Influence of steps temperature on microstructure and hardness of TiO2 thin films deposited by co-sputtering

TiO₂ thin films were synthetized by magnetron co-sputtering on silicon (100) substrates. Two targets were used: Ti and TiO inside an inert atmosphere of Argon gas at room temperature. Post-deposition thermal annealing treatments were performed with different numbers of step temperature segments to reach 500 °C for 3 hours. The effect of the variation of the number of step temperature segments in the micro hardness and microstructure of the films was studied, using XRD, Raman spectroscopy, SEM, AFM, photoluminescence (PL) and Vickers hardness. Vickers hardness evinced values between 14.7 and 19.8 GPa. Raman spectroscopy showed that the film without thermal annealing does not present any active bands, while films with post deposit annealing treatments had rutile and anatase phases with higher intensity as the number of step temperature segments increased, this behavior was corroborated by XRD. SEM and AFM showed a change in the morphology as the number of step temperature segments increased. Moreover, PL showed that oxygen defects decrease as the annealing time increases; which could be related to the change in hardness and morphology.