Sciences : histoire orale

WHITESIDES George, 2002-01-28

Sophie Jourdin — 2011-11-10T17:04:18Z

George Whitesides

Mallinckrodt Professor of Chemistry, Harvard University

George Whitesides' group in Harvard's Department of Chemistry and Chemical Biology works on many topics : Biomimetics, Biosurface Chemistry, Complexity / Emergence, Materials Science, MEMS, Microfluidics, Micro- / Nanofabrication, Photonics, Polyvalency, Self-Assembly, Surface Science, and Tools for Biophysics and Biology.

BERNADETTE BENSAUDE-VINCENT (BBV) : Do you see any changes that you would like to mention in your field over the past 20 years.

GEORGE WHITESIDES (GW) : 20 years ago there was not any materials science in my field, which is organic chemistry. People made polymers, but they didn't really think in terms of materials, and all of this stuff of electronics and optics and unusual functions and biocompatibility and things like that were - some of them were not even concepts and some were not considered materials science because nobody thought about materials science. Materials Science in the last 20 years has come from something that was done with airplanes to be a real part of chemistry - that is really interesting I think.

BBV : Have chemists been involved from the very beginning or did they jump on the bandwagon later ?

GW : Well, no, I guess my sense would be that chemists were involved from the very beginning in the sense that they made materials. Because after all most materials in the world are actually made by chemists.

We have metals, but ceramics often come out of chemical backgrounds, and all of polymers come out of chemistry but they were thought of as being fibers or coatings or something else and the idea of thinking about them as materials - it's a re-naming but it was helpful for the field to think about how to organize itself intellectually among other things, and then what was a little bit of a change was that at the beginning the financial support was primarily from the DoD for its own purposes which was primarily metals and ceramics for airplanes and armor and hot-sections in engines and things of this kind. It is recently that this has changed. Chemistry and chemical thinking is an increasingly important part of materials science which means there is now some money which means it is worth the effort for chemists to think about that as a community they might want to be involved in. But chemistry has gone from an area dominated by the notion of making natural products to an area in which probably the two interesting areas are bio - and most people would say this is the biggest deal in chemistry at this point - and materials. Synthesis becomes an accessory technology which enables one to make these materials that you might want for either biological applications or materials applications.

BBV : And what about the electronic applications for chemistry ? Is there any future in that ? You have been working a lot in that.

GW : I think that is going to be one of the big deals in electronics. The argument there is that there is a certain specific way of thinking about electronics which is silicon and semi-conductors and that works fine. But my prediction is that there is going to be a new class of devices that is going to be perhaps slower but much cheaper, so that the ratio of benefit to cost goes up but primarily because the denominator goes down rather than because the numerator goes up. The notion with these and with optical photonics systems and with organic LEDs is low cost, ease of fabrication, the ability to integrate a bunch of different kinds of functions in the same thing whereas if it is all polymers you don't have to worry about compatibility between the 500-degree processing step and an ion-beam step or whatever it might be. That is organic chemistry. There are two components : one is the laser and the second is the coating. Optical recording now dominates a certain segment of that industry and it is entirely because what chemistry has made possible. CDs are the same thing. These are optical CDs but the older CDs were the same thing. I think chemistry has found opportunities in thinking about the collective properties of matter as opposed to thinking of the properties of individual molecules - it is a little bit of a revelation but it opens all kinds of doors.

ARNE HESENBRUCH (AH) : Shall we try to get at the history of the last 20 years ? What in your opinion has been the most important changes in the last 20 years ? You have been in the field for that long.

GW : It is more like 20 years. I really began to think seriously about materials science when I came to Harvard. At MIT I was primarily concerned with inorganic chemistry and catalysis. So I came here and became involved, but what made a big difference from our point of view was the development of self-assembling monolayers. Self-assembling monolayers were particularly interesting - and I think actually very interesting for many chemists because they made the point that you could design molecules and thereby control macroscopic properties. You make a kind of molecule and a drop of water beads on the surface and you make another kind of molecule and a drop of water spreads on the surface. So that idea of being able to engineer macroscopic properties based on molecular-scale synthesis was a pretty interesting idea and fairly new at the time.

AH : When ?

GW : That happened ... the first identification of SAMs per se was early '80s and forget exactly when, whether it was '83 or '84, and then the real understanding that you could put them together was done by Ralph Nuzzo - he did the first identification of these as structurally ordered systems. And then we did a lot of the work that connected them with materials ; we were actually working on it at the same time and we started publishing papers in the period of 88-89. So it's really only been about a decade. Now polymers have been around for a long time and we have been working on polymer surface chemistry in the late '70s. But we didn't really call it materials, we called it polymers and it was very hard to do because you couldn't really get a grip on it. You'd start with a piece of polyethylene and we used to put in chromic acid solution and that burned the surface and introduced a bunch of carboxylic acid groups which we could use for various purposes but it was very hard to characterize these things and the surfaces were pitted as a consequence, so we never really had a good grip on the density of surface functionality, the roughness of the surface or any of those things.

AH : What did you do to characterize ?

GW : We used XPS and we developed a whole series of techniques like contact-angle titration - which is an idiot idea but the notion that you make the drop more and more basic and you see if it spreads more and that tells you if there is an ionizable group. This is the kind of thing a chemist thinks of first but not a materials scientist with a metallurgy background because they don't know that carboxylic acid groups exist. Self-assembled monolayers still are, I think, the best of all the materials systems - and this is almost independent of field : ceramic, metal or anything else. If you want something which you can control in exquisite detail it is this. If you want to understand how you go from atomic and molecular level structure to macroscopic property within the range of things that it can do, nothing beats SAMs.

AH : And you knew this in the early '80s already ?

GW : No, what you knew in the early '80s was that there were ordered structures. Strictly speaking, well before that, the electrochemical guys had known that organic silver compounds adsorbed on metal electrodes. So that was well understood and they'd been used empirically for a bunch of things having to do with adhesion so there was, as in everything in science if you look backwards you find, lots of precursor phenomena. And then Ralph Nuzzo and a guy named Dave O'Lara(?), who were at Bell Labs at that point got involved in this and I think their initial interest (I actually never asked Ralph why he got into but I think it was partially because they needed ways of doing coatings of metals and - anyway they were good spectroscopists - and Ralph looked at these structures and recognized from the infrared spectra that they were highly ordered so that the idea was that it was not just going on the surface as scrambled eggs but that it was crystalline. And then we did physical organic chemistry. We took that platform starting in the early '80s and put functional groups on the terminal positions so that after the thyols formed mono-layers, you just saw a monolayer of the terminal functional group, and the hypothesis was that this would control wetting. And it did. Then the process from there was that in the early '90s we had the idea that one might be able to make patterns with these self-assembled monolayers and we had several approaches to this - the earliest one was actually an experiment I did with my own two hands - which was to take a piece of a gold dish (gold on silicon), put on a hydrophilic thyol so that water spread on it. We took a razor blade and put some scratches on it and redipped it in a hydrophobic thyol, so one ended up with scratches about a 100 microns wide they were hydrophobic in this sea of stuff that was hydrophilic then put drops of water on it and the interesting fact was that the water would not cross the lines. Had the characterization changed by then ? By that point the characterization was in pretty good shape, the combination of reflection infra-red and XPS did a lot of it. I forgot when people first saw STM images but it was ...

AH : The Nobel Prize, DI began selling in 1989.

GW : Right, and they were hard to see at the beginning because they require the tip to be far away, so it was not the first thing that was done, but people began to see crystalline rays (?). We had done a fair amount of work in the mid-80s on transmission electron crystallography. We'd taken awfully thin gold foils and run electron beams through them and seen diffraction from the organic mono-layers I think those were the first real structural indicators other than the infra-red spectras that they were united. So anyway, we started the business of stamping. I think the first paper was 92, 93, something like that. That became the basis for micro-contact printing and then for soft lithography and that brought an entire new community into it who are now on the other side of the electronic guys who are looking for new ways of getting around diffraction limits and looking for a different economics. And it has not yet made an enormous difference in microelectronics although it may well in this next stage of all-organic electronics. But soft lithography was probably the most important thing in moving the micro-fluidics community away from silicon to polymers. Now, in the long run whether the microfluidic systems we use for genomics are based on polystyrene or PDMS or what, remains to be seen - it will be whatever is cheapest. The basic idea that you did not need silicon, and in fact didn't want silicon or glass for microfluidic systems : all you wanted was that it was cheap, transparent, and easy to work with, and that is polymers. And now you put those kinds of things together with the idea of conducting or photoactive polymers and ever-increasing resolution of these printing and stamping techniques and the economics which are just phenomenally better than traditional methods when you don't need the kind of precision that the photolithographic methods bring, and you find all of a sudden that there is a new approach to making micro- and nano-structures. It is an interesting evolution. What about the biological ? Well, the biological has also been a big deal and the issue there is interesting on a couple of levels : one of them is that biology since the 60s, which is when practical sequencing first really started, has been profoundly reductionist. The whole notion is that you get the gene sequence and everything comes from that by some unknown process. That is not true of course. People now understand that it is not clear what one does with the information of the genome : which will be useful, how you combine that with proteomics, which will be useful in cell biology, which will be useful in knock-outs, which will be useful in the ... and so on. These are all interesting questions that we don't know the answers to. Biology is pretty complicated. In developing biology, as in any field, you need new tools. And new tools are microfluidic devices for genomics, new ways of manipulating cells which have to be in fluids.

AH : Could you put some dates on those new tools ?

GW : They were done in silicon in, maybe, the 70s. The guy who did this was named Andreas Manz who is now at Imperial College in London. At that time he was at Sandor ... Ciba-Geigy ... I forget.

AH : Basel, anyway.

GW : He was in Basel - I think he was in Ciba-Geigy. Of course it was an internal project so none of it was published at that point. He had two post-docs, one named Mike Ramsay, the other named Jed Harrison who were both migrant ; Mike to Oak Ridge and Jed to Edmonton, Alberta, where they started to make microfluidic systems. And that is really where microfluidics started. Other people, Roger Howe, did have an important contribution. In fact, Andreas made some of his first systems out of PDMS - unpublished stuff - he recognized the virtues of this nice elastomeric polymer even back then. But he couldn't publish it and I think the company wasn't very interested, so it sort of languished for a period of time and then this genomics came along and there was this need to find better ways to crank out data large quantities of data. Then there was a real need for microfluidic systems that were parallel with which you could generate lots of information. That was an enthusiasm that began to build in the 80s, late 80s, and people had been making devices using silicon microfab technology and it was clear it was just too cumbersome - it took too long ; they didn't have any control over the surfaces and then we among others made the point that if you use self-assembled monolayers you could get exquisite control over the interface between the materials world and the biological world. We have done a lot of this in collaboration with a guy named Don Ingber here at the medical school. This is in the late 80s, actually the most interesting part of this began came fairly rapidly after we began contact printing or that is when you saw some really neat things. So this was, I would say, 1994 or 1993, I forget when the research was done, but in that period of time. So that was one theme in this : that you could make the inorganic materials of gold films, or whatever they were supporting, you could make them compatible with biology using self-assembled mono-layers. But at the same time other people had begun to tinker with different ways of making micro-fluidic systems. I don't know that I can say what all the threads were, but certainly one of the threads was a discovery that we made that instead of using photolithography and clean rooms and all the rest of that you could do the design, print them out on a printer at scales that were perfectly useful for this kind of work and then you could design quite sophisticated systems. Other people were designing quite sophisticated systems at the same time using conventional lithographic methods. We made a point that you could do it very easily using these soft lithographic methods and that provided quite a stimulus, not to the generation of the final systems necessarily, but to the process of invention because lots of people used those rapid prototypic methods for trying new kinds of devices. This has also been an area where the industrial groups, particularly start-ups, have had a very big influence on things. Probably the first company that was a serious effort in this was Caliper. Caliper was a Larry Box(?) special and it's doing okay as a company. It is focused now on micro-fluidic systems for high-throughput screening for the pharmaceutical industry - it was one of the first to do that. There was a fellow named Lee Hood(?) who was named Hunkerpillar(?) - I think a bioengineer - developed a series of devices for sequencing of DNA and proteins which were commercialized by a company called Applied Biosystems which was one of the early darlings of the biotechnology industry, and those were not intentionally micro-fabricated - they just turned out so because you needed lot of them and small. They ended up making nice small systems - not very small but small systems. And then there was another thread to this which was the whole notion of high-throughput screening which had a number of connections that tied together. One of them was just the need in industry to do lots and lots of experiments in parallel the acceptance of 96 ??? plate formats which was the first of these. And then the idea of parallel synthesis, combinatorial synthesis, parallel synthesis which came partly from Bruce Merrifield – he got the Nobel Prize for solid state synthesis of peptides - and partly from a bunch of people including, at least I give credit to, a man named Mario Geysen as being the first person to do combinatorial synthesis, parallel synthesis, on pins. They weren't terribly small but he had that notion. Out of that came the whole idea of very large-scale parallelism in synthesis which had a requirement for making things small which led to new requirements for small systems. It is an interesting area, the bio-area, both because it has had an important impact on genomics and drug discovery and also because it provides a bridge between these two areas of biology and materials science. This is where they come into contact.

AH : You have put together elements of techniques and ideas. I presume that funding structures have had impact on the history also ?

GW : Yes. Most of the funding for materials science in the US has come from DARPA. DARPA also got interested in the biological stuff in the mid-80s, maybe a little bit later than that. Their driving concern was with biological weapons - biological defense. The United States does not have an offensive program but it was clear that there was a potential problem there and then in the late 80s there was a Russian defector and then in the early 90s another, Ken Alabakoff(?), who spent a lot of time talking about what the Russian program had done. It was clear that the Russians had had a very very large program in biological weapons and it really bothered people. So there was a growing effort to think about how to build sensors and analytical systems, how does one put together a defensive program in this. That ended up being an important bridge between the materials community (which was the DARPA community) and the biological world. One of the things that DARPA does very well as that when it decides to go into an area to put in enough money for a sufficient period of time that it is actually worth people's effort to go and learn how to do that because they can run programs that make a difference. They get, I think, a lot of credit for building the biological component for micro-fluidics and then of course a very large fraction of soft lithography was funded by DARPA and their interest in that was largely new methods of circumventing the natural limits in photolithography for very high-density electronics. It has not in fact changed that - I mean these techniques are not used for high density electronics - but I think they are going to be the basis for low density low-cost electronics, the organic stuff. I think this whole area is one that DARPA gets the major credit for. Had DARPA not put the money in it would not have happened or it wouldn't have happened the way that it has. NIH has been very resistant to doing anything in this because NIH only does science, it doesn't develop tools. I think it is an enormous strategic mistake on their part but they have basically been parasitic on activities funded by other parts of the government or funded in industry, in start-ups, for the tools that they use and the biological community uses. Then of course there has been some work in the NSF and DoE but not big programs.

BBV : So do you see the contribution of your group as providing new tools for materials science ?

GW : The biggest contribution is to make the connection between physical organic chemistry and materials science - that is the idea that you can design molecules, or design matter by synthesis at the molecular level, and thereby influence macroscopic materials properties. The second is to put together a series of tools, particularly self-assembled monolayers and soft lithography and illustrations of the uses of these in microfluidics and particularly in bio which have caught people's attention. This is an interesting strategic decision : we decided at the very beginning that we were going to proselytize for the area, so we made a really big effort to have anyone who was interested. We invited them to the lab and tried to teach them everything that we knew. It is one of those interesting philosophical issues in science : when you have something that is new and interesting you either try to hold it close or you try to spread it as widely as possible, and we really made a big effort to spread it because I thought it was going to be very useful. Quite a large number of people would come for two-three days or a week over the course of time and then these people have gone out and started programs and then of course the graduate students come and learn how to do these things and they go off and start programs. So, the dissemination has been quite rapid, primarily because it is very easy to do. That is another philosophical issue : I like to do research that is really easy to do because other people can do it. If you want to have an impact on the community at large it is easier if you keep the bar low to people getting into the area rather than making the bar high. So, minimal capital investment.

BBV : And how much time do students need when they come to be trained in the techniques of self-assembly ?

GW : Two days.

BBV : Two days ? It is kitchen experiment !

GW : It is kitchen experiment. You take some wafer and you dip it and you pull down the stamp(?). That is not complicated. And stamping is literally no more difficult than putting a rubber solution on a rubber stamp and putting it down by hand and pulling it off and it's done. It obviously gets to be more complicated than that but you've got the basics at that point. There is a little issue there, which is : you say this is trivial, and in a sense it is trivial, but it is trivial because some very smart students spent a lot of time understanding these systems and figuring out which ones worked so well that they could not be made to fail. That is the criterion. The simplicity at the end is the result of a lot of hard thought along the way not just by us but by the whole group of people who was interested in self-assembly and related areas. The second thing is the tools and the third is the notion of self-assembly. Generally, organic chemistry has been largely concerned with making molecules by putting together covalent bonds and self-assembly is how you make materials through non-covalent interactions. So it is a switch in emphasis. We are certainly not the only ones who've worked on self-assembly but we have probably been more emphatic in making the case that it is a technique that can be used in materials science than other people who have been concerned with making structures in solution or how proteins fold or other things of that kind.

BBV : It is striking that other groups doing self-assembly have had biomimetic inspiration whereas in your group it was not a leading ...

GW : Well, we do biomimetic stuff. If you talk to some of the people around, Mila Boncheva, who I think with a little luck you will meet, has made this wonderful device. You basically have a string of something and you put this in suspension, it folds up and one part of it becomes a high-frequency ring oscillator and the other part becomes a shift register. It's quite intentionally patterned on the idea of protein folding so it is biomimetic in that sense. But the major issue is the generic problem, which is to understand molecular recognition in biology because if you want a single process in biology that is important it is the recognition of a ligand by an enzyme-active site, or whatever - that is the reductionist end of the working part of biology. There has been lots of work on that - and then self-assembly came in, as a result of two things : one was to try to model biological recognition and interestingly this has never really worked. There is an enormous amount of molecular recognition that has gone on in methylene chloride solution, but of course water doesn't go on in methylene chloride, so in organic solvents a lot of good work has gone on which has led to systems that are pretty efficient in molecular recognition. But noone has come really close to duplicating the efficiency of biological molecular recognition in water because we have to learn how to handle the hydrophobic effect and we don't know how to do that yet. So that is one theme. The second theme was the stuff that Jean-Marie Lehn, Cram, and Pedersen from DuPont got the Nobel Prize for, which was just understanding the crown ethers of the right size would wrap themselves around a sodium ion. That was not really molecular recognition, but it was self-assembly ... well ... Jean-Marie calls this supermolecular chemistry, so it is chemistry beyond molecules. It was an important first step in making the case that it isn't just making covalent bonds that's important but these events in which things recognize one another and get together without making covalent bonds are also important. So these two things came together in self-assembly. One virtue of this place is that students are very good and very independent, and the groups are big so that we can have biologists, chemical engineers, physicists, organic synthetic chemists, and materials scientists. That makes it much easier to think about putting biology and materials science together, or organic synthesis and microelectronics ; you know x and y, where x and y come from very different directions. It is a lot harder to do that in smaller groups.

AH : Do you think there is any purpose in doing history of science ?

GW : Oh yes. Understanding what this funny activity is of creation. Hang on, I'll be right back - this last question is important ...

History of science. If you look at history of science you can see where interesting things came from. Now, the question is, can one learn something from the activity, and I think the answer is yes. The question that comes up in this area is, is it sufficient just to put different research areas together in order for good things to happen, or do you have to have a brilliant conception ? No, I don't think in this case one needed a brilliant conception. It was putting things together - with some luck - self-assembled monolayers were an experimental observation, they were not a theoretical prediction confirmed by experiment. It still amazes me that soft lithography works as well as it did. In any event, one can ask where ideas came from, and from that point of view the history of science is an enormous contribution. The question which is never clear is, to what extent are there lessons that you can learn from one success or one failure that you can carry over into other areas ; and in particular : what is the mechanism by which whatever lessons you learn are transmitted to the people who are the ones who in principle would benefit most, who are the people just beginning their careers, but who are in general the least interested in listening because they are eager to get on with it. They have their own usually not very well-formed theories as to how to do things and it is based more on their own particular instinct. A lot of their instinct, in fact, turns out to be replication of the experience in graduate school. That is probably the least perceptible but longest lasting lesson of the graduate career, because people tend to do their research the way they learnt to do research which was the way their research director did research. That stylistic issue comes across. In a sense, one of the great sadnesses of science is to look at people at the age of 50 and realize they have spent their entire career working on their theses with minor variations on themes. It is not a happy outcome. What they learnt was, don't step too far out of this particular circle ; just sit there and fret away with this stuff. So, I think there is enormous opportunity for the history of science to be useful, and even predictive if one could figure out what to do with the information. As we made a big effort to teach people how to use soft lithography, I think all scientific enterprises, particularly with fields that move rapidly, which is what science does : it is always looking forward and almost never backward, one needs some clever way of figuring out what the short-form lessons are from what you do, what you have learnt. But I don't think the user will study things. A book which I think is a very interesting example of history of technology which has made a big difference is The Innovator's Dilemma. Have you read The Innovator's Dilemma ?

AH : I haven't read it.

GW : You should read The Innovator's Dilemma. It is by a guy named Christensen, who is somewhere here at Harvard or MIT. It's history - history meaning business school history, but it's close enough - and the question is : look around and you find big technology changes, and how do companies react to that ? And the answer is in general : incredibly badly. And this book has really caused people to think about how they run their technology programs (in companies) because the failures are so stark that as a big company person it really does not give you a lot of confidence that whatever you are doing is going to survive. One of the lessons in this is this : the mantra in the United States is listen to the voice of the customer ; the customer will tell you what you do. And one of Christiansen's lessons, loosely re-phrased is that if the field is technologically changing the thing that will kill you is to listen to the voice of the customer, because the customer never wants change - the customer has people trained in some technique, they've got capital investment and so on and so forth : the last thing in the world they want is change. So you listen to your very conservative customer and some little company who wants to take your customer away or create new customers, is going to zip around on the side. Now the interesting issue for you all is, you are doing all this stuff and my guess is that websites may be interesting for other historians of science but I don't think it will make any difference to scientists. So what you need is a nice short book which summarizes all of this in terms of lessons. What are the lessons that you can draw from this ? What has succeeded in what circumstances and why ? And what are the risks, and what has failed ? People hate failing. So look around and what are the failures, and what did they not do that prevented them from competing effectively ? I think if you think about history of science rather as the business school thinks about its analyses in terms of something that's branded in terms of suggestions for the next generation or the current generation of operators rather than sort of a passive observation it might have more impact. I don't know whether you care whether it has more impact or not.

BBV : We care about our impact.

AH : I care a lot.

BBV : Thank you very much !

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« Entretien avec George Whitesides », par Bernadette Bensaude-Vincent et Arne Hessenbruch, 28 janvier 2002 Sciences : histoire orale, https://sho.spip.espci.fr/spip.php?article130.
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Entretien avec George Whiteside, par Bernadette Bensaude-Vincent et Arne Hessenbruch, 28 janvier 2002 : on history of organic chemistry and materials research and on the purpose of history of science.

Lieu : Prof. Whitesides' office at Harvard University

Support : enregistrement sur cassette

Transcription : Bernadette Bensaude-Vincent et Arne Heseenbruch

Edition en ligne : Sophie Jourdin

ARRIBART Hervé, 2001-02-19, 05-29, 02-20

Sophie Jourdin — 2011-06-16T07:31:17Z

Hervé Arribart is the Scientific Director of Saint-Gobain Recherche, an international company of French origin with an emphasis on glass manufacture. He took his PhD from the Ecole Polytechnique in Paris in the mid-1970s and subsequently researched ionic transport using nuclear magnetic resonance. In the late 1970s he worked with Jean Rouxel's group at the University of Nantes. In 1981 he joined the company Elf to work in research and development. In 1985 he moved to Saint-Gobain, where at first a large portion of his research was closely related to the practical problems of production. In 1990 he started a laboratory (a joint venture of Saint-Gobain and the CNRS) on the basic science of glass surfaces, using a diverse set of tools and especially the Atomic Force Microscope. In 1999 he moved to the more managerial position of Scientific Director. Hervé is also on the staff of this project.

2001-02-19 :

HERVE ARRIBART (HA) : I studied at the École Polytechnique in Paris. The selection to the school is done mainly on mathematics. But during my studies I learnt to appreciate physics in particular. I decided to pursue research in solid-state physics. It was a good place to study physics. While in my last year as an undergraduate I did a Diplome d'Étude Approfondie in parallel (an intermediary between an M.Sc. and a PhD typically done for a year before starting one's PhD studies). In Orsay, near the École Polytechnique, there is a very famous place in solid state physics, a lab started by Jacques Friedel - a great name in solid-state physics. I followed this course and afterwards I did the PhD at the École Polytechnique in the field of condensed matter physics. In principle I ought to have started with a topic distant from materials science. I extracted spin-polarized electrons from semiconductors. This was in 1974.

ARNE HESSENBRUCH (AH) : How did one extract spin-polarized electrons in 1974 ?

HA : It is true of all solids, but in semiconductors it is especially interesting that when light falls upon a surface there is a coupling between the spin of photons (in classical physics : the polarization of light) and the spin of electrons. Electrons in the upper layer absorb light photons depending upon the spin. If by some technique you can extract electrons from the conduction band of the semiconductor, you can find ways to select electrons of specific spins. This was quite important at the time because at big-science institutions such as LEP [Large Electron Positron collider] or SLAC [Stanford Linear Accelerator Center], there was a need for spin-polarized electrons. And of course you then needed solid-state physics to do it. But the man who in principle was my supervisor decided to do something else. His name is Claude Weisbuch, and he is now a good friend of mine. For a few years he was the scientific director of the French Department of Defense. He is still working in solid-state physics, in the optics of semiconductors. But he decided to do something else and Bernard Sapoval, another professor at the lab, proposed that I work on new materials. At that time there was little contact between solid-state physics and solid-state chemistry. The idea was to link up with chemists. This is why very early on in my career I had contact with chemists. We worked with Parisian solid state chemists on a new material. We found a new way to draw single crystals of an already existing material. It was very nice because we could examine transport and NMR phenomena. And the material, a copper vanadium sulfide exhibited astonishing properties : a large spread of conductivity that one can measure in a standard experiment. We suspected that this was due to mixed conduction properties. Mixed conductivity refers to conductivity by both electrons and ions. The experiment appeared to verify our a priori suspicion. This gave me the possibility to present a model for mixed conduction in this material and to understand the influence of ion transport and electron transport. I also used NMR in order to understand which ions moved. It turned out that the copper ions moved. So, this was the subject of my first thesis. At the time, in France, there were two theses. The first one was called "thèse de troisième cycle". The second was the "Docteur es sciences". This degree does not exist any longer. The thesis that is done now is shorter.

I decided to continue to work with chemists. I decided to combine NMR and transport measurements. I changed my collaborators, turning to two different groups. In my PhD there had been two chapters on NMR. But I wanted to study proton transport. I had two reasons. One was that protons give a strong NMR signal. The second reason was that two reasons had been given for proton transport. In one, protons move in individual jumps. In the other the proton is a part of a more complex molecule such as the ammonium ion (NH4+) or hydroxonium (H30+). In the former case we can see the transport phenomenon as a result of molecule rotation and proton jump. The molecule would turn and the proton jumps to the neighboring molecule, which again turns and so on. This was called the rotation-jump model. The second model was for the whole complex ion to jump. This was called the vehicle model because the whole molecule acts as a vehicle. So I worked with one group of chemists in Nantes, at the Institut de Matériaux de l'Université de Nantes. It had just been created by Jean Rouxel, a chemist. With them I worked on a substance called antimony acid - a solid. I was able to show using NMR that transport occurred in this case with rotation-jump. Protons used H30+ as a complex rotator. I was also able to show that the jump was due to quantum mechanics within a certain temperature range. It was not the usual ion transport of classical mechanics.

AH : A tunneling effect ?

HA : Yes, this is one aspect of protons, because protons are very light ions allowing for this quantum effect. The other material I studied was ammonium beta alumina. This was the standard beta aluminium in which the sodium had been ion exchanged with ammonium. This material was very interesting from the perspective of NMR. All kinds of ionic motion took place at different temperatures. At the lowest temperatures, that of liquid helium (1-4K), there was rotational quantum motion. As the temperature increases the motion becomes classical.

AH : If I may make a comparison with Stanley Whittingham here. You were working on some of the same materials, you were using some of the same tools (NMR), but you were asking very different questions, right ?

HA : Yes, that is true. I was not at all involved in the application. For two reasons : French chemists were interested in materials and did not look to the application. And chemists were between me and the application, so I had no contact with attitudes such as Whittingham's. I was very happy working on the solid-state physics problems.

AH : And we are talking about the late 1970s now ?

HA : Yes, I began the proton transport research, I think, in 1976.

AH : And it went on for how long ?

HA : For five or six years.

AH : And you lived in Nantes ?

HA : No, I remained in Paris while collaborating with the Nantes group.

AH : Were you employed in Nantes ?

HA : No, not at all. At the beginning I was employed at the Ecole Polytechnique as a research assistant, and then I was hired by the CNRS - in 1977.

AH : So, the CNRS paid your salary, you were able to do basically whatever you wanted, and you collaborated with Jean Rouxel and coworkers because you found it interesting ?

HA : Yes. It was a chance to work with an outstanding chemist. French chemists were really very good. The problem, as we just said, was that there was little interest in application.

AH : What did you do next ?

HA : After my PhD thesis, I found it interesting to go to industry.

AH : I imagine that there were many advantages and disadvantages to leaving academia for industry. For instance, where was status greater, what paid better, where were working conditions better ?

HA : First of all, it was rare, even more so than today, for CNRS people, or people within the public system, to go to industry. I cannot give you a clear answer about my motivation - it was not even clear to myself at the time. I did get a higher salary in industry. I also had personal reasons for leaving Paris and going to the Elf company. I went to an Elf research lab in the Southwest of France, in a very nice place in the Pyrénées. I had small children at the time and it was much better for them to grow up in the countryside and in a very nice climate. I was also curious. So the decision involved many elements. And anyway, it was not irreversible. The CNRS allowed me to take a three-year leave after which I could have gone back. With regard to the working conditions : I was of course less free than I had been at the CNRS, but I found it more stimulating because there were a lot of different problems on the horizon, arriving almost every day. We could easily get the necessary equipment at the CNRS and at Elf, so there were no differences there.

AH : The restrictions at Elf had to do with what you were allowed to study ?

HA : Yes.

AH : What did Elf want you to do ?

HA : In principle I was hired to work on solid-state sensors. Because it was not in the direct line of my previous work I proposed that I work on solid-state sensors and ion conduction. We developed a family of sensors named ISFETs (Ion Sensitive Field Effect Transistors). It was a new kind of transistor at the time but now it is very common. You control the electrode using field effects, opening and closing the circuit between the two other electrodes. This is the way the transistor works. My idea - not an original one - was to replace this way of controlling the electrode, the gate, to replace it with a membrane, selective to such and such an ion. If you put the device in a solution containing the ion for which you have designed the system, the membrane will be charged. This charge will change the state of the solid-state transistor. It worked all right for protons. We could use the device to measure pH and afterwards we just had to change the nature of the membrane, choosing a different solid electrolyte, such as calcium fluoride.

AH : Your toolkit remained the same and you still used NMR ?

HA : Not NMR, but yes. You need large samples in order to do NMR. So it was mainly electrochemistry and surface analysis. This was between 1982 and 1985. But as I told you, in industry new projects can arrive almost every day. I had developed some skills in electronics using instrumentation at the École Polytechnique. Elf applied for a patent for a medical analysis system, a small instrument to be sold to private practitioners, as opposed to hospitals. This had nothing to do with solid-state ionics. But the people working on this project needed someone who knew about electronics, and so I got progressively more involved. After one or two years it had become my main project. This worked very well. I was very proud to design an electronic system that required no manual setting. It was set in the factory forever. This was a critical issue, because we thought that doctors could not be expected to deal with electronics - and I am sure that we were right in this. So there was nothing to check or calibrate - the system was self-calibrating. So it worked very well, and after only two or three years Elf built a plant and people were hired. But in 1984 and 1985 there were big changes in chemistry. And there was a great redistribution of all chemical industries. And Elf, that had been an oil company, in this period expanded to become also a chemical company. As a result a lot of the more diversified lines of business lost in importance. Many projects like ours were discontinued. But because we were already quite advanced we found a way to keep going. In fact it was Dupont de Nemours that found that our system was complimentary to some of theirs. The result was that Elf shipped the patent and everything else to Dupont. For a few months I considered following the project to Dupont and to the United States. In the end I decided against. I still wanted to work in solid-state physics and not to work completely in the instrument making business. But for one or two years I continued as a consultant.

2000-05-29 :

HA : For both personal and professional reasons, I decided to stay in Paris, and then Saint-Gobain offered me a position, working in a new research field : polymer adhesion on glass and other materials. It was a new topic for me too. At the time adhesion was not even considered a science. It was before Pierre-Gilles de Gennes's Nobel Prize in polymer adhesion [1991]. It was rather considered an art. Even though I had no background in the field I was interested. What interested me in the Saint-Gobain proposal was that real breakthroughs were to be expected in the science of adhesion when two materials are brought into contact. In fact this was my first real industrial experience. Of course CNRS had not been an industrial experience at all, and even at Elf I was always in the research lab. As I explained, my work at Elf had nothing to do with the industrial activities. I never visited factories. At Saint-Gobain I had to do this, at least in the beginning.

AH : Did you not say that your development of the medical analysis system resulted in the setting up of a plant ?

HA : Yes. I did participate in the design of the plan, in order to make it efficient. But I had no role in the plant itself after construction. It was also a small plant for high-tech activity.

AH : You had nothing to do with the fabrication side of it, situated in the plant – merely the R&D before the plant became functional ?

HA : Yes, exactly. Saint-Gobain of course has many plants all over France and Europe, and even the United States. But at that time, the company was still franco-français [French through and through] in its general spirit and culture, despite the many factories in other countries. There were only French directors and the system was based on the French system of education. There is a hierarchy from the École Polytechnique through the École des Mines and the École Centrale to lesser schools, and you carry the status of your school within you for the rest of your life. I remember that I strongly felt the weight of tradition when I first joined the company. It is true that winds of change were already blowing then, but they were barely noticeable and needed a couple of years before really expressing themselves. But eventually the company changed its culture, and now the company considers itself an international one. I think a deep change has taken place during my 15 years with the company.

So, anyway, this was the first time I gained experience of the industrial aspect of research. My first task was to examine and synthesize different kinds of adhesion in Saint-Gobain's products and processes. I decided to simultaneously pursue fundamental reflection and a practical approach, helping the factories improve their processes. This was a very instructive experience. I learnt many things although I am not sure that I helped the factories all that much. I certainly learnt for myself that I preferred to stay within R&D and not to progress into production. On the fundamental side, I developed a network of contacts in public labs in France and the US. This became useful later on. After three years in the field, and having created a small research lab, I decided to gain some distance from the practical aspect of my work. It was also obvious to me that fundamental research was required first. Progressively the idea came to me to propose the creation a special laboratory dedicated to the basic aspects of polymer adhesion - and of course also to related issues such as the surface science of glass. But I knew that Saint-Gobain was not ready to have a laboratory for basic science by itself, so my idea was to set up a lab jointly with the CNRS. This was in 1988. From the administrative point of view this was feasible : a number of such joint ventures already existed, an example of which is Rhône-Poulenc. Of course I had to convince both Saint-Gobain and the CNRS of the utility of the project which was not straightforward. Although I managed to convince Saint-Gobain in a manner of hours, CNRS needed more prompting.

AH : Would you explain the nature of Saint-Gobain's research before your proposed laboratory ?

HA : It was a quite common kind of R&D geared towards problem solving. Helping the development of new products and solving problems within production.

AH : So the research agenda was driven by questions arising out of production ?

HA : Yes, and my idea was to get a more fundamental understanding of the questions which would enable us to help with such questions in a much better way.

Figure 1. Saint-Gobain Recherche, Paris

At Saint-Gobain I had to sell the idea primarily to the Vice-President of R&D. He took the decision just before retiring. The CNRS process was more complex. It has a democratic organization where decisions are taken by committees. The members consist of both elected researchers and individuals named by the Ministry of Research. They are divided up into different scientific sections. So here I had to convince a diverse group of people, and not just one person, as at Saint-Gobain. As I mentioned, I had developed a network of relationships in the fields of adhesion and surface science and now this turned out to be useful. I knew that many people approved of my research agenda. My project was accepted without much fanfare, but it still took a while because of the administrational hoops that a proposal has to jump through within the CNRS. They meet only twice a year, and every decision has to be validated by the CNRS directors and so on. It took maybe 12 months. The laboratory started on January 1, 1990. But there was only a building and neither instruments nor people.

Figure 2. Joint lab : Saint-Gobain Recherche & CNRS

The three yellow arrows point to the units of the joint lab within the Saint-Gobain Recherche building.

In the meantime I conferred with scientists in many other labs trying to recruit people. Of course the CNRS could not order people to go, so I had to entice scientists away. I estimated that I needed three scientists from the CNRS in addition to three scientists from Saint-Gobain. Two of the latter had already worked with me, and they followed me to the new project. A further researcher came from somewhere else – it was a young Chinese woman. We also had two or three technicians and some PhD students. Altogether, it took a year or so to gather everyone together. We also had to buy instruments and the process of getting the laboratory shipshape lasted altogether something like 2 years. We began to actually do some research in late 1990. And from then on the activities progressed rapidly. In two to three years we reached a plateau of 20 people, a level that had been stipulated by the CNRS. A third of the people had come from the CNRS, a third from Saint-Gobain, with PhD students constituting the last third.

AH : Where did they come from ?

HA : The latter were doing industrial PhDs (Contrat à Durée Déterminée) with Saint-Gobain, and their salary came jointly from the French Ministry of Research and from Saint-Gobain. Of the entire staff, about half each came from chemistry and physics. It was crucial that we develop knowledge and expertise in both these fields. Later we also developed an interest in mechanical problems.

Figure 3. The SPM from Park Scientif Instrument

AH : What was the instrumentation ?

HA : There was a conjunction of the beginning of our lab with the very early days of scanning probe microscopy. This new kind of instrumentation offered a very exciting opportunity. There was a risk in this. We purchased the first Atomic Force Microscope (AFM) ever in France. We bought it from Park Scientific Instruments. Later we built the first AFM for UHV purposes. There were many people then who thought the instrument had no future, so it was a risk to invest time and money in it.

AH : Why did people think it had no future ?

HA : The objection was that it was not clear that atomic resolution could actually be achieved with the AFM. It was not until 1993 that Binnig showed true atomic resolution.

AH : Well, yes, but before he had claimed to achieve atomic resolution. In 1993 he only claimed that so far he had been mistaken and only in 1993 did he achieve true resolution. Is that not right ?

HA : Yes. But in 1993 the community was convinced. The reason I did not hesitate was that atomic resolution was not actually the big issue for our purposes. Even a resolution of 1 nanometer amounted to a great deal. Much could be done with such a resolution in the field of adhesion, and also in fracture mechanics and surface chemistry.

AH : I have the impression that since 1995 or so many people argue that atomic resolution is not really that important, and that in the early 1990s it was still considered the holy grail. So you were unusual in that you had this attitude so early ?

HA : You are right that atomic resolution had a special ring to it in those days.

AH : Did you emphasize the issue of atomic resolution in your application to the CNRS ?

HA : I am not sure. Even today, nobody has achieved atomic resolution in glass. So it would have been a hard sell, also then. The same goes for polymers. And those two were our substances under investigation.
There is a difference between STM and AFM. They obey two different logics. The STM has remained a tool of basic research, in surface science. The AFM, even early on (and this would be interesting to discuss with Calvin Quate or Gerd Binnig), there was a hope that it could be useful, for example in other fields of science, such as mine, or in technology, such as process control, microelectronics, semiconductors, and so on. Generally speaking, in early phases there are always many people who think that a novelty will never become common. We have to remember that in 1987 or 1988 solid probe microscopes were still big and unwieldy instruments. Of course miniaturization had set in by 1990, but it was a novelty. Only very few people were convinced that the AFM would become so common. Calvin Quate is one of the few. The STM has revolutionized basic research on metals and semiconductors. There was a reaction against it, because surface science was done using diffraction techniques working in reciprocal space. Surface scientists were formed in this mode of research. They resisted the change, feeling that newcomers would enter their field without the kind of abstraction that had hitherto been key to access to the field. Working in ordinary space was too easy ! Of course it has not actually become easy because the instrument has brought its own problems, and there are still people working with diffraction and in reciprocal space. The two complement each other.

AH : So this is the background against which your decision has to be seen. You went out on a limb.

HA : Yes. The beginning of my lab coincided with the first commercial scanning probe microscopes (SPMs). We had to grasp the opportunity.

AH : How did you know about the AFM ? Was it a very visible instrument at the time ?

HA : No. I knew about it from publications, but in order to actually see an instrument, I had to travel to California - although I guess I could have seen one at IBM Zurich. There was an STM at Marseille, because two physicists there (Salvan and Humbert) had worked at IBM Zurich, and they had brought one back with them. But they had no experience with the AFM. So I went to the US and visited the very few labs with AFM, both academic labs and the start-up companies of PSI [Park Scientific Instruments] and DI [Digital Instruments]. At Stanford University I met Calvin Quate and at UC Santa Barbara I met Paul Hansma.

AH : Was there a relationship between Paul Hansma and DI ?

HA : I don't remember. But at any rate it was not as close as the one between Quate and Park. I think Park was a former student of Quate's.

AH : So you purchased an AFM from Park. What about the other kinds of instrumentation you purchased for your lab ?

HA : Yes, we had to get other instruments, partly because it took a long time for the AFM to arrive. I had to go to the US to compare the DI and the Park instruments, and I discussed it with the physicists and chemists in our lab before ordering, and then we had to wait for the delivery – maybe 4 months or so. We got a 40% discount, because we were the first French customers, and they hoped that we would open the French market for them. I had very good discussions with Quate, and I think he trusted me to be a good advertisement for him in France. I think we paid 400,000 French Francs, so that the catalogue price was in the order of 800,000 French Francs [approximately US$100,000].

We bought also an infra-red spectrometer, in order to study molecular grafting on oxides. This we used as a complement to the AFM. And as I said in a previous part of the interview, our approach was to combine the traditional surface science (very clean surfaces) with “true surfaces” interacting with the environment. The infra-red spectrometer, XPS (X-ray Photoelectron Spectroscopy), and LEED (Low-Energy Electron Diffraction) were good tools for the traditional surface science approach working in UHV Ultra-High Vacuum). And also HR-EELS (High-Resolution Electron Energy Loss Spectroscopy). Our choice was risky, but it turned out to be correct. Our decision to build bridges between the two approaches was taken in 1992 or 1993. Quite early on in our project we built a surface force apparatus (SFA). It is not at all an AFM – there is no concept of high resolution, but it is similar in that you can get a direct measurement of the force interacting between two objects only a few Ångstroms apart. The idea is to make the measurement quantitative in order to study whether the interaction is due to van der Waals or electrostatic forces. In fact this project took six years – not for technical reasons but simply because we had to get the right people.

AH : Each instrument had its strengths and weaknesses in terms of resolution and the scale of the surface analyzed. And each instrument required special skills. The AFM, for example, requires quite some expertise to disentangle signal from instrumental artifacts, right ?

HA : Yes, artefacts were a real concern at the beginning, when we all had very limited experience. We had to pay much attention in order to ascertain the results.

AH : Can you explain how one separates signal from artefact ?

HA : There are different kinds of artefact. One that now seems quite natural but was hard to understand then is the tip effect. If the surface under examination has sharper topographic features than the tip, then the tip will be imaged rather than the surface. We had trouble with this kind of artefact. In fact, when studying tin oxide deposits on some substrate we got very nice images that we at first interpreted as small crystals having the similar orientation. We were very excited to find a growth mechanism of specific orientations on isotropic surfaces such as glass. I decided to present this result at a small meeting in Davos, Switzerland. The topic there was in fact “The AFM for Technological Applications”. Famous scientists attended, including Calvin Quate, Jim Gimzewski, and Heinrich Rohrer. There were only some 10 people there, because this was very early, maybe 1991. The night before my presentation, I began to wonder that the result was really too beautiful to be true. I telephoned my lab and asked people there to turn the sample by some angle and do the experiment again. That way, the features should have changed if they belonged to the surface. But they did not, and so we knew that the features belonged to the tip. So I did not present that particular slide in my talk.

AH : So rotating the sample by some degree is one way of identifying artefacts.

HA : Yes, that will eliminate this kind of artefact, the tip effect. There are also adhesion artefacts, some of which have been solved in the meantime thanks to new recording techniques such as the tapping mode.

AH : Digital Instruments has a patent for the tapping mode, right ?

HA : Yes.

AH : So the Park instrument that you bought did not have the tapping mode ?

HA : No it did not. The tapping mode did not become available until 1993 or so. Later on, Park Scientific Instruments did do something similar, but they may not call it tapping mode. The DI patent covers the name. And in the straightforward contact mode many artefacts were possible ; for example when looking at soft materials and polymers surface scratches easily occur. If you do that you image the substrate only. One way to identify this effect is to scan again with a smaller tip-surface interaction. In some cases you will find miniature small squares where the surface had been damaged in the course of the first scan. Some artefacts are very common, others are quite specific and harder to identify.

AH : In what you have explained, the identification of artefacts is internal to the instrument itself. It is not that you can go and compare the results of an AFM scan with those from a different instrument ?

HA : You can change the tip, and you should identify artefacts unless you are very unlucky to get the same tip. Everybody understood that the AFM has great potential not just as an imaging instrument but also to measure adhesion, hardness and so on.

AH : Using force-distance curves ?

HA : Yes, force-distance curves. This turned out to be very useful for us. For instance in order to understand the electrostatic interaction between oxide and a silicon nitride tip under water. This was original work. For example, in polymer adhesion we checked if it stayed on the substrate and what scratching would do. Of course such ideas were floating around at the time.

AH : Were you important to the subsequent spread of the AFM in France ?

HA : Yes, people came to our lab. Another lab, at the Institut Curie, that got an AFM at almost the same time. For a while we were a small community but then gradually we grew larger and larger. Yes, we were the pioneers. It was exciting.

2001-02-20 :

HA : I went with one of my sons who was 11 years old at the time to see Park Scientific Instruments. There were no more than 10 people working there, in fact I think it was more like three. It was very small and familial. We discussed and had tea. I enjoyed discussing with these people. It was nothing like an established company.

AH : What did it look like ? Did they work out of a garage ?

HA : Something like between a home and a garage. It was a small house. Even Digital Instruments started out like this. Already in those days DI, and especially Virgil Elings, was much more commercially aggressive, but they were very small too at the time.

AH : Did you stay in touch with some of these guys ?

HA : I stayed in touch with Calvin Quate for five or six years, until 1996. After that I lost the contact but he will probably remember me because we had many discussions. It was curious to see his impact upon materials science. In fact it was very difficult for him to get the first paper on the AFM accepted in Physical Review Letters. Some of it was considered just a pure mechanical profilometer. It had good resolution but it was not really anything new. His project now is very interesting from what I can tell reading his articles in the scientific journals. And he really is a very nice person. Maybe the last time I saw him is when I invited him to give a talk at Saint-Gobain Recherche.

AH : So you stayed in touch with him in the early 1990s, while you were developing your own AFM. I guess the use of the AFM changed the project from what you had originally envisaged ? Did you continue using all the other tools or did you focus exclusively on the AFM ?

HA : We used the other tools.

AH : What did you buy for your laboratory ?

HA : Infrared spectrometer, XPS, HR-EELS (High Resolution Electron Energy Loss Spectrometer), LEED. Quite quickly we had three AFMs. I wanted to develop a PSTM working in the infrared but unfortunately that particular project died because the physicist we had working on it left.

AH : What journals show the history of these instruments best ?

HA : In the beginning it was mainly in the general physics journals such as Applied Physics, Applied Physics Letters, Physical Review Letters, Surface Science. Now there are specialized journals. A journal like Journal of Scientific Instruments is not so important in this respect. Langmuir is also important for soft matter.

AH : Do any of these journals have review articles ?

HA : I am almost sure that all of them do.

AH : We were talking about the various instruments you had in your lab. How did you apply them to your research project ?

HA : The idea was to have two parallel approaches. We were mainly interested in adhesion, molecular grafting and so on. One approach is the classical view of surface science, the ideal surface approach. The other is the REAL surface approach, taking the environment as a part of the system.

AH : Not working in Ultra-High Vacuum (UHV) ?

HA : Yes. But we were trying to make the two approaches meet.

AH : So when you started working with the AFM in UHV, the point was to simplify the experiment ?

HA : Yes.

Figure 4. UHV Chamber et AFM in UHV Chamber

If a probe were to be introduced directly into the UHV chamber, it would take days of pumping to achieve UHV. Instead, it is first introduced into an antechamber, whereupon a vacuum is produced there. Only then can walls be opened without reducing the UHV too much. By pushing the rods labelled 1 and 2, the sample is transported in successive stages into the central chamber. Several instruments are attached to the chamber, including an XPS. On the right, an AFM can be discerned in the UHV chamber.

AH : How did the various instruments complement each other ?

HA : The spectrometers provided structural information. They give a chemical signature. One point of interest was silver on magnesium oxide. In order to have a simple model of glass we chose to study this problem within pure single crystal. We had the probe in situ in the same UHV chamber where we had the instruments to add the deposition techniques. In the case of silver it was just thermal evaporation. We wanted in situ real-time studies of the atoms arriving upon the substrate, the oxide surface. There were two models in this problem. One was that the atoms remain isolated or form small islands, so that the growth process is two-dimensional, so that you first get a perfect monolayer before a second layer is started upon. The other is that growth is three-dimensional with occasional collapses into flatness. To study this it is of course useful both to look directly and to use diffraction techniques. But in order to understand the process you need to grasp the interaction between the silver and the oxide. And only spectroscopic techniques will help here. We always tried to look at a problem from two differing points of view – in this case geometrical and chemical.

AH : You make it sound easy. You just use one tool and you get the topography, and then you use another and you get the chemical composition.

HA : Well of course it is not at all easy. It was very difficult because for instance, the STM works very well when you have a smooth surface but when you have corrugation it becomes much more difficult, because this corrugation interferes with the instrument. In spectroscopy you integrate over the size of the beam which is much larger than the surface scanned by the AFM. So you have to do many different experiments to see what effect the temperature has and so on. You also have to model the interaction. This was a little known problem. What is the mechanism of very small silver clusters on magnesium oxide with other silver clusters in the neighborhood ? It was a new problem. So it took time to understand the system.

AH : What is the measure of success ? It was partly CNRS, so you were under pressure to publish ?

HA : Yes.

AH : And since it was partly Saint-Gobain you had to get patents ?

HA : We had to do both. It was an interesting exercise in communication. In my position as head of the lab, I could not use the same words, the same way of presenting things when addressing different audiences. From time to time it was necessary to gather the scientific and the industrial people together under one roof.

AH : And what language did you speak then ?

HA : Fortunately everyone was happy with this lab, so it was not quite so difficult. The conditions were good. Nonetheless your question is quite correct. It was interesting.

AH : How did you convince Saint-Gobain that this would have a pay-off ? And how did you negotiate long- and short-term goals ?

HA : The short term was a problem. It was not straightforward to plan a new product for the company. The pay-off was very diffuse and difficult to identify. One way of motivating the directors was the argument that we trained very good PhD researchers for Saint-Gobain. And this was not expensive for Saint-Gobain, because they shared all the expenses with CNRS. Up until now this has not been a problem.

AH : Stanley Whittingham told me that in the last 15 years or so there has been a tremendous shift in company planning towards the short term in industry. Partly this was due to the MBA education and the fanning out of this new generation of business administrators into all nooks and crannies of industry. As a result the long-term disappeared, because everything had to fit into the financial year so that you have something to show to your shareholders.

HA : It is true that this has taken hold in industry. We had the good fortune that it was not very developed in Saint-Gobain. But also, the time required for the development of new glass materials just is acknowledged to be greater than that in electronics or informatics. When we start new projects, we are simply not able to show a product six months later. So we are less exposed than people in other fields, but the general development that you alluded to certainly has taken place. Maybe our situation will also change in the future. We may be excessive.

AH : Has the accountancy changed for you ? Did you have to write annual reports ? And has it changed over the last ten years ?

HA : In general ?

AH : Well, for the CNRS I can sort of imagine it. In academia you would specify the number of publications that you have produced and that is the measure. End of story. And that is very simple accountancy. But if you account to a company, keeping in mind the increasing influence of MBAs : did you have to account for your expenses in ever greater detail ?

HA : I do not think there has been such a change in the last decade.

AH : And do you write annual reports ?

HA : Bi-annual. But I am not in this lab anymore ; I left two years ago.

AH : Okay, so during the 1990s up until two years ago you wrote biannual reports to the company and in that period the structure of the reports did not change.

HA : That is correct.

AH : Did you have to specify just how much money you spent ?

HA : Yes, but also there, no change took place. And I always reported to the same person within Saint-Gobain. He was basically content with what we did, so it was never critical. It is true, it might have changed with a different person in charge.

AH : So, how did the instrumentation change throughout the 1990s ? The AFM became commercially available to an ever greater extent, you were able to buy many more things off the shelf. Is that true also of all the other instruments ?

HA : Yes, there are different aspects to your question. We used to build many instruments ourselves, and this was of great use for training. And this has changed. A reason the French PhD has been shortened is that equipment is being bought and not made in-house. That is a general trend. Science is changing as a result, because using a commercial instrument is not the same. When you develop an instrument yourself you know exactly how to get the result. In the specific case of AFM/STM : probably the AFM has been developed much more than the STM. In the STM the major breakthrough was with the driver and that was quite early. I think it was possible to purchase an STM driver already by 1992. Variable temperature was a little more difficult, but it was certainly available by 1994. Different ways of scanning and acquiring information were developed. Otherwise the evolution was purely technical : cheaper, and more diverse (such as an STM expressly for electrochemical research). By contrast the AFM has developed rapidly. Tapping mode and other modes where you measure not only the distance but also hardness, conductivity, adhesion, chemistry. It has become possible to map all these parameters. This explains why more and more people use the AFM.

AH : It has also become cheaper, right ?

HA : Yes.

AH : It has certainly become more user-friendly, adaptable to different circumstances.

HA : Yes. For the STM : there have very beautiful studies made of the coupling between tunneling and modulation. You might modulate the tunneling current with light for instance. You can even leverage the spin of the tunneling electrons. So you can do beautiful physics. But this contributes little to the democratization of the technique.

AH : I have the sense that Calvin Quate, by contrast, is working hard to increase throughput.

HA : Yes, that is right. There can be two reasons for doing that. To make the investigated part of the surface larger – of use in the semiconductor industry. And to shorten the time required for a scan. He is trying to use the system technologically.

AH : Okay. Two years ago you left your lab. Your own lab. Why ?

HA : I wanted to try something new and I was lucky to find someone who was well capable of taking over and for whom I have a lot of respect. He is from a different background. So now it is a different group. I became the Scientific Director of Saint-Gobain Recherche. There are two parts to the job ; one is to be the scientific manager, the other is to establish contacts in the outside world, and to promote innovations within the company, for instance with the marketing people.

AH : You were promoted ?

HA : Yes.

AH : And you have become slightly removed from lab work ?

HA : Yes, completely, I am now involved in organizational work.

AH : In fact, our project resembles your job in the sense that we stand back and look at the scientific research and try to gain a perspective ?

HA : Yes, you could say that.

Fin de l'enregistrement

Pour citer l'entretien :

« Entretien avec Hervé Arribart », par Arne Hessenbruch, 19 février, 29 mai et 20 février 2001, Sciences : histoire orale, /spip.php ?article47.

Pour citer l'entretien :

« Entretien avec Hervé Arribart », par Arne Hessenbruch, 19 février, 29 mai et 20 février 2001, Sciences : histoire orale, https://sho.spip.espci.fr/spip.php?article47.

Lieu : dans le salon (les 19 février et 29 mai 2001) et dans la petite salle de réunion (le 20 février 2001) du Dibner Institute, Etats-Unis.

Support : enregistrement sur cassette.

Transcription : Arne Hessenbruch.

Édition en ligne : Sophie Jourdin, Sacha Loeve.