Origins of structural and electronic discrepancies in elemental chalcogen glass

Abstract

Amorphous chalcogenide compounds have been extensively studied and widely utilized in advanced electronic and optical devices. In contrast to the significant attention devoted to these compounds, this work focuses on the structure and electronic properties of amorphous phases of elemental S, Se, and Te, investigated through ab initio molecular dynamics simulations. The results reveal that the local structures in amorphous S and Se predominantly consist of 2-coordinated configurations, leading to the formation of long chains. In contrast, amorphous Te exhibits defective octahedral configurations, resulting in interconnected network structures. As the electronegativity increases from Te to S, the void structures become significantly more pronounced, while the number of lone pair electrons shows a slight increase. Concurrently, the dynamic properties and bonding stabilities are markedly enhanced, which determine the stability of the glass. Moreover, the mobility gaps exhibit a notable enlargement with the increasing electronegativity. The localized mid-gap states, which facilitate electron migration, are observed in amorphous S, Se, and Te. However, these states are positioned near the valence bands in amorphous S and Se, whereas they reside deep within the mobility gap in amorphous Te. With the increase of electronegativity, the wide mobility gap and shallow localized state will make the electron migration become difficult in glass. This study offers profound insights into the nature of chalcogen glasses, paving the way for their strategic design and application in electronic and optoelectronic devices.