Change in Structure of Amorphous Sb–Te Phase‐Change Materials as a Function of Stoichiometry

• Published in: Physica status solidi. PSS-RRL. Rapid research letters Vol. 15; no. 6
• Main Authors: Ahmed, Shehzad, Wang, Xudong, Li, Heming, Zhou, Yuxing, Chen, Yuhan, Sun, Liang, Zhang, Wei, Mazzarello, Riccardo
• Format: Journal Article
• Language: English
• Published: 01.06.2021
• Subjects: amorphous phase; molecular dynamics; phase-change materials; Sb–Te alloys
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.202100064

Chalcogenide phase‐change materials (PCMs) are a leading candidate for non‐volatile memory and neuro‐inspired computing applications. Antimony telluride alloys can be made into fast and robust PCMs by proper doping. Depending on the compositional ratio, the amorphous state of these alloys shows either nucleation‐ or growth‐driven crystallization dynamics at elevated temperatures. In this work, thorough ab initio simulations are carried out to study the structural properties and bonding nature of six Sb–Te alloys with varied composition from 2:3 to 4:1. Despite all of the compounds showing similar local structural motifs consisting of defective octahedral configurations, a gradual change in medium range order and cavity concentration is observed as the Sb content increases. This trend is responsible for the reduction in the nucleation rate, thus leading to growth‐driven crystallization. In addition, the degree of charge transfer decreases as the composition approaches the Sb end, reducing the driving force for long‐term mass transport and phase separation upon extensive cycling in devices. Antimony telluride alloys are important phase‐change materials for memory devices. Depending on the stoichiometry, the amorphous state of these alloys shows either nucleation‐ or growth‐driven crystallization dynamics. In this work, ab initio molecular dynamics simulations shed light on this behavior by linking it to changes in the local structure of the amorphous network.