ION-BOMBARDMENT OF ALN FILMS DEPOSITED IN A REACTIVE SPUTTERING PROCESS WITH ACCURATE CONTROL OF THE MASS-FLOW OF THE REACTIVE GAS

Aluminum nitride (AlN) films can be used as tribological coatings in aggressive media to reduce wear and corrosion owing to its remarkable chemical stability and high decomposition temperature. In the present investigations AlN films were produced by r.f. sputtering under different conditions and then post bombarded by light ions to tailor the surface properties for low coefficient of friction and long wear life. AlN films deposited with varying sputtering conditions differ considerably in deposition rates, crystallinity, and stoichiometry. As-deposited and ion bombarded metal-rich AlN films exhibit a much lower coefficient of friction (less than 0.2) than stoichiometric AlN films (around 0.6). Metal-rich and stoichiometric AlN films exhibit an enormous improvement in wear life when bombarded with B+ ions or a mixture of B+ and C+ ions. The improvement factor due to ion bombardment is higher for metal-rich AlN films. Ionic bombardment of metal-rich AlN film results in improved crystallinity and increased grain size as a function of ion dose.