Effect of deposition temperature on the optical and structural properties of as-deposited CuInS2films

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Abstract
Structural and optical properties of thin films CuInS2 grown by thermal evaporation have been studied relating the effects of substrate heating conditions of these properties. The depositions were carried out at substrate temperatures in the range 65-295 °C. We obtain CuInS2 layers with high structural quality by growing at Ts 140 °C with the presence of an amorphous component and at Ts 240 °C with formation of In and Cu7 In4 as minority phases. From the optical transmission and reflection an optical absorption coefficient of 3 × 104 -105 cm-1 for 200 °C. Analysis of the absorption coefficient data revealed the existence of several energy gaps, direct and forbidden direct gaps. The direct gaps lie between 1.38 and 2.20 eV and the forbidden direct gaps are in the 0.61-1.97 eV range. The effect of the substrate temperatures on the grain size and surface roughness has been studied. It has been shown that the substrate temperatures Ts 140 °C and Ts 240 °C yield maxima of the grain size and minima of the surface roughness.