Preparation and characterization of CuIn0.75Al0.25Se2 thin films by co-evaporation

Single-phase CuIn0.75Al0.25Se2 thin films were deposited by four-source co-evaporation method on soda lime glass substrates held at 673 K. Post-deposition annealing of the films in selenium atmosphere was carried out for an hour at 723 K. X-ray diffraction (XRD) studies of the films revealed the structure to be chalcopyrite with a=0.577a=0.577 and c=1.141nm. Optical absorption studies of the films indicated three-fold band structure. Crystal field (ΔCF) and spin–orbit (ΔSO) splitting parameters were deduced from the optical band gap values obtained. The deformation potential was estimated by using quasi-cubic model and the percentage of hybridization of the orbitals was determined using linear hybridization model. The films are found to be p-type conducting and the temperature dependence of conductivity studies are carried out to determine the activation energies of the films.