Structural analysis of CuInSe₂ thin films prepared by selenization of Cu-In films

Abstract

This study involves the characterization of thin films of copper indium diselenide (CuInSe₂) deposited on soda-lime glass substrates using a two-step process. In this technique electron-beam-evaporated Cu-In precursor layers were reacted with an atmosphere containing H₂Se gas. The morphological and structural aspects of the CuInSe₂ layers were studied (by scanning electron microscopy and X-ray diffraction) as a function of the Cu-In film morphology and the selenization temperature profile and exposure time. It was found that the Cu-In precursor morphology has a significant influence on the structural properties of the final CuInSe₂ film. Selenization of the Cu-In alloys (irrespective of the structure considered) directly at high temperature resulted in films with poor structural properties. However, a vast improvement in the adhesion properties and morphology of the CuInSe₂ films were observed when the Cu-In films were exposed to a reactive selenium atmosphere while ramping the temperature between 150 ‡C and 400 ‡C. Selenization of triple-layer structures (Cu/In/Cu and In/Cu/In) resulted in films with good structural properties and excellent compositional uniformity.