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.<>     

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.     

Estimation of wave fields of incident beams in a transmission electron microscope by using a small selected-area aperture

The direction of an electron beam in a nanometer-sized area is measured directly by utilizing a selected-area aperture. By the measurements at several areas in a beam, the wavefront curvature and thus the defocus value of the beam are detected. From the defocus value, the wave field at the specimen plane is also reproduced in consideration of the influences of the condenser aperture and spherical aberration of the illumination lens. The result shows that phase deviation of 2π is caused only at about 10?nm apart from the beam center in a beam with a typical diameter for high-resolution transmission electron microscopy. Based on the defocus value, the convergence angle of the beam is also estimated to be about 6?mrad without being influenced by the partial coherence, that is, independently of the type of the electron gun. Measuring the defocus values for only two beam diameters enables us to determine geometrical parameters peculiar to the illumination system, based on which wave fields of any beam diameters by any condenser aperture sizes can be estimated. The technique proposed in this paper is effective in evaluating the influence of wavefront curvature of incident beams on various kinds of precise measurements conducted in transmission electron microscopes.     

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).     

Stability and accuracy of power‐series method for one‐dimensional heat conduction with non‐uniform grid systems

The power‐series method, a finite analytic approach to heat transfer and fluid flow problems that is based on power‐series expansion, was applied to a one‐dimensional heat‐conduction problem to evaluate its stability and accuracy. Application to a specific heat‐conduction problem with non‐uniform grid systems showed that it had stability within the ranges 10⁻⁵<Δt,Δx_E, and Δx_W,a<10⁵, and 10⁻⁵<β<10⁵. Comparison of its solutions with those by the fully implicit and Stefanovic–Stephan methods showed that this method yielded more accurate and robust solutions. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(7): 470–480, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20085     

CuPc/PbZr0.2Ti0.8O3/(La,Ba)MnO3 field effect transistor heterojunction photomemory

We investigated a photoconductor(PC)/ferroelectric oxide(OF)/semiconductor oxide(SO) POS-FET structure photomemory consisting of organic photoconductor CuPc/inorganic ferroelectric PbZr_0.2Ti_0.8O₃ heterojunction gate and a ferromagnetic oxide semiconductor La_0.87Ba_0.13MnO₃ channel. Visible light information detected by photoconductor CuPc can be memorized in ferroelectric PbZr_0.2Ti_0.8O₃, and non-volatile and non-destructive reading out process of light information memorized in this ferroelectric layer were achieved by reading out the resistance modulation of ferromagnetic semiconductor oxide La_0.87Ba_0.13MnO₃ channel under the photoconductor/ferroelectric gate.     

Analysis and discussion on conduction current based on simultaneousmeasurement of TSC and space charge distribution

A new analysis of conduction current distributed in dielectrics based on simultaneous measurements of thermally stimulated current (TSC) and time dependent space charge distribution is proposed. A new system pulsed electro-acoustic (PEA) method has been developed to enable simultaneous measurement of the TSC and the dynamic space charge and electric field distributions as a function of temperature within insulators. With the new system, the relationship between the TSC and the time dependent electric field distribution in electron beam (e-beam) irradiated PMMA has been investigated. From the time dependent electric field, the displacement current in dielectrics is obtained. The TSC is a typical external current which is represented as an addition of the displacement current and a conduction current in dielectrics. This paper makes it clear that the conduction current as a function of position is determined by the simultaneous measurement of the external current and the dynamic space charge distribution     

Teleoperation via computer network

In a teleoperation system, providing force information to a human operator can improve task performance. When a communication block between a master and a slave has a transmission delay, the system is easily destabilized. Anderson and Spong guaranteed passivity in the communication block by using scattering transformation and overcame this instability caused by the time delay. But this method can be applied to the communication block with a constant time delay. In a traditional teleoperation system, its communication block has a constant time delay. But time delay irregularly changes in a computer network because many users share telecommunication lines. This paper shows that the variable time delay destabilizes bilateral master-slave manipulator with scattering transformation and a new compensation method which keeps the time delay constant. This new compensation method has been implemented in a single-axis master-slave manipulator.