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.
Pb(ZrxTi1−x)O3 and PbZrO3 heteroepitaxial thin films were produced in an aqueous solution (10 M KOH) at ambient pressure and low temperatures (90–150 °C) on (001) SrTiO3 and LaAlO3 single crystal substrates. Growth of the Pb(ZrxTi1−x)O3 and PbZrO3 thin films initiates by the formation of {100} faceted islands. Energy dispersive spectroscopy (EDS) analysis of the Pb(ZrxTi1−x)O3 thin film shows that the Zr: Ti ratio is 45: 56, nearly identical to the molar ratio of the precursors. This route might provide a viable low temperature alternative for the formation of high dielectric constant thin films for applications such as dynamic random access memory (DRAM).
PbTiO 3 powders and heteroepitaxial thin films were produced by the hydrothermal method at 110-200°C using different bases (Na-, K-, Rb-, Cs-, TMA-, and TBA-OH). Microstructural characterization showed that the tetragonal perovskite films were epitaxial on the SrTiO 3 substrates, with a c-axis out-of-plane orientation. Sequential growth experiments showed that the growth initiates by the formation of 100 nm {100} faceted PbTiO 3 islands followed by coalescence. Small cation bases (Na-, K-, Rb-OH) produced 1.5-m {100} faceted blocky powders, whereas larger cation bases (Cs-, TMA-, and TBA-OH) formed fewer 500-nm interpenetrating platelets. Nuclear magnetic resonance results showed cation incorporation in the perovskite structure with local disorder on the Pb sites increasing cation size.
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