Electron irradiation induced reduction of the permittivity in chalcogenide glass (As2S3) thin film

TL;DR

This study demonstrates that electron beam irradiation significantly reduces the permittivity and refractive index of As2S3 chalcogenide glass, indicating notable changes in its optical properties due to bond dynamics under high energy exposure.

Contribution

It provides the first detailed analysis of how electron irradiation alters the dielectric properties of As2S3 glass using Electron Energy Loss Spectroscopy.

Findings

Permittivity decreases by up to 40% after irradiation

Refractive index reduces by approximately 20%

Bond dynamics are implicated in the observed property changes

Abstract

We investigate the effect of electron beam irradiation on the dielectric properties of As2S3 Chalcogenide glass. By means of low-loss Electron Energy Loss Spectroscopy, we derive the permittivity function, its dispersive relation, and calculate the refractive index and absorption coefficients under the constant permeability approximation. The measured and calculated results show, to the best of our knowledge, a heretofore unseen phenomenon: the reduction in the permittivity of <40%, and consequently a modification of the refractive index follows, reducing it by 20%, hence suggesting a significant change on the optical properties of the material. The plausible physical phenomena leading to these observations are discussed in terms of the homopolar and heteropolar bond dynamics under high energy absorption.