A cold plasma deposition of mixed tungsten and cobalt oxides-based thin films

Abstract Mixed tungsten and cobalt oxides-based thin films were fabricated using plasma-enhanced chemical vapor deposition with CpCo(CO) 2 and W(CO) 6 as precursors, providing a reliable method for producing materials with potential applications in various fields. The influence of varying the partial pressure ratio of the precursors (feed gas ratio) during the co-deposition process, while maintaining a constant total partial pressure, on the growth rate, surface morphology, and atomic composition was systematically investigated using scanning electron microscopy and x-ray photoelectron spectroscopy. The results indicate that W(CO) 6 exhibits a lower polymerization ability than CpCo(CO) 2 . The growth rate of the mixed CoO/WO 3 thin films corresponds to the combined contributions of each precursor under the applied plasma deposition parameters. Cauliflower-like globules in the films were attributed to the surface morphology of the calcined kanthal steel substrate. The atomic ratio of tungsten to cobalt in the films was slightly lower than in the precursor mixture, suggesting the preferential incorporation of cobalt into the film. Analysis of the [W]/[Co + W] and [C]/[Co + W] atomic ratios relative to the precursor feed gas ratio revealed the non-additive nature of the co-deposition process, highlighting the complex interactions between gas-phase species during the plasma deposition. These findings enable the fabrication of thin films with a predictable chemical structure in the plasma co-deposition process by adjusting the partial pressures of the precursors.