Preparation and Characterization of Epitaxial Bi2WO6 Thin Films Prepared by a Sol-Gel Process

Abstract

AbstractWe have succeeded in an epitaxial growth of bismuth tungstate (Bi2WO6, BWO) thin films, one of the bismuth layer-structure ferroelectrics (BLSF), on SrTiO3 (001) single crystal substrates by a spin coating process. BLSF are known to be one of the promising materials for ferroelectric random access memory (FeRAM) devices. A homogeneous coating solution was prepared with tungsten hexachloride and bismuth 2-ethylhexanoate as raw materials, and 2-(2-methoxyethoxy) ethanol and formamide as solvents. The as-coated thin films were sintered at temperatures from 500 to 800°C for lh in air. BWO crystallized at temperatures above 500°C. Any crystal phase was not observed in the thin films except for (001) phases of BWO in the XRD patterns. It was confirmed that the thin film was growing epitaxially by measurement of XRD pole figure. The crystallographic relationship of the film and substrate was BWO(001)//STO(001), BWO[110]//STO[100].