Tantalum oxide (Ta2O5) thin films were deposited as the protective layers for the metal surface finishing by the DC reactive magnetron sputtering system. The effect of the Ta2O5 film thickness, ranging from 25 nm to 200 nm, on the physical properties and the anti-corrosive performance were investigated. The grazing-incidence X-ray diffraction (GIXRD) and the atomic force microscopy (AFM) were used to examine the crystal structures and the surface topologies of the prepared films, respectively. The XRD results showed that the Ta2O5 thin films were all amorphous. The AFM micrographs demonstrated the film morphology with quite smooth surface features. The surface roughness tended to be rough when the film thickness was increased. To examine the protective performance of the films, the poteniostat and galvanometer was utilized to examine the electrochemical activities with the 1M NaCl as the corrosive electrolyte. The results from the I-V polarization curves (Tafel slope) indicated that, with the Ta2O5 thin film, the current density was significantly reduced by 3 orders of magnitude when compared with the blank sample. Such results were observed because of fully encapsulated surface of the samples were covered with the sputtered Ta2O5 thin films. The study also showed that the Ta2O5 thin film deposited at 50 nm yielded the most extreme protective performance. The Ta2O5 thin films therefore could be optimized for the smallest film thickness for highly potential role in the protective performance of the metal surface finishing products.
Cobalt-doped hematite thin films for electrocatalytic water oxidation in highly acidic media
