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The microstructure and transport properties of YBa2Cu3O(sub 7-delta)/La(sub 0.67)Ca(sub 0.33)MnO3 (YBCO/LCMO) bilayers are presented. The superconductivity and ferromagnetism coexisted in the bilayer with the YBCO thickness of 12.5 nm and they are related to the interaction between spin polarized electrons in the manganites and the copper pairs in the cuprates.

Determines the levels of strains in germanium (Ge) epilayers on silicon(100) substrates grown by molecular beam epitaxy using antimony as a surfactant. Direction Ge-Ge mode peaks as revealed by Raman spectra; Relationship between Raman shift of this mode and strain in partially relaxed samples.

X-ray diffraction measurements at different grazing angles for self-organized Ge dots grown on Si(001) are carried out by using synchrotron radiation as a light source. The lattice parameters parallel and perpendicular to the surface are determined from the grazing angle and ordinary x-ray diffraction spectra. A 1.2% lattice constant expansion parallel to the interface and a 3.1% lattice expansion along the growth direction, as compared with the Si lattice, are found within the Ge dots. Based on the Poisson equation and the Vegard law, the Ge dot should be a partially strain relaxed SiGe alloy with the Ge content of 55%. The composition change in Ge dots is suggested to be caused by the atomic intermixing during the islanding growth. In the small grazing angle x-ray diffraction spectrum, a peak located at the higher angle side of Si(220) is observed. The origin of this peak is attributed to the near surface compressive strain in the peripheral substrate regions surrounding the Ge dots. This compressive strain is induced by the formation of Ge dots and leads to a -0.8% lattice constant change parallel to the interface. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Modulation-doped Al0.22Ga0.78N/GaN heterostructure with 1000Å Si-doped n-Al0.22Ga0.78N barrier (n-AlGaN) were deposited on (0001)-oriented sapphire (α-Al2O3) by means of atmosphere-pressure metal-organic chemical vapor deposition. The reciprocal space mappings of symmetric reflection (0002) and asymmetric reflection (10 4) were measured with high resolution X-ray diffraction. The results indicate that the microstructure and strain status of barrier correlate to that of the underlying i-GaN layer. The barrier holds an “abnormal” strain-relaxation status, which probably results from the internal defects of n-AlGaN and the strain relaxation status at the i-GaN/α-Al2O3 interfaces. The results from grazing incidence X-ray diffraction show that the strain in barrier is nonuniform, which is consistent with the results from the reciprocal space mappings. [Copyright &y& Elsevier]

Abstract: La0.67Ca0.33MnO3 (LCMO)/YBa2Cu3O y (YBCO)/Ni trilayers were fabricated with varying thickness of the mid-superconducting YBCO layer. Two different deposition systems were used to avoid oxidation of the magnetic metal Ni and contamination of the deposition systems. Transport properties show that the temperature dependence of resistance goes from a metallic-to-metal–insulator transition (manganite-like behavior) to a superconducting behavior (M–M–S) with increase of the thickness of the YBCO layer. The magnetoresistance (MR) ratio is very small in comparison with LCMO/YBCO bilayers at low temperature. Such phenomenon may depend on the charge transfer and the magnetic spin interaction between the bottom and cap magnetic layers. [Copyright &y& Elsevier]

By using Eu2CuO4 (ECO) as a buffer layer, extremely smooth surface YBa2Cu3O7−x (YBCO) thin film on yttrium stabilized ZrO2 substrates was obtained. The microstructure of YBCO thin films with or without ECO buffer layer were studied by atomic force microscopy, scanning electron microscopy and X-ray techniques. It was found that the epitaxy and crystallinity and surface of the YBCO thin films have been significantly enhanced with ECO buffer layer. [Copyright &y& Elsevier]