Awardee Interviews | Yves Chabal - 2012 Medard Welch Award - Interview

Yves Chabal

2012 Medard Welch Award


HOLLOWAY:  Good afternoon. My name is Paul Holloway. I’m a member of the AVS History Committee. Today is Thursday November 1, 2012. We’re at the 59th International Symposium of the AVS in Tampa, Florida. This afternoon I have the privilege of interviewing Dr. Yves Chabal from the University of Texas, Dallas. He is the 2012 Medard Welch Award winner, and his citation reads, “for his exceptional studies of vibrations at surfaces, especially the development and application of surface infrared spectroscopy to understand the physics and chemistry of hydrogen-terminated silicon and atomic layer deposition.” So, Yves, congratulations on the award. Very well deserved, and very prestigious. So may I take this opportunity to ask you to give us your birthdate and birthplace?
 
CHABAL:  Yes, I was born on August 5th, 1952 in town of Pau in southern France.
 
HOLLOWAY: Your educational background, maybe we could start with that. Tell us where you went to primary school if you want to, or the first degree in a university.
 
CHABAL:  I was in middle and high school in France, and then did my very last year of high school in the French High Schoolin London (Lycée français de Londres)  , and then I came to the U.S. as an exchange student for one year in a Cleveland suburb to redo a year of high school. I then went to Princeton University for my undergraduate, where I actually had an opportunity to do a senior thesis with Steve Schnatterly, who later went on to Virginia but at that time was at Princeton. I did my graduate work at Cornell University under the guidance of Al Sievers, who is a well-know infrared spectroscopist. Those were very formative years where I learned a lot of spectroscopy. But I was his first student to actually build an ultrahigh vacuum system. He never had done any surface studies before. So I benefitted greatly from talking to students of Thor Rhodin, in particular Wes Capehart, who went to GM. Wes was a great mentor and taught me all about ultrahigh vacuum.
 
HOLLOWAY:  So your Princeton and your Cornell education was in the Department of Chemistry?
 
CHABAL:  Physics, actually. Yes, so both were in physics. I started my surface studies at that point, looking at hydrogen on tungsten with an interesting surface wave technique at the time.
 
HOLLOWAY:  It was a reflection technique, or a combination?
 
CHABAL:  Yes, it was actually coupling electromagnetic waves on the surface, so in effect exciting surface plasmons, and essentially studying vibrational spectroscopy that way. And from there I went to Bell Labs, first as a postdoc working with Jack Rowe. , This is where I learned all about semiconductor surfaces.
                                  
HOLLOWAY:  Semiconductor surfaces and synchrotron photoelectron spectroscopy.
 
CHABAL:  And all the traditional surface science techniques, exactly. So it was LEED, Auger, XPS, and synchrotron photoelectron spectroscopy. Actually, also UPS. It had a UPS in the chamber there.
 
HOLLOWAY:  In fact Jack was the Nerken prize winner—I think that was what he won a couple of years ago. So he has an interview on the web that you could take a look at.
 
CHABAL:  Yes, that’s right, that’s right, he won that prize.
 
HOLLOWAY:  So you were there for how long, from what year to what year?
 
CHABAL:  So I stated at Bell Labs in January of 1980, and I stayed there until December of 2002, so it was 22 years first with AT&T, and then with Lucent Technologies, and then Agere Systems.
 
HOLLOWAY:  They opened up the production facility down in Orlando, but it seemed like every other month they were renaming it to another company.  [Laughter]
 
CHABAL:  Exactly, yes. Those were the days.
 
HOLLOWAY:  They finally shut it down, but those were the days. So what group were you in? Jack was in the Surface Science Group?
 
CHABAL:  Exactly, yes. When I joined that was the Surface Physics Department, and the Department head was Homer Hagstrum, and then he stepped down and Maurice Rice stepped in for just a short time, and then Don Hamann who took over the leadership of that department.
 
HOLLOWAY:  That was quite a department. A lot of it had now scattered to the wind, I guess. Is that accurate?
 
CHABAL:  Yes, yes. Well, everybody is gone. This was the place where there was Eon McRae who was doing some electron diffraction and other very detailed structure determination on surfaces. Dave Aspnes was there also doing ellipsometry and went on when the first split occurred with BellCore at that point.
 
HOLLOWAY:  And then left there and went to North Carolina State where Jack is at now.
 
CHABAL:  Yes, that’s right, yeah.
 
HOLLOWAY:  So the world is a strange convergence from many different directions.
 
CHABAL:  Yes, yes.
 
HOLLOWAY:  So tell us how you use ultrahigh vacuum in your infrared spectroscopy studies.
 
CHABAL:  So I guess I was one of the first ones who combined well-defined ultrahigh vacuum surface studies with infrared spectroscopy. I think that this had been sort of attempted before, but I really used what I learned from Jack about how to prepare surfaces well and how to get well-ordered surfaces, and how to deposit hydrogen, and then started with that. So I think that made a big difference. I really coupled the expertise from surface techniques with spectroscopy.
 
HOLLOWAY:  Besides Jack, who else did you interact with at Bell Labs?
 
CHABAL:  At that time, several people made a difference in my career, Dave Aspnes, I really learned a lot about photon interaction with surfaces. And Mark Cardillo was also in that Department, so he was a lot of fun to have around.  [Laughs]  He was a character, and he was doing beam diffraction and beam interaction with surfaces. I think he had a good part, both he and Jack, in getting me hired as a permanent person in the department. So I was a postdoc for a year and a half, and during that time, during my postdoc actually Wilson Ho, who was another former winner of this award here a few years ago, was a member of technical staff, so he had just accepted a position at Bell Labs, and he was going to introduce vibrational spectroscopy at surfaces using electron energy loss. And then he got an offer from Cornell, so after a year he went there. In some ways, I sort of filled in that position, but instead of using electron loss spectroscopy I used infrared spectroscopy. And starting from that, I proposed to use synchrotron radiation to have more intense light to do surface spectroscopy, and that actually took a few years to get done. Eventually we did it, but I started with more standard equipment.
 
HOLLOWAY:  Have you worked with any of the second order techniques for reflectance off the surfaces?
 
CHABAL:  Yes. So later on in 1990 I joined forces with Philip Guyot-Sionnest in France, and now he’s in Chicago, and we did sum frequency generation, so used a nonlinear technique. That was quite exciting and very useful, and he continued that work later on and pushed it to its limits.
 
HOLLOWAY:  So what do you learn with your optical techniques that is different from what they learn with XPS and electron spectroscopies, for example?
 
CHABAL:  The main difference is really the sensitivity of infrared spectroscopy to very light atoms like hydrogen. And so one thing that XPS and any of those high energy spectroscopies just cannot do is to determine where hydrogen is and how much there is and so on. It’s just not sensitive to hydrogen. In contrast, infrared spectroscopy is really ideal for this. It’s very sensitive to hydrogen bonding through its vibrations, and it’s maybe not a complete accident that my career has evolved around hydrogen on silicon surfaces in all its forms. Although I tried several times to step away from it, somehow there was a always a new twist to bring me back. An example was after I had been working in ultrahigh vacuum using atomic hydrogen to deposit it in all its forms and so on, and said, “Okay, I think I’m done with this.” But my colleague Gregg Higashi and others were working with wet chemistry to clean silicon surfaces and so on. And so I got involved in trying to figure out whether when you do HF etching you end up with fluorine termination, which was what most of the community thought at that time, or hydrogen. And so we did the experiments and we found it was hydrogen, and so once again the infrared spectroscopy was very, very useful to unravel that issue. That’s an example. XPS was seeing some fluorine, and so since the silicon fluorine bond is very strong, it was natural to say that fluorine remained at the surface, which is why it was passivated. But we learned later that the thing with the fluorine is that it very easily attaches on top of a surface. You know, it’s hard to really rinse away. And so they were seeing some remnant of fluorine and not really what is bonded to the silicon. What was bonded to the silicon was hydrogen after the top silicon was removed with the fluorine attached to it.
 
HOLLOWAY:  Why does hydrogen termination stabilize the surface so strongly?
 
CHABAL:  Yes, that’s a very interesting point, because the Si-H bond is weaker, 3.5 eV instead of 5 eV for Si-F. But the main difference, it’s non-polar, and so what people discovered and was calculated later is that the polarity of the fluorine molecule really polarizes the silicon-silicon back bond, so you can then have one next reaction that is removing that top silicon with the fluorine and end up with hydrogen. And at that point, no further reactions are possible. It was a non-trivial situation, and infrared spectroscopy was very useful for this type of problem. And then what really got it going is that, again with Greg Higashi, we sort of were looking into why in industry they use buffered HF, and so we started to use higher pH in our HF solution, and stumbled on the fact that that would make atomically flat surfaces on silicon (111). It produced a remarkable spectrum. I always remember the first time I saw that, it was off the screen and it was so sharp, the line, that it was just completely mind-boggling.  [Laughs]  I was very excited. From that point on, of course we worked on this 100% of the time, and all kind of really neat physics came out of it. That’s where we use the sum-frequency generation, inelastic atom beam scattering, EELS, UPS and XPS and all kinds of other techniques on these surfaces.
 
HOLLOWAY:  Then you could look at it with…
 
CHABAL:  With all the techniques, yes.
 
HOLLOWAY:  Now you said earlier, and it’s true that electron spectroscopy can’t get to the vibrations that you can see with infrared.  [Right.]  But infrared is not notoriously surface sensitive.  [Exactly.]  So what tricks did you have to play in order to get that signal so large from the surface?


CHABAL:  I think at the beginning when the spectrometers were not so good and so stable, I think it was basically a lot of patience and care in setting up the experiments. Infrared is not only not surface sensitive, but it is one of those techniques that you cannot just take a spectrum like for XPS. You always have to have a reference. So you need to have a surface that you know that doesn’t have what you’re studying on it. And so the trick in really doing very good infrared studies is to set up the experiment in a way that you can perturb the system as little as possible except for what you’re doing to the surface. And our big advantage was that we were doing this in situ, so we had a sample inside the vacuum system and we were just doing all the chemistry with a gas phase in the vacuum. So we were not touching the sample, we were not moving anything, and we ended up getting the best spectra, the best baseline and so on.
 
HOLLOWAY:  A lot of energy and effort has been expended on hydrogen-terminated silicon. Is there a practical application of that knowledge and consequence from that?
 
CHABAL:  Yes. It turns out, and this is why it sort of picked up, is that it’s not only useful for microelectronics to control the surface, stabilize, clean and so on, but it has picked up a lot in many applications for all the functionalization. For instance, applications for biology, for sensors, and so on. When you want to functionalize the silicon surface, in other words attach some organic molecule for instance that has a functional group in the end, hydrogen terminated surfaces turn out to be really, really important. You can make much stronger self-assembled monolayers, you can make much better functionalization than on oxide surfaces.
 
HOLLOWAY:  So it prepares a standard surface that you can rely upon, and then contrast against that. 
 
CHABAL:  Yes, yes, yes.
 
HOLLOWAY:  Good. I still am curious. Let me make sure my understanding is correct, is that if I hydrogen terminate a surface of (111) or of (100) silicon surface, that it will be stable against pressures and Langmuir exposures of oxygen. Is that accurate?
 
CHABAL:  Yes, yes. In fact we studied that in great detail, and we showed that if it is pure oxygen in a very controlled environment, you can never oxidize at room temperature. And we had to raise the temperature where things begin to happen, which is around 300°C.
 
HOLLOWAY:  Now why is that so stable? Because there’s no defect in the layer, or the energy of the chemical bonds, or why is it so stable?
 
CHABAL:  As long as you have no defects, exactly. It is so stable because the only reaction possible if you have no defects is to break up the oxygen molecule to insert it into the system. If look at it a very simplistic fashion, you would have to come with O2, pick up a bound hydrogen atom with one oxygen and then have the other oxygen go in. And if you look at that type of reaction, the barriers are enormous. They’re several eVs, basically. There is, of course, a thermodynamic drive to get the oxygen into the silicon to form silicon oxide, so in terms of thermodynamics you will always oxidize the silicon. But the barrier for reaction is enormous.
 
HOLLOWAY:  And so that’s why if I have a filament reacting with O2 producing atomic oxygen, that I can stimulate by that filament oxidation of the hydrogen terminated surface?
 
CHABAL:  Sure. Atomic oxygen coming on hydrogen-terminated silicon will just react. And in fact that is why in air it is not so stable, because in air you have a little bit of ozone, you have some radicals, and they are the ones that react with a surface, and as soon as they react with a surface, then oxidation takes place.
 
HOLLOWAY:  That’s remarkable. It’s a remarkable system.
 
CHABAL:  Yes. We studied oxygen and water in great detail.
 
HOLLOWAY:  So have you complemented your optical infrared spectroscopy with high-resolution electron  energy loss?
 
CHABAL:  I’ve never done that, but I have used a lot of other techniques. I have XPS in the lab, we have ellipsometry, Raman, and recently low-energy ion scattering, which is a very neat technique, very surface sensitive.
 
HOLLOWAY:  Now that’s all at University of Texas at Dallas.  [Yes.]  Before that you were at Cornell. What did you have there?
 
CHABAL:  Cornell was my graduate work. Between Bell Labs and UT Dallas I went to Rutgers for five years. At Rutgers I had a lot less in terms of equipment. It was mostly infrared, and then I collaborated with other people for other types of measurements.
 
HOLLOWAY:  You were in the Department of Physics at Rutgers?
 
CHABAL:  I was actually split between the Department of Chemistry and Department of Biomedical Engineering, of all things [laughs], and I was affiliated with Physics.
 
HOLLOWAY:  So you got into the bio aspects, then, at Rutgers?


CHABAL:  Yes, I had two bio engineering students that worked more in the aspect of biosensors. So again, functionalization of surfaces to couple with the biological world.
 
HOLLOWAY:  So it was semiconductor surfaces, silicon surfaces.
 
CHABAL:  Yes, in both cases.
 
HOLLOWAY:  What sort of gases were you functionalizing to try to analyze or detect?
 
CHABAL:  I was using organic molecules with the right functionality so that I could then attach things like either DNA or proteins, or biomolecules.
 
HOLLOWAY:  And looking at electrical resistance change, or the current?
 
CHABAL:  That was the ultimate goal, but we never got there. We just worked on the chemistry.  [Chuckles]  Those are tough problems, yeah.
 
HOLLOWAY:  Those are difficult. But it’s like anything else, I tell my students it’s like trying to find your way out of a dark room. You feel the walls, but sometimes you can come to the door.
 
CHABAL:  Right!
 
HOLLOWAY:  So you spent the time split between bio and chemical at Rutgers. When you weren’t working on bio, what were you working on there at Rutgers?
 
CHABAL:  What I developed more at Rutgers was atomic layer deposition. That was one area I got in more seriously when I joined Rutgers.
 
HOLLOWAY:  What sort of material were you using?
 
CHABAL:  Initially we were trying to grow metal oxides, such as high K dielectrics, hafnium oxide, some aluminum oxide, lanthanum oxide.
 
HOLLOWAY:  The gate oxide question.
 
CHABAL:  Yes, the gate oxide. That was the…
 
HOLLOWAY:  Was that successful?
 
CHABAL:  Yes. So once again, our goal was to understand the initial interaction of those precursors used in atomic layer deposition to grow the film. And we were doing all this work in situ, and we designed our own atomic layer deposition reactors so we could look at the surface after each half pulse, if you want, each pulse of one precursor and then the other, and so on. And then we’ve continued this atomic layer deposition work at UT Dallas, expanding to the growth on metals also.
 
HOLLOWAY:  So you are there at Dallas now as a department chairman.
 
CHABAL:  Yes. That’s an additional thing, yes. So we started a new department in 2008 shortly after I arrived, and we’ve hired nine people on top of the people in the program.
 
HOLLOWAY:  So Bruce Gnade was a driving force in that, I believe.
 
CHABAL:  Right, exactly. So Bruce Gnade, Bob Wallace, and Moon Kim were the first three in the Material Science program.
 
HOLLOWAY:  All three of those moved over from North Texas, is that correct?
 
CHABAL:  Exactly, yes. They started a program within the Electrical Engineering Department, and added on Jiyoung Kim and later K. J. Cho who was in physics, and then I came and we continued growing the department.
 
HOLLOWAY:  Now Bruce Gnade is the Vice President for Research?
 
CHABAL:  For Research now, yes.
 
HOLLOWAY:  He and I worked together on some of the flat panel display. He was the DARPA program manager for that project, and we were active in that area. So he in my opinion is a very good guy.
 
CHABAL:  A very smart guy, yeah.
 
HOLLOWAY:  Do you work any with Bob Wallace?  [Yes.]  What areas do you overlap?
 
CHABAL:  There are mostly two areas we collaborate in. One is on high K dielectrics, now the effort is more on III-V substrates, and the other one is on graphene.
 
HOLLOWAY:  So what is your opinion of graphene?
 
CHABAL:  Well I don't know if I have an opinion. It looks as though graphene may be more versatile and more useable than carbon nanotubes. It certainly has extraordinarily interesting properties from a physics or chemistry point of view. But its ultimate use is still to be demonstrated. For devices, people are working very hard to make this happen. But we’ll see. [Laughs].
 
HOLLOWAY:  It’s exhibiting high conductivities, right, in the plane?
 
CHABAL:  Initially, yes.
 
HOLLOWAY:  But technology requires encapsulation and contacts and a number of those sorts of things. So all that has to be developed.
 
CHABAL:  Exactly, everything, yes, every single thing is being studied, but it is a big challenge. Contacts are an enormous challenge. You want to put metal in contacts that make good contact, that cannot be ripped off easily, but at the same time do not perturb the graphene itself too much. And so there are enormous challenges.
 
HOLLOWAY:  Yes, I know when I worked with contacts in the semiconductors, quite frequently the heat treatment would cause an interfacial reaction and change in interfacial chemistry to achieve that. But if you’re one layer thick, it’s really difficult to perturb the interface badly.
 
CHABAL:  Exactly. When you start forming carbine, that’s it; you don’t have graphene underneath anymore. But there are interesting issues. So if that’s the case, you really have like an end contact, if you want, instead of a sandwich contact. So lots of interesting science being developed, actually.
 
HOLLOWAY:  So tell me a little bit more. You continue working in the bio area at UT Dallas, I guess.
 
CHABAL:  A little bit, yes, we are continuing working on the biosensors. We linked forces with Eric Vogel, who was in the same department. He recently went to Georgia Tech. He was the device guy, so he really was making actual devices, the surface of which we would then functionalize, and then attach biomolecules and do the sensing. So with him we really did actual biosensing.
 
HOLLOWAY:  Something I like to address to give a hint to some of the young people that may read your interview is the fact that you were educated in Princeton and Cornell in Physics.  [Yes.]  There was no bio there.  [No.]  But you transitioned, and now you’re talking about functionalization and attachment of DNA, etc. How do you learn that? Did you go back and take classes on that?
 
CHABAL:  Actually I think this is a very important point, especially for younger people to realize, that a key aspect especially now is flexibility to go into directions that are not just the standard directions of what you learn. I feel that with physics you have a very good background, physics gives you a good basis and a good way to think and a good way to approach research. For the rest, I didn’t take courses. You just learned by interest from papers or by going to books and learning on your own. But what has been the most important thing is that I was completely open and interested in learning what I had to learn to make an impact.
 
HOLLOWAY:  You were curious.
 
CHABAL:  Curious, yes. And I never tried to be the expert in biology or anything like this. But what I really like and what I think is very important is the synergy that you can bring between two fields. So when I learned about bio, I learned with the eye of a physicist or a chemist, saying, “What can I bring to this? I just want to learn what problems the biologists have, and try to bring a different fresh approach to solving them. So I’m not trying to be an expert. I’m trying just to look at the places where I think the physics or chemistry could bring something.
 
HOLLOWAY:  Now one of the things that I’ve experienced in my career, and I’m curious as to whether you have or not, is the students come in and they get interested in bio, and they drag me kicking and screaming into that area, and I learn when they learn from that.
 
CHABAL:  Right, exactly.
 
HOLLOWAY:  So you can read a book, or you can talk to a colleague, or you can try to keep up with a student, and all of those are learning experiences.
 
CHABAL:  Absolutely. That’s a very good point. I think I have learned tremendously from students and postdocs who come with a very different background and want to pursue different things. And I tend to let the students and postdocs go the direction that they really want to go. I try to support that because I think they’ll do the best work in this way.
 
HOLLOWAY:  Absolutely. I tell them it’s my job to keep you out of the roughs. But where you are in the fairway, that’s your business.
 
CHABAL:  That’s a good way to put it, yeah. And being out of the roughs means that you have to do good science. No matter where you are, you have to be rigorous and you have to demonstrate your claims, and that sort of thing.
 
HOLLOWAY:  Are there specific students and postdocs that you remember as being particularly good?
 
CHABAL:  Oh yes. So I have been amazingly lucky. My very first postdoc at Bell Labs was Janice Reutt-Robey. She came from Berkeley with a background in gas phase beams spectroscopy—nothing to do with surfaces and so on. She was exceptionally good and very good also at instrumentation and building things up. So she put together a complete pulse molecular beam, and that was a beautiful example of synergy where this instrument made it possible to perform surface diffusion experiment using infrared. And that still stands as one of the best measurement of the surface diffusion because it is really looking at the microscopic hopping as opposed to more macroscopic diffusion when there are steps and defects along the way that affect measurements based on thermal desorption. However, this technique is so difficult that it wasn’t picked up by other people [laughs].
Then the second, absolutely outstanding postdoc was Melissa Hines. And Melissa came from Stanford in this case, from Dick Zeyer’s group, and she had also worked with molecular beams. In her case, she was analyzing the reflection of molecular beams after they interact with the surface. And Melissa was an even better experimentalist in the sense of never hesitating to do new things, construct things. During her postdoc she did two major things. One was to construct a laser so we could try to learn about photon-induced hydrogen desorption from surfaces, using an excimer laser and so on. The other one was to go to another lab where they had a Raman spectrometer and do the first non-enhanced Raman measurement of surfaces with this hydrogen-terminated silicon. She got beautiful results for that Raman work. Unfortunately, she never published the laser work where she had put enormous efforts, and in fact had gotten what I now know is very quantitative information. But for her she didn’t have a good enough explanation, so she wouldn’t publish it.  [Laughs]  Anyway, she was just extraordinary. What she did later shows her versatility. When she came in the lab, she of course learned surface infrared spectroscopy, but she picked up the Raman with another person. Then she left, went to Cornell and started putting together an STM on her own, she built an STM to do studies, and coupled that with infrared, and developed kinetic Monte Carlo techniques to analyze surfaces. She was very exceptional.
 
HOLLOWAY:  Extremely productive.
 
CHABAL:  Yes, an extremely good and rigorous scientist. If you look at her papers, they’re all top seminal papers. She doesn’t publish much, but each one of them is really a very important paper.
 
HOLLOWAY:  Where are those two at now?
 
CHABAL:  Janice is at the University of Maryland, and Melissa is at Cornell, both in chemistry. And then I had a number of great postdocs and students also. My first student was from Princeton, Veronica Burrows. She is now at ASU in chemical engineering. I had Kate Queeney who came later from Cynthya Friend’s group at Harvard and did a very nice postdoc, really nice work, and is now at Smith College. And so on. It was really a pleasure. I had quite a few students and postdocs in my lab, as compared to other people at Bell Labs.
 
HOLLOWAY:  All of us have to be blessed and lucky to get good students that are solid and productive.
 
CHABAL:  Yeah, yeah, yeah.
 
HOLLOWAY:  What are you into now? UT Dallas is loosely affiliated, I guess, with TI.
 
CHABAL:  Yes. In fact UT Dallas was essentially built thanks to TI. They were the founders of UT Dallas. It’s a very young university. It was put together in the late ’60s and started in the 1970s—very, very young. So we have an extremely good interaction with TI of course and with the industry in general. UT Dallas is located in a very good place.
HOLLOWAY:  So does that require you to look at semiconductor processing materials and science?
 
CHABAL:  Sure, because we get funding and so on for doing that sort of thing. So I have been continuing doing work for microelectronics. TI actually was very interested in bio-sensors, so that work was actually a TI-supported project.
 
HOLLOWAY:  Is that right? They see this as a new business direction for them potentially?
 
CHABAL:  Exactly, yes. They are interested in medical engineering and what they can bring to other fields with their electronics expertise.
 
HOLLOWAY:  Now you mentioned atomic layer deposition. We talked about it briefly. Tell me why you’re so interested in that.
 
CHABAL:  Well, atomic layer deposition is actually already used in industry, particularly for microelectronics, but the applications as just growing, mushrooming everywhere. It’s a low temperature growth technique, so people put it on viruses, put it on biological systems. There is a conference that was born not so long ago, about ten years ago, and it started with 50 people, and now it has over 500 people attending this conference, and they are from all applications besides microelectronics, in fact the conference is dominated by other applications. So it is a very interesting technique that in principle gives you extremely conformal growth. You have an extremely good control on the thickness by just changing the number of pulses, the number of cycles. But it a very badly understood technique, in fact, so it’s one of those cases where the industry had been jumping on it and using it well before the processes are well understood.
 
HOLLOWAY:  Right. I think it started in Finland.  [Yes.]  Soma? I’ve forgotten the name of the…
 
CHABAL:  Yes, Tuomo Suntola and co-workers developed the instrumentation that really made the field progress. The Finns are still among the leaders of ALD development. 
 
HOLLOWAY:  But they use it to grow layers for high-field electroluminescent materials.
 
CHABAL:  Right, exactly, so that was the beginning, yeah.
 
HOLLOWAY:  They used it to grow displays, but the science behind it wasn’t well understood, like you say.
 
CHABAL:  Exactly. So to me it was a gold mine, because if you have a technique that can really look in situ at what’s happening, you can really address a lot of the problems that people are facing. A simple one is the attempt at depositing high-k oxides on oxide-free silicon. It did not seem to be possible. And so understanding how that silicon oxide is formed, when and how in the cycles, and what controls the growth of an interfacial layer was critical, and that’s something that we were able to do extremely well.
 
HOLLOWAY:  Now is that actually in use for gate oxide growth?
 
CHABAL:  Oh yes, absolutely. And especially with the 3-D, the thinFETs, that is vertical structures, vertical transistors.
 
HOLLOWAY:  That gives a good rundown on your career. Are there other aspects of your career that you would like to add to the interview?
 
CHABAL:  Well, I think that especially for students and then people who are starting in the sciences, I just want to emphasize how important all the mentors I’ve had in my career have been, how important their role has been. Science is not developed in a vacuum, and so I learned from a number of people who gave their time. And Jack Rowe is an example. He spent countless hours teaching me. He has an encyclopedic memory about everything and he could I realized later, tell me all the important work done in any field. He often gave me crash courses on new areas of research. Plus he’s been a great support in my career at all stages. Don Hamann also was my department head for a long time, and really was a great department head in terms of dealing with the everyday things. He was an outstanding and wonderful scientist. As a theorist, he really challenged me in many, many areas, and he was always right on the spot. So it was really fantastic. He also remained a strong supporter of my career in general. In the end, Walter Brown—you probably know Walter Brown, right? Or not?
 
HOLLOWAY:  I know Walter Brown.
 
CHABAL:  Yeah. He is just an amazing person. He had been at Bell Labs well over 50 years, and I remember I could never go to his office and just leave 10 minutes later. We always started in some scientific conversation and it was more like two hours later that I would remember I had to leave. It was particularly great to have him at the very end, at sort of the collapse of Bell Labs because he made that last year very painless. We were so excited about the science that I didn’t suffer from not having any money to do anything, basically.
 
HOLLOWAY:  What do you think about the replacement of the capability of Bell Labs? Can it be conducted in university laboratories nowadays?
 
CHABAL:  I think it’s difficult. Many of us from Bell Labs have gone to universities, and I think we find it difficult to recreate what was there just because the dynamics are different in universities, the funding issues are different. So it’s strange to say, but there is more competition within universities than there was at Bell Labs. At Bell Labs, the essence was joint scientific contributions. There were a lot of scientific discussions and a lot of challenging done, but not a competition careerwise or anything like this. So we were able to collaborate very, very effectively in this way. So it’s difficult to recreate in a university environment where the research groups are larger and funding very competitive. It’s a different environment, I think. What happened to Bell Labs at the end, you know, with the Hendrick Shön’s situation and so on, is very sad, but it’s a great illustration of what worked before in the system and what can go wrong, and how quickly a system can be destroyed. What I really learned from this is that before at Bell Labs, there was constant examination of the work, constant critical review of the work. We always had our manuscript go around for review. There were constantly seminars about new ideas, especially if they were controversial and so on.  What happened then later on when we tried to justify our existence was the push to publish in prestigious journals or whatever would raise the visibility, right. So within the company, the struggle to survive essentially was the beginning of the end because it allowed dishonesty when for instance somebody was a bit pathological, like Hendrick Shön. He basically was allowed to completely go berserk in that sense, to do things that are so unethical.
 
HOLLOWAY:  That wouldn’t even had occurred to anybody.
 
CHABAL:  Wouldn’t even have occurred, and the environment became such that it became possible. And so it is really something that people who learn about history should not forget—I mean this is a very strong lesson on how important it is to have a system where you have critical reviews of the work, because otherwise you are susceptible to have an environment where somebody like this comes, and then it’s too late, basically. So I don’t think Bell Labs can be recreated, but I think a lot of very important lessons can be taken from its history.
 
HOLLOWAY:  I think you taught the audience some of that important lesson just now. Anything else?
 
CHABAL:  No. Just that I, again, what I said for the students is that they should always remember that they are the ones that are doing the work, they are the ones that are behind all the discoveries. That means two things. They should be motivated, and realize that what they do is very important. But the second is they should make sure that they are doing good work, and that they should be very critical so that they don’t fall into trying to publish quickly and have something wrong later on. That is actually much more negative for their career.
 
HOLLOWAY:  I must bring you back to the award ceremony last night, because I think you thanked somebody that was extremely important in your life, your wife. I thought that was quite a good move, because we don’t work just with the students and the university; we are supported by our families.
 
CHABAL:  And I think that especially for scientists it’s always a struggle to know how to balance your private life with the work. And I guess I feel very privileged because I’ve learned to do that a lot better thanks to my wife, who herself is an extremely illustrious scientist. She was a Bell Labs fellow, which is the highest recognition at Bell Labs, and I certainly didn’t get that. And she made an interesting change in her career by going to UT Dallas where she now is the Vice President for Diversity and Community Engagement, and is trying to really bring her experience and her overall—I mean both scientific experience and personal experience -- to help students go into sciences and see the education as the way out of economic difficulties or other hardships. She is actually a remarkable person. She went through tragedies in her life and a lot of hurdles, and she has made it all through because of her determination and sense of life. So it was heartfelt, what I said. Yes.
 
HOLLOWAY:  That was wonderful. Well Yves, thank you so much for the interview. And again, congratulations on the Welch Award.
 
CHABAL:  Okay. Thank you very much.


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