(117 intermediate revisions by the same user not shown) | |||
Line 1: | Line 1: | ||
− | = | + | = Electron Microscopy and Surface Physics - John Venables = |
== Introduction and Summary<br> == | == Introduction and Summary<br> == | ||
− | Sussex Physics was a wonderful place to get a first "proper job". After a PhD in Cambridge and a 3-year post-doc period in Illinois, it was great to have an exciting new job, and to return to a beautiful and vibrant part of the UK. I wish to pay tribute to Ken Smith, our foundation Professor of Experimental Physics. It was Ken who appointed me to Sussex in the Autumn term of | + | Sussex Physics was a wonderful place to get a first "proper job". After a PhD in Cambridge and a 3-year post-doc period in Illinois, it was great to have an exciting new job, and to return to a beautiful and vibrant part of the UK. I wish to pay tribute to Ken Smith, our foundation Professor of Experimental Physics. It was Ken who appointed me to Sussex in the Autumn term of 1964. I had known Ken in Cambridge, where I assisted in his Part II Physics Laboratory as a graduate student. Work on Electron Microscopy was very strong in Peter Hirsch's Metal Physics group [1], and so I was able to get a post-doc position in the USA at the University of Illinois, and then join Sussex at a formative stage. |
This page is about the Electron Microscopy and Surface Physics research group at Sussex. We were not isolated in our interests, but had overlaps with the group on [[Research-PSI|Particle-Solid interactions]] and also with other efforts in Condensed Matter Physics, Low Temperature Physics and Materials Science. Michael Thompson and Robert Cahn were both appointed to Professorships in 1965, in Physics and Materials Science respectively. These appointments and those that followed greatly increased the possibilities for collaboration, both in research and graduate level and specialist undergraduate teaching across departmental lines. And, although we were passionate about our Science and research in particular, Sussex was a place where many other activities, especially of an interdisciplinary nature, were encouraged. <br> | This page is about the Electron Microscopy and Surface Physics research group at Sussex. We were not isolated in our interests, but had overlaps with the group on [[Research-PSI|Particle-Solid interactions]] and also with other efforts in Condensed Matter Physics, Low Temperature Physics and Materials Science. Michael Thompson and Robert Cahn were both appointed to Professorships in 1965, in Physics and Materials Science respectively. These appointments and those that followed greatly increased the possibilities for collaboration, both in research and graduate level and specialist undergraduate teaching across departmental lines. And, although we were passionate about our Science and research in particular, Sussex was a place where many other activities, especially of an interdisciplinary nature, were encouraged. <br> | ||
Line 9: | Line 9: | ||
Sussex literally gave me, and by extension all of us, a chance to do my "own thing", and I feel very grateful to have been able to take that, and build on it in my/our own way. The "our" is important of course, since without collaborators, technical help, students and especially graduate students, one can do very little in experimental physics or any other experimental science. I have been particularly fortunate in all these aspects: the fact that we had an excellent Mechanical Workshop under Frank Schofield made all sorts of technical developments in Transmission Electron Microscopy possible from the start. Later, we also used the staff of the Electronics Workshop as well, to keep ahead of developments in Scanning Electron Microscopy. Some of these aspects will be described in the two sections that follow | Sussex literally gave me, and by extension all of us, a chance to do my "own thing", and I feel very grateful to have been able to take that, and build on it in my/our own way. The "our" is important of course, since without collaborators, technical help, students and especially graduate students, one can do very little in experimental physics or any other experimental science. I have been particularly fortunate in all these aspects: the fact that we had an excellent Mechanical Workshop under Frank Schofield made all sorts of technical developments in Transmission Electron Microscopy possible from the start. Later, we also used the staff of the Electronics Workshop as well, to keep ahead of developments in Scanning Electron Microscopy. Some of these aspects will be described in the two sections that follow | ||
− | One of the great possibilities offered by this Wiki form of history, is that all of our collaborators can contribute whatever they want or have time for. I am still very much in contact with one of my two first graduate students, [http://www.crcpress.com/product/isbn/9780849350245 George J. Thomas], and the other [http://davidjball.com/ David J. Ball], can be found via a simple Google searches. Both have had distinguished careers in the US National Laboratory system, and as a Professor/Consultant on Risk Management in the UK respectively. My long-term | + | One of the great possibilities offered by this Wiki form of history, is that all of our collaborators can contribute whatever they want or have time for. I am still very much in contact with one of my two first graduate students, [http://www.crcpress.com/product/isbn/9780849350245 George J. Thomas], and the other [http://davidjball.com/ David J. Ball], can be found via a simple Google searches. Both have had distinguished careers in the US National Laboratory system, and as a Professor/Consultant on Risk Management in the UK respectively. My long-term technical colleague Chris Harland subequently got a PhD himself, and after spells in Industry, became Reader in Electronics at Sussex. |
I am not planning to transfer the group publication list to this site, since there is already a complete list on my Arizona State University site [2]. I retired from Sussex in January 1995, but have been associated with the University since as an Honorary Professor, and currently as Emeritus Professor. The list of group members ends at 1995, but that is not the end of the story: Michael Hardiman, Senior Lecturer in Physics, continues research but in a somewhat different field. I have continued research in Arizona, at the London Centre for Nanotechnology at UCL, and with several colleagues around the world. | I am not planning to transfer the group publication list to this site, since there is already a complete list on my Arizona State University site [2]. I retired from Sussex in January 1995, but have been associated with the University since as an Honorary Professor, and currently as Emeritus Professor. The list of group members ends at 1995, but that is not the end of the story: Michael Hardiman, Senior Lecturer in Physics, continues research but in a somewhat different field. I have continued research in Arizona, at the London Centre for Nanotechnology at UCL, and with several colleagues around the world. | ||
Line 19: | Line 19: | ||
1. Members of the Metal Physics group were much in demand worldwide at the time, and produced the "Bible", Electron Microscopy of Thin Crystals (Butterworths, London, 1965) following a succesful summer school in July 1963. The authors, P. B. Hirsch FRS, A. Howie, R.B Nicholson, D.W. Pashley and M.J. Whelan, all be came very well known for a whole "School" of Electron Microscopy that spread round the world. The authors went on to lead groups in Oxford (Professor Sir Peter Hirsch and Professor Mike Whelan, FRS), Cambridge (Professor Archie Howie, CBE, FRS), Imperial College (Professor Don Pashley, FRS). Sir Robin Nicholson FRS, FREng was Chief Scientific Advisor, Cabinet Office from 1983-1985 during a long career in Industry and Academia. | 1. Members of the Metal Physics group were much in demand worldwide at the time, and produced the "Bible", Electron Microscopy of Thin Crystals (Butterworths, London, 1965) following a succesful summer school in July 1963. The authors, P. B. Hirsch FRS, A. Howie, R.B Nicholson, D.W. Pashley and M.J. Whelan, all be came very well known for a whole "School" of Electron Microscopy that spread round the world. The authors went on to lead groups in Oxford (Professor Sir Peter Hirsch and Professor Mike Whelan, FRS), Cambridge (Professor Archie Howie, CBE, FRS), Imperial College (Professor Don Pashley, FRS). Sir Robin Nicholson FRS, FREng was Chief Scientific Advisor, Cabinet Office from 1983-1985 during a long career in Industry and Academia. | ||
− | 2. Since 1985 I have been a Professor at Arizona State University in the Physics Department on a part-time basis. There I maintain a [http://venables.asu.edu/index.html home page], which contains all my professional details, including teaching, research, publcations and short-form CV.<br> | + | 2. Since 1985 I have been a Professor at Arizona State University in the Physics Department on a part-time basis. There I maintain a [http://venables.asu.edu/index.html home page], which contains all my professional details, including teaching, research, publcations and short-form CV.<br> |
== Research Activity 1: In-situ Transmission Electron Microscopy == | == Research Activity 1: In-situ Transmission Electron Microscopy == | ||
− | Shortly after my arrival in Sussex, Professor Ken Smith signed a purchase order for a Hitachi HU 11B Electron Microscope. This was for £11, 600 or thereabouts, a large sum of money in 1964: but of course without a microscope we could do nothing. This instrument became the workhorse of the early years of the group, and it got heavily modified, several times, in the process. I had decided to try my hand at what became known as ''In-situ ''Microscopy: performing experiments on the samples inside the microscope and observing them at the same time, or shortly afterwards with out breaking the vacuum. | + | Shortly after my arrival in Sussex, Professor Ken Smith signed a purchase order for a Hitachi HU 11B Electron Microscope. This was for £11,600 or thereabouts, a large sum of money in 1964: but of course without a microscope we could do nothing. This instrument became the workhorse of the early years of the group, and it got heavily modified, several times, in the process. I had decided to try my hand at what became known as ''In-situ ''Microscopy: performing experiments on the samples inside the microscope and observing them at the same time, or shortly afterwards with out breaking the vacuum. |
− | In particular, we constructed a variable temperature stage that was cooled by liquid helium. Liquid helium was in more or less plentiful supply at Sussex from early on, due to the presence in the Department of the Low Temperature group. The Mechanical Workshop staff were crucial in the fine scale machining needed to make several versions of the low temperature stages and accessories over a long period<br> | + | In particular, we constructed a variable temperature stage that was cooled by liquid helium. Liquid helium was in more or less plentiful supply at Sussex from early on, due to the presence in the Department of the Low Temperature group. The Mechanical Workshop staff were crucial in the fine scale machining needed to make several versions of the low temperature stages and accessories over a long period. Our group technician, John Notton, maintained the microscope, ran the photographic dark room, and helped with equipment and experimental set up. The results came out in the form of plates that had to be developed using wet chemistry: this was all long before the advent of digital recording and terabytes of data. The terabytes were all in the form of small silver crystals after development of the plates, plus a few kilobytes recorded by hand in "Plate" books, and hardback research notebooks! <br> |
With my first two graduate students, we started on our first two scientific topics, outlined below: "Electron microscopy of low energy ion damage in Metals" with George Thomas (DPhil 1969), and "Nucleation, growth and defect structure of Rare Gas Solids" with David Ball (D.Phil 1969). The first project involved construction a removable low energy ion gun to fit above the stage. The second involved various cells and directed gas beams to grow the crystals at well defined pressures and temperatures. While the projects started out in an exploratory manner, they nearly all became quantitative studies with T and p (and ion current) as the independant variables. | With my first two graduate students, we started on our first two scientific topics, outlined below: "Electron microscopy of low energy ion damage in Metals" with George Thomas (DPhil 1969), and "Nucleation, growth and defect structure of Rare Gas Solids" with David Ball (D.Phil 1969). The first project involved construction a removable low energy ion gun to fit above the stage. The second involved various cells and directed gas beams to grow the crystals at well defined pressures and temperatures. While the projects started out in an exploratory manner, they nearly all became quantitative studies with T and p (and ion current) as the independant variables. | ||
− | This (thermodynamic) motivation became particularly important later on, when the aging microscope was converted into a high precision diffraction camera. It was used to study the monolayer phases of rare gases adsorbed on graphite with high precision. The microscope and surrounding equipment is shown in this latest incarnation in Figure 1 | + | This (thermodynamic) motivation became particularly important later on, when the aging microscope was converted into a high precision diffraction camera. It was used to study the monolayer phases of rare gases adsorbed on graphite with high precision. The microscope and surrounding equipment is shown in this latest incarnation in Figure 1 (below left). For more details the relevant theses and publciations can be consulted, but for now, a lot of good work was accomplished on this machine by quite a few graduate students, post-docs, visitors and technical staff. Indeed I enjoyed taking some interesting pictures and diffraction patterns myself...<br> |
− | [[Image:TEM-1 001.jpg|left|500px]] | + | === [[Image:TEM-1 001.jpg|left|500px]]Low Energy Ion Damage in Metals<br> === |
− | + | This activity was a follow-up of work I had done on Ion Bombardment as a post-doc in Illinois: indeed George Thomas was an hourly worker in the Lab there, who made the courageous decision to follow me to Sussex for a PhD, courtesy of a grant from the US Air Force (who also supported David Ball). Low energy ion bombardment produces Interstitial atoms from the bombarded surface, and this was studied using Stereo-Electron Microscopy of gold containing vacancy terahedra (produced by quenching from high T as shown by John Silcox in his Cambridge PhD, now at Cornell). So the interstials migrate to the vacancy defects and cancel them out in a variety of wonderful ways, which were expected to depend on the bombardment temperature. The stereo-pictures were marvellous, and enabled depth-dependent data to be obtained. In the end we found out that the results depended on the purity of the starting material in the few ppm range, and not much on T, investigated in the range 25-283K. | |
− | + | The results contributed to ongoing sagas about Interstitials in metals, written up in a thorough paper by G.J. Thomas and myself (Phil. Mag. 28 (1973) 1171-1201). This paper was preceded by two reviews in 1969 and 1970 and several conference papers.The reviews were invited by Mike Thompson, by then well-established at Sussex and functioning as a group with Peter Townsend, Derek Palmer, Mike Lucas and their co-workers. | |
− | + | We also made a start to measure changes in resistivity during low energy ion bombardment, but despite efforts over a couple of years, this didn't really get anywhere. However, we had an interesting visiting researcher at that time, Bill Robinson, who at the end of his stay was pleased to get a job in the DSIR (Department of Scientific and Industrial Research) in his native New Zealand; he went on to great success in Earthquake protection (see http://www.rslnz.com) and was awarded the QSO (Queen's Service Order) in 2007; yesterday I wrote "belated congratulations, Bill, from the other side of the world!" and emailed him to ask him to proof-read this paragraph. Today, sadly I learned that he has died of a brain tumor on 17th August 2011... (pause for reflection, I'm afraid, statistically inseparable from an exercise of this nature). | |
+ | |||
+ | Two other researchers contributed to related types of activity: Klaus Ecker (DPhil 1973) and post-doc Dirk van Vliet. Both had a strong overlap with the Thompson group and published their work under their own names. Klaus's work involved high sensitivity detection of (transmission) sputtering at lower keV energies and the role of ion channeling, published in Radiation Effects, 23 (1974) 171-180; Dirk, already established as a computer simulation expert in radiation effects, published several papers around 1970 when attached to Sussex. Via the Harwell connections and the Atomic Collisions in Solids MSc course, we were involved in some further theses, but this area dried up as a research effort as we concentrated on the following two topics. | ||
=== Nucleation, Growth and Defect Structure of Molecular Solids === | === Nucleation, Growth and Defect Structure of Molecular Solids === | ||
− | + | The work started with David Ball on rare gas solids developed rapidly and in a number of exciting ways. By growing the crystals on graphite at different T and p, we found the type of behaviour expected for nucleation and growth on surfaces; this started an interest in Nucleation and Growth kinetics which has persisted to the present day. David's work was written up in several places, perhaps most prestigiously in Proceedings of the Royal Society A 322 (1971) 331-354. We used the review of Nucleation and Growth that visiting faculty member Dan Frankl and I wrote for Advances in Physics 19 (1970) 409-456 to interpret the results and compare with the theory of rare gas interatomic, and rare gas-graphite potentials. The microstructure of the rare gas crystals, and dislocations in these crystals, were also studied in some detail.<br> | |
+ | |||
+ | Before long, David was joined by further graduate students Colin English, Karl Niebel and post-doc Gordon Tatlock, who followed up on his work and took it in new directions. Colin branched out to other "simple" molecular solids, N<sub>2</sub>, O<sub>2</sub>, etc and we produced some wonderful microscopy, as shown in Figure 2 for alpha-N<sub>2</sub> (below left) and figure 3 for beta- O<sub>2</sub> (below right). We solved some long-standing questions about the crystal structure and twinning in these solids. This work was published initially in Phil Mag 21 (1970) 147-166 with a review in Thin Solid Films 7 (1971) 369-389, and then in Acta Cryst. B30 (1974) 929-935 In parallel, Colin (DPhil 1974) studied a simple model of the diatomic solids, Proc. Roy. Soc. A340 (1974) 57-80 and 81-90, the latter with Dennis Salahub. Dennis was then John Murrell's post-doc, and is now Professor of Chemistry in Calgary. After a post-doc period in our group in Sussex, Colin moved to Harwell (AEA Technology) Harwell, and is now a Visiting Professor at Oxford.<br> | ||
+ | |||
+ | [[Image:TEM-1 005.jpg|left]][[Image:TEM-1 007.jpg|center|600px]]Figure 2 (left) Images of solid alpha- N<sub>2</sub> with the cubic cystallography superimposed: the twins form on (111) planes, seen here in two different crystal orientations. Figure 3 (right) Images of solid beta-O<sub>2</sub> with the hexagonal crystallography superimposed: two differnet types of twins form on (0001) and (10bar-14) planes. In the TEM, the orientation is determined via electron difraction patterns from selected areas. Defects in the form of dislocations and dislocation loops are seen. | ||
+ | |||
+ | Karl Niebel concentrated on the role of stacking faults in the rare gas solids, and the measurement of their energy, directly related to the hcp-fcc energy difference, using dislocations in solid Xenon. He followed this up with a model of the hcp-fcc crystal structure "problem" in the rare gas solids, in Proc. Roy. Soc. A'''336''' (1974) 365-377. This is a topic that was also studied by John Murrell and Tony Leggett; all three were good reasons why life at Sussex at the time was stimulating. Robert Keyse (DPhil 1982) returned to this problem later, with a paper in J.Phys C '''18''' (1985) 4435-4441 <br> | ||
+ | |||
+ | Gordon Tatlock came to Sussex from Bristol as a post-doc, and mostly established his own program on layered compounds, which he can elaborate here if he wishes. He contributed skilfully to the work of the group, including on molecular solids with Colin and Karl. All this work, including figure 4 (above), was featured an excellent French conference in 1974 at Beaune, published in J.Phys Colloque '''C7''' (1974) 113-119. Later still Gordon was joined by post-doc Remy Mevrel for a detailed study of twinning in the low temperature alpha-phase of solid nitrogen, published in Phil Mag '''35''' (1977) 641-652. Gordon has been at Liverpool University for many years as Professor of Materials Science and Engineering and is now also a staff member at the SuperStem facility at Darebury Laboratory.<br> | ||
+ | |||
+ | In the same time frame, and independent experiment was done on the vapor pressure of Ar-O<sub>2</sub> alloys, in order to determine the hcp-fcc energy difference of Ar near its melting point. Terry Bricheno had done his PhD with Brian Smith, and we were able to get funding to study this problem using his PhD apparatus. This was one of the most satisfying results, in the sense that the method was fundamental, and the right people were in place to get the job done in a finite time. The papers are in J. Phys C'''9''' (1976) 4095-4108 and '''10''' (1977) 773-779, the latter theoretical paper with Remy as the first author. | ||
+ | |||
+ | In the late 1970's, due to the need for more microscope time, we bought a second-hand JEOL 200A (200 kV) microscope, and also added a side-entry liquid helium stage. This was used by Gordon Tatlock for his own work, and by Graeme Raynerd (DPhil 1987) and Robert Keyse for low-T studies of molecular solids SF<sub>6</sub>, Kr and Xe, grown inside an environmental cell which withstood greater gas pressures than before. This enabled the condensed gases to be annealed closer to their melting points, thus producing larger, more perfect crystals. The equipment was described by R.J. Keyse, G. Raynerd and myself in J. Phys E'''17''' (1984) 228-233, and the papers on the solids themselves appeared over the period 1982-1987; all very interesting, but this was the last work that we did on molecular solids and the crystal structure problem in rare gas solids. Work on rare gas layers adsorbed on graphite, using the HU 11B micrsocope largely as an electron diffraction camera, is described in the next sub-section <br> | ||
=== Monolayer Phases of Adsorbed Gases on Graphite === | === Monolayer Phases of Adsorbed Gases on Graphite === | ||
− | | + | Michael Kramer and Garth Price arrived in Sussex around 1970 from Germany and Australia respectively. They took our nucleation and growth work in a different direction, essentially by showing that the substrates David Ball and I were using could not have been clean at the monolayer level. The results we had obtained on island growth were inconsistent with the layer growth observed by other groups, notably by the French groups in Nancy and Marseilles. They had studied rare gas adsorption using (Physical Chemistry) volumetric techniques, and increasingly Surface Science techniques. As we started to correspond by letter, I realized that there was a huge literature out there, and a visit was definitely in order. I was priviledged to spend 6 months at the Marseille-Luminy campus over the Easter vacation, the Summer Term and Vacation in 1973; this developed into a longer term relationship with groups in the Physics Department (Michel Bienfait, Jean Suzanne, Jacques Derrien) and CRMC2-CNRS laboratory (Raymond Kern, Boyan Mutaftschiev and many co-workers). 1973 was a good year in many respects: not only a wonderful break from lecturing and time for writing, but also key to several types of work described here. |
+ | |||
+ | [[Image:TEM-1 012.jpg|border|right|683px]]Garth (DPhil 1973) absorbed the French literature and realized the rare gases (at least Ar, Kr and Xe) absorb on graphite in layers, and were expected to continue to grow as layers. These gases have a small misfit with respect to the lattice parameter of graphite. He constructed a new stage to enable us to flash-clean the graphite in-situ, as indicated in the schematic of figure 4, and a directed molecular beam to deliver the gas directly onto the graphite flake. Once he did this, Xenon condensed as layers, no islands to be seen, but considerable microstructure within the layers. Mystery solved, as published in Surface Science '''49''' (1975) 264-274, complete with examples of how, when one relaxed the contamination protection (for example by removing the film across the beam before the sample), he retrieved the results obtained by myself and Ball (1971). Michael (DPhil 1974) obtained some excellent pictures of epitaxial Ar, Kr and Xe crystals on graphite and other layer compounds as substrates, showing beautiful Moiré patterns containing dislocations in the rare gas layers. These pictures were published by him in J. Cryst. Growth '''33''' (1976) 65-76. | ||
+ | |||
+ | But in a sense the real excitement came just after this, when we realised that a single monolayer of Kr and Xe on graphite could be detected by transmission electron diffraction. Not only detected, but measured with high precision (Venables, Kramer and Price, Surface Science '''55''' (1976) 373-379 and '''57''' (1976) 782). The diffaction pattern gives the spacing of the gas layers, and this was shown to be a reproducible function of T and p. Now the scene was set for detailed work, in which the crystallography of, and phase transions in these layers was mapped out and compared with results in other laboratories, notably Marseille, MIT and University of Washington. Several students contributed, and the old Hitachi microscope was dedicated to the type of work over the next decade. Now we could claim that we were really doing quantitative Surface Physics, not "just" taking pictures. | ||
+ | |||
+ | [[Image:TEM-1 010.gif|border|right|702px]]Pablo Schabes-Retchkiman (DPhil 1980) was next up, with a detailed study of Kr and Xe layers, coupled with calcuations and statistical mechanical models based on prior work on rare gas and gas-graphite potentials by Garth Price. Several papers in the late 1970's, including an interesting French Conference (J. Physique '''C4''' (1977) 105-114), until the final paper of this series in Surface Science '''105''' (1981) 536-564. | ||
+ | |||
+ | A three-dimensional plot of the Kr/graphite data, with diffraction experiments from three laboratories is shown in Figure 5. The Sussex data (constant p at various T) are the points to the right of the plot, with the Washington and Marseille data (constant T at various p) are shown towards the left with open and closed symbols respectively. It is clear that these different data are all seeing the same phenomena: Kr first condenses in to a commensurate (C) phase, and then undergoes a Commensurate-Incommensurate (C-I) transition at lower T and/or higher p: this was very satisfying. | ||
+ | |||
+ | By this time we were in our stride on this topic, and three further graduate students, Abdul-Qader Faisal (DPhil 1987), Mohamed Hamichi (DPhil 1990) and Amine Zerrouk (DPhil 1993) contributed important results to large areas of the (T, p) phase diagrams particularly on Xe/graphite. This was aided by theory involving post-doc Bob Kariotis and visiting Faculty Lou Bruch from Wisconsin, as well as joint experiments and modelling with the Marseille group. Several papers were published between 1976 and 1994 by the above colleagues, mainly in Surface Science and in Phys Rev B. A complete list of joint work with Marseille colleagues over this period is available [http://venables.asu.edu/research/Crmc2.html here]. <br> | ||
+ | |||
+ | == Research Activity 2: Ultra-high Vacuum Scanning Electron Microsocopy == | ||
+ | |||
+ | There are three strands to be described here in outline. Historically the first, with Chris Harland, is the story of how we became involved in technique development for Scanning Electron Microscopy (SEM) after the purchase, by Mike Thompson's group, of a Cambridge Instruments "Stereoscan" around 1970; this is described in the second sub-section. The second arose from our experience with adsorption and crystal growth, where it had become 100% clear that, in order to do Surface Science, we needed an ultra-high vacuum (UHV) instrument. This lead to a major grant application, jointly with Chris Harland, Roger Doherty in Materials, Ron Mason in Chemistry and Bruce Joyce at Philips Redhill, for the development of an UHV-SEM for surface studies. This development is described in two sections. First we describe the commisioning and development of the instrument itself. In the final subsection we describe some of the science done with the instrument, and some further developments. <br> | ||
+ | |||
+ | === Instrument Design and Delivery === | ||
+ | |||
+ | The instrument itself was built by VG Scientific Ltd of East Grinstead, later VG Microscopes Ltd. The delivery of the instrument in 1975 was the start of a long-time relationship with VG (originally Vacuum Generators Ltd), and a close relationship between our students and their staff. Notably, Ian Wardell who was their Electron Optics specialist, is now in retirement a Visiting Researcher with Mike Hardiman, and Gareth Jones, when last located, was Managing Director of VG Scientific, now called something quite different... But several other group members had jobs at East Grinstead following their period in our group: Adrian Janssen, David Fathers, Robert Keyse, Gareth Jones and Tim Doust, plus maybe some more lurking somewhere.<br> | ||
+ | |||
+ | [[Image:SEM-1_002.jpg|border|right|778px]]The UHV SEM was housed in Physics (now Pevensey) I, in a converted suite of labs that in retrospect feels like the height of luxury. Air-conditioned with an overpressure to keep out dust, double doors to provide a modest airlock, adjacent offices for myself and coworkers. Basically, this was lab heaven, except for Basil Spence's curved arches and flat roof leaks...<br> | ||
+ | |||
+ | The instrument as delivered, shown in figure 6, was equally pristine. As we found on several occasions, the boundary between what was delivered by VG, and what we needed to do next, was by the nature of the beast rather fluid. See all those blank flanges? They are for future detectors and experimental add-ons: Auger spectrometers, evaporation sources and shutters, all up to us. | ||
+ | |||
+ | Fresh from the factory, and in the run-up to the Institute of Physics' Electron Microscopy and Analysis Group (EMAG) conference in Bristol, I wrote an article for Physics Bulletin (August 1975, 359-362) and the introduction to the Proceedings (Academic Press, 1976), containing a small part of a similar image. That image was captured in "More Random Walks in Science", with the caption: "It's only once you have tightened up all the nuts and bolts, that you realize you left out an O-ring"... Yes, well, our most well-known publication for a while. | ||
+ | |||
+ | Hosting the same conference in Sussex four years later was an opportunity to show the microscopy community what it became. I wrote summary articles with Adrian Janssen and Chris Harland (Physics Bulletin '''29''' (1978) 307-311) and the International Congress on Electron Microscopy with an invited paper on Scanning Auger Microscopy (Toronto, vol '''3''' (1978) 280-291). We had several invited and contributed papers there and in the EMAG proceedings (IoP Conference Series volumes '''41''' (1978) and '''52''' (1980)). The word was getting out that we were enjoying ourselves.<br> | ||
+ | |||
+ | But first we should backtrack to explain how we got to this point, because, without the prior experience of SEM using the Stereoscan, our grant applications would not have been credible. This period is described in the next subsection. | ||
+ | |||
+ | === SEM Experience with the Stereoscan === | ||
+ | |||
+ | People involved with this development: Barry Farmery, Chris Harland, Peter Pollard, Barrie Griffiths, Ramli Bin-Jaya, and several other MSc students | ||
+ | |||
+ | Chis Harland arrived at the University of Sussex as a Junior Technician in 1967, and left it for senior positions in Industry in 1995, with a PhD in Electronics, granted in 1986. In between there were several episodes, but all involved running SEM's, developing two EM laboratories, and Electronic and Instrument development. He started in Applied Sciences, and formally joined our group from 1971, first as Senior and Chief Technician, and following the PhD, as Scientific Officer. Later he returned to Applied Sciences as a Research Fellow, then Senior Research Fellow and finally Reader in Electronics. This is a success story, and for my part, I feel proud to have helped as a mentor/ co-worker. Let me be quite clear here: without someone of Chris's ability in electronics, design and organisational skills over a long period, we would simply not have been able to pursue the developments that are described here. | ||
+ | |||
+ | To be continued<br> | ||
− | == Research | + | === Some Research highlights using the UHV SEM === |
− | == Research Activity 3: Related Theoretical and Computational Studies == | + | People involved: Adrian P. Janssen (RF), Bruce A. Joyce (VF, Group leader at Mullards/ Phillips Redhil), George S. Samuel (GS), Klaus Hartig (VR, Research student at Bochum), Parvez Akhter (GS), Gary D. Archer (GS, MSc student), Jeff Spain (TS), Geoff D.T. Spiller (RF), David J. Fathers (RF), Michael Hardiman (F, "New Blood" Lecturer from 1983), Jean-Jacques Metois (VF, CRMC2-CNRS Marseille), Margrit Hanbücken (RF, subsequently CRMC2-CNRS Marseille), Jean-Marie Bermond (VF, Professor at Aix-Marseille III), David R. Batchelor (GS), Masaaki Futamoto (VR, Hitachi Central Laboratories, Tokyo), Gareth W. Jones (GS), Oladipo (Ladi) Osasona (VR, Universiy of Ile-Ife, Nigeria), Gerhard Cox (GS, MSc student, and Diplom 1986, RWTH, Aachen),Timothy Doust (GS), Parmjit S. Flora (GS), Min Huang (GS), Frances L. Metcalfe (GS), Jesus M. Marcano (RF), E. Hoffman (VE), Pontus Stenström (VE, 1991), Robert H. Milne (F, 5-year fixed term Lecturer from ?), Mohamed Azim (GS with Bob Milne), Michael Stumpf (VE, 1993), Örjan Bodin (VE, 1993), T. J. Martin (PS? with Bob Milne), Raj Persaud (RF), Hisato Noro (GS), Akira Sugawara (VR from Japan and Arizona State) |
+ | |||
+ | To be continued<br> | ||
+ | |||
+ | == Research Activity 3: Related Theoretical and Computational Studies<br> == | ||
+ | |||
+ | Personnel involved: Almost everyone, but in addition Dan Frankl (VF-Pennsyvania State University), Robert Kariotis (RF), David Fathers (RF), Albert Curzon (VF Simon Fraser University), Jean-Marie Bermond (VF Universite Aix-Marseille III), Ludwig (Lou) Bruch (VF- University of Wisconsin); | ||
+ | |||
+ | This section aims to describe related developments that are not uniquely related to in-house microscopy. Any experimental group leader has to be part theoretician, and increasingly that means also doing computer-based calculations. So this implies that, in parallel with the work described in the last two sections, we were able to publish papers, and especially review artictles which became quite well cited and used by other groups. Also many of the experimental papers contained theoretical and computational sections; this is of course not unique to our group, it is widespread. | ||
+ | |||
+ | But somehow, the initial division at Sussex into Experimental and Theoretical Physics (it even appeared in my job title: Lecturer (then Reader) in Experimental Physics), meant that I felt one had to explain oneself a bit. In reality, it was probably just a good strategy for the founding fathers, Ken Smith and Roger Blin-Stoyle, to get to a viable size very quickly. The alternative problem, never being large enough, was noticeable in the New Universities that followed Sussex. The first appointments in Physics were in 1962-3, but growth was essentially shut down by 1968. This growth is documented [[People#Staff_members|here]] and the graphs are quite revealing: faculty numbers grew to over 40 by 1967, and therafter declined to 20 in 1994. Similar changes were occuring throughout the University system, and not just to faculty numbers: ask any member of Technical staff, and be prepared for an explosive reply. | ||
+ | |||
+ | However, alongside these social and organisational changes, there has been a shift within Physics away from small-scale University Lab-based experiments in favor of theory and computation, and also to experiments based in the National and International laboratories, where the organisational structures and the scale of budgets can be quite different. The smart money is on having your feet in more than one of these camps.<br> | ||
+ | |||
+ | To be continued | ||
== Appendix: Group Members == | == Appendix: Group Members == | ||
Line 153: | Line 217: | ||
Jean-Marie Bermond (VF, Professor at Aix-Marseille III) | Jean-Marie Bermond (VF, Professor at Aix-Marseille III) | ||
− | Robert J. Keyse (GS) | + | Robert J. Keyse (GS, then RF) |
David R. Batchelor (GS) | David R. Batchelor (GS) | ||
Line 159: | Line 223: | ||
Masaaki Futamoto (VR, Hitachi Central Laboratories, Tokyo) | Masaaki Futamoto (VR, Hitachi Central Laboratories, Tokyo) | ||
− | Gareth W. Jones (GS) | + | Gareth W. Jones (GS, and part-time TS) |
Oladipo (Ladi) Osasona (VR, Universiy of Ile-Ife, Nigeria) | Oladipo (Ladi) Osasona (VR, Universiy of Ile-Ife, Nigeria) | ||
Line 174: | Line 238: | ||
Gerhard Cox (GS, MSc student, and Diplom 1986, RWTH, Aachen) | Gerhard Cox (GS, MSc student, and Diplom 1986, RWTH, Aachen) | ||
+ | |||
+ | Annette Langenfeld (VE, 1989) | ||
Timothy Doust (GS) | Timothy Doust (GS) | ||
Line 183: | Line 249: | ||
Min Huang (GS) | Min Huang (GS) | ||
− | Frances L. Metcalfe (GS) | + | Frances L. Metcalfe (GS) |
=== 1990-1995 === | === 1990-1995 === | ||
Line 191: | Line 257: | ||
Jesus M. Marcano (RF) | Jesus M. Marcano (RF) | ||
− | E. Hoffman (VE) | + | E. Hoffman (VE)<br> |
Pontus Stenström (VE, 1991) | Pontus Stenström (VE, 1991) | ||
Line 198: | Line 264: | ||
Mohamed Azim (GS with Bob Milne) | Mohamed Azim (GS with Bob Milne) | ||
+ | |||
+ | Hakan Rensmo (VE, 1992) | ||
+ | |||
+ | Sarah Wallin (VE, 1992) | ||
+ | |||
+ | Philippe Carle (VE, 1992-3) | ||
Michael Stumpf (VE, 1993) | Michael Stumpf (VE, 1993) | ||
Örjan Bodin (VE, 1993) | Örjan Bodin (VE, 1993) | ||
+ | |||
+ | Anneka Karlsson (VE, 1993) | ||
+ | |||
+ | Gabor Horvath (VR from Hungary, 1993) | ||
T. J. Martin (PS? with Bob Milne) | T. J. Martin (PS? with Bob Milne) |
Latest revision as of 17:20, 30 December 2011
Contents
- 1 Electron Microscopy and Surface Physics - John Venables
Electron Microscopy and Surface Physics - John Venables
Introduction and Summary
Sussex Physics was a wonderful place to get a first "proper job". After a PhD in Cambridge and a 3-year post-doc period in Illinois, it was great to have an exciting new job, and to return to a beautiful and vibrant part of the UK. I wish to pay tribute to Ken Smith, our foundation Professor of Experimental Physics. It was Ken who appointed me to Sussex in the Autumn term of 1964. I had known Ken in Cambridge, where I assisted in his Part II Physics Laboratory as a graduate student. Work on Electron Microscopy was very strong in Peter Hirsch's Metal Physics group [1], and so I was able to get a post-doc position in the USA at the University of Illinois, and then join Sussex at a formative stage.
This page is about the Electron Microscopy and Surface Physics research group at Sussex. We were not isolated in our interests, but had overlaps with the group on Particle-Solid interactions and also with other efforts in Condensed Matter Physics, Low Temperature Physics and Materials Science. Michael Thompson and Robert Cahn were both appointed to Professorships in 1965, in Physics and Materials Science respectively. These appointments and those that followed greatly increased the possibilities for collaboration, both in research and graduate level and specialist undergraduate teaching across departmental lines. And, although we were passionate about our Science and research in particular, Sussex was a place where many other activities, especially of an interdisciplinary nature, were encouraged.
Sussex literally gave me, and by extension all of us, a chance to do my "own thing", and I feel very grateful to have been able to take that, and build on it in my/our own way. The "our" is important of course, since without collaborators, technical help, students and especially graduate students, one can do very little in experimental physics or any other experimental science. I have been particularly fortunate in all these aspects: the fact that we had an excellent Mechanical Workshop under Frank Schofield made all sorts of technical developments in Transmission Electron Microscopy possible from the start. Later, we also used the staff of the Electronics Workshop as well, to keep ahead of developments in Scanning Electron Microscopy. Some of these aspects will be described in the two sections that follow
One of the great possibilities offered by this Wiki form of history, is that all of our collaborators can contribute whatever they want or have time for. I am still very much in contact with one of my two first graduate students, George J. Thomas, and the other David J. Ball, can be found via a simple Google searches. Both have had distinguished careers in the US National Laboratory system, and as a Professor/Consultant on Risk Management in the UK respectively. My long-term technical colleague Chris Harland subequently got a PhD himself, and after spells in Industry, became Reader in Electronics at Sussex.
I am not planning to transfer the group publication list to this site, since there is already a complete list on my Arizona State University site [2]. I retired from Sussex in January 1995, but have been associated with the University since as an Honorary Professor, and currently as Emeritus Professor. The list of group members ends at 1995, but that is not the end of the story: Michael Hardiman, Senior Lecturer in Physics, continues research but in a somewhat different field. I have continued research in Arizona, at the London Centre for Nanotechnology at UCL, and with several colleagues around the world.
I look forward to possibly remaking contact with several other former co-workers via this celebration of Sussex@50. If any of you wish to elaborate on my account here, that will be wonderful.
References
1. Members of the Metal Physics group were much in demand worldwide at the time, and produced the "Bible", Electron Microscopy of Thin Crystals (Butterworths, London, 1965) following a succesful summer school in July 1963. The authors, P. B. Hirsch FRS, A. Howie, R.B Nicholson, D.W. Pashley and M.J. Whelan, all be came very well known for a whole "School" of Electron Microscopy that spread round the world. The authors went on to lead groups in Oxford (Professor Sir Peter Hirsch and Professor Mike Whelan, FRS), Cambridge (Professor Archie Howie, CBE, FRS), Imperial College (Professor Don Pashley, FRS). Sir Robin Nicholson FRS, FREng was Chief Scientific Advisor, Cabinet Office from 1983-1985 during a long career in Industry and Academia.
2. Since 1985 I have been a Professor at Arizona State University in the Physics Department on a part-time basis. There I maintain a home page, which contains all my professional details, including teaching, research, publcations and short-form CV.
Research Activity 1: In-situ Transmission Electron Microscopy
Shortly after my arrival in Sussex, Professor Ken Smith signed a purchase order for a Hitachi HU 11B Electron Microscope. This was for £11,600 or thereabouts, a large sum of money in 1964: but of course without a microscope we could do nothing. This instrument became the workhorse of the early years of the group, and it got heavily modified, several times, in the process. I had decided to try my hand at what became known as In-situ Microscopy: performing experiments on the samples inside the microscope and observing them at the same time, or shortly afterwards with out breaking the vacuum.
In particular, we constructed a variable temperature stage that was cooled by liquid helium. Liquid helium was in more or less plentiful supply at Sussex from early on, due to the presence in the Department of the Low Temperature group. The Mechanical Workshop staff were crucial in the fine scale machining needed to make several versions of the low temperature stages and accessories over a long period. Our group technician, John Notton, maintained the microscope, ran the photographic dark room, and helped with equipment and experimental set up. The results came out in the form of plates that had to be developed using wet chemistry: this was all long before the advent of digital recording and terabytes of data. The terabytes were all in the form of small silver crystals after development of the plates, plus a few kilobytes recorded by hand in "Plate" books, and hardback research notebooks!
With my first two graduate students, we started on our first two scientific topics, outlined below: "Electron microscopy of low energy ion damage in Metals" with George Thomas (DPhil 1969), and "Nucleation, growth and defect structure of Rare Gas Solids" with David Ball (D.Phil 1969). The first project involved construction a removable low energy ion gun to fit above the stage. The second involved various cells and directed gas beams to grow the crystals at well defined pressures and temperatures. While the projects started out in an exploratory manner, they nearly all became quantitative studies with T and p (and ion current) as the independant variables.
This (thermodynamic) motivation became particularly important later on, when the aging microscope was converted into a high precision diffraction camera. It was used to study the monolayer phases of rare gases adsorbed on graphite with high precision. The microscope and surrounding equipment is shown in this latest incarnation in Figure 1 (below left). For more details the relevant theses and publciations can be consulted, but for now, a lot of good work was accomplished on this machine by quite a few graduate students, post-docs, visitors and technical staff. Indeed I enjoyed taking some interesting pictures and diffraction patterns myself...
Low Energy Ion Damage in Metals
This activity was a follow-up of work I had done on Ion Bombardment as a post-doc in Illinois: indeed George Thomas was an hourly worker in the Lab there, who made the courageous decision to follow me to Sussex for a PhD, courtesy of a grant from the US Air Force (who also supported David Ball). Low energy ion bombardment produces Interstitial atoms from the bombarded surface, and this was studied using Stereo-Electron Microscopy of gold containing vacancy terahedra (produced by quenching from high T as shown by John Silcox in his Cambridge PhD, now at Cornell). So the interstials migrate to the vacancy defects and cancel them out in a variety of wonderful ways, which were expected to depend on the bombardment temperature. The stereo-pictures were marvellous, and enabled depth-dependent data to be obtained. In the end we found out that the results depended on the purity of the starting material in the few ppm range, and not much on T, investigated in the range 25-283K.
The results contributed to ongoing sagas about Interstitials in metals, written up in a thorough paper by G.J. Thomas and myself (Phil. Mag. 28 (1973) 1171-1201). This paper was preceded by two reviews in 1969 and 1970 and several conference papers.The reviews were invited by Mike Thompson, by then well-established at Sussex and functioning as a group with Peter Townsend, Derek Palmer, Mike Lucas and their co-workers.
We also made a start to measure changes in resistivity during low energy ion bombardment, but despite efforts over a couple of years, this didn't really get anywhere. However, we had an interesting visiting researcher at that time, Bill Robinson, who at the end of his stay was pleased to get a job in the DSIR (Department of Scientific and Industrial Research) in his native New Zealand; he went on to great success in Earthquake protection (see http://www.rslnz.com) and was awarded the QSO (Queen's Service Order) in 2007; yesterday I wrote "belated congratulations, Bill, from the other side of the world!" and emailed him to ask him to proof-read this paragraph. Today, sadly I learned that he has died of a brain tumor on 17th August 2011... (pause for reflection, I'm afraid, statistically inseparable from an exercise of this nature).
Two other researchers contributed to related types of activity: Klaus Ecker (DPhil 1973) and post-doc Dirk van Vliet. Both had a strong overlap with the Thompson group and published their work under their own names. Klaus's work involved high sensitivity detection of (transmission) sputtering at lower keV energies and the role of ion channeling, published in Radiation Effects, 23 (1974) 171-180; Dirk, already established as a computer simulation expert in radiation effects, published several papers around 1970 when attached to Sussex. Via the Harwell connections and the Atomic Collisions in Solids MSc course, we were involved in some further theses, but this area dried up as a research effort as we concentrated on the following two topics.
Nucleation, Growth and Defect Structure of Molecular Solids
The work started with David Ball on rare gas solids developed rapidly and in a number of exciting ways. By growing the crystals on graphite at different T and p, we found the type of behaviour expected for nucleation and growth on surfaces; this started an interest in Nucleation and Growth kinetics which has persisted to the present day. David's work was written up in several places, perhaps most prestigiously in Proceedings of the Royal Society A 322 (1971) 331-354. We used the review of Nucleation and Growth that visiting faculty member Dan Frankl and I wrote for Advances in Physics 19 (1970) 409-456 to interpret the results and compare with the theory of rare gas interatomic, and rare gas-graphite potentials. The microstructure of the rare gas crystals, and dislocations in these crystals, were also studied in some detail.
Before long, David was joined by further graduate students Colin English, Karl Niebel and post-doc Gordon Tatlock, who followed up on his work and took it in new directions. Colin branched out to other "simple" molecular solids, N2, O2, etc and we produced some wonderful microscopy, as shown in Figure 2 for alpha-N2 (below left) and figure 3 for beta- O2 (below right). We solved some long-standing questions about the crystal structure and twinning in these solids. This work was published initially in Phil Mag 21 (1970) 147-166 with a review in Thin Solid Films 7 (1971) 369-389, and then in Acta Cryst. B30 (1974) 929-935 In parallel, Colin (DPhil 1974) studied a simple model of the diatomic solids, Proc. Roy. Soc. A340 (1974) 57-80 and 81-90, the latter with Dennis Salahub. Dennis was then John Murrell's post-doc, and is now Professor of Chemistry in Calgary. After a post-doc period in our group in Sussex, Colin moved to Harwell (AEA Technology) Harwell, and is now a Visiting Professor at Oxford.
Karl Niebel concentrated on the role of stacking faults in the rare gas solids, and the measurement of their energy, directly related to the hcp-fcc energy difference, using dislocations in solid Xenon. He followed this up with a model of the hcp-fcc crystal structure "problem" in the rare gas solids, in Proc. Roy. Soc. A336 (1974) 365-377. This is a topic that was also studied by John Murrell and Tony Leggett; all three were good reasons why life at Sussex at the time was stimulating. Robert Keyse (DPhil 1982) returned to this problem later, with a paper in J.Phys C 18 (1985) 4435-4441
Gordon Tatlock came to Sussex from Bristol as a post-doc, and mostly established his own program on layered compounds, which he can elaborate here if he wishes. He contributed skilfully to the work of the group, including on molecular solids with Colin and Karl. All this work, including figure 4 (above), was featured an excellent French conference in 1974 at Beaune, published in J.Phys Colloque C7 (1974) 113-119. Later still Gordon was joined by post-doc Remy Mevrel for a detailed study of twinning in the low temperature alpha-phase of solid nitrogen, published in Phil Mag 35 (1977) 641-652. Gordon has been at Liverpool University for many years as Professor of Materials Science and Engineering and is now also a staff member at the SuperStem facility at Darebury Laboratory.
In the same time frame, and independent experiment was done on the vapor pressure of Ar-O2 alloys, in order to determine the hcp-fcc energy difference of Ar near its melting point. Terry Bricheno had done his PhD with Brian Smith, and we were able to get funding to study this problem using his PhD apparatus. This was one of the most satisfying results, in the sense that the method was fundamental, and the right people were in place to get the job done in a finite time. The papers are in J. Phys C9 (1976) 4095-4108 and 10 (1977) 773-779, the latter theoretical paper with Remy as the first author.
In the late 1970's, due to the need for more microscope time, we bought a second-hand JEOL 200A (200 kV) microscope, and also added a side-entry liquid helium stage. This was used by Gordon Tatlock for his own work, and by Graeme Raynerd (DPhil 1987) and Robert Keyse for low-T studies of molecular solids SF6, Kr and Xe, grown inside an environmental cell which withstood greater gas pressures than before. This enabled the condensed gases to be annealed closer to their melting points, thus producing larger, more perfect crystals. The equipment was described by R.J. Keyse, G. Raynerd and myself in J. Phys E17 (1984) 228-233, and the papers on the solids themselves appeared over the period 1982-1987; all very interesting, but this was the last work that we did on molecular solids and the crystal structure problem in rare gas solids. Work on rare gas layers adsorbed on graphite, using the HU 11B micrsocope largely as an electron diffraction camera, is described in the next sub-section
Monolayer Phases of Adsorbed Gases on Graphite
Michael Kramer and Garth Price arrived in Sussex around 1970 from Germany and Australia respectively. They took our nucleation and growth work in a different direction, essentially by showing that the substrates David Ball and I were using could not have been clean at the monolayer level. The results we had obtained on island growth were inconsistent with the layer growth observed by other groups, notably by the French groups in Nancy and Marseilles. They had studied rare gas adsorption using (Physical Chemistry) volumetric techniques, and increasingly Surface Science techniques. As we started to correspond by letter, I realized that there was a huge literature out there, and a visit was definitely in order. I was priviledged to spend 6 months at the Marseille-Luminy campus over the Easter vacation, the Summer Term and Vacation in 1973; this developed into a longer term relationship with groups in the Physics Department (Michel Bienfait, Jean Suzanne, Jacques Derrien) and CRMC2-CNRS laboratory (Raymond Kern, Boyan Mutaftschiev and many co-workers). 1973 was a good year in many respects: not only a wonderful break from lecturing and time for writing, but also key to several types of work described here.
Garth (DPhil 1973) absorbed the French literature and realized the rare gases (at least Ar, Kr and Xe) absorb on graphite in layers, and were expected to continue to grow as layers. These gases have a small misfit with respect to the lattice parameter of graphite. He constructed a new stage to enable us to flash-clean the graphite in-situ, as indicated in the schematic of figure 4, and a directed molecular beam to deliver the gas directly onto the graphite flake. Once he did this, Xenon condensed as layers, no islands to be seen, but considerable microstructure within the layers. Mystery solved, as published in Surface Science 49 (1975) 264-274, complete with examples of how, when one relaxed the contamination protection (for example by removing the film across the beam before the sample), he retrieved the results obtained by myself and Ball (1971). Michael (DPhil 1974) obtained some excellent pictures of epitaxial Ar, Kr and Xe crystals on graphite and other layer compounds as substrates, showing beautiful Moiré patterns containing dislocations in the rare gas layers. These pictures were published by him in J. Cryst. Growth 33 (1976) 65-76.But in a sense the real excitement came just after this, when we realised that a single monolayer of Kr and Xe on graphite could be detected by transmission electron diffraction. Not only detected, but measured with high precision (Venables, Kramer and Price, Surface Science 55 (1976) 373-379 and 57 (1976) 782). The diffaction pattern gives the spacing of the gas layers, and this was shown to be a reproducible function of T and p. Now the scene was set for detailed work, in which the crystallography of, and phase transions in these layers was mapped out and compared with results in other laboratories, notably Marseille, MIT and University of Washington. Several students contributed, and the old Hitachi microscope was dedicated to the type of work over the next decade. Now we could claim that we were really doing quantitative Surface Physics, not "just" taking pictures.
Pablo Schabes-Retchkiman (DPhil 1980) was next up, with a detailed study of Kr and Xe layers, coupled with calcuations and statistical mechanical models based on prior work on rare gas and gas-graphite potentials by Garth Price. Several papers in the late 1970's, including an interesting French Conference (J. Physique C4 (1977) 105-114), until the final paper of this series in Surface Science 105 (1981) 536-564.A three-dimensional plot of the Kr/graphite data, with diffraction experiments from three laboratories is shown in Figure 5. The Sussex data (constant p at various T) are the points to the right of the plot, with the Washington and Marseille data (constant T at various p) are shown towards the left with open and closed symbols respectively. It is clear that these different data are all seeing the same phenomena: Kr first condenses in to a commensurate (C) phase, and then undergoes a Commensurate-Incommensurate (C-I) transition at lower T and/or higher p: this was very satisfying.
By this time we were in our stride on this topic, and three further graduate students, Abdul-Qader Faisal (DPhil 1987), Mohamed Hamichi (DPhil 1990) and Amine Zerrouk (DPhil 1993) contributed important results to large areas of the (T, p) phase diagrams particularly on Xe/graphite. This was aided by theory involving post-doc Bob Kariotis and visiting Faculty Lou Bruch from Wisconsin, as well as joint experiments and modelling with the Marseille group. Several papers were published between 1976 and 1994 by the above colleagues, mainly in Surface Science and in Phys Rev B. A complete list of joint work with Marseille colleagues over this period is available here.
Research Activity 2: Ultra-high Vacuum Scanning Electron Microsocopy
There are three strands to be described here in outline. Historically the first, with Chris Harland, is the story of how we became involved in technique development for Scanning Electron Microscopy (SEM) after the purchase, by Mike Thompson's group, of a Cambridge Instruments "Stereoscan" around 1970; this is described in the second sub-section. The second arose from our experience with adsorption and crystal growth, where it had become 100% clear that, in order to do Surface Science, we needed an ultra-high vacuum (UHV) instrument. This lead to a major grant application, jointly with Chris Harland, Roger Doherty in Materials, Ron Mason in Chemistry and Bruce Joyce at Philips Redhill, for the development of an UHV-SEM for surface studies. This development is described in two sections. First we describe the commisioning and development of the instrument itself. In the final subsection we describe some of the science done with the instrument, and some further developments.
Instrument Design and Delivery
The instrument itself was built by VG Scientific Ltd of East Grinstead, later VG Microscopes Ltd. The delivery of the instrument in 1975 was the start of a long-time relationship with VG (originally Vacuum Generators Ltd), and a close relationship between our students and their staff. Notably, Ian Wardell who was their Electron Optics specialist, is now in retirement a Visiting Researcher with Mike Hardiman, and Gareth Jones, when last located, was Managing Director of VG Scientific, now called something quite different... But several other group members had jobs at East Grinstead following their period in our group: Adrian Janssen, David Fathers, Robert Keyse, Gareth Jones and Tim Doust, plus maybe some more lurking somewhere.
The instrument as delivered, shown in figure 6, was equally pristine. As we found on several occasions, the boundary between what was delivered by VG, and what we needed to do next, was by the nature of the beast rather fluid. See all those blank flanges? They are for future detectors and experimental add-ons: Auger spectrometers, evaporation sources and shutters, all up to us.
Fresh from the factory, and in the run-up to the Institute of Physics' Electron Microscopy and Analysis Group (EMAG) conference in Bristol, I wrote an article for Physics Bulletin (August 1975, 359-362) and the introduction to the Proceedings (Academic Press, 1976), containing a small part of a similar image. That image was captured in "More Random Walks in Science", with the caption: "It's only once you have tightened up all the nuts and bolts, that you realize you left out an O-ring"... Yes, well, our most well-known publication for a while.
Hosting the same conference in Sussex four years later was an opportunity to show the microscopy community what it became. I wrote summary articles with Adrian Janssen and Chris Harland (Physics Bulletin 29 (1978) 307-311) and the International Congress on Electron Microscopy with an invited paper on Scanning Auger Microscopy (Toronto, vol 3 (1978) 280-291). We had several invited and contributed papers there and in the EMAG proceedings (IoP Conference Series volumes 41 (1978) and 52 (1980)). The word was getting out that we were enjoying ourselves.
But first we should backtrack to explain how we got to this point, because, without the prior experience of SEM using the Stereoscan, our grant applications would not have been credible. This period is described in the next subsection.
SEM Experience with the Stereoscan
People involved with this development: Barry Farmery, Chris Harland, Peter Pollard, Barrie Griffiths, Ramli Bin-Jaya, and several other MSc students
Chis Harland arrived at the University of Sussex as a Junior Technician in 1967, and left it for senior positions in Industry in 1995, with a PhD in Electronics, granted in 1986. In between there were several episodes, but all involved running SEM's, developing two EM laboratories, and Electronic and Instrument development. He started in Applied Sciences, and formally joined our group from 1971, first as Senior and Chief Technician, and following the PhD, as Scientific Officer. Later he returned to Applied Sciences as a Research Fellow, then Senior Research Fellow and finally Reader in Electronics. This is a success story, and for my part, I feel proud to have helped as a mentor/ co-worker. Let me be quite clear here: without someone of Chris's ability in electronics, design and organisational skills over a long period, we would simply not have been able to pursue the developments that are described here.
To be continued
Some Research highlights using the UHV SEM
People involved: Adrian P. Janssen (RF), Bruce A. Joyce (VF, Group leader at Mullards/ Phillips Redhil), George S. Samuel (GS), Klaus Hartig (VR, Research student at Bochum), Parvez Akhter (GS), Gary D. Archer (GS, MSc student), Jeff Spain (TS), Geoff D.T. Spiller (RF), David J. Fathers (RF), Michael Hardiman (F, "New Blood" Lecturer from 1983), Jean-Jacques Metois (VF, CRMC2-CNRS Marseille), Margrit Hanbücken (RF, subsequently CRMC2-CNRS Marseille), Jean-Marie Bermond (VF, Professor at Aix-Marseille III), David R. Batchelor (GS), Masaaki Futamoto (VR, Hitachi Central Laboratories, Tokyo), Gareth W. Jones (GS), Oladipo (Ladi) Osasona (VR, Universiy of Ile-Ife, Nigeria), Gerhard Cox (GS, MSc student, and Diplom 1986, RWTH, Aachen),Timothy Doust (GS), Parmjit S. Flora (GS), Min Huang (GS), Frances L. Metcalfe (GS), Jesus M. Marcano (RF), E. Hoffman (VE), Pontus Stenström (VE, 1991), Robert H. Milne (F, 5-year fixed term Lecturer from ?), Mohamed Azim (GS with Bob Milne), Michael Stumpf (VE, 1993), Örjan Bodin (VE, 1993), T. J. Martin (PS? with Bob Milne), Raj Persaud (RF), Hisato Noro (GS), Akira Sugawara (VR from Japan and Arizona State)
To be continued
Research Activity 3: Related Theoretical and Computational Studies
Personnel involved: Almost everyone, but in addition Dan Frankl (VF-Pennsyvania State University), Robert Kariotis (RF), David Fathers (RF), Albert Curzon (VF Simon Fraser University), Jean-Marie Bermond (VF Universite Aix-Marseille III), Ludwig (Lou) Bruch (VF- University of Wisconsin);
This section aims to describe related developments that are not uniquely related to in-house microscopy. Any experimental group leader has to be part theoretician, and increasingly that means also doing computer-based calculations. So this implies that, in parallel with the work described in the last two sections, we were able to publish papers, and especially review artictles which became quite well cited and used by other groups. Also many of the experimental papers contained theoretical and computational sections; this is of course not unique to our group, it is widespread.
But somehow, the initial division at Sussex into Experimental and Theoretical Physics (it even appeared in my job title: Lecturer (then Reader) in Experimental Physics), meant that I felt one had to explain oneself a bit. In reality, it was probably just a good strategy for the founding fathers, Ken Smith and Roger Blin-Stoyle, to get to a viable size very quickly. The alternative problem, never being large enough, was noticeable in the New Universities that followed Sussex. The first appointments in Physics were in 1962-3, but growth was essentially shut down by 1968. This growth is documented here and the graphs are quite revealing: faculty numbers grew to over 40 by 1967, and therafter declined to 20 in 1994. Similar changes were occuring throughout the University system, and not just to faculty numbers: ask any member of Technical staff, and be prepared for an explosive reply.
However, alongside these social and organisational changes, there has been a shift within Physics away from small-scale University Lab-based experiments in favor of theory and computation, and also to experiments based in the National and International laboratories, where the organisational structures and the scale of budgets can be quite different. The smart money is on having your feet in more than one of these camps.
To be continued
Appendix: Group Members
This list includes all categories of colleagues in approximate historical order (of starting), and is not at present complete. I would like to hear of omissions.
The abreviations are: Faculty associated with the group, even if loosly (F), Graduate Student (GS); Research Fellow (RF), Technical Staff (TS), Visiting Faculty (VF), Visiting Researcher (VR), Visiting and Exchange Student (VE), Project Student (PS), typically for a final year project.
Names, graduation dates and thesis titles for Physics D.Phil and M. Phil students are given in the list on this site.
There is no detail on the source of funding for anyone person or project, since this typically changed with time.
1964-1969
For thesis dates and titles click Research-dphil_p_by_year_early
John A. Venables (F)
George J. Thomas (GS)
David J. Ball (GS)
John S. Notton (TS)
Henry R. Gylde (RF with Brian Smith)
Daniel R. Frankl (VF- Professor, Pennsylvania State University)
Dirk van Vliet (RF)
Colin A. English (GS)
H. Michael Kramer (GS)
Keith Davies (TS)
1970-1979
For thesis dates and titles click here
Christopher J. Harland (TS)
Barrie W. Griffiths (GS)
Karl F. Niebel (GS)
Klaus H. Ecker (GS)
Garth L. Price (GS)
Gordon J. Tatlock (RF)
Ramli Bin-Jaya (GS, MSc student)
Adrian P. Janssen (RF)
Bruce A. Joyce (VF, Group leader at Mullards/ Phillips Redhil)
Terry E. Bricheno (RF, also GS with Brian Smith)
Michel Bienfait (VF, Professor at Aix-Marseille II)
Jonathan H. Klein (GS, MSc student)
Remy Mevrel (RF)
George S. Samuel (GS)
Pablo Schabes-Retchkiman (GS)
Klaus Hartig (VR, Research student at Bochum)
Parvez Akhter (GS)
Jacques Derrien (VF, Professor at Aix-Marseille II)
Gary D. Archer (GS, MSc student)
Jeff Spain (TS)
Arthur C. Sinnock (VF with Brian Smith, Brighton Polytechnic)
1980-1989
For thesis dates and titles click here
Geoff D.T. Spiller (RF)
Graeme Raynerd (GS, then RF)
Jean Suzanne (VF, Professor at Aix-Marseille II)
David J. Fathers (RF)
Michael Hardiman (F, "New Blood" Lecturer from 1983)
Jean-Jacques Metois (VF, CRMC2-CNRS Marseille)
Ludwig W. Bruch (VF, University of Wisconsin)
Margrit Hanbücken (RF)
Jean-Marie Bermond (VF, Professor at Aix-Marseille III)
Robert J. Keyse (GS, then RF)
David R. Batchelor (GS)
Masaaki Futamoto (VR, Hitachi Central Laboratories, Tokyo)
Gareth W. Jones (GS, and part-time TS)
Oladipo (Ladi) Osasona (VR, Universiy of Ile-Ife, Nigeria)
Abdul-Qader D. Faisal (GS)
Marilyn Whitehouse-Yeo (TS)
Mohamed Alikacem (GS, MSc student)
Mohamed Hamichi (GS)
Albert E. Curzon (VF, Professor at Simon Fraser University, Burnaby, BC)
Gerhard Cox (GS, MSc student, and Diplom 1986, RWTH, Aachen)
Annette Langenfeld (VE, 1989)
Timothy Doust (GS)
Robert Kariotis (RF)
Parmjit S. Flora (GS)
Min Huang (GS)
Frances L. Metcalfe (GS)
1990-1995
For thesis dates and titles click here
Jesus M. Marcano (RF)
E. Hoffman (VE)
Pontus Stenström (VE, 1991)
Robert H. Milne (F, 5-year fixed term Lecturer from ?)
Mohamed Azim (GS with Bob Milne)
Hakan Rensmo (VE, 1992)
Sarah Wallin (VE, 1992)
Philippe Carle (VE, 1992-3)
Michael Stumpf (VE, 1993)
Örjan Bodin (VE, 1993)
Anneka Karlsson (VE, 1993)
Gabor Horvath (VR from Hungary, 1993)
T. J. Martin (PS? with Bob Milne)
T.E. Amine Zerrouk (GS)
Raj Persaud (RF)
Hisato Noro (GS)
Akira Sugawara (VR from Japan and Arizona State)