Influence of 120 MeV Ag swift heavy ion irradiation on the optical and electronic properties of As-Se-Bi chalcogenide thin films

Abstract

Ion beams of widely varying energies from keV to GeV have played a significant role in the modification of materials. The manuscript reports the influence of 120 MeV Ag swift heavy ion irradiation (SHI) at two different fluence on As40Se58Bi02 and As40Se45Bi15 thin films. The irradiation has shown strong impact on the optical constants like transmittivity, absorption coefficient, extinction coefficient, optical band gap and disorderness with no structural change. The optical transmittance decreased while absorption coefficient and extinction coefficient increased with increase in the fluence from 5 × 1012yions/cm2 to 5 × 1013ions/cm2. The decreased optical band gap with irradiation is explained on the basis of bond distribution model and density of defect states with increase in disorder. The p-type to n-type conductivity switching was observed at higher Bi content and the Hall measurement showed the increase in conductivity with irradiation. The Raman study on these ion irradiated films also confirmed no structural transformation. The surface morphological evolution of the films by Ag ion irradiation was studied by Field Emission Scanning Electron Microscopy.