Chemical solution deposition of biaxially oriented (Ba,Sr)TiO₃ thin films on 〈100〉 Ni

Biaxially oriented Ba_1−xSr_xTiO₃ (BST) thin films were fabricated under a highly reducing atmosphere (oxygen partial pressure ∼10⁻¹⁸ atm) on base metal substrates (〈100〉 Ni) using a fluorinated chemical solution deposition method. The degree of film orientation was investigated with respect to film annealing temperature and composition (x = 0, 0.33, 0.5, 0.67, 1). The solution synthesis route included fluorinated solvents, donor-dopants, and chelating agents for control of orientation, defect chemistry, and morphology. Free-energy and phase diagrams guided solution development using halide addition to avoid intermediate BaCO₃ formation and instead produce direct crystallization of BaTiO₃-type materials from BaF₂. The degree of (200) orientation of BST films deposited on 〈100〉 Ni substrates displayed a compositional dependence for 0 < x < 1, with a maximum orientation Lotgering factor approaching unity. Low-temperature (500 °C) crystallization of highly oriented films was demonstrated for solution-derived BST on Ni, which may have enabling materials integration implications for capacitors and other applications.