Structural characterization of polycrystalline Ag-In-Se thin films deposited by e-beam technique

The Ag-In-Se thin films were deposited by e-beam evaporation of the Ag₃In₅Se₉ single crystal powder under high vacuum without intentional doping. Energy dispersive X-ray analysis (EDXA) showed the decreasing behavior of Se and Ag in the structure depending on the annealing. X-ray diffraction (XRD) analysis showed that as-grown films have amorphous structure while annealing the films under nitrogen environment at 200 °C transformed from the amorphous to polycrystalline structure. The crystallinity of the films improved as annealing temperature increases up to 400 °C by 100 °C-step. The polycrystalline films show mixed binary and ternary crystalline phases. Each phase was determined by comparing XRD patterns with complete data cards as Ag₃In₅Se₉, AgInSe₂, In₄Se₃, In₂Se₃, InSe, Se₆ and Se. The existence of Se segregation was supported by the formation of Se aggregates in crystalline phases of Se₆ and Se. The X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis have been carried out in order to obtain detailed information about the atomic composition, chemical states and morphology of the thin film surface. The decomposition of In 4d, Se 3d and Ag 3d photoelectron peaks revealed the existence of In-In, In-Se, In-Ag, Se-Se and Ag-Ag bondings in as-grown thin films. After annealing the thin films at different temperatures, the concentration of In-Se and In-Ag bonds decreases significantly, which results in an In-rich, but Ag- and Se-deficient thin film structure. The roughness of the film surface as a result of application of post-annealing in between 200 and 400 °C monitored by AFM technique was observed to change from 1.81 to 22.89 nm.