Optical constants change in As40Se60 and As50Se50 : A comparative study by FTIR and XPS

In this manuscript, the As40Se60 and As50Se50 samples of 800nm thickness were deposited onto glass substrate by thermal evaporation technique. The as-deposited films were characterized using X-ray diffraction (XRD) and FTIR Spectrophotometer. The prepared samples are amorphous type. The transmission is found to be decreased for As50Se50 film. The indirect optical transition mechanism for the photon absorption happens inside the studied film. The optical band gap is decreased with change in As and Se content. The density of state model and increase in disorder is responsible for the reduction of optical band gap in the studied films. The addition of more % As creates localised states in the gap which results the tailing of the band edges. The Urbach energy which gives the degree of disorder changes that indicates the more disorderness of As50Se50 than As40Se60 film. The XPS As3d, Se3d core level spectra variation infers the optical changes in the film and such type of film can be used for optical materials and optoelectronics.