Up Close: University College London Department of Electronic and Electrical Engineering
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University College London (UCL), the largest and oldest college within the University of London, established the first chair in Electrical Technology in the United Kingdom some 101 years ago. It was here in 1904 that Ambrose Fleming patented the thermionic valve, a device that could be considered to have initiated modern electronics. The 1980s have seen one of the biggest expansions in the department's history. As a consequence of the government's shift-to-engineering scheme, student places have been expanded by 50%, and the addition of 10 new members has increased the number of academic staff to 30. Several major research awards, together with generous industrial funding from the General Electric Company have greatly assisted in expanding an evergrowing materials-based research environment. The department annually attracts a turnover of more than £2M and contributes an average of 75 papers per year to the scientific literature. The department is divided into three major operating groups of Physical Electronics, Systems, and Computing under the direction of Prof. J.E. Midwinter, who occupies the British Telecom Chair of Optoelectronics, Prof. D.E.N. Davies, head of the department, and Prof. J.B. Davies. Current research efforts in materials within these groups are described below.
ular beam epitaxy for oxide film deposition has led to a novel method for the growth of LiNb0 3 layers for waveguiding application on both LiNb0 3 and sapphire substrates. Figure 1 shows the equipment used at UCL. A two-chamber system with sample transfer facility enables growth and substrate/film studies to be undertaken in an optimized vacuum environment. The diagnostic chamber also serves as a load-lock, preserving a 10"9 torr vacuum while changing samples. One of the source materials, niobium, has a very low vapor pressure and requires heating to very high temperatures (~2400°C) so that electron beam evaporators are used as elemental sources for both the niobium and lithium beams. Gaseous oxygen is admitted via a multichannel capillary array mounted close to the substrate. Extensive cryoshielding is employed for improved vacuum in the deposition region; together with differential pumping in the substrate region, this minimizes the oxygen overpressure in the rest of the chamber. The substrate holder can be heated by electron bombardment to over 1000°C. This new growth method for producing epitaxial layers of lithium niobate may offer an alternative fabrication process for devices previously fabricated in Ti:LiNb03. The growth of epitaxial layers on semicon-
ducting substrates is currently being investigated. The integration of electronic, optical, and acoustic devices on a single substrate may then be achievable. Current work is directed at improved control of the film crystal structure; optical, acoustic, and electro-optic characterization; and measurement of the optical-damage threshold of the film. Laser Processing of Microstructures
One of the newer areas of thin film processing recently initiated at UCL involves the localized l
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