Effect of texture and formation rate on ionic and electronic properties of passive layers on Ti single crystals

Potentiodynamic (slow) and potentiostatic (fast) TiO2 layer formation on different oriented Ti single crystals of a coarse grain sample is compared. The crystal orientations were determined by the new AME-method (Anisotropy Micro Ellipsometry). Cyclovoltammograms, impedance, transient and electron transfer reaction (err) measurements were carried out on each crystal applying the new nl photoresist droplet method. For slowly grown layers a clear texture dependence occurs. The microcoulometrically determined charge (layer thickness) increases and the defect state concentration decreases with decreasing package density of the substrate surface. Etr reveals both direct and resonance tunnelling. Texture dependence vanishes completely for fast formed layers as is proved by transient and impedance measurements. Due to the low defect state density err shows direct tunnelling only. The influence of texture reappears for TiO2 layers formed potentiodynamically on top of the fast grown oxides.