Awardee Interviews | Leonard J. Brillson - 2006 Gaede-Langmuir Award - Interview

Leonard J. Brillson

2006 Gaede-Langmuir Award - Interview


Interviewed by Paul Holloway 2006
 
HOLLOWAY: I'm Paul Holloway, a member of the American Vacuum Society (AVS) History Committee. I am here today at the 53rd Symposium of the AVS in San Francisco, California. The date is Wednesday, November 15, 2006. I am interviewing Professor Leonard Brillson, the 2006 winner of the Gaede-Langmuir Award. The citation reads "For demonstration of the fundamental importance of semiconductor interfacial bonding, metallurgical reactions and defect formation upon solid-state material for device properties." So Len, it's a real pleasure to have you here today and participate in this interview. Congratulations on the Gaede-Langmuir Award.

BRILLSON: Thanks, Paul. It's great to be here, and I'm delighted to have a chance to tell you a little bit about what's happened in my life and my career.

HOLLOWAY: Good. We look forward to that. Let me get us started by asking you to give us a little bit about your background, your educational history and where it took place, etc.

BRILLSON: Well, I went to college at Princeton University in New Jersey and then went on to graduate school at the University of Pennsylvania, where I got my Ph.D. That's where my life with semiconductors started as a graduate student working for Professor Eli Burstein in the Department of Physics. Eli was a big influence in my life, first of all just by showing me how exciting it can be to have a life in the community of science, the social interactions and, of course, the science itself. He had many friends in industry, which got me motivated to think about working in industry as well.

HOLLOWAY: Did you actually participate as a student in industrial research projects or anything like that?

BRILLSON: No, but I met a lot of his friends - especially from IBM and Bell Labs - and so I realized this was an exciting thing. The thesis that I pursued involved putting metals on semiconductors - not so much to study Schottky barrier formation, which became a focus of my research later, but rather to take advantage of the electric fields near the interface that break the symmetry rules of these crystalline lattices that semiconductors are composed of, and in that way to reveal new phonon scattering as it turned out that you could not otherwise observe, that was symmetry-forbidden. But in the process of that work I became fascinated with how these electric fields - the Schottky barriers - form and how the associated charge transfers between the metal and the semiconductor. That actually led me to a career at Xerox Corporation in Rochester, New York.

HOLLOWAY: You went to Xerox right after you finished your Ph.D.?

BRILLSON: Yes. I finished my Ph.D. in 1972 in Philadelphia and went directly to Rochester, New York. I think I was hired because I had some experience with semiconductor surfaces and interfaces and Xerox is a company that is based on semiconductors, particularly charging up of surfaces and then illuminating them with light and having charge move around and form images.

HOLLOWAY: Right.

BRILLSON: And so this idea of surface charging and the states that these charges fit into was something that was near and dear to their hearts.

HOLLOWAY: Do you recall who the manager was who hired you ?

BRILLSON: It was Charlie Duke. 

HOLLOWAY: Is that right?

BRILLSON: Charlie Duke had just come from the University of Illinois and was anxious to start a group in the area of surfaces and interfaces. But he had a reputation as a tough evaluator and put me through the ringer during my job interview.

HOLLOWAY: Not Charlie. Come on now!

BRILLSON: But I survived. In fact he commended me later for surviving it. 

HOLLOWAY: That was one of the criterion for being hired apparently.

BRILLSON: Exactly. So thereupon began a friendship that has lasted to this day. And in fact Charlie has been a guiding light in my career, both in helping me navigate the world of industrial research as well as looking at some of the exciting science and technology that one can do in that kind of environment. I might add, by also giving me a very realistic perspective on life in physics, in general, as opposed to the somewhat idealistic picture I had as a graduate student.

HOLLOWAY: Charlie was always good about bringing your feet back onto the ground. He was not shy about telling you when you were doing well, nor when you were not performing well. 

BRILLSON: That's right. You needed to be able to listen and to learn from that kind of feedback. Well, I got started in 1972, as I said right after my graduate career, and got a small surface science chamber. There was only a modest amount of money available to get me started, and luckily folks such as Paul Palmberg at Physical Electronics and their sales rep Ed Graney who since retired, really helped me out. They helped me put together a system that could really do something on a very limited amount of money. When I think today about the amount of money I had to work with back then, it's hard to believe. But anyway, this allowed me to get started - albeit on a shoestring - and put together my own homemade evaporator and quartz crystal oscillator and Kelvin probe and cold stage. One of the people who helped me actually was a friend, Paul Nielsen. Paul was a staff scientist, who loved to build things from scratch and who showed me how I could save a lot of money just by building a lot of things myself.

HOLLOWAY: Those people are invaluable. They give you an assist and provide critical infrastructural support.

BRILLSON: Yes, that helped me a lot. It really got me going and I was able to start getting publishable results. And one of the first journals I published in was JVST.

HOLLOWAY: Is that right?

BRILLSON: Yeah.

HOLLOWAY: What did you have inside the chamber then? You had Auger electron spectroscopy?

BRILLSON: In other words I had an electron gun and I had a double-pass cylindrical mirror analyzer.

HOLLOWAY: Did you have LEED in there as well?

BRILLSON: I had a small LEED screen, and I had a metal evaporator but that was basically-

HOLLOWAY: That was for evaporated metal contacts?

BRILLSON: Yep.

HOLLOWAY: What semiconductor were you looking at?

BRILLSON: I was looking at cadmium sulfide for the most part, because Xerox at the time was moving away from selenium as a photoreceptor and they were looking at these polycrystalline layers of cadmium, sulfur and selenium. And they really needed to understand charge transfer through these films and from the film into conducting interfaces. They also needed to know what kind of defects and traps were inside these particles, so that became the motivation to get my program started. One of the techniques that I used first was something called surface photovoltage spectroscopy that you may have heard of. It involved a Kelvin probe and a monochromator to shine monochromatic light at the semiconductor and monitor the work function changes as states are being populated and depopulated to and from the conduction band, into and out of defects or surface states.

HOLLOWAY: What wavelength of light were you using for this?

BRILLSON: Well, wavelengths from about 2 microns to maybe 1/4 micron. In other words, the entire visible range. Cadmium sulfide has a band gap of 2.4 electron volts, but you could also look at the optical transitions down into the infrared. So that got me started, and I was able to observe how surface states appeared and disappeared depending on whether you put a metal on the surface or whether you expose it to oxygen. One of our consultants at Xerox was Harry Gatos from MIT, who was a big proponent of this technique. He was also very helpful and very encouraging. The surface photovoltage spectroscopy only went so far. Many people who were studying semiconductor interfaces were using photoemission, and that was the technique of choice. And I was lucky to have a colleague at Xerox PARC, Bob Bauer, who made it possible for me to come up to the synchrotron ring at Stanford, SSRL, and take some data on cadmium sulfide and cadmium selenide .I found that putting just one monolayer of a metal on these semiconductors would actually produce a reaction. And you could tell by looking at the core level shift. You could see that the bonding of, let's say, a metal such as aluminum on cadmium sulfide was shifted away from that of metallic aluminum. But as soon as you built it up a few more monolayers, it shifted back to metallic aluminum. So that got me thinking that maybe these chemical reactions were something to be considered in the whole picture of charge transfer between one material and another.

HOLLOWAY: Did you take your own system to SSRL or use a system that was online?

BRILLSON: I used the one that was there, and I can tell you that was really tough because at the time Stanford had very low beam currents and we had to come in with a system that Bob Bauer and Bob Bacharach had created at the Palo Alto Research Center and had trucked over to Stanford. The entire apparatus was put into a cage so that you couldn't get exposed to X-rays. And the beam line ran day and night in our period - we were allotted two weeks - and so we worked like dogs.

HOLLOWAY: You were bleary-eyed after two weeks I'm sure.

BRILLSON: That's right. But you know I got a real feeling for surface science working with these guys. And then I was invited by a good friend of mine, Georgio Margaritondo, who at that time was at the University of Wisconsin in Madison. And he got me started by having me work in his chamber before I was able to truck out my own chamber. And then I was actually able to do a much more extensive set of experiments with many different semiconductors and many different metals at what was first the Tantalus synchrotron storage ring, and subsequently Aladdin, a much larger synchrotron that generated much more intense light. From there, it was possible to make a lot of progress and to show that there was a real systematics to this chemistry and that you could examine it on an atomic scale and show that even near room temperature, reactions were taking place along with major differences in the atoms, the anions and cations and semiconductor and the way they moved in and out of the metal.

HOLLOWAY: You abandoned California to go to the warm weather there in Madison, huh?

BRILLSON: Yeah. I was in Rochester, New York, so Madison, Wisconsin was really no different in terms of the very cold and snowy winters.

HOLLOWAY: The only difference between that is not the temperature, it's the lack of snow in Wisconsin I guess, right?

BRILLSON:. Actually, we had plenty of snow, and I remember being in a blizzard getting back into the synchrotron and sort of holing up and doing an experiment while the storm raged outside.

HOLLOWAY: You got extra beam time that way.

BRILLSON: That's right. In a way, it was a bonus to work in the winter season there. It was just around that time that I became involved more heavily with the AVS. I should say that Charlie Duke introduced me to the AVS and encouraged me to actually take a bigger role. I became the program chair for the 1982 National Symposium in Boston, the same as this 53rd Symposium which is currently being held here in San Francisco. And that really opened up my eyes in a big way because I began to meet lots of people from all over the Society and made a lot of friends. I learned a lot about science in general as opposed to my relatively small world at Xerox. And from there I became a Director, actually twice, and I chaired the EMPD Division once. At the same time, I was able to bring in a postdoc to help me with my work - courtesy of the Office of Naval Research. George Wright, who has since retired, was instrumental in that. And I was also asked to manage a group at Xerox. Up until that time I was resisting the idea of going into management because I really wanted to devote myself to science. But they said, "Well, you can have a postdoc and that will help you and you can manage a group of scientists too." This was good, because the alternative was managing a technology group and getting more and more heavily involved in the technology development in the programs.

HOLLOWAY: What year was this?

BRILLSON: I think around 1984 or '85 I became what was called a project leader. It was sort of like a trial in order to see whether you could actually manage. And then a year later I became a manager of a group.
HOLLOWAY: A postdoc management position, huh?

BRILLSON:Yes, that's exactly right. And when I became a manager they said, "Well, your job is to bring in some talented people and do good science and do something for the company." And so I hired some really talented people -people like Lisa Delouise and Joe Kubby, among others, who have gone on and done very good science as well as technology. But having the postdocs really helped me do both jobs. Otherwise I definitely would have had a lot of trouble. By the late '80s, I became a department head. In that position, I was managing fifty or fifty-five scientists and engineers, and that really was demanding. I had four managers reporting to me and it became much harder to do the science.

HOLLOWAY: What were the science areas that were under you at that level? Surely it wasn't all surface science then.

BRILLSON: Oh no. As I think of it, for the most part this department which was called the Materials Research Laboratory focused on the components, the advanced components that went into Xerox machines - components that, for example, might be rubber that acted as electrical insulators but conducted heat. This was a very unusual combination of properties. It was one of the parts that would go into fuser rolls, donor rolls or pressure rolls inside of the machines that have to perform multiple functions, electrical, thermal and mechanical functions, so that the paper would follow a path through the Xerox machine, acquire the toner, which was then fused to it and then come out at the rate of 2 pages a second. And we also would look at our competitors. We would do reverse engineering and see how other companies like Canon were able to put together inexpensive machines that really performed very well. And we also had material scientists and chemists who were making new types of toner as well as new types of developers and photoreceptors. So it was really very much focused on development, technology development.

HOLLOWAY: But it was a broad spectrum of science that you had to be aware of and keep abreast of.

BRILLSON: Right. For the most, everyone was an expert in a particular area and knew a lot of basic science that they could bring to bear and identify good candidates who would serve the purpose that we wanted to develop. And that's really where the basic science came in. We were able to narrow down the field of what we needed to explore in order to develop something that actually worked the way we needed it to.

HOLLOWAY: Right.

BRILLSON: Then by the late '80s Xerox was becoming much more focused on product delivery and yield on investment]. They were much like other companies, like AT&T and IBM, where scientists were feeling the pressure of not doing academic style research in industry. It was around then that I started to look around. And actually Paul, it was you who told me that I really shouldn't bother looking at positions like deanships and so on. In fact you told me this here in San Francisco in Chinatown after lunch one day. I still remember this.

HOLLOWAY: Advised you to join as a faculty member, eh?

BRILLSON: It's much more fun and much more conducive to doing science if you join as a faculty member. It doesn't sound as impressive, but actually it's much better. And you were right.

HOLLOWAY: Well, check that off. That's the first time in my life I was right, I believe. That's an interesting recollection. I am glad that you related that. 

BRILLSON: So by 1996 I had to have made a decision not to go higher up in management. There were opportunities and I was asked to make a choice, but I decided I really wanted an academic career. I knew many friends in academia, and it seemed such an exciting way to have a career. At that time Ohio State and William and Mary both offered me very attractive positions. I ultimately took a chaired professorship at Ohio State University. The position, which is called the Center for Materials Research Scholar, really allowed me to pursue a major research program for the first time. And I was able to build it up very quickly, courtesy of my friend and colleague, Charlie Duke, who was a vice president at Xerox at the time. He made it possible for me to take all my equipment, my entire lab, all the surface science chambers and things that I had put together over many years, with me to OSU. And of course you know very well that a starting professor has a tough time building up a lab and getting the first results in order to be competitive and get a grant. So having my equipment at the start really helped me a lot.

HOLLOWAY: Yes. That's a tremendous advantage for you. It's again a good example of having friends that support and endorse what you are trying to do, and giving you the loyalty that you deserve.

BRILLSON: Well, he is a very, very good friend and continues to be. And of course Ohio State is a very fun place to be. It's a big school, it has huge numbers of students and faculty and they also play a little football.

HOLLOWAY: They have a big game coming up this weekend apparently.

BRILLSON: That's right. It's Michigan! 
So in recent years I have been able to take this technique that I started at Xerox, cathodoluminescence spectroscopy, and turn it into a surface science tool. I have now extended it using scanning electron microscopy and imaging SIMS and this is really opening new doors which are also very exciting.

HOLLOWAY: Good. Well that's a long and very storied history that you've related to us. Give me a comparison on how you find research in the university versus research at Xerox for example.

BRILLSON: Well, it's very different. Xerox, at the time I was involved, allowed you to do research as long as there was some believable connection and hopefully a productive connection between your work and the company's products. In my case I was studying charge transport across semiconductor films, which really are at the heart of the Xerox machine. At Ohio State or at any university, the range of work that one can do is so much wider. I'm working on complex oxides and wide band gap semiconductors and insulators such as hafnium oxide, and even biological materials. I am collaborating with a professor in the medical school and in biomedical engineering. So it's possible to do all kinds of things, and you really can follow your interest and your capability to do some meaningful work.

HOLLOWAY: For the young aspiring professor or current graduate student out there who is looking at this, what is your most daunting challenge if you wanted to start, without any industrial experience, as a professor at a major research university for example?

BRILLSON: Well, I think the young folks who are out there looking for faculty positions and a long-term career in science need to establish themselves as able to perform high-quality work and publish it. Having a track record of good publications, either as a graduate student or as a postdoc, is very helpful. Also, having a broad view of science and a view of research in an area that extends outside of a particular discipline, be it physics, chemistry, electrical engineering or material science, and being able to take the best of each one and combine it in order to address really important questions can be very helpful. There are just so many things to study. And one wants to be able the test the most fundamental, the most interesting and the most exciting questions you can.

HOLLOWAY: Right. I often tell my students that you must learn to prioritize. You are always going to have more ideas than you can possibly pursue, and so you learn how to select the best ones.

BRILLSON: That's right.

HOLLOWAY: And the most important ones to try to pursue.

BRILLSON: Right. And you know, one thing that I learned at Xerox is that you can also do great things by working with others, with people who are experts in their field, and by combining forces and expertise you can get something done that's bigger than the sum of the parts.

HOLLOWAY: Let me come back to that and ask the question relative to the people you've worked with. You've met most of them by networking through the professional societies, and you've mentioned the AVS as being a premier example of that.

BRILLSON: Right.

HOLLOWAY: Would you make some comments for the young people out there of the importance of that networking issue?

BRILLSON: Yes, I will. Networking is really important, and a society like AVS is ideal for this sort of thing, because it's a society that serves as a bridge between science and technology. So you get to meet people who are doing some of the most fundamental science today, and at the same time people who are involved in technologies that are really important - the microelectronics industry, the optoelectronics industry, transportation, communication and many others. And these people come together at AVS, and they come together from all different disciplines so you really can meet a wide variety of people - people from academia, from industry, from Federal labs - and you can really get insight into what it's like to work at these places. And also what are some of the more important issues that each field faces.

HOLLOWAY: One issue when you are a young aspiring faculty member just getting started, is the challenge of getting research funds to support graduate education and research programs. Again I presume that that was helped by the networking through the professional societies.

BRILLSON: Yes, I think so. I think having people know your work and your overall approach to science and engineering is very important, because many of these people will become the peers who evaluate you, one way or the other, in terms of proposals, in terms of writing letters of recommendation for tenure or for funding, and you quickly learn what other people consider important and how to improve yourself.

HOLLOWAY: Yeah. That's very important. What about the interaction you have with scientists as an industrial science research manager versus students at the university? Is there a difference in the relationships? Do you enjoy that?

BRILLSON: Well, I certainly try to interact with all of my colleagues and students as mature individuals. The students sometimes take a little longer. But by the time you become a college student or graduate student you are already a grownup. As a parent I'm not always so sure of that, but certainly by the time they are a graduate student you should be able to treat students in a very mature way and set them well-defined expectations and show them why what they do is important. I think that's really an important consideration. It should not be that if someone asks a student, "Why are you doing this experiment?" that they have a tough time explaining. They really need to be able to do that. The counterpart when you're a scientist in industry you probably have a pretty good idea of why you are doing a particular experiment both scientifically and in the context of the company. So I think one way to relate to people, is to say, "Here are great job opportunities for you," or "Here is a great research opportunity for you, and here is why other people value it."

HOLLOWAY: A name that I know you have worked with in the past is Jerry Woodall I wondered if you would indicate how he fit into the picture.

BRILLSON: Jerry is an important piece of all this and I should have mentioned him earlier. When I was doing soft X-ray photoemission spectroscopy, it became clear that Jerry would be a great person to collaborate with. Now he and I met earlier on through AVS and also especially through the PCSI conference. Jerry is a character, but of course he is an outstanding scientist and technologist. 

HOLLOWAY: But he is a character.

BRILLSON: He is definitely a character, but one that I fully enjoy. And we became very close friends and decided we would try to do great things together. One way we tried was for him to grow samples that we could perform soft X-ray photoemission experiments and—

BRILLSON: ...gallium arsenide, indium gallium arsenide and similar materials we were able to learn things about semiconductor surfaces and interfaces that actually will shed a whole new light on the field of Schottky barrier formation. We found that these materials were much higher in quality than the material that people were using up to that point, and as a result we were able to see new effects that really changed our view of what was going on at Schottky barriers, at metal-semiconductor interfaces. On top of that, Jerry gave me a lot of courage to stand up to some of the tug-of-war that used to ensue when we debated Schottky barrier formation. Everyone had their own theories, and people took it very seriously.

HOLLOWAY: I remember well some of those pointed questions that were asked and heated discussions that ensued as a result of those questions at AVS meetings. Those were good times. They were exciting. 

BRILLSON: Right. They certainly were exciting. I'm glad I survived.

HOLLOWAY: I think they were exciting if you were sitting in the audience enjoying the show.

BRILLSON: More like a bloodbath!

HOLLOWAY: I know that one of the things that you worked on with Jerry was the encapsulation of the surface so you could transport samples from one system to another and then desorb the surface layer and try to maintain a pristine surface in one system or another. Did that work well?

BRILLSON: Yes. I got the idea for that technique from some folks at Rockwell who had kept - Steve Kowalczyk, I think it was who first did this - and I told Jerry, I said, "We could do this too. We can cap in arsenic and then you can put your MBE samples inside of a stainless steel cross and backfill it with nitrogen and then seal it under pressure and then ship it to me by mail." And then we would take it to Wisconsin and we would open it up and quickly put it in the vacuum and then heat it very gently and you could actually watch the arsenic peel off the surface at around 150°C. This gave you a clean, ordered, defect-free surface on which you could subsequently study the Fermi level, study the chemical interactions, and evaporate metal, and we could really do some very refined experiments.

HOLLOWAY: And that seemed to work really well for you. Another individual that you have mentioned, I wondered if you would care to amplify, on is Georgio Margaritondo. He is certainly a very good friend and influential person in your life too.

BRILLSON: I think so. Georgio really helped me out because I knew that I needed to do more photoemission, and it really was not easy to do this at Stanford. There just wasn't enough time available. And Georgio stepped in at exactly the right time and invited me to come out. And in the course of spending weeks in Wisconsin taking data, I got to know Georgio personally, and his wife Marina, and I discovered that you could be a scientist and be a class act at the same time. He had a great enjoyment of life. He played the piano, he sang, and he seemed to know wine very well, as I got to learn having dinners at his house. And in that way I also learned about the international aspect of our field of condensed matter research. So he is a delightful individual, a raconteur, and a man with great style. Right now I think he leads a division of the Federal Institute in Lausanne, Switzerland and is one of my very good friends - who by the way sends me Christmas gifts every year. Swiss chocolate.

HOLLOWAY: A class act as you said. Well good. There have been many influential people in your life and you have done a marvelous job in using the opportunities that came in your direction. I was wondering if there is anything else you would like to add for the interview today.

BRILLSON: I also want to thank someone who came in very early in my life - not very early in my life but early in my scientific career - and that is Professor Eli Burstein, my thesis advisor, who also opened my eyes to what it's like to be in the community of science. I learned that going to my first APS meeting as a graduate student and watching him walk down this crowded hallway in the hotel where they were holding the meeting - and this was in Philadelphia - and having one person after another for what seemed like half a mile, saying, "Hi Eli, I need to talk to you about this," or about that, and "When can we get together and resolve this scientific issue?" or "I'm organizing a conference. Will you help me?" and I realized then that science could be a great social event and a way to make friends as well as a way to learn from others and to just enjoy other people. And he also showed me how to maintain a balance in my life between science,,my family and life in general.

HOLLOWAY: That is absolutely critical, so those are valuable life lessons.

BRILLSON: Yeah.

HOLLOWAY: Anything else?

BRILLSON: Nope. Can't think of anything offhand.

HOLLOWAY: All right. Well then, thank you very much Len, it's a pleasure. Congratulations again on the Gaede-Langmuir Award, and thanks for participating in the interview.

BRILLSON: Thank you, Paul.


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