Phase Relations and Microstructure in Bulk Materials and Thin Films of the Ternary System Cu-In-Se

Cu-In-Se bulk crystals were grown by melting small amounts of material. The crystals were investigated by differential thermal analysis, X-ray diffraction, scanning electron, and transmission electron microscopy. New data led to the modification of the phase diagram Cu₂Se-In₂Se₃ in the regime of 15–30 at.% Cu and between 20–900°C. There are notable differences between literature data and our present results: Phase boundary lines differ from those of published phase diagrams. To assess the applicability of the modified phase diagram to thin films, we investigate polycrystalline thin films of Cu-In-Se in a range of composition and substrate temperature. Here we found a shift of the α-phase boundary line due to the presence of sodium.