Theoretical modelling of oxide thin film growth by pulsed laser sources

This paper considers theoretical modelling and experimental investigation of TiO₂ film growth on Ti films previously deposited on glass substrates. The Ti oxidation occurs due to film surface heating by a moving beam of a pulsed Nd: YAG laser that sweeps the surface at a constant speed of 2 mm/s, under atmospheric environment. The model takes into account the self-consistent solutions of the three-dimensional heat diffusion and oxidation rate equations. Numerical results obtained for 100 and 200 pulses of 290 ns and 3.17 MW/cm² with a repetition frequency of 100 and 200 Hz, showed that maximum temperatures of approximately 850 and 1200 K are reached after the action of the fiftieth pulse. The occurrence of surface cooling between two consecutive pulses is observed up to the repetition frequency of 100 Hz, and the surface temperature and the film thickness profiles closely match the Gaussian shape of the spatial laser beam profile. This strongly indicates that heat diffusion may be neglected during the laser pulse duration. Theoretical predictions for the TiO₂ film thickness dependence on laser intensity are in close agreement with the experimental data in the range between 2.4 and 3.2 MW/cm².