Preparation of Bi₄Ti₃O₁₂ films on a single-crystal sapphire substrate with electron cyclotron resonance plasma sputtering

Bi-Ti-O oxide thin films were prepared on a sapphire single-crystal substrate by electron cyclotron resonance (ECR) plasma sputtering. The target used was a sintered Bi₄Ti₃O₁₂(BIT) and the substrate was controlled in the temperature range 400-640°C(T _sub). The film sputtered at T_sub=400°C was a pyrochlore type oxide(Bi₂Ti₂O₇), which changed to a Bi₄Ti₃O₁₂ oxide in the polycrystalline state at 500°C and in the single crystalline state at 640°C. In the film sputtered at 640°C, the (001) plane of the Bi₄Ti ₃O₁₂ grew parallel to the (112̄0) and (11̄02) planes of the sapphire substrate, and the (104) plane of Bi₄Ti ₃O₁₂ grew parallel to the (0001) plane of the sapphire substrate. The deposition rate was about 200 Å/min independent of the sputtering conditions.