Broers began his research career in the Engineering Department of the University of Cambridge in 1961 working with Professor
Charles Oatley, and later with Dr William C Nixon, on the in situ study of surfaces undergoing ion etching in the scanning electron microscope (SEM). The microscope he used had originally been built by Oatley and had then been modified Garry Stewart who had also added an ion source that focussed ions onto the sample surface. Garry Stewart, who was another of Professor Oatley's students, then moved to the
Cambridge Instrument Company where he oversaw the design and building of the world's first commercial SEM, the Stereoscan. During his PhD studies, Broers rebuilt the SEM fitting a magnetic final lens in place of the original electrostatic lens thereby improving the microscope's resolution to about 10 nm, and after examining ion etched surfaces, used the microscope's electron beam for the first time to write patterns, subsequently using ion etching to transfer these patterns into gold, tungsten and silicon structures as small as 40 nm. These were the first man-made nanostructures in materials suitable for microelectronic circuits opening up the possibility for the extreme miniaturization of electronic circuits that was to occur in the decades to come. After graduating from Cambridge, Lord Broers spent nearly 20 years in research and development with IBM in the United States. He worked for sixteen years at the Thomas J Watson Research Centre in New York, then for 3 years at the East Fishkill Development Laboratory, and finally at Corporate Headquarters. His first assignment at the T J Watson Research laboratory was to find a long life electron emitter to replace the tungsten wire filaments used in electron microscopes at the time. IBM had built the first billion bit computer store using an electron beam to write on photographic film and the relatively short lifetime of the tungsten filament sources was not acceptable. To solve this problem he developed the first practical electron guns that used
LaB6 emitters. These emitters not only solved the lifetime problem, but also provided higher electron brightness than tungsten filaments, and in the late 1960s and early 1970s he built two new SEMs for examining surfaces that took advantage of this and produced higher resolution than previous SEMs (3 nm in the secondary electron surface mode) and then a short focal length instrument with 0.5 nm beam size. He used the second SEM to examine thin samples in the transmission mode and to examine solid samples using the high energy electron scattered from the surface of the sample, the electrons that had been called 'low-loss electrons by Oliver C Wells who had proposed their use in the SEM. Initially this high resolution low-loss mode was used to examine bacteriophage and blood cells in collaboration with researchers at NYU, and at the Veteran's Administration Hospital in New Jersey however, the bulk of his work was devoted to using the microscopes as tools to scribe things using the lithography techniques that were becoming familiar for making silicon chips. He and his colleague Michael Hatzakis used these new electron beam lithography to make the first silicon transistors with micron dimensions. and sub-micron dimensions showing that it would be possible to scale down the dimensions of electron devices well below the dimensions that were being used at the time. "I had a marvellous time doing research in the IBM research laboratory" he recalls "I had essentially turned my hobby into my career." He remembers having a roomful of electronics and was overjoyed to spend his time building new things and testing them. There he spent around 16 years in research in one of the best 'playhouses for electronics' in the world, building microscopes and equipment for the fabrication of miniature components. In 1977 he was given the enviable position of being an IBM fellow, an honour accorded to, at that time, only around 40 out of IBM's 40,000 engineers and scientists. This gave him the freedom to follow whatever road of enquiry he wished and he continued his work pushing the limits of what was called at the time microfabrication. Over the next ten years he conducted a series of careful experiments measuring the ultimate resolution of electron beam lithography and then used the highest resolution methods to fabricate electronic devices. One of the deleterious effects that limited resolution was the fogging effect of the electrons backscattered from the bulk of the sample. To avoid this Broers and Sedgwick invented a thin membrane substrate using technologies used to make inkjet printer heads. The membrane was thin enough effectively to eliminate the backscattered electrons. These membrane substrates allowed the first metal structures with dimensions below 10 nm to be fabricated and tested. Because these dimensions were now measured in single nanometers he and his coworkers decided to call these nanostructures and the techniques used to make them nanofabrication rather than use the prefix micro that had been common parlance until then. These membrane samples also found application many years later in MEMs (Micro-Electro-Mechanical) devices, and also as 'cantilevers' in biomedical applications. Early experiments with X-ray lithography also used similar membranes. When he arrived back in Cambridge, Lord Broers set up a nanofabrication laboratory to extend the technology of miniaturisation to the atomic scale by developing some of the novel fabrication methods that he had discovered at IBM. He modified a 400 kV transmission electron microscope (JEOL 4000EX) so that it operated in a scanning mode and produced a minimum beam size of about 0.3 nm. He used this system working in collaboration with researchers at the IMEC microelectronics research laboratory in Leuven, Belgium, to build some of the smallest and fastest field effect transistors that had ever been built. He describes his research on nanolithography and electron microscopy in Volume 231 of Advances in Imaging and Electron Physics, 2024. ==References==