High-performance low-cost phase-shifter design based on ferroelectric materials technology

A novel approach to ferroelectric phase-shifter design using Ba/sub x/Sr/sub 1-x/TiO/sub 3/ (BSTO) films in a multilayer dielectric coplanar waveguide structure is described. By including a low-loss dielectric layer (SiO/sub 2/) between the coplanar waveguide conductors and a layer of ferroelectric materials, significant reduction in insertion loss can be achieved in conjunction with a threefold increase in figure of merit (/spl deg//dB).     

Electron holographic 3-D nano-analysis of Au/TiO2 catalyst at interface

Three-dimensional (3-D) nanostructures of gold catalysts supported on TiO2 were analysed by electron holography and high-resolution electron microscopy. The contact angle of the gold particle on TiO2 tended to be >90 degrees in the case of gold particles with a size (height) of >4 nm and it tended to be <90 degrees for gold particles with a height of <2 nm. The change in morphology increases the perimeter at the Au/TiO2 interface as the particle size decreases. This change in 3-D structure should be attributed to a change in electronic structure at the interface. It was found that electron holography enabled 3-D analysis at the atomic level and was effective for analysing nanostructured particles.     

On-line control of feed-speed in circular sawing

An adaptive control optimization system was developed to produce a desired surface finish roughness by automatic control of the work-piece feed-rate in circular sawing. The system developed in this study consists of the interconnection of an adaptive controller with a numerically controlled circular saw. The AE signals and cutting forces were measured to monitor the machining process continuously in this system. The signals were provided to the adaptive controller to evaluate the surface finish roughness and adjust the workpiece feed-rate automatically in the machining process. Sensing of AE signals and of cutting forces was compared to determine which technique is more convenient. Experiments were carried out with a carbide-tipped circular saw. Cross cutting was done with counter-cutting during the experiments. The cutting parameters controlled were workpiece feed-rates and cutting speeds. Japanese beech (Fagus crenata Blume) and Yezo spruce (Picea jezoensis Carr.) were used as the workpiece. Experimental results indicated that adaptive control optimization took place in the system developed for circular sawing. The desired surface finish roughness was produced by automatic control of the workpiece feed-rate using the sensing technique of AE signals as well as that of cutting force. However, the system using AE signals is more convenient than taht using cutting force.     

A monolithic three-channel LD-PD array with vertically staggeredfacets for autofocusing reflectivity sensors

A monolithic three-channel LD-PD array with vertically staggered facets is proposed for an autofocusing reflectivity sensor which uses light feedback. The focus-sensing characteristics are investigated using an array with a radiation facet displacement of 12 μm and an interchannel distance of 130 μm, fabricated on an 830-nm AlGaAs/GaAs multiple-quantum-well laser substrate with buried-heterostructure stripe geometry waveguides. High focus-sensing accuracy is achieved. A potential application of the array to optical heads for phase change media is discussed     

Differences in Si doping efficiency in tertiarybutylarsine,monoethylarsine and arsine for GaAs and AlGaAs grown by MOVPE

We investigate differences in Si doping of GaAs and AIGaAs between group-V sources. Si₂H₆ and SiH₄ doping dependence on growth temperature, V/III ratio, total flow rate, growth rate, and off angle of substrate orientation was examined using tertiarybu-tylarsine (TBAs), monoethylarsine (EtAs), and arsine with a horizontal atmospheric pressure reactor. With either dopant source, Si incorporation for films grown using TBAs or EtAs was always higher than that using arsine. Using silane, dependence of Si incorporation on growth temperature and total gas flow velocity is different between group-V sources. Using disilane, dependence on V/III ratio and total gas flow velocity is different between group-V sources. These results imply that gas phase reactions play an important role. From the kinetic simulation of the decomposition of group-V sources, we verified that the concentrations of AsH₃, AsH₂, and AsH in vapor near the substrate are quite different among group-V sources. AsH₂ is dominant reactant when using TBAs. We propose that H₂AsSiH₃ (silylarsine) is formed by the reaction between AsH₂ radical and SiH₄ and silylarsine should contribute Si incorporation reactions, resulting in high Si incorporation efficiency with TBAs and EtAs. We also suggest that AsH₃ inhibits Si incorporation.     

Scaling theory for double-gate SOI MOSFET's

A scaling theory for double-gate SOI MOSFETs, which gives guidance for device design (silicon thickness t_si; gate oxide thickness t_ox) that maintains a subthreshold factor for a given gate length is discussed. According to the theory, a device can be designed with a gate length of less than 0.1 μm while maintaining the ideal subthreshold factor. This is verified numerically with a two-dimensional device simulator     

Large nonlinear optical effect in an InGaAs/InAlAs multiquantum well waveguide

All-optical refractive nonlinearity in a passive InGaAs/InAlAs multiquantum well waveguide is evaluated for TE and TM modes at 1.55 mu m wavelength and room temperature. A quarter wavelength change in the optical path length is observed at an input pump light power of 6.5 mW for 1.47 mu m wavelength in a 960 mu m long device. Nonlinear refractive index n/sub 2/ is evaluated to be -1.2*10/sup 6/ and -0.5*10-6cm/sup 2//W for the TE and the TM modes, respectively.<>     

Tensile strained QW structure for low-threshold operation of short-wavelength, AlGaInP LDs emitting in the 630 nm band

The amount of tensile strain introduced into QWs and the optimum QW structure are evaluated for low-threshold operation of AlGaInP LDs in the wavelength range 630-640 nm. Very low threshold current of 32 mA under CW operation at 20 degrees C is achieved in an index-guided SQW LD emitting at 632 nm.<>     

Nitridation of the Sol–Gel-Derived Titanium Oxide Films by Heating in Ammonia Gas

Dip-coated sol–gel-derived TiO₂ films on an alumina substrate were converted to nonstoichiometric titanium nitride (TiN _x ( x ≦ 1)) films by heating at approxmately 1000°C in NH₃ gas. TiO₂ films made from TiO₂ sols prepared from Ti(O– i -C₃H₇)₄ and stabilized by diethanolamine were more easily nitrided than those from sols containing HCl as a deflocculant reagent. This appears to be a result of the more porous structure of the former films.     

Fatty marrow in the vertebrae. A parameter for hematopoietic activity in the aged

Fatty alteration of bone marrow was analyzed in upper lumbar vertebrae obtained from 94 autopsies. Of these, 85 were from individuals over 60 years of age. Fatty marrows were classified grossly into three groups: Group I, a massive type, Group II, a moderate or less significant type; Group III, a nonfatty type. Fatty marrows of Groups I and II were found most frequently in the older subjects. They were not observed (0/9) below 60 years of age, but were present in 42% (5/12) in the 6th decade, 61% (23/38) in the 7th decade, 76% (25/33) in the 8th decade, and 100% (2/2) in the 9th decade. This may relate to a decreasing volume of a reservoir stem cell compartment for blood cell generation. Since the vertebral marrow is the last reserve site for hematopoietic activity, the volume of fatty marrow in the vertebrae may be used as a parameter for the estimation of hematopoietic activity in the entire skeletal system in the aged.