Awardee Interviews | Robert Hamers - 1993 Peter Mark Award - Interview

Robert Hamers

1993 Peter Mark Award


Interviewed by Max Lagally, November 17, 1993
LAGALLY: Good morning. We're here in Orlando at the 40th American Vacuum Society meeting. My name is Max Lagally. I have the pleasure here today to be speaking with Robert Hamers, who is the recipient of the 1993 Peter Mark Award. Bob is presently at the University of Wisconsin. He got his bachelor's degree at the University of Wisconsin and his Ph.D. from Cornell. After that, he went to IBM, and he's now returned to Wisconsin. Good morning, Bob.

HAMERS: Good morning, Max.

LAGALLY: How are you?

HAMERS: Good. How are you?

LAGALLY: Kind of early to be up doing these things at eight in the morning.

HAMERS: Well, I'm an early morning person, so… [Chuckles]

LAGALLY: What we're interested in doing here in this little interview is to find out how you came out to science. First of all, congratulations on the Award. That's a wonderful thing.

HAMERS: Thank you.

LAGALLY: As we know, the Award is for someone under 35 who has established himself in a tremendous, new way. How did you start in science? How did you get the spark to become a scientist in the first place?

HAMERS: Well, I think I was initially started in science by my grandfather and my uncle. My grandfather was a machinist by trade, and, when he retired, he decided to bring an entire metal lathe into his basement. One of the things that he did was to spend his retirement years building a 12-inch reflector telescope, which was as large as his garage! When I was a kid, we'd go out at night and point it up at the moon and the stars and watch things go by. At that point, I got very interested in astronomy, which continued for a long time. And then my Uncle Jack, my mother's brother, he was always very interested in science, and he would enroll me in some of these little science projects for kids.

LAGALLY: You did that, right?

HAMERS: Yeah. I got very interested in chemistry. Somewhere along the line, someone gave me a "chemistry for kids" book, and I took off from there.

LAGALLY: And you studied chemistry at the university.

HAMERS: Right. I was a bachelor's in chemistry, yeah.

LAGALLY: You mentioned last night at the Award Ceremony that John Wright had a considerable influence on you. Tell us a bit about that.

HAMERS: When I first applied to the University of Wisconsin, I was undecided about whether to go into engineering or chemistry. So I enrolled at the University, and somewhere in my freshman year, I found out that undergraduates could participate in research. After my first semester there, I went knocking on doors, trying to get someone interested in taking on an 18-year-old freshman to do some research. I got a couple "no"s, and then I got a "yes" from John Wright, who started me on some very basic analytical projects that were essentially helping Ph.D. students with some auxiliary projects to finish their degree. That worked very well, and then he gave me my own projects and got me involved in doing some laser spectroscopy in low-temperature solids. And so I continued doing that until I finished. By the time I had finished with my bachelor's degree, I had a complete paper in Journal of Chemical Physics based on my research as an undergraduate.

LAGALLY: Fantastic!

HAMERS: So that got me very enthusiastic about science.

LAGALLY: Did that set the path in terms of graduate school? You know, like the laser things and so on?

HAMERS: Well, actually, when I went to graduate school, what I knew I was interested in was surfaces. I knew that.

LAGALLY: You already knew that.

HAMERS: I already knew that. That was one of the things that I was looking for when I went to graduate schools. At Cornell, there were a number of people who were involved in it, and at that point, Paul Houston was just starting up a new project that involved some non-classical surface science. It was molecular beam scattering combined with laser spectroscopy to study state-resolved energy transfer and molecule-surface collisions, so it combined a little bit of what I already knew about laser spectroscopy with what I wanted to learn, which was surface science, and so I got involved in that project.

LAGALLY: But how did you decide already at such a young, tender age that you wanted to do surface science? Where did you read about surface science?

HAMERS: I can't tell you. It was just something that--

LAGALLY: Was it just there?

HAMERS: It was just there.

LAGALLY: And then, after that, you went to IBM.

HAMERS: Yes. Well, one of the areas that I was always very interested in was vibrational spectroscopy as a tool for getting chemical information about molecules on surfaces. When I was in graduate school, I had been doing a lot of infrared laser spectroscopy using F-center lasers and high-resolution spectroscopy. When I was finishing up, I decided that I wanted to pursue the vibrational spectroscopy a little bit more, so I applied to IBM, to Joe Demuth as a post-doc, and called out there to be interviewed. When I got there, I found he was building this thing called the scanning tunneling microscope. And at that point, I remembered that, sometime when I was graduate school, Heinrich Rohrer1 had come through Cornell and given a talk on the scanning tunneling microscope. It must have been around 1982, when they had images of steps but not atomic resolution. And I hadn't really followed it. But when I found out that they had since gotten atomic resolution on silicon and that they were trying to build one at IBM Yorktown and I could really get in on the ground for what I thought was going to be a really exciting area, it was just an absolute perfect match of, I think, my abilities and what I was interested in. Just fit perfectly. So, we took off from there.

LAGALLY: Pretty lucky.

HAMERS: Yeah, very lucky.

LAGALLY: You got your Award, obviously, for the scanning tunneling microscopy work. Can you give me some highlights in those efforts that really stuck out for you? Things that were really exciting or really made a difference in terms of the research community?

HAMERS: Well, there are several things, but one of the first things was - I got there in February of '85, and by May of '85, we got an atomic resolution on silicon. Then, we started on silicon (111), and then we tried to get atomic resolution on silicon (100). That happened in July of 1985, so that was very exciting because that was a surface that no one had ever gotten atomic resolution on before. A little bit later than that, we decided to try to take advantage of the fact that we thought that the STM might somehow be sensitive, not to the physical positions of the atoms, but to the electronic properties of the surfaces. So then we went back, and we were trying to figure out how to get this kind of spectroscopic or energy level information from the STM, and that involved a certain amount of building. I guess by about May of 1986 or early 1986, we had done that; set up a system that allowed us to measure the current as a function of voltage. 

The first experiment I remember very well. It was so pretty because you could gate the feedback loop for the STM and ramp the voltage up, and you would see curves that would dance across the oscilloscope. So as the tip moved across the individual atoms, you'd see these dancing, wiggling curves. Then we were recording it. But it was just exciting being able to see that, in fact, you could get that information. So that was one of the highlights.

And then, as a chemist, another one of the highlights was, going back to silicon (100), we had always done experiments with a negative voltage on the sample, so we were always tunneling at a particular electronic level. Once we realized how sensitive, in fact, the STM was to the electronic structure, we went back to the silicon (100) surface and did experiments both at negative bias and positive bias, looking at empty and filled states, and we realized that the difference there really reflects the detailed spatial distribution of electrons in a particular molecular orbital. I happen to like the silicon (100) surface because one could easily understand it from a fairly simple molecular orbital picture, and it really has π energy levels and π* energy levels. But for me, as a chemist, the kicker was to realize that one could actually see a node in a wave function at positive bias on silicon (100). So that was another highlight.

After that, of course, we pursued a lot of experiments where we started putting down molecules on surfaces. We did what were the first studies looking at chemical reactions on surfaces, such as the reaction of ammonia with the silicon (100) surface to form the hydrogen-terminated silicon (100) surface. And then, later on, I eventually wanted to go back and try to take advantage of some of the background that I had in optics and somehow try to marry STM with optical techniques. We were scratching our heads and, at the same time, we're realizing that the people at IBM who are device-related people are always wondering, "Why can't we see the difference between n-type and p-type material?" We decided that one way of doing that was to marry STM with optics and try to look at photovoltaic effects of surfaces; so that naturally led to that set of experiments, which lasted for several years. Once those worked, we realized that we could perhaps get very fast time resolution using, instead of a continuous laser, picosecond lasers. So we went on, did some demonstration experiments there, getting carrier lifetime information on nanosecond time scales.

And then, finally, when I moved back to Wisconsin, one of the things I had wanted to pursue was getting back to the issues of surface chemistry. Now that we understand so much more about how the STM works and how to use it as a tool, we are trying to use it to study details of chemical reactions and really get mechanistic information.

LAGALLY: This is very interesting. I guess some of your stuff has made it to the New York Times or on television and so on. Interviews!

HAMERS: A little bit of it, yeah.

LAGALLY: How do you react to those kinds of things? I mean, lots of people would like to have the opportunity to be interviewed, and now you've had those opportunities.

HAMERS: Yeah, it's always very exciting. I guess the things that made it in the New York Times are primarily the studies looking at the electronic structure of the silicon (111). But yeah, that made it in the New York Times, the Science Times on Tuesdays, and made it in Scientific American and a few other places. Very exciting for a guy who's a couple years out of graduate school. [Laughter]

LAGALLY: Now you're back at the University.

HAMERS: Correct.

LAGALLY: You have your own graduate students, and the philosophy is somewhat different than it would have been at IBM or graduate school. Do you have anything to offer in terms of what your philosophy is in terms of producing students, or getting students, or getting good work out of students? I mean, these are the kinds of questions that we can easily ask someone who has done this for 40 years, but it'd be very interesting to compare the answers with someone who is really relatively new at that game and seeing what advice… Would you advise a student to go into science these days and to, say, work with you? Or work with anyone at all?

HAMERS: Well, I still think that my philosophy is, if a student is really interested in science and wants to do science, then they should do science. But I don't think that we should be encouraging people who aren't necessarily already interested in science to go in that direction. As you know, there's a perceived oversupply of scientists right now, so I don't feel justified in trying to encourage more and more people. I think that we'd be better off perhaps training fewer scientists, but training them better, rather than just training more scientists. So that has, to some extent, reflected itself in some of my decisions not to necessarily accept everyone who walks in my door, but simply trying to get the best students.

LAGALLY: Are you having success with that?

HAMERS: I think for the most part, yeah. I've got some extremely good students, I think.

LAGALLY: Good. That worried me. [Laughter] I say that because we're both at the University of Wisconsin, and we collaborate. It's been a lot of fun. 
Do you have anything else, Bob, that you'd like to share before we finish this interview in terms of insights or viewpoints or things that you would like to say for the record?

HAMERS: Just that I'd like to thank those people who have been instrumental in getting me to where I am. So, people like John Wright, Paul Houston, and Bob Merrill at Cornell, Joe Demuth, who was my postdoctoral advisor; and you, who helped to steal me away from IBM.

LAGALLY: That was a classic move.

HAMERS: Dragged me back to the University of Wisconsin.

LAGALLY: It wasn't hard to drag you back. [Laughter]

HAMERS: No, it wasn't.

LAGALLY: The hard part was convincing them, but mainly because of the system. Okay. Thanks a lot, Bob. Appreciate it.

HAMERS: Thank you, Max.

1. Heinrich Rohrer was the recipient of the Nobel Prize in Physics in 1986

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