Effect of SrTiO₃ buffer layer on the phase formation and properties of direct-patternable BiFeO₃ thin films fabricated using photochemical metal-organic deposition

Abstract

The formation of BiFeO₃ without impurity phases, such as excess bismuth and iron, has been possible in only a narrow pressure-temperature-stoichiometric window. A direct-patterned BiFeO₃ film using photochemical metal-organic deposition (PMOD) was fabricated without a conventional etching. BiFeO₃ film was formed on a SrTiO₃ buffer layer with a perovskite structure and a lattice constant of 3.905 Å in order to study the substrate effect during phase formation. This study showed the phase formation and electrical properties of the direct-patternable PMOD BiFeO₃ thin films. The SrTiO₃ buffer layer was found to somewhat prevent the formation of a Fe excess phase in BiFeO₃ after anneal at 550°C for 20 min under O₂ and N₂ atmospheres. The measured remnant polarization (P_r) and coercive field (E_c) values of the Pt/BiFeO₃(200 nm)/SrTiO₃(40 nm)/Pt/Si structure were 10 µC/cm² and 300 kV/cm, respectively. Leakage current of perovskite BiFeO₃ film was found to be dominated by Poole–Frenkel emission as other perovskite ferroelectrics. To obtain an image, a spin-coated BiFeO₃ film was exposed to UV for 15 min and then rinsed in hexane. From this work, it was revealed that the direct-patterning of BiFeO₃ films could be applicable for the fabrication of micro-patterned systems using a SrTiO₃ buffer layer with controlled reactant stoichiometry.