Tantalum oxide films produced from anodic oxidation and thermal oxidation at 400 and 800°C have been investigated with respect to long- and short-range structure by X-ray diffraction and X-ray absorption spectroscopy, respectively. Films formed at 800°C show orthorhombic structure (β-Ta2O5) with greater disorder compared to the β-Ta2O5 powder reference, where six O atoms were observed at an avenge radial distances of 1.957 ± 0.014 (Ta2O, powder) and 1.971 ± 0.007 Å (800°C Ta oxide film). Lower temperature films consist primarily of metastable TaOx (Ta 2O) and appear to be relatively stable for extended times of treatment with a first shell not unlike that of β-Ta2O 5, based on a linear combination analysis. Furthermore, using a linear combination of β-Ta2O5 and α-Ta metal, the amorphous anodic oxide films studied as a function of thickness were observed to exhibit a relatively ordered local structure consistent with the high-temperature (i.e., 800°C) phase. This work demonstrates that the nanoscale oxide films formed on tantalum exhibit an ordered local structure, reflecting the very compact nature that enhances its corrosion resistance.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry