Phase-change materials (PCMs) are employed in both electrical and optical devices exploiting the property contrast between their amorphous and crystalline states. Binary antimony sesqui-chalcogenides such as Sb2Se3 and Sb2S3 are recently shown to be suitable PCMs for low-loss optical applications. In this work, ab initio simulations of arsenic sesqui-chalcogenides are carried out, including As2S3, As2Se3, and As2Te3 to unravel the bonding and optical properties of their crystalline and amorphous phases. Due to the metavalent character of its chemical bonds, crystalline As2Te3 shows a high optical response. However, in crystalline As2S3 and As2Se3, the alignment of p orbitals is fully broken, which results in a very low-extinction coefficient that is already comparable to their amorphous phase. Although As2S3 and As2Se3 display good low-loss optical properties, the overall optical contrast upon phase transition is not sufficient for practical applications. Therefore, it is concluded that arsenic is a useful alloying element in reducing the optical loss of conventional PCMs, but its concentration should be kept at a relatively low level to balance the optical loss and contrast window.

Link：Ab Initio Investigation of Amorphous and Crystalline Arsenic Sesqui‐Chalcogenides: Optical Properties Explained by Metavalent Bonding - Chu - physica status solidi (RRL) – Rapid Research Letters - Wiley Online Library