First Principle Study of Phase Change Properties of Ag- and In-doped Sb-Te compound as Phase Change Material

Ag- and In- doped Sb-Te binary compounds (AIST) are widely attracted as base material of phase change random access memory (PCRAM) with its fast recrystallization time (ps scale) and less energy consumption in the phase transition than GeTe-Sb₂Te₃ pseudo-binary compounds (group 1) which are most famous as phase change material (PCM). Although AIST has better phase change behavior than group 1, it has much less investigated such as local structural environments or roles of Ag and In atoms. To reveal phase change properties and local atomic behavior in AIST, we performed molecular dynamics (MD) simulations using ab initio density functional theory. AgInSb₁₈Te₄ is selected as an exemplary model configuration. We identify its crystalline phase with various atomic configurations and evaluating their total energy. Amorphous phase, a representative expanded structure to be a 2×2×2 supercell, is constructed with MD simulation which mimics the melt-quenching experiment process. We explore the phase change mechanism by evaluating the radial distribution function, angle distribution function, solid angle distribution, and order parameter, and find that the In atom plays an important role not only in the phase transition process but also in retaining or stabilizing amorphous phase.