Composition-structure relationships for multisource evaporated CuGaSe2 thin films

Abstract

X-ray diffraction (XRD) analysis of doublet formation and peak shifts were used to observe the compositional dependence of the order–disorder transition in polycrystalline CuGaSe2 thin films deposited by multisource evaporation. Cu-poor material had a strong tendency to disorder as evidenced by the simultaneous presence of both the chalcopyrite and sphalerite phases. Stoichiometric and Cu-rich material contained only the tetragonal phase as observed by XRD. Comparison of Cu-poor XRD patterns with theoretical calculations reflecting probable defect chemistries (VCu, GaCu, VSe) suggests an interesting microstructure. The absence of higher index group (iii) reflections, notably the (103) and (211) peaks, in chalcopyrite material suggest that the tetragonal phase maintains a near-stoichiometric composition. Overall Cu-poor film compositions may therefore be obtained by adjustment within the cubic phase which implies compositional segregation between the phases.