Rutherford backscattering analysis of anodic tantalum--titanium oxides

Sputtered tantalum-titanium alloy thin films have been anodized in 0.01% aqueous citric acid, and the atom distribution, stoichiometry, and thickness determined by Rutherford backscattering analysis and stylus measurement. The anodic oxide film consists of a uniform amorphous mixture of Ta2O5 and TiO2 with about 3% of the oxide at the electrolyte interface consisting of almost pure TiO2. During anodization a small fraction of the titanium dissolves in the electrolyte. The apparent growth constant of the anodic oxide on Ta0.49Ti0.51 films is 1.88 +- 0.02 nm/V. The density of the oxide is determined as (5.9 +- 0.2) x 103 kg/m3. From aqueous contact capacitance measurements, the dielectric constant of the alloy anodic oxide is 24.7 +- 0.9. 9 figures, 5 tables