Anodisation of sputtered titanium films: an electrochemical and electrochemical quartz crystal microbalance study

Smooth titanium films were deposited by cathodic sputtering on glass substrates in order to avoid the more sophisticated polishing procedure of bulk titanium. The titanium films were then anodised in a sulphuric acid solution, using two different procedures: galvanostatic (1.5 mA/cm2) and potentiostatic (10 V vs. Ag-AgCl) conditions. Atomic force microscopy (AFM) shows that the potentiostatic TiO2 is rougher than the galvanostatic one. Mott-Schottky experiments confirm the n-type semiconductor behaviour of both TiO2 films. However, differences between their flat-band potentials and their donor concentration values are apparently due to this difference of roughness. Finally, electrochemical quartz crystal microbalance (EQCM) measurements were carried out and appeared necessary to study the kinetics of the TiO2 growth.