Statistical experimental design to optimize RF-sputtered NiTiO3 thin films

An original statistical approach was developed to improve the features of the as-grown photoactive semiconducting Nickel titanate (NiTiO₃) thin films by radio frequency (rf) magnetron co-sputtering process. NiTiO₃ deposition requires two metallic targets (Ni and Ti) targets with argon (Ar) and oxygen (O₂) gas mixture. The key parameters for the film synthesis consist in the partial pressures of Ar and O₂ gas inside the deposition chamber, the rf co-sputtering power levels related to metal targets, the deposition time and the substrate temperature. So undeniably, the above parameters require optimized values to achieve a thin film growth with controlled features such as the stoichiometry, microstructure, crystalline structure and surface morphology. Two successive statistical Design of Experiments (DoE) were carried out and precise evaluations of the effects of the various deposition parameters were obtained. The approach contributes to draw judiciously the best rf co-sputtering conditions for the synthesis of NiTiO₃ thin films with the possibility to extend the approach to similar structures and compositions.