 Good morning. My name is John Weaver. I'm from the University of Illinois in the United States. My departments are Materials Science and Physics. And today, the topic is an overview of nanoscience and technology. This is a particularly relevant topic these days, because countries around the world are investing in what are perceived to be particular opportunities for advancement in science and engineering. Now, if we think about what nanoscience is, if you have a group of 10 people gathering around trying to define the topic, you'll have 10 different perspectives. What was done in 2000, the year 2000, was that the American National Science Foundation and other organizations put together a national technology initiative. And in that, they had people who were biologists, physicists, chemists, material scientists, people from a wide variety of areas who sat together and defined what the topic was. And if we look at the transparency or at the slide, you'll see that it's a combination of topics which fit everyone. So everybody is a little bit happy, and everyone buys into this topic. What is important is that this is materials. It deals with materials or systems of materials which have structures and components that are novel to have specifically improved physical, chemical, or biological properties. That is, if I have something that's a centimeter cubed and I simply reduce it to a smaller size, but it has the same properties as the larger size, that doesn't count. It has to have something that's new and novel that lets me take advantage of those special properties in new technologies. So these would be physical, chemical, and biological properties, phenomena, and processes that are related to their size. And that seems to be a definition which has been accepted around the world. Now, if we define what nanotechnology is, whether it's science or science fiction, you can find both. But today I'm going to talk about the science and leave out the science fiction. What we think of as nanoscience, it is the understanding of atomic scale processes. That is, it's understanding, not necessarily manipulation. It is the understanding of processes at the atomic scale because the atomic scale defines the size of an atom and about three or four atoms in a row would be a nanometer, and that's the length scale that we think of. So if we think of a cubic nanometer, we're thinking about three by three by three, roughly 30 atoms, making up my particular system. So that's the small, and I'll go a little bit larger than that. Nanoscience, it is a technology. It's an enabling technology, not an industry. An industry, I would say, would be the automobile industry. It is not going to replace the automobile industry. Instead, the automobile industry will use nanoscience and nanotechnology, and already does, in making their products. An example, an analogy, would be understanding the flow of electrons in an applied electric field. Those problems were faced by the scientific community a century ago, and we learned to understand how to manipulate charge. From that understanding, we could then make resistors and then transistors and then devices and then the internet and then digital cameras and everything that we have around it. That is, it's a understanding of a process that gets used in a wide variety of different applications. That's what nanoscience is going to be. Now, if we think about what the potential is, we say that there should be an enormous potential. Now, if you ask me where specifically we're going to have breakthroughs, that's more difficult, but I think that scientists from a large number of fields see within their field breakthroughs. For example, in medicine, what you'd like to do is have drug delivery. You'd like to avoid taking it through the stomach because that's a complicated chemical process that you'd like to get away from. You'd like to be able to inject it. You'd like to be able to have a medication which over time senses the need of the body to have a particular jolt of chemistry from the drug applied. That is possible, should be possible, through nanotechnology. There are companies around the world, pharmaceutical companies, that are focusing on those kinds of things we could expect breakthroughs. One hopes that 20 years from now, we'll look back upon medicine as it's practiced today and say that these were the dark ages and that the 20 year from now, future of medicine is quite different, but of course those are promises and we cannot guarantee those things. Now if you ask when nanoscience emerged, you can think about nanoscience processes that have been taken into, that have been used for centuries. For example, if you look at this image, you can see a very attractive cup that was developed, the Lycurgis Cup, in the fourth century in Rome. And what it shows is that depending upon the angle of incidence of the light, the color changes. So it's green or it's red and that's a process called opalescence, which now we understand is related to the fact that there are gold particles in that cup. I am quite sure that the Romans did not know what gold nanoparticles were, but they did know how to take advantage of a technology and make attractive artwork. The same would be true of the Chinese. About a thousand years ago, they used gold particles in porcelain. Coloring was important. Gold nanoparticles, though they didn't know what they were, gave them the particular properties that they wished. A century ago, we developed ways to improve the wear of automobile tires by putting carbon black in them. At that point, we had discovered with periodic table and we know more about the chemistry than the Romans did, but I'm not sure that we knew all the details of the carbon black and its processes. So all of these things, which we can look back on and say are nanoscience, I would not include as my definition, the current definition of what is nanoscience. I require that we understand the processes. These people did not have the chemical periodic table, so they couldn't have understood it. Often the identification of the starting point or the vision for nanoscience and technology is traced to Feynman, and a lecture that he gave in 1959 to the American Physical Society. And he said, and let me quote, I am not afraid to consider the final question as to whether ultimately, so he has no timeline but a long time in the future, in the great future we can arrange the atoms, the way we want them, one by one, the very atoms, which are the constituents of matter, the way we want them all the way down to the size where there are two or three or 10 put together. Then he says, what would happen if we could do that? What kinds of breakthroughs would there be if that were possible, and when can we possibly do it? Well, that was 1959. So if we add 22 years, we're in 1981. In 1981, Benny and Rohrer, who immediately got the Nobel Prize for the breakthrough that they had, developed a scanning tunneling microscope. The scanning tunneling microscopes lets you see corrugation of atoms, not my knuckles, but atoms on a surface. You could see the atoms. So not many years after Feynman, you had a technique, an instrument that was developed that allowed you to see atoms on surfaces. That wasn't manipulating them yet, but it was seeing them. And then in 1989, eight years later, Don Eigler in his group, showed that you could manipulate them. And so if you look at this image that shows 35 xenon atoms on a surface, spelling out the letters I, B, M, and of course he worked for IBM at the time. One will never make products out of writing IBM at low temperature with xenon atoms, but the discipline that you would adapt in doing that can then carry forward into other processes which will, we believe, have applications. Now the expansion of nanotechnology or what had been the driving forces for nanotechnology have been many. One has been, for example, the electronics industry. We've all heard about the Moore's law and the increase in speed and reduction in size for devices with time. That has been one size. We want faster, we want better, we want different kinds of devices. I would also say that there have been discoveries made over the years, as is always the case in science, so that we can build on the previous generation of work. And the particularly important advances, I would say are those related to surface science. Because if I understand surfaces, then I can think about modification and manipulation of atoms on surfaces. We've had the development of theory so that we now can predict the properties of matter without having to do the experiment. We can design things and then go into the laboratory and try to make them. In the 90s, there was the breakthrough that gave rise to studies of carbon structures called fullerines, C60, and higher structures. And then carbon nanotubes. And then there was the work on self-assembled monolayers. All of those breakthroughs combined set the stage for something that we call now nanoscience and technology. But which, of course, goes back earlier in time. As we are now and as we have been for the last half dozen or so years, we believe that in the next century, the physical sciences will marry the biological sciences. That is, there will be a merger as the physical sciences are able to provide new insights, the mathematical skills that we have, and the biological sciences are able to tell us what the important issues are. And together, we're going to have a great new future. And I think that's certainly going to be true. And it's going to be reflected in nanomedicine, nanotechnology, disease detection, and therapy. There's always the question of, are we using nanotechnology? Where, if I get up in the morning, will I find nanotechnology? Well, a very simple application, or not so simple application, but one that's common, is right here in a laser pointer. And the image that you see behind me is showing how a laser pointer works. There are a series of atoms buried in the center of a device that have a particular crystal structure and chemical makeup that are different chemical makeup that's different from those around them, so that if I inject an electron and a hole, they will go to that very small object in the center, combine, and give off a photon. So I have a laser, which is very much nanotechnology. There is an interesting website by the Department of Energy which shows length scales. And it says on one side, this is man-made, and this is natural. And we start off at the large size where, of course, we have ants. And we can say that they're millimeter in size and something that we can make the head of a pin, which would correspond to the man-made side. And we can work all the way down. And as we work down, we can identify the length of the photon, the photon energy that corresponds to that dimension. And the image that I show here, relative length scale, provides a collection of different examples of what are man-made and what are natural. Things that are natural spherical objects would be the fly ash that comes from a coal burning furnace, where in the combustion process, you burn the coal, but there are other impurities that are not burned. Aluminum oxide, which forms a spherical structure because it's at a high temperature as it goes up the smokestack. That would be a natural. Correspondingly, on the other side, you could have a microelectromechanical device that we can make that would give particular sizes. This image shows that the very smallest size, the DNA, where the coil length is a nanometer approximately, and on the other side, something that I'll show again later, that is an assembled structure of atoms on a surface. So we can deal with all these lengths, and we're making progress at manipulating structures. It's an example of the challenge that's identified. And this, for example, this particular example says, let's develop a way of harvesting light. So let's have something which is photosynthetic, capture the photon, convert it into energy, and store it in an inorganic material. So this is the combination of a molecular structure, a complex molecular structure, combining with something which stores the energy and that can be used in the future. We don't know how to do that, but that's something which is the challenge. A point of nanoscience is one that identifies how many atoms of a particular structure are the surface and how many are in the bulk. If I have one atom, it's clearly all surface. If I have one surrounded by six, three and three in the top, I have 13, but 12 of those are the surface. If I go then to the next level, I can continue expanding this structure to the point where, for example, and this image shows that if I have 12 as a shell, then I'll have approximately 5,000 atoms, but 12,000 of them are going to be on the surface. So a significant fraction of anything that we make at the nanoscale is surface. So I must understand surface science and I must be able to protect these structures because if I make something like this, that this small and I expose it to the environment and it reacts, then it's no longer what I made and I have to develop ways to protect that. So the grand challenges in what we're doing are synthesis, how to make these things, ways to do it, size selection, because if we say that the properties are related to the size, I need to be able to choose the size so that I can make the device that I want. I need to stabilize, that is to get away from those surface problems. I need to characterize. I need to come up with new ways to look at the process. S scanning tunneling microscopy is an example of a way to characterize these processes. And then if I make something that's really neat and has fascinating properties, I've gotta be able to somehow build that into a larger structure. If it exists in vacuum, that's not particularly useful. It has to somehow be connected to other things that have wires that go out to the outside world. I'll come back to this issue of communication with the public because it's one that's very important and one that scientists often do not do adequately and with nanoscience as a new technology, there will naturally be people who are afraid of it and we have to make sure that they understand what nanoscience really is. Now let's work our way through nanoscience and technology. I wanna start by growing a thin film. Thin film will be a nanometer in one dimension. It'll be made up of atoms. I want it to have the discipline to think about those atoms. So let's start off with a clean surface and a source of atoms. What will happen if I have this in a vacuum system and I evaporate atoms from the source, they will arrive at the surface. Some of them will stick depending upon whether it's reactive site, some of them will bounce off and I can characterize those processes. If I do that and think about that surface in a little bit more detail, that is I make a ball and stick model, then I can imagine what a surface really looks like. A surface could have flat areas, it could have steps, it could have a kink, an atom arriving on the terrace can diffuse, it can come to the step. If it comes to the step from the lower side, it can get stuck. If it goes to the kink and then that's the best place to bond, then I'll have this top layer growing over the bottom layer. In addition, I can have atoms on the surface that will find each other and they'll form clusters. And those clusters can be stable after a particular size. Or if I give them temperature, I can have big clusters and little clusters and thermodynamically, the big clusters will eat the little clusters, so they will grow. In addition, I can have three-dimensional structures depending upon the details of the energies associated with a surface, the film of the cluster and the interface. And the idea there is just like water beating up on your car. Depending upon the details, I'll get layer by layer or layer with a blob or blobs. And these images show in a very simple cartoon the process is associated with it. First, I have a planar structure. I can grow another layer on top of it and that layer continues to grow layer by layer and that's what I'll do if I'm making semiconductor devices for lasers. That's the structure that I want. On the other hand, I could have a wedding layer followed by blobs. Or I could have, as the third one shows, a simple conversion. Let's see, I've gone ahead. The center one was blobs. The third one is the layer followed by blobs. The fourth one is the one which is most likely to be the case. That is, chemistry occurs. Reactions occur. And that means that atoms that I've added and atoms of the strep straight have mixed to form a new compound. These are the only four possibilities that I can deal with for thermodynamic structures. This image shows examples of three of them. The one on the left shows gold atoms that have been deposited on a surface which are not reactive and so they'll form three-dimensional structures or what I call blobs. The one in the center shows germanium growth on silicon where the first layer wets it and then for reasons of strain subsequent layers grow as blobs, huts. And the third one is layer by layer where this particular set of images shows an indium arsenide and an indium gallium arsenide, a superstructure, a heterostructure. Now there's some other things that are important which are not part of the equilibrium which give me kinetically constrained features. And one would be a barrier associated with an atom coming up to a step and jumping over. If there is a barrier, and this cartoon indicates that, developed by a colleague of mine named Kurt Erlich some 40 years ago, if there's a barrier that keeps you from jumping over then you're going to accumulate on the top of the island. So if I have two islands and I deposit and everything that arrives on the island stays on the island until it forms another layer and then another, what I'll end up with is this so-called wedding cake structure which shows many, many, many, many layers and then areas in between where there's nothing. Now, if I'm trying to grow layer by layer I better know the details of what the reality is that tells me how it really grows as opposed to how I might think it grows. There are a number of ways of growing things. The molecular beam epitaxy is one which is used in the semiconductor industry which involves layer of one material substituted for it and then a second material and then back to the first and a second so that I have a variety of different kinds of layers all built up in a very periodic array. That's molecular beam epitaxy. The image shows several different sources. So here's a target. Here is one source providing aluminum, for example. Here is another source providing gallium. Here is another source for arsenic and another source for phosphorus. And if I want to make complicated combinations I shut off the source that I'm not using. So up here I'm accumulating the materials that come from these two or these two or these two. So I have a wonderful way of developing blue lasers or green lasers or other structures. Both of those kinds of processes, physical vapor processes give me growth when I can see the target, that's line of sight. But if I want to cover something that's more complicated I have to change the chemistry. I can't use that particular process because line of sight doesn't coat things uniformly but I want to. And a process that's been developed is chemical vapor deposition and that's a particularly nice process because it takes advantage of the tendency of the vapor to stick to the substrate being very, very low. And that means that I can have a gas over a surface that's complex in morphology with a very small chance of it sticking. And that means that I don't have say a filling, an occlusion of the top of a crack. The image that's shown shows a deep trench. Now a deep trench can be filled if the probability of a reaction occurring is very small. That means it's going to be equally likely up here on the flat part and down here on the side. So I will grow uniformly. Other processes would very quickly gum up the top and you'd never get to the bottom. The example that I show is a hafnium compound in the gas phase being delivered to the surface where reaction occurs and the hafnium stays behind as a hafnium boron compound and the other gases get transported away. So that's chemical vapor deposition. Another way of growing materials would be a more energetic process that is instead of having a hot source where I'm evaporating, let's think about a target where I am driving atoms at it and sputtering atoms that is kicking them off from the target and then they go and they stick on what I'm growing. That gives me an enormous amount of control over the processes because I have the kinetic energy of the incoming particle and I have the ionization state of the particles that are rejected. And this is a very popular technique for making hard coatings, for making materials where you want to control the structure and the engineering of it. Another process for growth would be analogous to what we have in say a smokestack and that is where you have a small particle and it diffuses and it comes in contact with another one and it sticks and it diffuses and it comes in contact with another one and they stick and with distance from the source in this gas I have larger and larger particles that form and the picture that's shown shows that these are small, get to a particular size and at any point I can pull off that size. If I let them get too big well then they're no longer useful because they've started to agglomerate but I can control the size of the particle by where it is in the stack and I can control the size by the density of the gas and the kind of gas. So this is a very useful technique called gas phase condensation. Another technique which is important particularly in carbon nanotubes for example would be to take a very simple system. Let's have an electrode and another electrode and my arms go connected to a battery so that as my fingers come lower and lower there's a lightning strike, there's a discharge. And that process means that I'm evaporating the atoms from one of the electrodes and there can be some interesting chemistry that results. If you have both of these as carbon you can produce yourself a carbon nanotube and that was done by Rick Smalley and Don Bethune and others about a decade ago and Tom Ebison in the lower portion of this image shows carbon nanotubes that have been developed by this process and this image shows that there are two different kinds. One is where the electrode is pure and the other one where it is doped with a catalyst and depending upon the chemistry of the problem and the details you could either get single-walled or multi-walled carbon nanotubes. Yet another way of growing things builds on good basic material science that is if I have a compound and I mix it with another melting temperature is going to drop. So in this example we could have germanium and being flowed over a collection of gold where the gold is hot and the germanium hits the gold, dissolves in it, super saturates it and as this image shows the melting temperature drops but if I keep feeding germanium into it at some point I reach the point where I'm super saturated and the germanium must come out if I'm going to add more in and that gives you an interesting way of growing as the image shows a wire underneath this cluster. So here's my cluster sitting on a surface. It's accumulating germanium and eventually it starts to spit germanium out and it's a crystal structure on top of the support and then it rises as the process occurs. So it's growing a nanotube in this case germanium but it works for many other things as well. The TEM images that I show here follow the process. The first one shows just the particle the second one shows the particle getting a little fatter as it absorbs material the third one even fatter and then the fourth one where it's starting to pull off and then the fifth and sixth show the wire developing. Wonderful technique for making new and novel structures of materials. Those have, well everything I've talked about so far has been a solid state process. You can also do chemistry. So our colleagues in the chemistry side look at colloidal structures and there they have a molecular beaker which they coin after our molecular beam molecular beam, molecular beaker, epitaxy. The idea is simple the process isn't necessarily. I inject one material that's carrying the atoms of what I want and another and in this hot soup the two things that are injected dissociate the atoms that I want are now free to swim around and find each other in an appropriate medium and they can grow and when they grow to a particular size I want to try to control their subsequent growth and that I can control by the soup that they're in. So this is nice process and here's what the idea is the physics of the process. I inject I go way super saturation and that means uniformly in the whole bath I start to nucleate small particles. That means that the concentration drops rapidly and when I get to a particular point I want to make sure that those small particles don't grow anymore so that when I'm all done I have a uniform collection. In the image that I show they continue to grow. The indication over there on the right if I were to add something to the system then that would prevent their growth. And here is an example of a capping agent. A capping agent is just exactly what it sounds like it's something that protects it provides a cap so that my two particles don't come together they stay apart and that means that when I remove them from the bath I'm able to make a particular structure. So, so far we've talked about ways of growing things now let me spend a little bit of time talking about characterization. One way to characterize materials is with a transmission electron microscope and I strongly believe that any materials laboratory needs such a device because you're able to see things in real space as the image on the right hand portion shows real space image I can do diffraction as the inset shows or I can get really small and focus beam and focus on the atomic structure of the particle so it's a wonderfully diverse technique and everyone should have one. Something which is perhaps not quite so common would be a scanning tunneling microscope and a scanning tunneling microscope is what I depicted here there's several parts of this image and it's a little bit complicated so let me talk you through it. The cartoon on the left shows a sharp object over an array of a surface so I can scan along the direction of my fingers or across my fingers and what I want to be able to do is see when I come up on the knuckles so that means I need something which has extreme sensitivity in the vertical direction and control in the x and y direction and that's what this shows connected to a servo loop so that I can control the current flowing so what the idea is that I'm passing current from the tip to the sample or the other way around and measuring the current and holding the current fixed in general. The real system is shown on the upper right and that's a picture of one of the instruments in our laboratory showing that this microscope is just a small portion of a bigger system and that if I get even closer then I have the portion on the bottom right which shows the active parts of the microscope and I'm not sure if you can see it but there is something that's horizontal which has the capability of moving x and y and also advancing in the z direction where I'm making z the direction of my finger and a sample that's sitting here at the end so that I can approach and then scan. Now we think of a tip as being sharp and the picture there shows a sharp tip but it's sharp on two different length scales one is when you've got a fairly low resolution and that looks sharp but when you get up really close to the size of the nanometer it's more curved. That's the reality of what a tip looks like. Here's a cartoon of a tip and a cartoon showing what STM does. There is a tip where there is one atom on the apex and all of the charge flows through that atom and because of the equation that I've written there the current depends exponentially on the distance between the tip and the sample. If the current were to emanate from the second atom it would be down by if it's two angstroms away by a factor of 10 from the one at the tip. So the one at the tip is controlling all the current flow and the moving picture then shows you that as you move across the surface you want the current to be fixed which means you rise up and down and since that's easily measured you're getting a topograph of the surface. You can see steps like that depicted. Scanning tunneling microscope. Binning and Rohrer's development that immediately led to a Nobel Prize. As an example let me show you a silicon surface. Silicon is one of our favorite materials in microelectronics. It's been studied for decades. It's very well understood. With STM you can make new advances in understanding what the processes are. The image shows you a surface that's been miscut. It's like this table. This table is flat over here but then there's a step and then another terrace and then another step. That's exactly what you see. On the top terrace the atom rows are running one way on the next one they're running the other way and so you can see rows going one way and then the other. With STM we can zoom in on that. We can see what the atoms are doing whether they're dynamic. If you look carefully along the row in that lower portion you'll see that there's something that's bright and the bright goes up and down and up and down. Well that's easily understood now of course by saying that if I were a silicon atom I would have two back bonds and two dangling bonds and if you create the clean surface I wanna get rid of these dangling bonds. I wanna move a little bit and form a bond with my partner who looks just like me like that. Now I have a dangling bond only one. That's what these Lawson's like things look like in the current image. The fact is that there's this very small barrier that keeps me from moving up and down and my partner from moving up and down so that at room temperature we're both doing this. With my STM I can't tell that because it's too fast but if I have a defect or if I'm at low temperature then I can capture one frozen down and the other one frozen up and that gives rise to that zigzag row that you see. So we've learned something about the dynamics of the surface and barriers associated with it. The lower portion of the image on the right shows what happens when one atom forms a dimer as it's called with the other and the consequence of dimer rows on the terraces. Here's another process that you can have that lets you get up even closer and that is suppose that I wanna do this at low temperature. Suppose that I know that if I drop the temperature this thermally activated process will quench out. I wanna understand more about that. So let's reduce the temperature and you can see from these two images that the atoms are moving up and down so that the lozenges look uniform. You're down with a partner that's up. My partner over here is down with his partner up. The repeat length is one, two, three, four. So it's a four by two structure. I'm learning something about the dynamics. I'm learning about things at the atomic scale which I can then use for subsequent growth studies of silicon. Now there was the Feynman picture of I'd like to see things at the atomic level all the way down and this image lets you see a single atom and identify what it looks like. This is a silicon surface that has a partial coverage of bromine on it and it shows you a dimer that has bromine on it and a dimer that doesn't. The dimer that does has two little bright spots. So if you can see in the center of the image there are rows running upper right to lower left with two bright spots and then an undistinguishable object and two bright spots. Though each of those bright spots is an individual atom and you can see them and you can see them routinely and you can see them for a variety of different materials and that opens up just an enormous amount of surface science and nanoscience. Seeing atoms, knowing what the processes are. A scanning tunneling microscopy can be done at fixed temperature but it can be done at elevated temperature and at elevated temperature I can watch movies of things changing. So if this works I should have a movie, I do, a movie of a silicon surface that is slightly reacted with chlorine on it at a temperature of 700 Kelvin and the time between scans is only eight and a half minutes and if you focus on a particular part, take your choice, look on a particular object and see how it changes with time. The bright features are silicon atoms that have come from where the dark ones are, they've gone onto the terrace, they've left behind a pit, they've formed an island. And you can see how those islands change and the pits change. And now you can think about what the energetics are for each of those processes and it just gives you an unparalleled opportunity to see what's going on. So obviously I like scanning tunneling microscopy. STM lets you do as we showed earlier what Eigler did that is manipulate atoms. So I have a tip, I have an applied voltage, therefore I have a field and if I come to a particular place I can pick up an atom, I can make it move from the surface to the tip, I can go over here, change the bias and put it down, I can manipulate it or I can shove it. And here are a couple of real space depictions of the evolution from a collection of atoms on a surface to an ordered array on the surface which has been accomplished because the person behind the microscope wanted to. So the upper left hand quarter you see a portion an arc of atoms and these are iron atoms on a copper surface and then it gets a little bit better and a little bit better and a little bit better and pretty soon you have a circle. And now you see some interesting things on the inside that reflect the waves of the electrons of that surface within the corral. That is they're spreading out from the center, they reflect, they form standing waves and from quantum mechanics we can calculate what those wave distributions look like and now we can actually see for the first time electronic waves in solids. This is a beautiful experiment. Don Eigler has a particular gift for doing artwork as well as science and this is a very famous picture that's appeared in many places which shows those waves and shows those iron atoms greatly enhanced but it shows the picket fence around the outside and the waves contained on the inside. So we're making quantum corrals and the space between those, this dimension is just a few nanometers. This is a picture of Don and a couple of his students, it's a little bit older picture than the earlier one because in time we do age. Here's a, this is an interesting cascade. He started off with an array of CO, carbon monoxide atoms on a surface that's stable and then he says let's move one of them a little bit so that it destabilizes the recipient and that destabilized one passes something over to the next one and the next one. It's a domino, just exactly the game domino. So one falls and it makes the other fall. Let me show you this movie. So the upper left hand corner, the tip comes, it moves a CO molecule which destabilizes one which moves and moves and moves and you can follow that and if you back off you see that if you started on one place you have a particular logic traced out and if you started someplace else you have a different domino line and the argument is that he can then create a logic gate and a sorter. Again we're not going to do that in the next generation of computer because this has to be done in a vacuum system at low temperature in a controlled way. But the fact that you can do it challenges us to make things that we really will be in our next technologies. Okay, let me talk about another technique which gives me insights into atomic processes and that's atomic force microscopy. When I talked about scanning tunneling microscopy I said I have a tip and a surface and charge flowing from one to the other, current. That means that the tip and the surface have to be either metallic or semiconductors. If one is an insulator then I cannot flow charge from here to there and then to ground because I would simply build up charge. So I do not get a map of the surface with scanning tunneling microscopy. And that's just not acceptable. At that point all the people who want to study soft matter say come up with something that lets us study biological matter, polymers, features that are not metals or semiconductor and of course the first thing to do is to say well if you've got a scanning tunneling microscopy image or a system why don't you just add on a little cantilever so that the cantilever comes down and senses the surface. All of the rest of this thing is already built and so as this moves you can take advantage of the feedback and understand something about what the insulating material is. Here's a picture of showing a tip with a reflecting surface like my fingernail and over here would be a photo detector and as my fingernail moves the reflected beam moves on different size of the detector and since this is very sensitive to motion I'm able to get a map of the surface. Here are a couple of examples of what the process looks like in a cartoon mode. AFM in contact like my finger across the table I'm rubbing across it, I come down, I flop down, boom, I come across. It's okay but the problem might be that I'm going to scratch the surface or modify the surface. If I've got something on it like that I can move it away and I don't want to do that. So instead I'll come up with a slightly different technique and now I'm going to be moving like this coming closer and backing off. As I'm far away I have a particular vibrational frequency. As I come closer and start sensing the potential of the surface the frequency changes and I say good stop, no closer, let's stay in that mode. So there we are at one mode now we're in the non-contact but close enough that I know the surface is there and now I can scan across. So that's a non-contact mode and it's a wonderfully effective way of investigating surfaces. I can think of many other ways. Here's another non-contact system whereas the frequency shifts, changes, I move and as I move I know what I'm doing and that means that I can tell how far off the surface I am. You can also use a tip to modify the surface. This is called dynamic plowing lithography or dynamic name. So now you're coming and actually pounding into it with the tip. You're removing material where you want to and then going to the next line and removing material so that you can make a three-dimensional object and when we finish this line we'll rotate up and you'll see what has been made and you can make anything you want. And so that's a person's face with dynamic plowing lithography. Now we can think about the electronic structure of nanostructures and if we do that we want to start with the macroscopic and shrink first one dimension, then two, then three. And what this slide shows is just that process. There is a three-dimensional structure that might be copper that would have a particular distribution of electronic states and one plots the density of states versus the energy and it's a parabola. If I shrink it down in one dimension then I become quantized in the smaller dimension and the other two are less so and that means that the density of states has steps. If I then shrink it in the second dimension then I have a rod which gives me again a unique distribution of states, spikes, the decay. And if I shrink it down in all three dimensions then I have something that might be a super atom that is I have particular eigenstates that correspond to the states of the solid now called the atom. And the image shows you what those look like that is the density of states has spikes that show up. No, why is that important? That's important because I can think about how the material absorbs light and how it emits light. If that nanostructure has specifically well-defined levels then I can tune those levels so that they give me particular kinds of light coming out. What this shows is some indium-phosphide small particles that were grown by that colloidal process. The ones you see the absorption and you see the absorption edge shift with the particle size. And as the particle size goes from eight nanometers at the top to two nanometers at the bottom I have a shift to the blue because of quantum confinement just what we saw a moment ago. And then if I look at the colors that are emitted after a photon is absorbed that is photoluminescence I see green and yellow all the way to red all the way across the visible spectrum that's because of the size of the particle and I can control the size of the particle. Now, why that might be interesting could be in a medical application. Suppose that I have a particular cellular structure where a particular part would like to interact with size A and the other part would size B but I don't really know what the details are. So I can expose the material and then do a light map across it that is illuminating with light and looking at what comes back. And what this image shows is that there's some parts that are blue and some that are pink and some that are yellow and those from that we can get an indication of how reactive or how sensitive those portions of the larger structure were to the nanostructure. I can also make ordered magnetic particles in this colloidal process. So the cartoon shows again the process. There's a particular compound that carries platinum with it and another compound that has iron. I inject them in a particular bath and from that I get iron platinum particles at the top and then I can spin those onto a surface. If I do that at room temperature the structure is not particularly useful because I haven't rearranged the blue and the red atoms into the magnetic state that I want. But if I cook it a little bit, then I do and now I have a magnetic array that's based on nanoparticles. Why is that useful? It is useful because I can pattern a surface. Now I have a larger array where these particles are all scattered over it and I can come along and I can magnetize. I can change the magnetic state as I wish and that's what is done here. We have an array as we just had on that last slide and then with the AFM I can come across and I can create the pattern that I want depending upon the distance, change the separation of the aligned particles from one direction or the other. So the idea here is that you can have an enormously high density of magnetic information. Okay, just to wrap up, what we've talked about in the last few minutes is the development of materials by design and that is I understand the physics and the chemistry and I think about what I want as a product and based on the understanding and our ability to manipulate it, I can create that product. That is I can create a particular function and I can use that function. That's materials by design rather than by random luck. The challenges are to integrate organic and inorganic materials and that's being done at a rapid rate in laboratories around the world. We are developing new tools, synchrotron radiation facilities, neutron radiation facilities, AFMs of variety of kinds, STMs. We're forcing ourselves to come up with new ways of seeing the world around us. The effects of hyperbole, that's worth the moment. Every time there is a breakthrough in a field, the press tends to rush in and ask you what you're doing that's going to revolutionize the world and if you tell them something that's fairly mundane, that isn't going to satisfy them. They want you to say something that is exciting, something that will let them write an article that says the world will change because of X, Y and Z. I would say that's hyperbole. Most of science is of steady progress where we build and build and build and at the same time spin off wonderful new products but the hype I think doesn't do us any good at all. There are issues that we do not yet understand related to health. Smaller and smaller particles may interact with our bodies differently and we don't know much about that. We do know that there can be damaging effects. We know that asbestos is not good for us and it's a small structure and it's made up of silicon oxide in particular chains. It's the same silicon oxide that's made up of glass but it's a particular structure, it's particularly robust. That's not good for us if we had known a generation ago that that was the problem we never would have put asbestos in our insulation. We want to avoid the kinds of things that could lead to asbestos in the future and the way to do that is to understand what the chemistry is and the interaction of the particles with the human body and other bodies. So health issues are very important and a reason that they're very important for the obvious component is that we don't want to introduce something bad but the other is we don't want to frighten the public. We don't want to have another example of the genetic engineering. The Europeans are terrified of genetic engineering. The reasons that I don't understand, they say that that's been man-made, you've modified the genetic structure, therefore that tomato isn't good. Well, the tomato's fine. Why are you afraid of eating that tomato? In the public perception of nanostructures, there is something called gray goo and gray goo is the material which the scientists are working away in a laboratory making things and a piece of it escapes and it gets outside and it self-replicates and it's smart enough that it then forms a swarm that comes in and attacks mankind. We are certainly not smart enough to create such an object but we want to communicate to the public that we're not smart enough to create them and that there really isn't a danger associated with the science, the fundamental science that we're doing. We need to communicate, we need to avoid overstating, over-promising. We need to make sure that the public who are paying the bills for all of this work and who will benefit from this work truly understand what we're doing and buy in and so it's a complex process. It's a feedback process. So with those final words, let me thank you for your attention. I hope this is covered in some small way. The enormous field of nanoscience and technology, if you had a different person speaking, you'd get a different perspective because nanoscience is not something simple. It is overarching in many, many disciplines.