Tunable lattice strain in vertically aligned nanocomposite (BiFeO ₃) _x: (Sm₂ O₃)_1-x thin films

Unique epitaxial two-phase vertically aligned nanocomposite (VAN) (BiFeO₃)_x: (Sm₂ O₃)_1-x thin films were deposited on SrTiO₃ (001) substrates by pulsed laser deposition. The VAN thin films exhibit a highly ordered vertical columnar structure with high epitaxial quality. We demonstrate that the strains of the two phases in both out-of-plane and in-plane directions can be tuned by the deposition parameters during growth, e.g., deposition frequency and film composition of the nanocomposite. The strain tunability is found to be directly related to the systematic variation in the column widths in the nanocomposite. The dielectric property measurement shows that increasing vertical strain control will lead to a systematic dielectric loss reduction in the VAN thin films. This study suggests a promising avenue in achieving tunable strain in functional oxide thin films by using VAN structures.