3 March 2008

Professor Walter Spear

Professor Walter Spear FRS, FRSE, pioneer of thin film and large area electronics, died on February 21st in Dundee, aged 87. His work on amorphous semiconductors laid the foundation for much of today's multibillion dollar flat panel display and thin film photovoltaic industries.

Walter Spear was one of the most outstanding experimentalists of his age. He was born in Germany in 1921 and came to Britain just before the war. He studied at Birkbeck College, University of London, where his practical skills and delight in experimentation emerged. Whilst at Birkbeck, he developed and built, with Werner Ehrenberg, the microfocus X-ray generator that was to be given to Maurice Wilkins, and used by Franklin and Gosling in the study of DNA in a moist environment, contributing to the x-ray diffraction work that lead to the discovery of the double helix structure.

Walter Spear then joined the academic staff at the University of Leicester, where he spent fourteen years, and where he met his then student and future collaborator, Peter LeComber. The two joined the staff of the University of Dundee in 1969, Walter as Harris Professor of Physics, and established the Amorphous Materials Research Group in a then disused textile store or 'Jute Shed' (the laboratory bearing this name to this day). In the days when cash was not always forthcoming, or a main imperative of research, Walter continually showed his inventiveness, and was famed for often building complex circuits and devices in tobacco tins to provide electrical screening, and for recycling brass components for vacuum chambers from one experiment to another. This frugality was to enable remarkable strides to be made with very modest resources. His early work in electronic transport in solids was widely recognized and led to his election as Fellow of the Royal Society.

Although electronics then as now was dominated by the crystal form of silicon, there was an emerging interest in the disordered state and amorphous semiconductors. Much of the underlying theories of this were developed by Nobel prize winner, Professor Sir Nevill Mott, CH, FRS. The two developed a long term friendship, Walter introducing him to the joys of malt whisky during their conversations long into the night on Mott's frequent visits to Dundee.

The Spear group's initial efforts at Dundee were purely curiosity driven and followed Walter's fascination with the movement (transport) of charge carriers through disordered or low mobility solids such as solidified rare gases like argon or krypton.. Soon however, usingthe 'glow discharge' or Plasma Enhanced Chemical Vapour Deposition (PECVD) methods developed at STL in Harlow, Spear and LeComber started to look at thin film amorphous silicon. They and their students used the drift mobility or time of flight technique, pioneered by Walter at Leicester, to look at the underlying electron transport mechanisms. This basic ersaechwas to take a very applied turn.

Theoretical predictions by Mott suggested that the 'doping' process, on which the whole of silicon technology depends, would not be possible in the amorphous state. However, in a landmark paper by Spear and LeComber in 1975, it was demonstrated that it was indeed possible to incorporate substitutional pentavalent and trivalent impurities into a tetrahedral amorphous semiconductor, giving dramatic changes in conductivity. This started a revolution in the field of amorphous semiconductor research by making inexpensive silicon based thin film electronic devices possible. Companies and groups across the world started studying the material. Spear and LeComber, working as one of the most remarkable and durable partnerships in the history of experimental physics, were generally a step ahead, and produced a number of world firsts. They made the first amorphous silicon p-n junction, the building block of electronic devices, and showed that it had photovoltaic properties. These properties were soon realized in the form of thin film solar cells by researchers in the RCA laboratories in the US. In the period immediately following the seminal 1975 paper, attention was closely focused on improving the performance of the first photovoltaic devices. In the widely held belief that oil reserves might soon be exhausted, many major oil companies began investing in this area of research. It soon became apparent that fears of the immediate end of the oil era were unfounded as new reserves were discovered, and oil companies scaled down their efforts considerably.

This caused no problem for the Dundee Group as the world was to be stunned by another world first when the amorphous silicon thin film transistor was announced. This was followed by a demonstration of its use in the active matrix liquid crystal display made jointly at RSRE (the Royal Signals and Radar Establishment) in Malvern. This device found in virtually every notebook display ad mobile phone screen in the world, forms the basis of the multibillion dollar market in flat panel displays.

Walter was also a gifted teacher and conveyed his enthusiasm for his subject at all levels, from undergraduate to international conferences. There was always a buzz of excitement at conferences when Walter would start to present his latest paper, and they would always lead to spirited debate. He started postgraduate education in this area, attracting students from all over the world to the Dundee laboratories. Many of his students went on to form important research groups across Europe and the United states. It is a measure of his modesty that he was always more proud of his students and their successes than his many awards. He was particularly pleased when Peter LeComber was elected to the Royal Society and devastated when soon after in 1992, Peter died suddenly at an early age. This event unquestionably hastened Walter Spear's essentially complete withdrawal from the field of active research at that time.

Of course such a distinguished career led to many international prizes, including the European Physical Society Europhysics Prize in 1976, the Max Born Medal and Prize for Physics in 1977 the Rank Prize in Optoelectronics in 1988 and the Royal Society Rumford Medal in 1990. In 1988 he delivered the Bakerian Lecture to the Royal Society.

When not immersed in his work, Walter had a keen interest in European culture. He was a very accomplished cello player, and in his retirement could be found playing in chamber groups around Dundee. His work and influence will be long remembered by those fortunate enough to have worked or studied in the Dundee laboratories. His legacy, held as so much jointly with his close friend and colleague Peter LeComber, is the ubiquitous liquid crystal display of the mobile information age.

Walter is survived by his wife Hilda, two daughters, Gillian and Kathryn and two grandchildren.

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