Influence of deposition parameters on the structure and microstructure of Bi12TiO20 films obtained by pulsed laser deposition

The structure, morphology and surface roughness of Bi₁₂TiO₂₀ (BTO) thin films grown on R-sapphire by pulsed laser deposition (PLD) were studied at different substrate temperatures, target-substrate distances, oxygen pressures and laser-pulse repetition rates. Although the substrate temperature seems to be the most important experimental parameter, the gas pressure and the target–substrate distance played important role on the phase formed and film thickness, with a significant effect of the laser-pulse repetition rate on the films thickness and preferred orientation of the deposited film. Single-phase γ-Bi₁₂TiO₂₀ was obtained on substrates at 650?°C, while several BTO metastable phases were observed in films deposited on substrates at temperatures between 500 and 600?°C. By the first time, thin films of pure and textured δ-Bi₁₂TiO₂₀ were successfully growth on substrates at 450?°C. When annealed, all the films deposited at lower temperatures resulted in the thermodynamically stable γ-Bi₁₂TiO₂₀.