Growth and characterizations of dual ion beam sputtered CIGS thin films for photovoltaic applications

The growth of CIGS thin films on soda-lime glass substrates at different substrate temperatures by dual ion beam sputtering system in a single-step route from a single quaternary sputtering target with the composition of Cu (In-0.70 Ga-0.30) Se-2 was reported. The effects of the substrate temperature on structural, optical, morphological and electrical properties of CIGS films were investigated. Stoichiometry of one such film was investigated by X-ray photoelectron spectroscopy. All CIGS films had demonstrated a strong (112) orientation located at 2 theta similar to 26.70(o), which indicated the chalcopyrite structure of films. The value of full-width at half-maximum of (112) peak was reduced from 0.58A degrees to 0.19A degrees and crystallite size was enlarged from 14.98 to 43.05 nm as growth temperature was increased from 100 to 400 A degrees C. However, atomic force microscope results showed a smooth and uniform surface at lower growth temperature and the surface roughness was observed to increase with increasing growth temperature. Hall measurements exhibited the minimum film resistivity of 0.09 Omega cm with a hole concentration of 2.42 x 10(18) cm(-3) and mobility of 28.60 cm(2) V-1 s(-1) for CIGS film grown at 100 A degrees C. Film absorption coefficient was found to enhance nominally from 1 x 10(5) to 2.3 x 10(5) cm(-1) with increasing growth temperature from 100 to 400 A degrees C.