Hierarchical Short- and Medium-Range Order Structures in Amorphous GexSe1-x for Selectors Applications

TL;DR

This study uses classical molecular dynamics to reveal hierarchical short- and medium-range order structures in amorphous GexSe1-x, highlighting how composition influences atomic arrangements relevant for selector applications in memory devices.

Contribution

It demonstrates that nanosecond-long classical molecular dynamics simulations can effectively model the structural features of amorphous GexSe1-x, capturing temperature-dependent hierarchical structures beyond ab initio capabilities.

Findings

Hierarchical structures vary with Ge content and temperature.

Simulations reveal differences between melt and glassy phases.

Structural insights relate to electrical properties of switching materials.

Abstract

In the upcoming process to overcome the limitations of the standard von Neumann architecture, synaptic electronics is gaining a primary role for the development of in-memory computing. In this field, Ge-based compounds have been proposed as switching materials for nonvolatile memory devices and for selectors. By employing the classical molecular dynamics, we study the structural features of both the liquid states at 1500K and the amorphous phase at 300K of Ge-rich and Se-rich chalcogenides binary GexSe1-x systems in the range x 0.4-0.6. The simulations rely on a model of interatomic potentials where ions interact through steric repulsion, as well as Coulomb and charge-dipole interactions given by the large electronic polarizability of Se ions. Our results indicate the formation of temperature-dependent hierarchical structures with short-range local orders and medium-range structures, which vary with the Ge content. Our work demonstrates that nanosecond-long simulations, not accessible via ab initio techniques, are required to obtain a realistic amorphous phase from the melt. Our classical molecular dynamics simulations are able to describe the profound structural differences between the melt and the glassy structures of GeSe chalcogenides. These results open to the understanding of the interplay between chemical composition, atomic structure, and electrical properties in switching materials.