High-throughput synthesis and characterization of anodic oxides on Nb-Ti alloys

摘要

Composition spread thin film samples of Nb and Ti were prepared by co-sputtering. The composition range from Nb-5 at.%Ti to Nb-78 at.%Ti was achieved and characterized by high resolution field emission scanning electron microscopy and grazing angle X-ray diffraction. Nb stabilized the β-Ti phase over the entire range studied. The structure was cubic with a continuous change in the lattice constants with composition. Several distinct compositional zones were identified in the as-deposited film morphology. Then, anodic oxides were grown potentiodynamically and characterized by electrochemical impedance spectroscopy using a scanning droplet cell to yield a comprehensive description of oxide film properties including dielectric permittivity, resistivity, thickness and film formation factor. Mott-Schottky analysis of potentiostatically grown oxides showed how the alloy composition influences the flat band potential and the donor density of the mixed n-type semiconducting oxides. Complementary X-ray photo electron spectroscopy as a chemical analysis revealed differences in the oxide compositions as compared to the as-deposited metal resulting from the different ion transport numbers.