Lattice parameter determination of a strained area of an InAs layer on a GaAs substrate using CBED

All the six lattice parameters (a, b, c, alpha, beta and gamma) of a strained area of an InAs layer grown on a GaAs substrate were determined without any assumption of the crystal lattice symmetry from the higher-order Laue zone (HOLZ) lines appearing in one convergent-beam electron diffraction (CBED) pattern. The analysis was performed with three steps. Firstly, the parameters alpha and beta were determined from the deviations of the HOLZ lines from the mirror symmetry perpendicular to the [001] direction. Secondly, the parameter c was determined from the distance between the intersections of the HOLZ lines, which have the same h and k indices but different l indices. Finally, the parameters a, b and gamma were determined simultaneously from several distances between the intersections of the HOLZ lines. The lattice parameters determined for the strained area were a = 0.611(2) nm, b = 0.615(1) nm, c = 0.6119(7) nm, alpha = 89.5(1) degrees, beta = 89.0(2) degrees and gamma = 89.1(2) degrees. This result implies that the cubic lattice of InAs is elongated approximately in the [111] direction and the exact lattice symmetry is triclinic. The same analysis procedure was applied to another two specimen areas. It was found that the areas have orthorhombic distortions with lattice parameters a = 0.607(2) nm, b = 0.604(1) nm and c = 0.6085(7) nm for one area, and with a = 0.607(2) nm, b = 0.605(1) nm and c = 0.6065(7) nm for the other area. It is should be emphasized that the present analysis of lattice distortions is immediately applicable to the other semiconductors, such as Si, SiGe or GaAs layers, without assuming any crystal system.     

Contact-Barrier Free,High Mobility,Dual-Gated Junctionless Transistor Using Tellurium Nanowire

The gate-all-around nanowire transistor, due to its extremely tight electrostatic control and vertical integration capability, is a highly promising candidate for sub-5 nm technology nodes. In particular, the junctionless nanowire transistors are highly scalable with reduced variability due to avoidance of steep source/drain junction formation by ion implantation. Here a dual-gated junctionless nanowire p-type field effect transistor is demonstrated using tellurium nanowire as the channel. The dangling-bond-free surface due to the unique helical crystal structure of the nanowire, coupled with an integration of dangling-bond-free, high quality hBN gate dielectric, allows for a phonon-limited field effect hole mobility of 570 cm² V⁻¹ s⁻¹ at 270 K, which is well above state-of-the-art strained Si hole mobility. By lowering the temperature, the mobility increases to 1390 cm² V⁻¹ s⁻¹ and becomes primarily limited by Coulomb scattering. The combination of an electron affinity of ≈ 4 eV and a small bandgap of tellurium provides zero Schottky barrier height for hole injection at the metal-contact interface, which is remarkable for reduction of contact resistance in a highly scaled transistor. Exploiting these properties, coupled with the dual-gated operation, we achieve a high drive current of 216 μA μm⁻¹ while maintaining an on-off ratio in excess of 2 × 10⁴. The findings have intriguing prospects for alternate channel material based next-generation electronics.     

Observation of iron silicide formation by plan-view transmission electron microscopy

The formation and the phase transitions of iron silicide by solid-phase epitaxy have been investigated by means of plan-view transmission electron microscopy, which enables us to observe a clean interface between Fe and Si. Layers of Fe were deposited on Si (100) at room temperature in an ultrahigh vacuum chamber. The sample was annealed in the electron microscope at a temperature between 673 and 1073 K. After annealing at 673 K, FeSi crystallites were formed with various orientations. When the annealing temperature was increased to 973 K, we found that the crystallites suddenly started to coalesce into grains of several hundreds of nanometers in size and polycrystalline beta-FeSi2 was formed. These phase transitions were also confirmed with electron energy-loss spectroscopy.     

Evaluation of solar energy potential and PV module performance in the Gobi Desert of Mongolia

Here, we present the results of evaluation of solar energy potential and photovoltaic (PV) module performance from actual data measured over a period of more than 2 years in the Gobi Desert of Mongolia. To allow estimation of solar energy potentials and durability of PV systems in the Gobi Desert area, a data acquisition system, including crystalline silicon (c‐Si), polycrystalline silicon (p‐Si) modules, and two sets of precision pyranometers, thermometers, and anemometer, was installed at Sainshand City in October 2002. This system measures 23 parameters, including solar irradiation and meteorological parameters, every 10 min. High output gain was observed due to operation at extremely low ambient temperatures and the module performance ratios (PRs) were high (>1·0) in winter. In summary, the present study showed that a PV module with a high temperature coefficient, such as crystalline silicon, is advantageous for use in the Gobi Desert area. Copyright © 2006 John Wiley & Sons, Ltd.     

Advanced Wireless Access System

The key words for the future telecommunications are personalization, multi-media services and high accessibility to the network. These trends naturally lead to radio media application to access links. In this sense, this paper proposes an advanced wireless access system with a capacity supporting broadband video and data services.Concept of the system can be defined as a new radiocommunication category with advantages of both fixed and mobile systems.The system is designed to transport ATM-based signals using SHF (or EHF) bands to wireless terminals, interconnected with optical fibers at the network side. The basic system configuration is presented as well as examples of system parameters.For radio aspects the maximum service coverages of the radio base stations are calculated based on availability consideration. Preferred frequency bands for actual operation are also discussed.     

High-performance C60 and picene thin film field-effect transistors with conducting polymer electrodes in bottom contact structure

C₆₀ and picene thin film field-effect transistors (FETs) in bottom contact structure have been fabricated with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) electrodes for a realization of mechanical flexible organic FETs. The C₆₀ thin film FETs showed n-channel enhancement-type characteristics with the field-effect mobility μ value of 0.41 cm² V^?1 s^?1, while the picene thin film FET showed p-channel enhancement-type characteristics with the μ of 0.61 cm² V^?1 s^?1. The μ values recorded for C₆₀ and picene thin film FETs are comparable to those for C₆₀ and picene thin film FETs with Au electrodes.     

Energy transmission transformer for a wireless capsule endoscope: analysis of specific absorption rate and current density in biological tissue

This paper reports on the electromagnetic influences on the analysis of biological tissue surrounding a prototype energy transmission system for a wireless capsule endoscope. Specific absorption rate (SAR) and current density were analyzed by electromagnetic simulator in a model consisting of primary coil and a human trunk including the skin, fat, muscle, small intestine, backbone, and blood. First, electric and magnetic strength in the same conditions as the analytical model were measured and compared to the analytical values to confirm the validity of the analysis. Then, SAR and current density as a function of frequency and output power were analyzed. The validity of the analysis was confirmed by comparing the analytical values with the measured ones. The SAR was below the basic restrictions of the International Commission on Nonionizing Radiation Protection (ICNIRP). At the same time, the results for current density show that the influence on biological tissue was lowest in the 300-400 kHz range, indicating that it was possible to transmit energy safely up to 160 mW. In addition, we confirmed that the current density has decreased by reducing the primary coil's current.     

Solution‐Processed Silicane Field‐Effect Transistor: Operation Due to Stacking Defects on the Channel

2D silicon nanomaterials have unique potential for use in applications owing to their many different exotic electronic properties. Field‐effect transistors are fabricated based on free‐standing silicanes through a solution process. Owing to the sensitive surface and the nanometer thickness, the devices require the use of fabrication conditions similar to those of lithium‐ion batteries to prevent oxidation of the sheets. Reliable transistor performance is observed at room temperature in a channel thinner than 3 nm, as drain voltage dependent transfer curves current modulation, depending on the edge effect of the silicane, although the transistor property is modest (hole mobility of 1.8 cm² V^?1 s^?1). The results suggest the feasibility of other air‐sensitive 2D nanomaterials for applications in nanoelectronic devices.     

Reliability of Liquid Crystal Display

This paper reports the reliability of twisted nematic liquid-crystal display for basic applications such as watches and calculators. We have studied significant stress factors such as voltage, temperature and humidity, and their corresponding failure modes. The main failure mode is LCD misalignment; many different modes appear corresponding to different stress conditions as well as material and process for the LCD. We have analyzed the accelerated test results by Weibull distribution, elucidated accelerating factors, and estimated life time. The life is inversely proportional to 1.78-2.45 power of applied voltage, depending upon misalignment modes. The distribution of life is well expressed by Weibull distribution with shape parameter between 2.5-3.0, and proportional to the square of coefficient of variation of life. We conclude that the acceleration factors could be determined and 99.9% of tested displays will live more than 10 years. The knowledge on reliability of LCD can be now applied to new fields of LCD, such as industrial use, home appliance, and automotive instruments.     

Source-to-drain nonuniformly doped channel (NUDC) MOSFET structuresfor high current drivability and threshold voltage controllability

The source-to-drain nonuniformly doped channel (NUDC) MOSFET has been investigated to improve the aggravation of the V_th lowering characteristics and to prevent the degradation of the current drivability. The basic concept is to change the impurity ions to control the threshold voltage, which are doped uniformly along the channel in the conventional channel MOSFET, to a nonuniform profile of concentration. The MOSFET was fabricated by using the oblique rotating ion implantation technique. As a result, the V_th lowering at 0.4-μm gate length of the NUDC MOSFET is drastically suppressed both in the linear region and in the saturation region as compared with that of the conventional channel MOSFET. Also, the maximum carrier mobility at 0.4-μm gate length is improved by about 20.0%. Furthermore, the drain current is increased by about 20.0% at 0.4-μm gate length