separate into GeO2 and TeO2, which inhibits the technologically useful abrupt change in properties. Increasing the oxygen content in GeTe-O reduces the difference in film thickness and mass density between the amorphous and crystalline states. For oxygen concentrations between 5 and 6 at.%, the amorphous material and the crystalline material have the same density. Above 6 at.% O doping, crystallisation exhibits an anomalous density change, where the volume of the crystalline state is larger than that of the amorphous. The high thermal stability and zero-density change characteristic of Oxygen-incorporated GeTe, is recommended for efficient and low stress phase change memory devices that may operate at elevated temperatures.

Highlights

Phase change memory (PCM) has emerged as one of the most promising candidates for the generation non-volatile memory applications
It is noteworthy that the amorphous-crystalline mass density difference increases when the films are further annealed at higher temperatures
The decrease in mass density upon crystallisation anomaly, which was observed for films with more than 6 at.% oxygen is by no means common, and there are only a few reports of similar effects in the literature: Ge-rich Ge-Sb35, Sb-rich Ga-Sb36, and Cu-Ge-Te37 alloys

Summary

Introduction

Phase change memory (PCM) has emerged as one of the most promising candidates for the generation non-volatile memory applications. Compositions based on GeTe alloys show high scalability to nanometric cell sizes, rapid switching speed, and good cyclability[1,2] These materials are being investigated for application in active photonic circuits[3] and metamaterials[4,5]. This study has led to a GeTe-O composition with a unique set of phase change characteristics that includes a phase transition without volume change, which shows increased stability at high temperature. We believe that this composition is a promising candidate for PCM applications that require high thermal stability

Objectives

Methods

Results

Conclusion