Atomistic origin of doping-enhanced rapid crystallization in Ag-doped Ge-Sb-Te alloys: a joint experimental and theoretical study

TL;DR

This study combines experimental EXAFS analysis and ab-initio simulations to reveal how Ag doping modifies the atomic structure of GST alloys, leading to faster crystallization by converting Ge sites and favoring Ag-Te bonding.

Contribution

It provides new atomistic insights into how Ag doping accelerates crystallization in GST alloys through structural modifications.

Findings

Ag doping significantly alters Ge local environment

Ag prefers bonding with Te over Ge or Sb

Ag enhances the conversion of Ge sites from tetrahedral to octahedral

Abstract

We have applied extended X-ray absorption fine structure (EXAFS) analyses and ab-initio molecular dynamics (AIMD) simulations to study the atomic structure of Ag-doped (up to 42%) Ge1Sb2Te4 alloys. Analysis of the models that are consistent with the EXAFS experiment reveals that the Ge environment is significantly modified by Ag doping whereas those of Sb and Te are barely affected (except for high Ag concentrations), and suggests that Ag prefers bonding with Te to Ge or Sb. Doping with Ag promotes the conversion of tetrahedral Ge sites to octahedral Ge sites and enhances the speed of crystallization of Ge-Sb-Te (GST) alloys as evidenced directly from the MD simulations. Our study shed light on the atomistic mechanism of rapid crystallization of GST alloys enhanced by Ag doping.