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

In this paper, 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 a heretofore unseen phenomenon: a reduction in the permittivity of >= 40%. Consequently a reduction of the refractive index of 20%, hence, suggests a conspicuous change in the optical properties of the material under irradiation with a 300 keV electron beam. The plausible physical phenomena leading to these observations are discussed in terms of the homopolar and heteropolar bond dynamics under high energy absorption. The reported phenomena, exhibited by As2S3-thin film, can be crucial for the development of photonics integrated circuits using electron beam irradiation method. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789602]