High atomic diffusivity during pulsed laser irradiation of TiON quasi-amorphous films

Quasi-amorphous titanium oxynitride (TiON) films were obtained by annealing sol-gel anatase TiO2 films in NH3 atmosphere at 600 °C. These films were irradiated with 50 laser pulses using the fourth harmonic (266 nm) radiation of the Nd-YAG laser, with an average fluence of 20 mJ/cm2. HRTEM observations of the pulsed laser irradiated films evidenced the rutile TiO2 nanocrystallites formation. The rutile structure was not present either in the TiON films before the laser irradiation, or in the initial sol-gel anatase TiO2 films. During the laser irradiation, the film structure remains in the solid state phase, as it results from the temperature estimation and microscopic observations. For the rutile nanocrystals formation, the atomic diffusion length of the oxygen and titanium atoms should be in the nanometric range during the laser pulse action, which implies a diffusivity close to the values observed in the liquid phase. We consider that the rutile phase formation is a proof of the fast atomic diffusion in the solid amorphous matrix, during the laser irradiation.