Controllable interfacial strain can manipulate the physical properties of epitaxial films and help understand the physical nature of the correlation between the properties and the atomic microstructures. In this presentation, we demonstrated that the interface strain in epitaxial thin films can be well controlled by adjusting the miscutting angle of a vicinal single-crystal substrate via a surface-step-terrace matching growth mode. Epitaxial perovskite or perovskite-like oxide thin films such as CaCu₃Ti₄O₁₂ (CCTO) and (Ba,Sr)TiO₃ were grown on vicinal (001) single-crystal LaAlO₃ (LAO) substrates with various miscutting angles of 1.0°, 2.5°, and 5.0° by a polymer assisted deposition (PAD) technique. High-resolution X-ray diffraction were employed to study the epitaxial nature and interface strains induced by the substrate step terrace dimensions. It is found that the strain is determined by the mismatch between the lattice of the thin film and the substrate step terrace dimensions. A model is proposed that both compressive and tensile strained domains would form in the film to fit the size of each step terrace whereas the ratio of the two kinds of domains can be tuned by the miscutting angle. Based on this growth mode, a proper design of the substrate step terrace dimension can tune the properties of the thin films. For example, an optimized design of a CCTO thin film on a 5^o-miscutting (001) LaAlO₃ substrate can maintain a similar dielectric constant and reduce the dielectric loss by half an order of magnitude compared with the films grown on the regular (001) LaAlO₃ substrates, briefly by releasing a large part of the interfacial stress through the complementary strained domains instead of dislocations.

This work is supported by the National Basic Research Program of China (973 Program) under Grant No. 2015CB351905, the National Natural Science Foundation of China (Nos. 51172036, 11329402, and 51372034), and the Technology Innovative Research Team of Sichuan Province of China (No.2015TD0005).