The Thermal Oxidation of TiAlN High Power Pulsed Magnetron Sputtering Hard Coatings as Revealed by Combined Ion and Electron Spectroscopy

摘要

The thermal oxidation of TiAlN hard coatings deposited by High Power Pulsed Magnetron Sputtering (HPPMS) is investigated at room temperature and 800 K at oxygen pressures ranging from 10?6 to 10?2 Pa by means of in situ X-ray and Ultraviolet Photoelectron Spectroscopy as well as Low Energy Ion Scattering. The spectra reveal that oxygen binds selectively to titanium during the initial chemisorption step and simultaneously some oxygen is dissolved into subsurface layers, which stay metallic. Enhanced oxidation results into continuous formation of a multilayered oxide film including oxynitride TiAl(O,N) as a metastable reaction product buried below an oxidic top layer. This top layer is either composed of mixed TiAlO after oxidation at 800 K or of segregated TiO_2 and Al_2O_3 when oxidizing at 293 K. Additionally, evaluation of UV-valence bands reveals nitrogen doping of the surface oxide films. The results are of high relevance for tailoring of the surface characteristics of TiAlN after deposition, for the design of TiAlN multilayers and for an improved understanding of the interactions of gas particles with these coatings.