Effect of temperature on the initial, thermal oxidation of zirconium

A novel, methodological approach by combined in situ ellipsometry and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) has been applied to investigate the initial oxidation of zirconium within the temperature range 373–773 K. The effective-depth distributions and individual sublayer thicknesses of the non-stoichiometric and stoichiometric oxide species within the developing oxide film, as established with AR-XPS, are in good agreement with the corresponding results as determined independently with ellipsometry. Oxidation starts with the very fast, electric-field controlled growth of non-stoichiometric Zr-oxide up to a certain limiting thickness that increases with increasing temperature up to about 423 K. Subsequent, continued (for 423 K < T < 523 K) growth is realized by the linear overgrowth of stoichiometric ZrO2 under influence of the kinetic potential. For T > 573 K, oxide-film growth becomes predominated by the extensive dissolution of oxygen into the substrate that is accompanied by partial decomposition of the growing oxide film.