The deposition parameters used during the sputtering process are instrumental in determining the properties of the deposited films and can be optimised to produce thin film coatings that are suitable for specific engineering applications. Deposition parameters such as radio frequency (RF) power, oxygen flow rate, and substrate temperature can be varied during deposition to alter or tune the film structure, stoichiometry, and invariably the functional properties of the prepared thin films. In this paper, chromium oxide thin films prepared by reactive magnetron sputtering under various RF powers were characterised for their work function property and stability in Ringer’s solution. The structural, oxide phase and growth modes of the films were probed with X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The electrochemical stability and corrosion behaviour of the films were evaluated using an open circuit potential (OCP) measurements, cyclic polarisation, and Mott–Schottky analysis, while the work function (WF) was determined with a Kelvin probe. The XRD and Raman investigations showed that the films are predominantly amorphous with Cr2O3 being the main oxide phase. A mixture of columnar and layer-by-layer growth modes was observed in the deposited films with 500 W, 10 sccm sample showing rougher morphology due to the higher sputtering power. The OCP and cyclic polarisation results showed that the film prepared at a deposition power of 300 W and at an oxygen flow rate of 10 sccm possesses higher film passivation and breakdown potentials, hence, better corrosion resistance when compared to films prepared at higher deposition powers. The finding is further supported by the Mott–Schottky and work function investigations where the same film also showed lower defect density and higher work function values compared to the films deposited at higher powers. A correlation was found between the corrosion, work function and defect density which suggests that both parameters can possibly be used to predict and rank corrosion in thin films. We expect our findings to be significant for future corrosion and wear applications for metals/alloys requiring protection against environmental degradation. Graphical abstract: [Figure not available: see fulltext.].
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry