Photo-induced volume changes in selenium. Tight-binding molecular dynamics study

TL;DR

This study uses tight-binding molecular dynamics to investigate how photo-excitation causes structural changes and volume expansion in selenium clusters and glassy networks, revealing bond breaking and defect formation.

Contribution

It provides the first detailed simulation-based analysis of photo-induced volume changes and defect dynamics in amorphous selenium.

Findings

Photo-excitation causes bond breaking in Se clusters.

Illumination leads to volume expansion in glassy Se.

Coordination defects increase significantly under light.

Abstract

Tight-binding molecular dynamics simulations of photo-excitations in small Se clusters (isolated Se$_8$ ring and helical Se chain) and glassy Se networks (containing 162 atoms) were carried out in order to analyse the photo induced instability inside the amorphous selenium. In the cluster systems after taking an electron from the highest occupied molecular orbital to the lowest unoccupied molecular orbital a bond breaking occurs. In the glassy networks photoinduced volume expansion was observed and at the same time the number of coordination defects changed significantly due to illumination.