CuGaSe2- CuGa3Se5 phase transition in CCSVT-grown thin films

The system CuGaSe2- CuGa3Se5 in thin films has been investigated. Layer synthesis was carried out by chemical close-spaced vapour transport (CCSVT) using Cu precursors on Mo/soda-lime glass substrates. The extension of deposition times in a two-step process led to final film compositions with [Ga]/[Cu] ratios ranging from 1 to 3, allowing the study of the phase transition mentioned above. Films showing chalcopyrite (1:1:2), OVC (1:3:5) and two-phase were grown. X-ray emission spectroscopy and x-ray diffraction (XRD) techniques have been combined for a compositional and structural study of this material system probing both bulk and near surface properties of the films. This analysis was also extended to the rear-surface investigation of selected two-phase thin films and complemented with surface sensitive photoelectron spectroscopy (PES). From these results a growth model is presented for CuGa3Se5 formation in gallium-rich, CCSVT-grown CuGaxSey-films