Donard de Cogan

Transmission‐line‐matrix modeling of grain‐boundary diffusion in thin films

The use of the transmission‐line‐matrix (TLM) method for analyzing the grain boundary and interfacial diffusion problems in thin films is demonstrated. The method employed has a variable mesh and automatic time‐stepping capability, and is highly versatile in treating complex structures and incorporating various boundary conditions. The present model takes account of separate diffusion coefficients in grain boundaries, grains, interfaces, and the substrate. The combined diffusion problems are solved as a function of position and time, and the concentration distributions are presented as clearly visible isometric projections and contour plots. The results are compared with those of semi‐infinite samples (Whipple’s analysis [Philos. Mag. 45, 1225 (1954)]) and idealized thin‐film systems (Gilmer and Farrell’s analysis [J. Appl. Phys. 47, 3792 (1976)]), with the emphasis being placed on the differences due to the treatment of concentration flux along the interface between the film and the substrate and into th...

Transient analysis of surface supersaturation after crystal face submersion using the analytical and transmission-line matrix (TLM) methods

The time-dependent equation of Burton, Cabrera and Frank (BCF) is analytically solved for transient-state growth conditions occurring immediately after submersion of crystal face in supersaturated solution. The time-dependent BCF model is also solved using the transmission-line matrix (TLM) numerical method. We find that the time necessary to attain the steady-state value of surface supersaturation does not depend on bulk supersaturation but increases with increasing interstep distance. Calculated results obtained by the two methods are shown to be in excellent agreement, indicating a promising potential of the TLM method for solving analytically intractable problems of interest.

TLM Algorithms for Laplace and Poisson Fields in Semiconductor Transport

This paper provides an introduction to some novel aspects of the transmission line matrix (TLM) numerical technique with particular reference to the modeling of processes in semiconductor materials and devices. It covers the relative merits of different forms of network representation of physical problems. Current progress with TLM algorithms for the Laplace and Poisson equations is reviewed.

Nonlinear thermal effects in metal/non-metal systems†

Abstract This paper presents observations on some electronic components where non linear thermal effects play a dominant role. Our interpretation has been assisted by the use of novel numerical modelling techniques which can either solve for a single field variable, or can be used in coupled form to investigate systems where different field variables may interact. Non linear thermal effects appear to be responsible for premature failure in metal film resistors when operated under pulsed conditions. This is thought to be due to the effects of competing thermal paths which involve the metal and non-metal parts of the device. There is also a discussion on some relatively novel ideas concerning the operation of the electric fuse.

A numerical model for submarine telegraph communication

Transmission Line Matrix (TLM) is a modern numerical method which is particularly suited to treating electromagnetic problems This paper describes the application of TLM to the propagation of telegraph signals in ocean cables. It is shown that the non-ideal properties of the cable, the transmitter and the receiver were significant factors in the ability to receive signals at a time when people had no concept of the importance of impedance matching. The paper concludes with a demonstration of the benefits of a cable whose electrical parameters comply with the Heaviside distortionless condition.

Simple models for crystallization processes

Cellular Automation modeling the repeated application of simple rules can result in very complex behavior and is being increasingly used to simulate physical process. This paper outlines the technique with special emphasis on ordered states and order/disorder transitions.

Application of transmission line matrix techniques to the modeling of solid state problems

Transmission Line Matrix is a numerical technique which models physical phenomena by the establishment of analogues with electrical networks which include transmission lines. These enforce time discretization. There have been many significant developments in this rapidly expanding field. This paper discusses the formulation of algorithms in the areas of: semiconductor carrier transport, crystallization, chemical kinetics and effective bounding of very large models.Transmission Line Matrix (TLM) is a numerical technique which models physical phenomena by the establishment of analogues with electrical networks which include transmission lines. These enforce time discretisation. There have been niany significant developments in this rapidly expanding field. This paper discusses the formulation of algorithms in the areas of: semiconductor carrier transport, crystallisation, chemical kinetics and effective bounding ofvery large models.

Crystal advances to the fore in Zakopane

Abstract The ‘First International Conference on Solid State Crystals (ICSSC): Materials Science and Applications’ was held in Zakopane, Poland, from 12–16 October 1998. Building on an earlier conference series, the event continues to serve as a information platform for the latest advances in this important research area.

Recent advances in TLM algorithms for semiconductor transport

Transmission Line Matrix (TLM) is a numerical technique which can be used to simulate wide range of physical process. In the area of semiconductor device modeling the correct choice of electromagnetic analogue can have a strong influence on the stability, accuracy and efficiency of algorithms. This paper reviews recent progress in TLM with particular attention to the drift-diffusion process in carrier transport in semiconductors.