Structural analysis of CIGS film prepared by chemical spray deposition

Abstract

We have fabricated Cu(In 1-xGa x)Se 2 (CIGS) films by chemical spray deposition under air environment. CIGS films were made with various Ga content ( x) from 0 to 1. With increase of x, lattice parameters, a and c, were observed to be decreased, and Raman A1 mode peak was shifted to higher frequency. These results indicate that CIGS films with arbitrary Ga concentration can be fabricated by using spray pyrolysis. However, it was found that sprayed CIGS films were grown with mixed phase of chalcopyrite ordering and CuAu ordering, where chalcopyrite faction was 0.59–0.76 for the x range of 0–0.31. The chalcopyrite fraction was measured to be increased with Ga substitution, indicating that alloying small amount of Ga into CuInSe 2 suppressed CuAu ordering. For comparison, we made CIGS films by using sputtering and selenization method. Compared to as-sprayed CIGS films, the CIGS films made by sputtering and subsequent selenization showed better crystallinity (X-ray diffraction result), larger grain size (scanning electron microscopy result), and higher chalcopyrite fraction, 0.9–0.92 for Ga contents less than 0.4 (Raman spectroscopy result). The other growth properties of CIGS films are discussed in this paper.