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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.

Fe films with the different thicknesses are grown on c(4*4) reconstructed GaAs (001) surfaces at low temperature by molecular-beam epitaxy and the in-plane uniaxial magnetic anisotropy is determined. The studies have shown that magnetic anisotropy is not affected after in situ annealing, but in-pla ne strain is completely changed.

Two genes with a common region that is characteristic of theTPSI1/Mt4family were cloned from a Pi-starvation-induced cDNA library of rice roots using suppression subtracted hybridization (SSH). Based on the consensus sequence of these two genes, members of theTPSI1/Mt4family were found in maize, wheat and barley.blastand a cluster analysis in the eight members of theTPSI1/Mt4family showed two classes of four genes each among monocots. The first gene from rice was designatedOsIPS1based on a comparison of the consensus sequence withAtIPS1, and consequently the second gene, which has been previously reported asOsPI1, was designatedOsIPS2. Accumulation of the mRNA ofOsIPS1/2was examined by northern blotting and quantitative reverse transcriptase-polymerase chain reaction in whole-root and split-root experiments under treatment with phosphate (Pi) and the Pi analogue phosphite (Phi).OsIPS1showed much higher mRNA accumulation in roots thanOsIPS2, and an opposite trend was seen in shoots.OsIPS1/2showed both systemic and local responses to Pi starvation, and less than 10% of the overall induced mRNA level was due to the local Pi concentration in roots. The results indicate that Phi may interfere with earlier events in roots that are associated with a local Pi signalling pathway. An analysis of transgenic plants showed thatOsIPS1/2are independently responsive to Pi signalling and are mainly expressed in lateral roots and in the vascular cylinder in the primary root. Exogenous cytokinin (6-BA) almost completely suppressed systemic Pi starvation signalling and partially suppressed local Pi signalling. Exogenous abscisic acid remarkably reduced Pi starvation signalling. In contrast, exogenous auxin enhanced Pi signalling, especially local Pi signalling in roots. Exogenous ethylene (ethyphon) and the ratio of auxin to cytokinins did not appear to affect the expression of these two genes. [ABSTRACT FROM AUTHOR]

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: Perovskite manganite La0.9Ba0.1MnO3(LBMO) films were deposited on (001)-oriented single crystal yttria-stabilized zirconia (YSZ) substrate by 90° off-axis radio frequency magnetron sputtering. The film thickness ranged from 10nm to 100nm. Grazing incidence X-ray diffraction technique and high resolution X-ray diffraction were applied to characterize the structure of LBMO films. The LBMO film mainly consisted of (001)-orientated grain as well as weakly textured (110)-orientated grain. The results indicated that an amorphous layer with thickness of about 4nm was formed at the LBMO/YSZ interface. The strain in LBMO film was small and averaged to be about –0.14%. The strain in the film was not lattice mismatch-induced strain but residual strain due to the difference in thermal expansion coefficient between film and substrate. [Copyright &y& Elsevier]

Abstract: Perovskite manganite La0.7Ca0.3MnO3 (LCMO) films were deposited on (001)-oriented single crystal MgO and SrTiO3 (STO) substrates by 90° off-axis radio frequency magnetron sputtering. The thickness of LCMO/STO film was 50nm. The thickness of LCMO/MgO films ranged from 5nm to 200nm. LCMO films were well (001)-oriented grown with high crystalline quality. Grazing incidence X-ray diffraction technique and normal X-ray diffraction were applied to characterize the in-plane and out-of-plane lattice strains and strain relaxation. The in-plane growth orientations of LCMO films with respect to substrate surface were also studied. The results indicated that the lattice strain of LCMO films began to relax when the film thickness is less than 5nm. The mechanism for strain relaxation in LCMO films is perhaps different from that for tetragonal distortion. The in-plane growth orientation of LCMO/MgO film studied by grazing incidence X-ray diffraction technique is consistent with that from transmission electron microscopy. [Copyright &y& Elsevier]

Abstract: Both cracked and crack-free GaN/Al0.55Ga0.45N multiple quantum wells (MQWs) grown on GaN template by metalorganic chemical vapor deposition have been studied by triple-axis X-ray diffraction, grazing-incidence X-ray reflectivity, atomic force microscope, photoluminescence spectroscopy and low-energy positron annihilation spectroscopy. The experimental results show that cracks generation not only deteriorates the surface morphology, but also leads to a period dispersion and roughens the interfaces of MQWs. The mean density of dislocations in MQWs, determined from the average full-width at half-maximum of ω-scan of each satellite peak, has been significantly enhanced by the cracks generation. Furthermore, the measurement of annihilation-line Doppler broadening reveals a higher concentration of negatively charged vacancies in the cracked MQWs. The combination of these vacancies and the high density of edge dislocations are assumed to contribute to the highly enhanced yellow luminescence in the cracked sample. [Copyright &y& Elsevier]

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]