The preparation and formation mechanism of barium strontium titanate/silicon nanoporous pillar array composite film by sol-gel method

Silicon nanoporous pillar array (Si-NPA) with micron/nanometer hierarchical structure was fabricated by hydrothermally etching method, and then the Ba_0.5Sr_0.5TiO₃ (BST) sol was spin-coated on Si-NPA substrate to form composite film. The structure, morphology and chemical formation mechanism of composite film were studied. The intrinsic structural characteristics of Si-NPA were inherited in composite film. BST xerogel underwent isomer conversion and formed chelate network structure combined by enol and Ti-alkoxid at high temperature, in which the chelating agent acetylacetone played a modulating role and facilitated the stabilization of the BST sol. The formation of BST perovskite structure via a solid-state reaction of intermediate phases (Ba, Sr)Ti₂O₅CO₃. Annealed under 500°C, the composite film was amorphous, but it began to crystallize at 600°C. A well crystalline BST/Si-NPA composite film was achieved at the annealing temperature of 700°C.