Structural stability and metallization of orpiment at high pressure

Abstract

Binary arsenic sulfide compounds have garnered significant attention owing to their wide-ranging physical properties and promising potential in the domains of electronics and optoelectronics. As a naturally abundant and historically significant semiconductor mineral, orpiment (crystalline As2S3) has encountered limited utilization in the realm of optoelectronics due to its considerable bandgap width. For orpiment with its quasi-two-dimensional layered structure, pressure is one of the most effective methods to regulate its crystal structure and physical properties. In this work, the structural behavior, optical and electrical properties of orpiment under high pressure have been investigated systematically utilizing a combination of experimental methods and theoretical calculations. The monoclinic structure of orpiment is stable up to 48 GPa without structural phase transitions involving changes in the space group occurred. The noticeable changes of lattice parameters, axial ratios, and interatomic distances above 20 GPa are ascribed to a transformation from a two-dimensional layered structure to a quasi-three-dimensional crystal framework. Continuous lattice contraction upon compression is accompanied by gradual bandgap narrowing, which leads to metallization of orpiment. The pressure-induced metallization of orpiment occurs above 40 GPa. The structural behavior, optical and electrical properties of orpiment at high pressure exhibit reversible hysteresis upon pressure release. This study offers a high-pressure approach for modulating crystal structure and physical properties of orpiment to expand its potential applications in the fields of electronics and optoelectronics.