Modeling InSe Phase-change Materials
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HH3.7.1
Modeling InSe Phase-change Materials K. Kohary1, V.M. Burlakov1, D. Nguyen-Manh2, and D.G. Pettifor1 Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK 2 Theory and Modelling Department, EURATOM/UKAEA Fusion Association, Culham Science Centre, OX14 3DB, UK 1
ABSTRACT
The amorphous structure of InxSey has been studied by a first principles tight-binding molecular dynamics technique using the program package PLATO (Package for Linearcombination of Atomic Type Orbitals). The three-dimensional amorphous structures with different densities were prepared by quick quenching from the liquid phase. The characteristics of short-range order such as coordination numbers, radial and bond angle distributions, and ring statistics have been analyzed.
INTRODUCTION Indium monoselenide (InSe) is a phase-change material: both the crystalline and the amorphous phases are stable at room temperature [1]. Beside applications such as solar cells and ionic batteries, InSe has recently attracted considerable attention because of its potential application as a data storage medium. Amorphous bits (~100 nm) have been created and annihilated by short laser and electron beams in epitaxial films [2-5]. Nevertheless, the structural, electrical and optical properties need to be well understood before the device applications can be optimized. In recent years, different compounds of indium and selenium were studied very extensively. The most important crystalline compounds are InSe, In2Se3 and In4Se3. The structure of these materials is based on the local tetrahedral bonding configuration. One would expect that the same local atomic configuration can be observed for the amorphous structure, but its details are less well known. The most advanced experimental studies were performed by Burian et al., who used wide-angle X-ray scattering (WAXS) and extended X-ray absorption fine structure (EXAFS) techniques to study the structure of amorphous InxSey containing 50, 60, and 66 at.% Se [6-8]. The goal of these experiments was to study the short range ordering in the amorphous films with the help of the radial distribution function. This function, however, only gives onedimensional integrated information about the disordered structure. It is clear that in order to understand the physical properties of disordered materials it is also important to model the amorphous structure on the atomic scale. In this paper we report the first ab initio study of the amorphous structure of different InxSey systems.
HH3.7.2
SIMULATION DETAILS We have performed first principles tight-binding molecular dynamics simulations to study amorphous InSe, In2Se3, and In4Se3 systems. The three-dimensional amorphous structures in a cubic cell with periodic boundary conditions were prepared by quick quenching from the liquid phase. Each structure contained 64, 65, and 63 atoms for amorphous InSe, In2Se3, and In4Se3, respectively. For each composition the simulations were performed in the (N,V,T) ensemble with densities 5.0, 5.4, 5.8, and 6.2 g/cm3
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