Electrochemical and photoelectrochemical modification and characterisation of thin passive films

The number of charge carriers and their distribution within thin films can be easily modified and characterised in electrochemical systems. Thin passive films on Ti with n-type character in contact with an electrolyte are presented as example. A separation between surface and bulk carriers has been carried out by photo-induced variation of the number of charge carriers. Additional modification of the system was performed in situ by potentiostatic polarisation. C−2/U plots were used for the determination of the defect concentration and the flatband potential. During polarisation at cathodic potentials protons will either move into the oxide and act as dopants or remain at the surface forming additional charged states. Further charge carriers will be formed during illumination.