Anisotropic in-plane strains and dielectric properties in (Pb,Sr)TiO3 thin films on NdGaO3 substrates

Anisotropic in-plane strain can be induced in (Pb,Sr)TiO3 (PST) thin film by using orthorhombic NdGaO3 (110) as a substrate. High-resolution x-ray diffraction was used to measure the strain of the PST thin film. A rocking curve with full width at half maximum of ∼0.04° illustrated that the film had nearly perfect single-crystalline quality. Reciprocal space maps around the (001), (103), and (013) reflections of the PST film revealed anisotropic in-plane strain of 485 ppm along [100] and 26 ppm along [010], respectively. Coplanar capacitance measurements also showed systematic changes in the dielectric constant and tunability due to strain; about a 15% difference in tunability at surface field of 50 kV/cm and a 20% difference in the zero-field dielectric constant were observed along [100] and [010], respectively.