Transmission-electron-microscopy study of quasi-epitaxial tungsten-bronze (Sr_2.5Ba_2.5Nb₁₀O₃₀) thin film on perovskite (SrTiO₃) single crystal

Strontium barium niobate (Sr_2.5Ba_2.5Nb₁₀O₃₀) thin films were deposited on (001) SrTiO₃ single-crystalline substrates by pulsed laser deposition. The growth nature was investigated by transmission electron microscopy (TEM). Selected-area electron diffraction and high-resolution transmission electron microscopy revealed the existence of six types of grains. These grains grew on the substrate in a partially epitaxial fashion. Geometrical models were built, which were confirmed by TEM observations. Based on the TEM results and geometrical analysis, a crystallographic model was developed. The strain nature resulting from the growth columns is discussed in this report.