Characterization of CuIn_0.7Ga_0.3Se₂ Thin Films Deposited by Single Stage Thermal Evaporation Process

Single phase CuIn_0.7Ga_0.3Se₂ (CIGS) thin films are successfully deposited on glass substrates via a single stage thermal evaporation from a stoichiometric powder of CIGS. X-ray photoelectron spectroscopy measurements reveal the existence of Cu- and Ga-rich surface of the as-grown CIGS thin films. The post-growth annealing process lead to migration of the metallic atoms from the surface region into the bulk during the crystallization process, which subsequently causes a significant reduction in the reflection and a change in the mechanism of conduction. From the photoconductivity measurements it was deduced that the deposited CIGS films demonstrated a drastic decrease in resistivity under different illumination intensities. The post-growth annealing effect on the morphology and structure of CIGS thin films is investigated by means of the atomic force microscopy and X-ray diffraction measurements, respectively. Results show that there is a significant change in surface roughness as well as in degree of crystallinity of the films following the annealing process at different temperatures.