Epitaxial growth mechanism and ferroelectric property of c-oriented bismuth-layered CaBi₂Nb₂O₉ film

Exploring the epitaxial growth mechanism and ferroelectricity of CaBi2Nb2O9 (CBN) films is of great significance for its high-quality integration and application in ferroelectric memory. Herein, a high-quality (00l) CBN film was epitaxially grown on a NH4-HF solution etched SrTiO3 (STO) substrate by pulsed laser deposition. The epitaxial relationship of the CBN/STO heterostructure is (001)[100]CBN//(100)[110]STO, revealed by HRXRD and HRTEM. The single-layer Ca-O and double-layer Bi-O initial growth layers of CBN films were observed at the atomic scale and also discussed to clarify the factors affecting the growth modes. By comparing with the interface initial growth layer of BWO films, it is believed that the number of perovskite layers is an important factor affecting the quantity of the initial growth layers and growth mode in CBN films. In addition, the in-plane ferroelectricity of CBN thin films was demonstrated and the in-plane polarization switching was achieved by PFM measurement.