Growth and characterization of CuInSe2 films by close-space evaporation

CuInSe₂ thin films were prepared on mica substrates using an evaporation technique which involved varying the distance between the source and the substrate. Films evaporated on substrates at distances less than 1 cm from the source exhibited preferential orientation in the (112) direction. The grain size increased from 0.5 to 1.0 μ m as the source substrate distance decreased from 3 to 1 cm. The conductivity increased with a decrease in the distance between the source and substrate. Electron probe microanalysis of these films showed that films coated on substrates farther away from the source had a slight selenium deficiency and an excess of indium. Three characteristic energy gaps of 1.01, 1.25 and 2.4 eV were obtained from an analysis of the optical absorption spectrum. The optical transition probability for valence band to conduction band transitions was estimated to be 10.91 eV which gives an admixture of copper d states to the valence band of 32%.