XPS analysis and structural characterization of CZTS thin films deposited by one-step thermal evaporation

Earth abundant and non-toxic CZTS films were grown by one-step thermal evaporation from as prepared and calcined powders followed by a sulfurization process at 400 °C.400 °C. X-ray diffraction and Raman studies have shown polycrystalline quality of the samples with kesterite structure, which are preferentially oriented along the (112) plane. The structural parameters of all CZTS samples were estimated before and after sulfurization. The structural properties indicate an enhancement of crystallinity after the sulfurization process. Scanning electron microscopy demonstrates significant morphological changes in the films after the sulfurization. Compositional analysis made by energy dispersive spectroscopy shows that the composition of the films moves towards the theoretical 2:1:1:4 stoichiometry due to sulfurization process. Finally, we have investigated the oxidation state of all the elements in CZTS after sulfurization by using XPS. We found that all the films were formed with the valence state of Cu+, Zn2+, Sn4+ and S2−.