Modulation-doped Al0.22Ga0.78N/GaN heterostructure with 1000 A Si-doped n-Al0.22Ga0.78N barrier (n-AlGaN) were deposited on (0001)-oriented sapphire (-Al2O3) by means of atmosphere-pressure metal-organic chemical vapor deposition. The reciprocal space mappings of symmetric reflection (0002) and asymmetric reflection (1014) 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" strainrelaxation status, which probably results from the internal defects of n-AlGaN and the strain relaxation status at the i-GaN/-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.

With varying thickness of the spacer near the second oscillatory GMR peak in Co/Cu system, a series of glass/Fe/[Co/Cu]20/Co multilayers are prepared by magnetronsputtering technique. The MR values are relatively small. High angle X-ray di raction shows that the copper crystallizes in fcc structure with (111) texture and the cobalt crystallizes in hcp structure with (002) preferential orientation. There is a mixed amorphous CoCu layer at the interface due to the di usion between cobalt and copper, which may decrease the MR value. The thickness, the mass density for each sub-layer and the surfacial and interfacial roughnesses are re ned from the X-ray specular reflectivity measurement.

The film of La2/3Ca1/3MnO3 (LCMO), YBa2Cu3O7−δ (YBCO) and YBCO/LCMO bi-layer were prepared by rf off-axis magnetic sputtering technique on SrTiO3 (STO) substrate. The structures, including the surface and interfacial morphology, the interfacial diffusion and so on, have been characterized by X-ray diffraction (XRD), auger electronic energy spectroscopy (AES) and atomic force microscopy (AFM). Through a 50-200eV energy range, a single layer of YBCO shows a very small reflectance (<2%), while a single layer of LCMO shows a higher reflectance of about 25% at the energy of about 75eV, which is much higher than that of metal W. Even higher reflectance (>50%) at about 75eV has been observed in the LCMO/YBCO bi-layers.

Lai. 85Sro. 15Cul-yMy04 ceramic cuprates with M-Zn, Ni, Mg, and). ≤0.30 have been synthesized. The superconduct-ing critical temperatures and the room temperature resistivities for M doping have been determined by a standard four-probemethod. The width of each reflection of X-ray diffraction for each sample is analyzed by Rietveld refinements which is related to the average grain size and the average lattice microstrain. In this way we attempt to explain the stronger suppression for non-magnetic doping such aS Zn or Mg than that for magnetic doping such as Ni.

We we have successfully fabricated ceramic superconductors of Hg-1223 with substitution of Pb for Hg, i. e. Hg1-xPbxBa2Ca2Cu3ov, by using encapsulation and short time annealing techniques. Samples fabricated in this manner may have nearly single phase structure and some enhancement ofTc can be achieved through this method. The materials of this ceramic with x ranging from 0 to 0.5 exhibit high-temperature superconductivity at temperatures falling in the range from 103 to 135K. The sample with optimum doping of Pb of x=0.34 and 6=0.40 has a highest Tc of 135K and its diamagnetic onset temperatureTdiac=143K. The composition of this sample has been found experimentally and is specified by a formula of Hg0.66Pb0.34Ba2Cal. 98Cu2.9708.4. The valence number for the copper constituent is given byvcu=2.30