Self-assembled Perovskite Epitaxial Multiferroic BiFeO_3 Nanoislands

摘要

Perovskite epitaxial multiferroic BiFeO_3 nanoislands were grown on SrTiO_3 (100) and Nb-doped SrTiO_3 (100) single crystal substrates by chemical self-assembled method. Their phase structure and morphology were characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy, respectively. The results showed that epitaxial multiferroic BiFeO_3 nanoislands were obtained via post-annealing process in the temperature range of 650 - 800°C, and their lateral sizes were in the range of 50 - 160 nm and height of 6 -12 nm. With increasing the post-annealing temperature, the morphology of BiFeO_3 nanoisland in the (100) growth plane evolved from tri-angled to squared, and then to plated shapes. By using piezo-force microscopy, ferroelectric characteristics of a single epitaxial BiFeO_3 nanoisland (with lateral size of ～50 nm and height of 12 nm) grown on Nb-doped SrTiO_3 (100) single crystal substrate, was characterized. The results demonstrated that fractal ferroelectric domains existed in the single BiFeO_3 nanoisland, and self-biased polarization was also observed within this multiferroic nanoisland. This phenomenon can be ascribed to the interfacial stress caused by the lattice misfit between the BiFeO_3 nanoisland and the SrTiO_3 single crystal substrate.