Microstructure and properties of (Sr, Ca)CuO2/(Sr, Ca)RuO3 multilayers

Epitaxial multilayer thin films of infinite-layer (Sr, Ca)CuO₂ and perovskite (Sr, Ca)RuO₃ have been prepared on (100) SrTiO₃ substrates by multitarget rf magnetron sputtering. X-ray diffraction analyses revealed that the multilayer structure of (Sr, Ca)CuO₃/(Sr, Ca)RuO₃ was successfully fabricated with a minimum layer thickness of 20 Å. Transmission electron microscopy measurements of the multilayers indicated that there was no dislocation which normally exists in single-layer films with an infinite-layer structure. Resistivities of multilayer films at room temperature ranged from 1 to 10 m cm and showed semiconductor-like dependence against the temperature.     

Rational Filters for Passive Depth from Defocus

A fundamental problem in depth from defocus is the measurement of relative defocus between images. The performance of previously proposed focus operators are inevitably sensitive to the frequency spectra of local scene textures. As a result, focus operators such as the Laplacian of Gaussian result in poor depth estimates. An alternative is to use large filter banks that densely sample the frequency space. Though this approach can result in better depth accuracy, it sacrifices the computational efficiency that depth from defocus offers over stereo and structure from motion. We propose a class of broadband operators that, when used together, provide invariance to scene texture and produce accurate and dense depth maps. Since the operators are broadband, a small number of them are sufficient for depth estimation of scenes with complex textural properties. In addition, a depth confidence measure is derived that can be computed from the outputs of the operators. This confidence measure permits further refinement of computed depth maps. Experiments are conducted on both synthetic and real scenes to evaluate the performance of the proposed operators. The depth detection gain error is less than 1%, irrespective of texture frequency. Depth accuracy is found to be 0.51.2% of the distance of the object from the imaging optics.     

Effect of poly(acrylic acid) on the preparation of thick silica films by electrophoretic sol–gel deposition of re-dispersed silica particles

Thick silica films were prepared by the electrophoretic sol–gel deposition technique in the presence of poly(acrylic acid) (PAA) using monodispersed silica particles; the particles were prepared by the sol–gel method, pre-heat treated and then re-dispersed in the mixture of H2O and ethanol. The weight of deposited silica films was maximized when 0.2 mass % of PAA against the whole amount of sol was added. The particles constructing the thick silica films were packed densely when the amount of added PAA was less than 0.2 mass%. The weight of the film increased with decrease in the content of H2O in the sol when a fixed amount of PAA was added. After the heat treatment of deposited films at 800 °C, crack-free silica films of about 30 m thickness were prepared. © 1998 Chapman & Hall     

Soft magnetic properties of NiFeTa thin films for biasing film applications in magnetoresistive elements

The effects of Ta addition on the magnetic properties of permalloy thin films have been investigated. The alloy compositions on a weight basis are (Ni₈₁Fe₁₉)_1-x Ta _x with 0 x 0.105, and the films are sputtered onto a glass substrate at between room temperature and 300 C. The saturation magnetization and anisotropic magnetic field decrease with increasing Ta content. The saturation magnetization is 0.75 T at 5 wt % Ta. The coercivity remains constant at 125 Am^-1. The electrical resistivity increases linearly with increasing Ta content, then saturates at approximately 7.5 wt% Ta. The saturation resistivity is approximately 1.00 m. The magnetoresistivity ratio (/) decreases with increasing Ta content, mainly due to increased electrical resistivity (). The magnetostriction changes from negative to positive with increasing Ta content and reaches nearly zero at 2 wt% Ta. The NiFeTa films containing 5–6 wt% Ta have potential for use as the soft-biasing film in magnetoresistive elements.     

Discharge properties and chemical stability of SrZrO films

Abstract— MgO thin film is currently used as a surface protective layer for dielectric materials because MgO has a high resistance during ion sputtering and exhibits effective secondary electron emission. The secondary‐electron‐emission coefficient γ of MgO is high for Ne ions; however, it is low for Xe ions. The Xe content of the discharge gas of PDPs needs to be raised in order to increase the luminous efficiency. Thus, the development of high‐γ materials replacing MgO is required. The discharge properties and chemical surface stability of SrO containing Zr (SrZrO) as the candidate high‐γ protective layer for noble PDPs have been characterized. SrZrO films have superior chemical stability, especially the resistance to carbonation because of the existence of a few adsorption sites due to their amorphous structure. The firing voltage is 60 V lower than that of MgO films for a discharge gas of Ne/Xe = 85/15 at 60 kPa.     

An adaptive observer for a spacecraft–manipulator system using a camera mounted on its spacecraft

This paper deals with a motion control system for a space robot with a manipulator. Many motion controllers require the positions of the robot body and the manipulator hand with respect to an inertial coordinate system. In order to measure them, a visual sensor using a camera is frequently used. However, there are two difficulties in measuring them by means of a camera. The first one is that a camera is mounted on the robot body, and hence it is difficult to directly measure the position of the robot body by means of it. The second one is that the sampling period of a vision system with a general-purpose camera is much longer than that of a general servo system. In this paper, we develop an adaptive state observer that overcomes the two difficulties. In order to investigate its performance, we design a motion control system that is constructed by combining the observer with a PD control input, and then conduct numerical simulations for the control system. Simulation results demonstrate the effectiveness of the proposed observer.     

Defect distribution near abraded surface of III–V compound semiconductors

Microstructures of damaged layers near the abraded surface of GaP, GaAs_0.6P_0.4 and GaAs single crystals have been observed with a transmission electron microscope. The damage due to 0.3 m Al₂O₃ abrasion consists of dislocations. Dislocation densities in the abrasion band and other regions are larger than 5×10¹¹ cm^–2 and about 10¹¹ cm^–2, respectively. Dislocation density decreases with increasing distance (depth) from the abraded surface. The depths of the damage layers for GaP, GaAs_0.6P_0.4 and GaAs are about 0.4, 0.55, and 0.8 m, respectively. The Burgers vector of dislocations is a/2[1 1 0], and A and B dislocations are observed. During annealing, the dislocations are rearranged and eliminated by the reaction of the dislocations with different Burgers vectors and climbing motion. The rearrangement temperatures for dislocations in GaP and GaAs are about 500 and 450° C, respectively. Electrical resistance changes in the damaged layer of GaP are recognized by electrical resistance measurements.     

Dielectric Dispersion of Polycrystalline Aluminum Nitride at Microwave Frequencies

Complex permittivity of polycrystalline AlN was measured over the frequency range 100 MHz to 13 GHz using reflection coefficient and cavity resonator methods. Dielectric relaxation peaks of loss tangent were observed in the frequency range 200 MHz to 3 GHz. The maximum value of loss tangent was ∼200 × 10⁻⁴. Relative permittivities decreased by ∼4% with increased frequency at the region of relaxation peaks. It was shown that these dispersion frequencies were inversely proportional to the grain sizes of AlN and independent of purities and processes. Model calculations for elastic vibration of a single-crystal grain of AlN were performed to investigate the origin of the dielectric dispersion due to piezoelectric effect. The calculated results of elastic sphere and 14-faced-polyhedron models showed a good quantitative agreement with the observed dispersion frequencies, which suggested that the dispersion was due to a piezoelectric vibration of a single grain of AlN ceramics at microwave frequencies.     

Strength Analysis of Yttria-Stabilized Tetragonal Zirconia Polycrystals

Tensile strength of Y₂O₃-stabilized ZrO₂ polycrystals (Y-TZP) was measured by a newly developed tensile testing method with a rectangular bar. The tensile strength of Y-TZP was lower than that of the three-point bend strength, and the shape of the tensile strength distribution was quite different from that of the three-point bend strength distribution. It was difficult to predict the distribution curve of the tensile strength using the data of the three-point bend strength by one-modal Weibull distribution. The distribution of the tensile strength was analyzed by two- or three-model Weibull distribution coupled with an analysis of fracture origins. The distribution curve of the three-point bend strength which was estimated by multimodal Weibull distribution agreed favorably with that of the measured three-point bend strength values. A two-modal Weibull distribution function was formulated approximately from the distributions of the tensile and three-point bend strengths, and the estimated two-modal Weibull distribution function for the four-point bend strength agreed well with the measured four-point bend strength.