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An analysis of the axially symmetric TM/sub 011/ mode in a dielectric-loaded cavity is presented and a technique of using a TM/sub 011/ mode dielectric-loaded cavity is introduced for measurements of microwave surface resistances of HTS thin films. A dielectric resonator with /spl epsiv//sub r//spl ap/39 is used for this purpose. It turned out that Q of the TM/sub 011/ mode dielectric-loaded cavity is very sensitive to the surface resistance of the material at the bottom plate, especially to the surface resistance of the area under the dielectric resonator, which can be used to investigate local microwave properties of large HTS thin films in a nondestructive, simple way. Experiments on YBCO thin films with the dimensions of /spl sim/2/spl times/2 cm/sup 2/ are performed using this technique, which revealed inhomogeneity in the microwave surface resistance of the thin films at different sites and demonstrated the usefulness of this technique. [ABSTRACT FROM PUBLISHER]

We have investigated the spatial distribution of superconducting transition in an epitaxial YBa[sub 2]Cu[sub 3]O[sub 7] film using variable temperature scanning laser microscope (VTSLM). VTSLM creates an image of the ac voltage response, δV(x, y), due to an ac modulated laser beam, which is proportional to dRdT(x, y). In the resistive transition region, there is a strong correlation between the VTSLM images and the resistance of the sample. When the sample is making a poor thermal contact to the heat bath, the large δV(x, y) region shifts toward the ends of the bridge while the sample resistance decreases. This result is due to the variation of surface temperature along the sample created by the heating at the contact resistance and/or the poor thermal contact between the sample and the heat bath. However, even after improving thermal contact, we still observe the distribution of superconducting transition. Since the local superconducting transition occurs within 1 K, we conclude that any samples with superconducting transition width larger than 1 K have local nonuniformity. [ABSTRACT FROM AUTHOR]

Attempts to show that lanthanum-substituted bismuth titanate thin films provide a promising alternative for ferroelectric random access memories (FRAM). Similarity of the structure of FRAM to that of conventional dynamic random access memory; Impact of use of strontium bismuth tantalate or related oxides.

Investigates the role of the perovskite layers on fatigue behaviors in SrBi[sub 2]Ta[sub 2]O[sub 9] (SBT) and Bi[sub 3]TiTaO[sub 9] (BTT) films. Preparation of the thin films by pulsed laser deposition; Growth behaviors, electrical properties and retention characteristics of the SBT and BBT films.

Studies the differences in nature of defects between SrBi[sub 2]Ta[sub 2]O[sub 9] and Bi[sub 4]Ti[sub 3]O[sub 12] thin films. Use of x-ray photoemission spectroscopy in the study; Relation of the difference in stability of the metal-oxide octahedra to different fatigue behaviors of the films.

We have heteroepitaxially deposited Ba[sub 0.6]Sr[sub 0.4]TiO[sub 3] (BST) thin films on (001)-oriented MgO substrates using pulsed-laser deposition. By optimizing the deposition temperature and adjusting the film thickness, we have successfully increased the dielectric nonlinearity and decreased the dielectric loss of BST films. BST thin films grown at 750 °C with a thickness of 1.1 μm showed a dielectric constant tunability of greater than 65% and a tunability/loss of 43 at a surface electric field of 80 kV/cm at room temperature. X-ray diffraction and transmission electron microscopy analyses indicated that the tunability and dielectric loss were closely related to the crystallinity of the BST films. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report a systematic study of the microstructure and dielectric properties of barium strontium titanate, Ba[sub 1-x]Sr[sub x]TiO[sub 3], films grown by laser ablation on LaAlO[sub 3] substrates, where x=0.1-0.9 at an interval of 0.1. X-ray diffraction analysis shows that when x<0.4, the longest unit-cell axis is parallel to the plane of the substrate but perpendicular as x approaches 1. Dielectric constant versus temperature measurements show that the relative dielectric constant has a maximum value and that the peak temperatures corresponding to the maximum relative dielectric constant are about 70 °C higher when x≤0.4 but similar when x>0.4, compared with the peak temperatures of the bulk Ba[sub 1-x]Sr[sub x]TiO[sub 3]. At room temperature, the dielectric constant and tunability are relatively high when x≤0.4 but start to decrease rapidly as x increases. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: TiO2 thin films were deposited by e-beam and the refractive index and extinction coefficient of the films were measured. When the oxygen pressure increases from 1.3×10−5 to 2.2×10−4 Torr, while the substrate temperature (300±10 °C) and the depositing rate (0.1 nm/s) were kept constant, the refractive index of the films decreases from 2.41 to 2.12 (at λ =550 nm). The structures of the films were investigated by X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM). XRD measurements revealed that the films deposited in a higher substrate temperature (300±10 °C) were partially crystalline. The AFM investigation confirmed that lower oxygen pressure, higher deposition rate and higher substrate temperature produce a higher surface roughness of TiO2 film. When the deposition rate (0.1 nm/s) and the substrate temperature (300±10 °C) were kept constant, and the oxygen pressure was varied from 1.3×10−5 to 2.2×10−4 Torr, the roughness (Root-Mean-Square) of as-deposited films was changed from 3.53 to 1.91 nm. [Copyright &y& Elsevier]

We report the effect of Co 2 N impurity on the superconducting properties of δ-MoN thin films grown by polymer-assisted deposition on c -cut sapphire (Al 2 O 3). The films show a superconducting transition temperature of 10.4 K and an upper critical field H c2 (0) perpendicular to the film surface around 3 T. The latter corresponds to a relatively large coherence length ξ, which enhances the two-dimensional limit when the magnetic field is applied parallel to the film surface. In comparison with pure δ-MoN films, the inclusion of Co 2 N impurity in the δ-MoN films could significantly modify the critical current density at the vortex-free state. The ability to tune the superconducting properties of metal-nitride superconductors by introducing chemically and structurally compatible impurity may find potential applications for superconducting single-photon detectors. • Co 2 N addition modifies the properties of δ-MoN. • Upper critical field reduces in comparison with pure films. • The films display low critical current densities at the vortex-free state. [ABSTRACT FROM AUTHOR]