Author/Editor     Milošev, I; Strehblow, HH; Navinšek, B; Metikoš-Huković, M
Title     Electrochemical and thermal oxidation of TiN coating studied by XPS
Type     članek
Source     Surf Interface Anal
Vol. and No.     Letnik 23
Publication year     1995
Volume     str. 529-39
Language     eng
Abstract     X-ray photoelectron spectroscopy (XPS) has been used to investigate the electrochemical and thermal oxidation of titanium nitride (TiN) coatings prepared by physical vapour deposition (PVD) at 200 degrees C. Electrochemical oxidation of TiN was carried out at various potentials in phthalate buffer solution (pH 5.0). Evaluation of the XPS Ti 2p and N 1s spectra showed the presence of nitride, oxynitride and oxide species in the layer formed by anodic oxidation. The electrochemical oxidation of TiN to TiO2 proceeds through the formation of a mixed oxynitride/oxide layer, which transforms into oxide (TiO2) at sufficiently positive potentials (E > 1.1 V sv. SHE). The oxidation of TiN to TiO2 is accompanied by the formation of molecular nitrogen (N2). The thickness of the oxide layer reaches aproximtive 7 nm after oxidation at the highest potential (1.9 V). A complete coverage of the TiN surface by TiO2 leads to an anodic peak in the polarization curve. On the basis of angle-resolved XPS measurements, two types of oxynitride species are identified, which are distributed differently thoughout the oxidized layer. X-ray photoelekctron spectroscopy depth profiles of TiN oxidized at 450 degrees C and 600 degrees C in an oxygen flow reveal tht at the lower temperature na oxynitride layer is formed, whereas a thick TiO2 layer appears on top of TiN at the higher temperature. The interface between the nitride and oxide phases is relatively sharp. It is suggested that the mechanism of TiN oxidation proceeds by a progressive replacement of nitrogen by oxigen. The TiN coatings can be used up to 600 degrees C as a protective coating in an oxygen atmosphere. Valance band spectra of TiN, as well as of electrochemically and thermally oxidized TiN, are presented and discussed.
Descriptors     TITANIUM
ALLOYS
CORROSION
SPECTROMETRY, X-RAY EMISSION
TEMPERATURE
MATERIALS TESTING
ELECTROCHEMISTRY