COMPETING REACTIONS OF EXISTING Ni SILICIDE AND Ni OR Si INDUCED BY THERMAL ANNEALING AND MeV Si ION BEAM MIXING

The competing reactions between existing Ni silicides surrounded by Si and Ni were investigated by thermal annealing and MeV Si ion beam mixing. With high energy irradiation, the energy deposition at both interfaces, Ni/Ni silicide and Ni silicide/Si, is equal. Two MeV He~- RBS and TEM were used to obtain the reacted layer composition and epitaxial orientation, respectively. Also glancing angle Co K_a. X-ray diffraction was utilized to identify phase formation. The main results indicate that the existing silicides preferentially react with Ni layer, and that there are pronounced differences of Ni silicide phase transition between thermal annealing and MeV Si ion beam mixing, even though the mixing was performed in radiation enhanced diffusion regime. The results can be explained in term of the heat of silicide formation and surface energy change.     

Nonlinear GaAs MESFET modeling using pulsed gate measurements

The effects of traps in GaAs MESFETs are studied using a pulsed gate measurement system. The devices are pulsed into the active region for a short period (typically 1 μs) and are held in the cutoff region for the rest of a 1-ms period. While the devices are on, the drain current is sampled and a series of pulsed gate I-V curves are obtained. The drain current obtained under the pulsed gate conditions for a given V_GS and V_DS gives a better representation of the instantaneous current for a corresponding V_gs and V_ds in the microwave cycle because of the effects of traps. The static and pulsed gate curves were used in a nonlinear time-domain model to predict harmonic current. The results showed that analysis using pulsed gate curves yielded better predictions of harmonic distortion than analysis based on conventional state I-V curves under large-signal conditions     

Surface snow properties effect on millimeter-wave backscatter

The authors examine the relationship between 94-GHz backscatter from snow cover and the properties of the snow, using statistical analysis of observations made in West Germany in 1986. For terrain covered by dry snow, 94-GHz backscatter does not appear to depend significantly on any of the measured snow properties. Backscatter from wet snow is found to be sensitive to volumetric liquid water content, with the dependence inverse-exponential in form. Backscatter from wet snow is also found to depend on surface roughness, especially the cross-polarized return. Comparison of the 1986 data with similar data obtained in 1984 shows two major disagreements in the response of the vertical transmit vertical receive polarization backscattering coefficient to wet snow surface roughness, and the response of cross-polarized. The backscattering coefficient to snow surface wetness. The 1986 results are considered more reliable     

Introduction to wavelets in engineering

The aim of this paper is to provide an introduction to the subject of wavelet analysis for engineering applications. The paper selects from the recent mathematical literature on wavelets the results necessary to develop wavelet-based numerical algorithms. In particular, we provide extensive details of the derivation of Mallat's transform and Daubechies' wavelet coefficients, since these are fundamental to gaining an insight into the properties of wavelets. The potential benefits of using wavelets are highlighted by presenting results of our research in one- and two-dimensional data analysis and in wavelet solutions of partial differential equations.     

Transport properties of the organic conductor (TMTSF)2BrO4: Evidence of variable-range hopping

A study of d.c. and microwave conductivity and thermoelectric power of the organic conductor (TMTSF)₂BrO₄ is presented. The transport properties are in qualitative agreement with charge transport via variable-range hopping among localized states. The localization is attributed to the anions, which are ordered only over short ranges, probably due to impurities.     

Structure and electronic properties of bismuth anodic oxide films—I. Photoeffects

Estimates of the conduction electron mobility, lifetime and trap density of anodic bismuth oxide films, obtained by measuring the transient response of a polarized bismuth anode to an intense flash of white light, showed that the films had a highly defective structure. for thicker films (～240 nm) the photo-response arose from the production of electron-hole pairs in the bulk of the film, but for very thin films (～5 nm) the response arose from photo-emission of electrons from the metal into the film, and effects attributed to the decay of space charges of both electrons and mobile ions were observed.The photo-response was used to investigate the possible formation of films of bismuth oxo-halides under conditions in which these compounds were thermodynamically stable. Incorporation of iodide and bromide into the very thin films at pH 5 was detected. No effect of chloride was observed. Comparison with cyclic voltammetric results indicated that an anodic layer of bismuth oxoiodide might be formed by direct nucleation on to the metal surface.     

Failure experience of programmable logic controllers used in emergency shutdown systems

Microprocessor-based programmable logic controllers (PLCs) are often used in applications to safety shut down a process or facility if unsafe conditions are detected. Increased use of quantitative reliability analysis requires additional and more detailed failure rate estimates for analyzing PLCs. This technical note presents failure rates derived from PLC performance in emergency shutdown (ESD) systems for natural gas compressor stations. The PLCs analyzed operate with roughly 40 inputs processed through three input modules and generate approximately 20 control signals through two output modules. Failure rates range from 0·072/year when the PLC alone was considered to 0·32/year when all types of failures were considered. (All failures include effects that are not necessarily attributable to the PLC microprocessors, such as human errors while working in the PLC cabinets and failures of common power supplies.)