Opto-electronic properties of Co-Zn-Ni-O films deposited by RF-sputtering at ambient-temperature

Abstract

Co-Zn-Ni-O thin films were grown on glass at ambient temperature (TS < 65 °C) by co-sputtering from Co3O4, ZnO, and NiO targets to determine the structural and opto-electronic properties across the ternary composition space. Compositional domains with spinel, wurtzite, rock-salt, and mixed phases were observed, albeit with very weak X-ray diffraction peaks, overall suggesting the likely presence of a co-existent amorphous component. The electrical conductivity had a maximum value of ∼35 S/cm that occurs where the optical absorption is also the strongest. The work functions range from 5.0 to 5.8 eV for all samples, but with no clear composition-based trends. Overall, it appears that the optoelectronic properties of the Co-Zn-Ni-O materials are much less sensitive to substrate temperature compared to other p-type oxide semiconductors, resulting in technologically-relevant ambient-temperature-deposited thin films.