Epitaxial anatase TiO2 thin films were grown on (001)-oriented single-crystal SrTiO3 substrates by liquid-phase deposition at 150°C . The out-of-plane alignment of the film was found to be at least 1 order of magnitude better than many other anatase films grown at much higher temperatures. The films were very smooth and made of nanosized crystallites, formed by a repeated nucleation mechanism rather than the oriented-attachment mechanism. The films also exhibited very large dielectric dispersions, which were largely attributed to dipolar and interfacial polarizations of hydroxyl groups and water molecules.

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Epitaxial perovskite KTaO 3 films were grown hydrothermally on ͑100͒ oriented single-crystal SrTiO 3 substrates in a 7 M KOH solution at 170°C. Transmission electron microscopy, Rutherford backscattering spectroscopy, and optical measurements showed that despite the low growth temperature, the obtained films were highly crystalline. Also, determination of the residual strain due to grain coalescence, lattice mismatch, and thermal expansion mismatch indicated that differential contraction between the substrate and film during cooling generated sufficient compressive stress to cause film buckling at poorly bonded regions between the film and substrate. The perovskite KTaO 3 is an incipient ferroelectric that exhibits a dielectric nonlinearity at low temperatures near the transition temperature of high T c superconductors, making it useful as a tunable element in microwave circuits. 1 In addition, due its close lattice match with KNbO 3 , KTaO 3 is ideal as a substrate or buffer layer for the growth of epitaxial KNbO 3 films. 2 Epitaxial KNbO 3 films have the largest reported electromechanical coupling constants, making KNbO 3 highly desirable as surface acoustic wave ͑SAW͒ substrates for use as filters in telecommunications and signal processing. 3 Alloying with niobium, the cubic phase of KTa 1−x Nb x O 3 ͑KTN͒ is a good candidate material for electro-optic applications, such as band filters, light modulators, and IR detectors, due to its large quadratic electro-optic coefficient and photorefractive effect. 4 Because bulk single crystals of KTaO 3 and KTN are difficult and expensive to grow, attention has been focused on the growth of epitaxial films.To date, epitaxial KTaO 3 films have been grown by pulsed laser deposition while KTN films have also been grown by metallorganic chemical vapor deposition and chemical solution deposition. 2,4,5 These processes require temperatures in excess of 650°C either during deposition or for postdeposition calcination. Alternatively, epitaxial KTaO 3 films can be grown by a low temperature ͑Ͻ200°C͒ solution technique known as hydrothermal epitaxy that utilizes aqueous chemical reactions to form heteroepitaxial thin films. 6,7 Generally, high processing temperatures are undesirable because this can lead to interdiffusion and reactions at the film/substrate interface, both of which would be detrimental to device properties. Therefore, the significantly lower processing temperatures employed together with the lower capital and operating costs of the hydrothermal growth method ͑as vacuum or environmental control equipment are not required͒ makes understanding the structure and integrity of KTaO 3 films an important topic.In a previous report, 6 it was shown that epitaxial KTaO 3 films can be grown hydrothermally on ͑100͒ oriented single-crystal SrTiO 3 substrates at Ͻ200°C. In this study, it is shown by a variety of characterization techniques that despite the low growth temperatures, the as-grown films are of high crystalline quality. In addition, it was observed that buckling cra...