Effect of substrate temperature on properties of Cu(In, Ga, Al)Se2 films grown by magnetron sputtering

Cu(In, Ga, Al)Se-2 (CIGAS) thin films were deposited by magnetron sputtering on Si(100) and soda-lime glass substrates at different substrate temperatures, followed by post-deposition annealing at 350 or 520 A degrees C for 5 h in vacuum. Electron probe micro-analysis and secondary ion mass spectroscopy were used to determine the composition of the films and the distribution of Al across the film thickness, respectively. X-ray diffraction analysis showed that the (112) peak of CIGAS films shifts to higher 2 theta values with increasing substrate temperature but remains unchanged when the films were annealed at 520 A degrees C for 5 h. Scanning electron microscopy and atomic force microscopy images revealed dense and well-defined grains for both as-deposited and annealed films. However, notable increase in grain size and roughness was observed for films deposited at 500 A degrees C. The bandgap of CIGAS films was determined from the optical transmittance and reflectance spectra and was found to increase as the substrate temperature was increased.