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

Abstract

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 Ga0.30) Se2 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 2θ ~26.70o, which indicated the chalcopyrite structure of films. The value of full-width at half-maximum of (112) peak was reduced from 0.58° to 0.19° and crystallite size was enlarged from 14.98 to 43.05 nm as growth temperature was increased from 100 to 400 °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 Ω cm with a hole concentration of 2.42 × 1018 cm-3 and mobility of 28.60 cm2 V-1 s-1 for CIGS film grown at 100 °C. Film absorption coefficient was found to enhance nominally from 1 × 105 to 2.3 × 105 cm-1 with increasing growth temperature from 100 to 400 °C. © 2014 Springer Science+Business Media New York.