Electrical characterization of BaTiO₃ heteroepitaxial thin films by hydrothermal synthesis

The electrical properties of hydrothermally grown epitaxial pseudocubic BaTiO₃ thin films formed on epitaxial electrode layers of SrRuO₃ on SrTiO₃ single crystal substrates have been evaluated by variable frequency dielectric testing. The initial as-synthesized BaTiO₃ film displayed a dielectric constant of 450 with very high losses (tan δ ˜ ~ 100%) at 10 kHz due to OH⁻ and H₂O, incorporated during growth, contributing to migration losses within the film. Improvements were seen with increasing postprocessing heat-treatment time and temperature with improved properties seen after a heat treatment at 300 °C for 24 h (ε ˜ ~ 200, tan δ ˜ ~ 8%). Relationships were established for dielectric constant and loss tangent with structural changes observed by Fourier transform infrared spectroscopy, thermal gravimetric analysis, nuclear magnetic resonance spectroscopy, and x-ray diffraction.