IOP Groups
Modelling, Simulation and Design of Dielectrics
Cambridge 2005
Increasing our ability to design-in specific dielectric properties or tailor specific dielectric behaviour, often under specific conditions of frequency, temperature and field strength, is of central importance in many scientific and technological applications. Liquid crystal TFT displays that now threaten the extinction of the cathode ray tube are a prime example. It is advances in computing power and computational techniques, as well as the discovery of new composite and artificially engineered materials, which are opening up new opportunities for modelling and tailoring a diverse range of dielectrics and dielectric response. This conference, being held at Homerton College in Cambridge from 6 to the 8 April, provided a timely overview of activity in the field from the perspective of modelling, simulation and design, highlighting new approaches and tools available to scientists and engineers alike. The meeting was well supported by a broad-based international audience mirroring the group of invited speakers who promoted the main themes of the conference.
Modelling activity has been characterised by phenomenological approaches for many decades, however, ab initio molecular modelling is making a significant impact in many areas of science, notably in chemistry, molecular dynamics and biotechnology. This topic was a key theme of the conference, which afforded an opportunity to investigate the ways that molecular modelling can and is being extended into dielectric and electrical transport studies to enable dielectric properties to be understood directly in terms of molecular and meso-scale physics.
Hence, the conference opened with an engaging keynote talk given by Professor Marshall Stoneham, University College London, on the topic of “Dielectrics in action:the atomistic modelling of performance and failure”. Professor Stoneham cautioned that it was all too easy to use modelling and simulation tools simply to demonstrate phenomena without adding value in terms of knowledge and understanding, before expounding the benefits of the emerging techniques with regard to their role in bringing the field of dielectric science to a threshold of understanding for practical problems in electrical breakdown. The talk and resulting discussion set the context for the whole meeting and was an excellent introduction to the first session on Ab-initio Molecular Modelling, opened by Professsor Mike Payne of Cambridge. Mike gave an overview of current and next generation first principles simulations, as embodied in the Accelrys software, highlighting the development of order N techniques that provide a step increase in the scale of system that can be studied.
The first afternoon was concluded with a short review paper and discussion presented by Professor Gary Stevens and Dr Ian Youngs, officers of the Dielectrics Group committee, on trends in dielectrics research from a national, European and world-wide perspective. The review set out to consider three questions:
- Is dielectrics research in growth or decline?
- How is it different geographically?
- How has its scope changed with time?
It was shown that the volume of publications is growing globally and that China may lead the world within 6-10 years. The UK share is decreasing slowly in line with many established countries, whilst the SE Asia share of publications is increasing rapidly. It was found that there were only subtle differences between geographic regions and that the UK blend of research was well correlated with European and Global activity. In terms of changes with time over the last 25 years, it was observed that there has been a shift away from polymer science and atomic & molecular physics to applied and condensed matter physics, and optics; with electrical & electronic engineering remaining very strong. The current hot topic in dielectrics is high permittivity dielectrics for electronics applications, which aligned well with the excellent industrially based talk presented by Professor Yakov Roizin of Tower Semiconductors in Israel, which opened the session on Electronic and Optical Materials.
The first morning sessions were devoted to breakdown and field modelling, charge transport and space charge. These were opened by Professor Len Dissado from the University of Leicester and Dr Pierre Segur from the University of Paul Sabatier, France. The presented papers covered a broad range of interests from the latest theories of electrical tree initiation and pre-breakdown processes to modelling of low frequency electromagnetic fields in humans (fortunately we are safe to continue cooking with induction hobs!), polymer nano-composite materials for advanced capacitors, charge transport in insulators and semiconductor devices, and liquid crystal defects in novel optical devices.
The afternoon opened with a comprehensive review, presented by Professor Christian Brosseau from the University of Brest in France, on the use of finite element methods, similar to those exhibited by Ansoft, to model the properties of composite or heterogeneous mixtures. This was complemented by papers on alternative methods including the spectral density function and circuit modelling techniques, the latter highlighting emergent response in complex networks that is remarkably elegant in its simplicity and read across to other constitutive material properties.
The final morning brought together two sessions covering topics which can be viewed as extremes of dielectrics science. The first opened by Professor Peter Raynes from Oxford with a talk on liquid crystals, as strange but useful dielectric liquids, considered the more traditional topic dielectric relaxation phenomena. The second focused on the rapidly growing field of structured and meta-materials in which there is currently an explosion of interest due to the prospects for new levels of dielectric and electromagnetic functionality, including extraordinary local-field enhancement, interactions with sub-wavelength structures and negative refractive index phenomena. Indeed, following the Foresight “Exploiting the Electromagnetic Spectrum” project, it is clear that modelling, simulation and design of new dielectric materials will be central to the pervading developments of wireless communications in our everyday lives. The opening talk for this final session was given by Professor Roy Sambles from Exeter University, who explained with his usual enthusiasm, how it was possible to squeeze centimetre waves into micron-sized metal structures, highlighting the important role of the finite conductivity of metals.
As is typical of Group conferences, the excellent technical programme stimulated much interesting discussion and debate and was perfectly complemented by a small but very strong group of sponsors/exhibitors: namely Accelrys, Ansoft and Novocontrol. Moreover, it was a pleasure to have such a significant proportion of young researchers and students contributing to both the oral and poster sessions, providing the winner of the 2005 Mansell Davies Award for the best paper by a young researcher - Mr Ennio Capria from Cranfield University for his paper on manipulation of PZT fibres using dielectrophoresis. A selection of papers from the conference will be published in a forthcoming issue of the Journal of Physics D: Applied Physics and the Organising Committee wish to thank the sponsors, and all speakers and delegates for making this a successful conference.
Ian Youngs (May 2005)
^ To the top ^