Effects of annealing on structural and morphological properties of e-beam evaporated AgGaSe2 thin films

Polycrystalline AgGaSe2 thin films were deposited by using single crystalline powder of AgGaSe2 grown by vertical Bridgman-Stockbarger technique. Post-annealing effect on the structural and morphological properties of the deposited films were studied by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDXA) measurements. XRD analysis showed that as-grown films were in amorphous structure, whereas annealing between 300 and 600 °C resulted in polycrystalline structure. At low annealing temperature, they were composed of Ag, Ga2Se3, GaSe, and AgGaSe2 phases but with increasing annealing temperature AgGaSe2 was becoming the dominant phase. In the as-grown form, the film surface had large agglomerations of Ag as determined by EDXA analysis and they disappeared because of the triggered segregation of constituent elements with increasing annealing temperature. Detail analyses of chemical composition and bonding nature of the films were carried out by XPS survey. The phases of AgO, Ag, Ag2Se, AgGaSe2, Ga, Ga2O3, Ga2Se3, Se and SeO2 were identified at the surface (or near the surface) of AgGaSe2 thin films depending on the annealing temperature, and considerable changes in the phases were observed.