Spectroscopic studies of (AsSe)100−xAgx thin films

Thin (AsSe)100−xAgx films have been grown onto quartz substrates by vacuum thermal evaporation or pulsed laser deposition from the corresponding bulk materials. The amorphous character of the coatings was confirmed by X-ray diffraction investigations. Their transmission was measured within the wavelength range 400-2500 nm and the obtained spectra were analyzed by the Swanepoel method to derive the optical band gap Eg and the refractive index n. We found that both parameters are strongly influenced by the addition of silver to the glassy matrix: Eg decreases while n increases with Ag content. These variations are discussed in terms of the changes in the atomic and electronic structure of the materials as a result of silver incorporation.