Zinc Diffusion into InP via a Narrow Gap from a Planar Zn<Subscript>3</Subscript>P<Subscript>2</Subscript>-Based Source

An original technology of zinc diffusion into InP via a narrow gap is described, which allows reproducible formation of p–n junctions with preset depth of doping and retained surface morphology of the doped layers. Using the proposed method, desired charge carrier distribution profiles in Zn-doped InP layers were obtained. It has been experimentally confirmed that the method of cross-sectional scanning electron microscopy allows to precision measure of the zinc diffusion depth.     

Micro-milling performance of AISI 304 stainless steel using Taguchi method and fuzzy logic modelling

In this study, micro-milling of AISI 304 stainless steel with ball nose end mill was conducted using Taguchi method. The influences of spindle speed, feed rate and depth of cut on tool wear, cutting forces and surface roughness were examined. Taguchi’s signal to noise ratio was utilized to optimize the output responses. The influence of control parameters on output responses was determined by analysis of variance. In this study, the models describing the relationship between the independent variables and the dependent variables were also established by using regression and fuzzy logic. Efficiency of both models was determined by analyzing correlation coefficients and by comparing with experimental values. The results showed that both regression and fuzzy logic modelling could be efficiently utilized for the prediction of tool wear, cutting forces and surface roughness in micro-milling of AISI 304 stainless steel.     

PETOOL: MATLAB-based one-way and two-way split-step parabolic equation tool for radiowave propagation over variable terrain

A MATLAB-based one-way and two-way split-step parabolic equation software tool (PETOOL) has been developed with a user-friendly graphical user interface (GUI) for the analysis and visualization of radio-wave propagation over variable terrain and through homogeneous and inhomogeneous atmosphere. The tool has a unique feature over existing one-way parabolic equation (PE)-based codes, because it utilizes the two-way split-step parabolic equation (SSPE) approach with wide-angle propagator, which is a recursive forward–backward algorithm to incorporate both forward and backward waves into the solution in the presence of variable terrain. First, the formulation of the classical one-way SSPE and the relatively-novel two-way SSPE is presented, with particular emphasis on their capabilities and the limitations. Next, the structure and the GUI capabilities of the PETOOL software tool are discussed in detail. The calibration of PETOOL is performed and demonstrated via analytical comparisons and/or representative canonical tests performed against the Geometric Optic (GO) + Uniform Theory of Diffraction (UTD). The tool can be used for research and/or educational purposes to investigate the effects of a variety of user-defined terrain and range-dependent refractivity profiles in electromagnetic wave propagation.

Program summary

Program title: PETOOL (Parabolic Equation Toolbox)Catalogue identifier: AEJS_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJS_v1_0.htmlProgram obtainable from: CPC Program Library, Queen?s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 143 349No. of bytes in distributed program, including test data, etc.: 23 280 251Distribution format: tar.gzProgramming language: MATLAB (MathWorks Inc.) 2010a. Partial Differential Toolbox and Curve Fitting Toolbox requiredComputer: PCOperating system: Windows XP and VistaClassification: 10Nature of problem: Simulation of radio-wave propagation over variable terrain on the Earth?s surface, and through homogeneous and inhomogeneous atmosphere.Solution method: The program implements one-way and two-way Split-Step Parabolic Equation (SSPE) algorithm, with wide-angle propagator. The SSPE is, in general, an initial-value problem starting from a reference range (typically from an antenna), and marching out in range by obtaining the field along the vertical direction at each range step, through the use of step-by-step Fourier transformations. The two-way algorithm incorporates the backward-propagating waves into the standard one-way SSPE by utilizing an iterative forward–backward scheme for modeling multipath effects over a staircase-approximated terrain.Unusual features: This is the first software package implementing a recursive forward–backward SSPE algorithm to account for the multipath effects during radio-wave propagation, and enabling the user to easily analyze and visualize the results of the two-way propagation with GUI capabilities.Running time: Problem dependent. Typically, it is about 1.5 ms (for conducting ground) and 4 ms (for lossy ground) per range step for a vertical field profile of vector length 1500, on Intel Core 2 Duo 1.6 GHz with 2 GB RAM under Windows Vista.     

Transport properties of LaSrNi1 − x ScxOy solid solutions

The formation of LaSrNiO₄-and LaSrScO₄-based solid solutions with the general stoichiometry LaSrNi_{1 ? x} Sc_xO₄ (0 < x < 1) has been studied in air at temperatures from 700 to 1300°C. According to x-ray diffraction results, the former solid solutions exist in the composition range 0 < x ≤ 0.2. Their lattice parameters have been determined, and their resistivity and thermoelectric power have been measured as functions of temperature. Oxygen release and absorption measurements at temperatures from 20 to 1000°C and oxygen partial pressures from 2 to 330 Pa suggest that the presence of scandium has a stabilizing effect on the oxygen sublattice of the solid solutions. The possible mechanisms of this effect are discussed.     

Experimental investigation of the current-induced breakage of metal-coated polymer films

We have experimentally studied the phenomenon of current-induced breakage of thin (∼20-to 30-nm-thick) metal films deposited onto poly(ethylene terephthalate) (PETP) and poly(propylene) (PP) substrates. Two mechanisms leading to the current-induced breakage of the metal film are established, which are characterized by different average threshold current densities: j _H ∼ 1.5 × 10¹⁰ A/m² and j _L ∼ 0.7 × 10¹⁰ A/m². The possible nature of these mechanisms is discussed.     

Edge electroluminescence in small-area silicon p +-n diodes heavily doped with boron: Analysis of model representations

The experimental results and model representations of the edge electroluminescence of two published studies for small-area silicon p ⁺-n diodes heavily doped with boron are analyzed. In one of these studies it was assumed that edge electroluminescence appears in the p ⁺ region of the diode, and in the other, in the n region of the diode. In the latter case, it was demonstrated that electroluminescence indeed arose in the n region and was caused predominantly by the radiative recombination of free excitons. It is shown that similar model concepts are also applicable to the other study. Based on several independent experimental studies (of edge photoluminescence, electroluminescence, and radiation absorption by free carriers), it is demonstrated that the linear or close-to-linear dependences of the edge-luminescence intensity on the excitation intensity, observed in single-crystal silicon at high injection levels, are caused by the close-to-linear dependences of the exciton concentration on the free-carrier concentration. The results of this study extend the capability of luminescence methods for determining the carrier lifetimes to the region of high injection levels.