Treffer: Flux-mediated epitaxy for ferroelectric Bi4Ti3O12 single crystal film growth

We propose the Flux-mediated epitaxy as a novel concept for the growth of single crystalline films of incongruent, volatile, and high-temperature-melting compounds. In flux-mediated eptitaxy, by supplying materials precursors from the gas phase through the liquid flux films pre-deposited on the substrate, a quasi-thermodynamic equilibrium condition is obtained at the interface between the growing films and the flux films. This process has been demonstrated in this paper by fabricating ferroelectric Bi4Ti3O12 films, which has volatile Bi oxide. The most important step in this process is the selection of the right flux material, which is hard to predict due to the lack of an appropriate phase diagram. In order to overcome this problem, we have selected the combinatorial approach. A series of ternary flux libraries composed of two self-fluxes (Bi2O3 and Bi4Ti3O12) and a third impurity flux were fabricated on SrTiO3 (001) substrates. After that, stoichiometric Bi4Ti3O12 films were grown on each of these flux libraries at a temperature presumed to melt the flux. High-throughput characterization with the concurrent X-ray diffraction method resulted in the identification of CuO containing Bi2O3 as the flux material for the growth of single crystalline Bi4Ti3O12 films. Stoichiometric Bi4Ti3O12 films fabricated by using a novel CuO containing Bi2O3 are qualified to be single crystalline judging from their large grain size and the electrical properties equivalent to bulk single crystal's.