COMPOSITION, BINDING STATES, STRUCTURE, AND MORPHOLOGY OF THE CORROSION LAYER OF AN OXIDIZED TI0.46AL0.54N FILM

A metastable, single-phase, polycrystalline Ti0.46Al0.54N film was dep osited on a HSS substrate by reactive magnetron sputtering ion plating and oxidized in synthetic air at 800 degrees C. The build-up of the o xidic overlayer formed during 1 h of oxidation was analyzed with the f ollowing results: Scanning electron microscopy (SEM) micrographs taken at the inner profile of a crater sputtered through the oxide overlaye r showed a glassy morphology of the near surface region and, between t he near surface region and the nitridic film, a sublayer consisting of crystals embedded irt a glassy matrix. Electron probe microanalysis ( EPMA) cl ater edge linescan analysis revealed that the oxide overlayer consists of two sublayers, which differ significantly in the Al and T i content. At the surface and in the near surface toplayer the composi tion corresponds to Al2O3,. whereas with increasing depth a compositio n conforming with Al2O3, and TiO2, was detected. The binding states of the components Al, Ti, O, and N were determined with increasing depth by high resolution Auger electron spectroscopy (AES) multipoint analy sis at the inner profile of the crater. Evaluation of the spectra reve aled that oxygen is present in two binding states. In the toplayer, ox ygen is bonded to AI in Al2O3, and in the underlying layer, to Al in A l2O3 and to Ti in TiO2-x. Transmission electron microscopy (TEM) and h igh energy electron diffraction (HEED) analyses revealed that the Al2O 3 rich toplayer is present in an amorphous state. With structure analy sis by thin film X-ray diffraction (XRD), two modifications of TiO2,: namely anatase and rutile, were detected. (C) 1998 Elsevier Science S. A.