Preparation of CuInSe(2) thin films by selenization of co-sputtered Cu-In precursors

Abstract

CuInSe(2) thin films have been prepared by high Se vapor selenization of co-sputtered Cu-ln alloy precursors within a partially closed graphite container. Cu-ln alloys with different compositions were investigated. X-ray diffraction (XRD) analysis of the films showed mainly CuIn(2) and Culling phases and the Culling peak intensity was found to increase as the alloy composition tended towards Cu-rich. A linear dependence of the alloy composition on the Cu/In deposition power was observed from energy dispersive analysis by X-rays (EDX). A three-fold volume expansion was exhibited by all the CuInSe(2) films after selenization at 500-550 degrees C. Scanning electron microscopy (SEM) analysis of the films showed large and densely packed crystal structures with sizes above 5 mu m. The CuInSe(2) films exhibited single phase chalcopyrite structure with preferential orientation in the (1 1 2) direction. The EDX composition analyses of the films showed Cu/In ratio ranging from 0.43 to 1.2, and Se/(Cu + In) ratios from 0.92 to 1.47. The measured film resistivities varied from 10(-1) to 10(5) Ohm cm. The Cu-In alloy precursors with Cu/In ratio less than 0.70 were found to form CuIn(3)Se(5) a defect chalcopyrite compound. All films were Se rich, with the exception of samples with very high Cu content. (C) 1998 Kluwer Academic Publishers.