Synthesis and optical properties of CuInSe2 films

The growth of CuInSe2 films via evaporation from a compound source is studied by x-ray diffraction and x-ray fluorescence analysis. It is shown that, on heating, CuInSe2 dissociates into copper and indium selenides, which partially vaporize before film deposition. At the beginning of the deposition process, the source consists mainly of Cu2Se, CuInSe2, and In2Se3 in different ratios, depending on the source temperature. During deposition, two phases vaporize for the most part: CuInSe2 and In2Se3 or Cu2Se and CuInSe2, depending on the source temperature. As a result, some of the selenium, a highly volatile component, is lost, and the grown films consist of Cu2Se, (x less than or equal to 1), Se-deficient CulnSe(2), and InSe. At a source temperature of 1040degreesC, the impurity phases vaporize at approximately equal rates, and the grown films consist of CuInSe2 only. During continuous heating of the source, all the decomposition products are transferred to the substrate, and the film is very close in composition to the source. The chemical composition and structure of the films are determined, and their optical absorption spectra are measured near the fundamental edge at 290 K. The absorption data are used to evaluate the band-structure parameters of CuInSe2. A technique is proposed for assessing the band structure of this compound.