Morphology and optical properties of CuAlS2 crystals prepared using the solid-phase Al and S precursors

Copper dithiocarbamate and aluminium dithiocarbamate were prepared and then characterized by infrared spectroscopy.  The combination of the prepared precursors in different ratios was deposited on glass substrates using metal-organic chemical vapour deposition (MOCVD) technique at 450^oC through the pyrolysis of the precursors to yield Cu-Al-S thin films. Compositional, morphological, structural and optical characterizations were then carried out. The compositional analysis revealed that the ratio of Cu to Al in the precursor is not preserved in the films. Morphological study showed that the films are polycrystalline in nature whose homogeneity and grain size distribution decrease with a decrease in Al content of the films. The crystallinity of the films was further revealed from the PXRD results with the formation of the Cu-Al-S crystal structure as the Al content increases in the precursor. The energy gap obtained falls between 2.63 and 2.75 eV which decreases as the Al content in the films decreases. Optical constants such as refractive index and extinction coefficient exhibit a decreasing trend as the Al content in the film decreases.