XPS AND ELECTROCHEMICAL STUDIES OF THIN TIN LAYERS

TiN layers were prepared by implantation of 3 keV N2+ into Ti. The resulting layer thickness was 8 nm. Implantation, XPS and electrochemical studies were carried out in a closed system. Therefore no air oxidation took place between preparation and analysis. The electrochemical investigations (current, capacity, electron transfer and photoelectrochemical measurements) revealed the stability of TiN up to 1.3 V. At higher potentials oxidation to TiO2 and N2 dissolved in TiO2 took place. The reaction products could be detected with XPS. Sputter depth profiles revealed a layer structure Ti/TiN/TiO2. The layer thicknesses of TiO2 were smaller than on Ti at the same potentials. Photoelectrochemical experiments indicated similar electronic properties for the oxide layers on Ti and TiN. During oxidation no photocurrent was observed for TiN below 1.5 V. The stability of TiN against oxidation is explained by a N3- layer at the surface with a large electron density screening the underlying Ti ions and inhibiting oxidation.