Annealing effect on in-plane alignment and surface morphology of epitaxial Bi₄Ti₃O₁₂ thin films prepared by the chemical solution deposition

Bi₄Ti₃O₁₂ thin films were grown epitaxially on SrTiO₃(100) substrates by chemical solution deposition using metal naphthenates as starting materials. Homogeneous Bi–Ti solution with toluene was spin-coated onto the substrates and pyrolyzed at 500 °C for 10 min in air. Highly c-axis-oriented Bi₄Ti₃O₁₂ thin films were crystallized by annealing pyrolyzed films at ≥650 °C. The x-ray pole-figure analysis indicated that the Bi₄Ti₃O₁₂ thin films have an epitaxial relationship with the SrTiO₃(100) substrates. The surface morphology of the films annealed at lower temperature, i.e., 650 °C, exhibited flat and smooth surfaces, while films annealed at higher temperatures, i.e., 750 and 800 °C, were characterized by three-dimensional outgrowth.