N + ion implantation effects on microhardness and adhesion in TiO 2 films

Abstract

The epitaxial films of TiO 2 rutile (100) could be grown on sapphire (0001) substrates at 500°C by means of reactive ionized cluster beam (RICB) deposition. To achieve epitaxial growth at low substrate temperature, ionization of Ti vapor and O 2 gas was necessary. The difference of mechanical properties in epitaxial rutile films on sapphire and polycrystal rutile films on Si wafer has been studied by microhardness and scratch adhesion measurements. Epitaxial films are more hard about 1.9 times and adherent about 1.3 times than polycrystal films. High-energy (3 MeV) implantation has a stronger hardening and adhesion effects than low-energy (90 keV) implantation. In epitaxial films, the spread of interplanar spacing of rutile (200) planes occurred due to implantation-induced internal stress and strain. In polycrystal films, a phase transformation of crystalline rutile to anatase of TiO 2 occurred due to the relaxation of internal strain. The adhesion of TiO 2 films to the substrates could be increased about 27% in both epitaxial and polycrystal films by high energy (3 MeV and 400 keV respectively) implantation due to interface mixing and reaction between film and substrate.