We have used two polytypes of silicon carbide single crystals, 4H-SiC and 6H-SiC, as the substrates for MgB 2 thin films grown by hybrid physical-chemical vapor deposition ͑HPCVD͒. The c-cut surface of both polytypes has a hexagonal lattice that matches closely with that of MgB 2. Thermodynamic calculations indicate that SiC is chemically stable under the in situ deposition conditions for MgB 2 using HPCVD. The MgB 2 films on both polytypes show high-quality epitaxy with a Rutherford backscattering channeling yield of 12%. They have T c above 40 K, low resistivities, high residual resistivity ratios, and high critical current densities. The results demonstrate that SiC is an ideal substrate for MgB 2 thin films.

We have prepared 1-m-thick epitaxial BaTiO 3 thin films on GdScO 3 (110) using pulsed laser deposition. The structural perfection of the films was revealed by a rocking curve width of ⌬ϭ0.13°for the 002 BaTiO 3 reflection and a Rutherford backscattering spectrometry/channeling minimum yield, min , of 0.5% measured for the Ba signal behind the surface peak. High-resolution transmission electron microscopy revealed an epitaxial relationship between BaTiO 3 and GdScO 3 and a sharp interface between the substrate and the film. The refractive index of the BaTiO 3 film was n o ϭ2.329Ϯ0.002 and n e ϭ2.307Ϯ0.002 at a wavelength of 632.8 nm and n o ϭ2.248Ϯ0.002 and n e ϭ2.228Ϯ0.002 at a wavelength of 1523 nm. The optical losses were less than 2 dB/cm at a wavelength of 632.8 nm.

Ferroelectric thin films of BaTiO 3 and BaTiO 3 / SrRuO 3 epitaxial heterostructures on different single-crystalline substrates were fabricated by pulsed laser deposition. The BaTiO 3 films of 100-400 nm thickness show high structural perfection and c-axis-oriented growth. For the electrical characterization of the BaTiO 3 in a thin-film capacitor structure, Pt top electrodes were deposited by e-beam evaporation. The results are compared to the current experimental and theoretical models. Special consideration is given to the model of charge injection from the electrodes.

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