Epitaxial waveguide structures of c-axis oriented BaTiO 3 thin films on MgO͑001͒ have been grown by pulsed laser deposition. The structural properties of the samples have been characterized by Rutherford backscattering spectrometry/ion channeling ͑RBS/C͒, x-ray diffraction, and atomic force microscopy. We found excellent crystalline quality even up to thicknesses of a few microns. This has been confirmed by RBS/C minimum yield values of 2%-3%, a full width at half maximum of 0.36°of the BaTiO 3 ͑002͒ rocking curve, and a rms roughness of 1.1 nm for a 950 nm BaTiO 3 film. The out-of-plane refractive index was measured to be close to the extraordinary bulk value with the birefringence being about one third of the bulk value. Waveguide losses of 2.9 dB/cm have been demonstrated.

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The correlation between the morphology of ramps in YBazCus07-a thin films prepared by ionbeam etching and the properties of ramp-type junctions was investigated in detail. Ramp-type junctions were fabricated using PrBazCuz gGao 1 0 7 -6 as the barrier material. We examined the influence of different fabrication parameters on the ramp properties by Atomic Force Microscopy (AFM). Properties of junctions, which were fabricated by employing a postbaking of the etching mask, were compared with those of junctions prepared without any special treatment. Junctions containing the improved ramps showed I-V characteristics and a temperature dependence of the normal resistance RN typical for resonant tunneling.The other junctions, having also an order of magnitude lower values of RN, exhibited a metallic temperature dependence of RN, which can be possibly explained by contributions from metallic channels in the PrBazCuz 9Gao 1Q.i-6-barrier.

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