Graphene: From the 2010 Nobel Prize in Physics

The 2010 Nobel Prize in Physics was awarded to two physicists in the UK, Andre Geim and Konstantin Novoselov, for their contributions to graphene research. This year's physics award has several different places.

First of all, this is the first physics prize on carbon in history. We know from high school that carbon has two crystal forms, one is diamond, used on the most expensive jewelry, and the other is graphite, used in the most common pencil. We also know that diamond is the hardest natural material. Graphite is very "fragile". The crystal structure of graphite is layered. The carbon atoms in each layer form a solid hexagonal structure, and the bond between layers is much weaker. Therefore, graphite is easily split in the direction of the layer. Among the common substances we have, the “two-sidedness” of carbon can be said to be unique.

But the story has only begun. In 1985, it was discovered that carbon has other forms: 60 carbon atoms (C60) can form a ball, as shown in Figure 1. The structural model of the C60 is similar to a football, so it is also called football. The discovery of the C60 won the Nobel Prize in Chemistry in 1996. Later, people discovered the so-called "carbon nanotubes", a tubular structure composed of carbon atoms, which is about 1 nanometer in diameter, but can be several centimeters long. The award-winning graphene is a single-layer film of carbon atoms, which is one layer of graphite. Although carbon is the most familiar element and the main component of our body, and the object of physics for many years, the work on carbon structure is the first time to win the Nobel Prize in Physics.

The 2010 Physics Awards were the first award-winning work to be made in the 21st century (2004). One of the winners, Noosalov, was the youngest physics winner since 1973. Usually, the Nobel Prize in Science is a bit "archaeological" in nature, and only a handful of jobs will soon win prizes. The importance of graphene has been widely recognized since its inception. Take the most authoritative journal in physics, PhysicalReviewLetters. Before the awarding work of Gamm and others, there were only 21 articles on graphene. By the time the Nobel Prize was announced in October 2010, there were 1,476 articles in the article. Even before the Nobel Prize was announced, the citation rate of Noosholov's papers was already among the best in the physical world. It can be seen that this work has created a new field and has quickly gained a high degree of attention. Therefore, this graphene work is nominated for the "green eye", it should be said that it is well deserved.

Graphene "famous" is by no means accidental, but because it is indeed a very magical material. In theory, two-dimensional electronic systems have many unique properties, and the quantum Hall effect research has won two Nobel Prizes. For many years people have been looking for a suitable experimental platform for two-dimensional electronic systems. Graphene is the first true two-dimensional system. Its crystal lattice is very regular, so it is a good experimental material, and it can display many interesting quantum phenomena even at normal temperature. The development of the development of graphene research also allows us to obtain other two-dimensional lattice materials.

More importantly, the equivalent mass of electrons in graphene is zero due to its unique band structure. This means that these electrons (strictly speaking, equivalent carriers) follow the law of relativity like photons, although their speed of motion is only a few hundredths of the speed of light. For example, they have physical parameters like "polarization." Therefore, graphene is still a platform for observing and verifying quantum relativism.

From the application point of view, graphene is a very attractive electronic material. Since it has only one layer of atoms, its electron density and conductivity are easily controlled by applied voltage. And its crystal lattice is almost perfect, so the electrons move very fast. At present, the triode made of graphene has reached a frequency of one trillion Hz, which is several hundred times higher than the clock frequency of current ordinary computers. This frequency has been connected to the far infrared, eliminating the gap between electronic frequency and optical frequency. Graphene also has unique optical properties that may bring new technology options to displays and solar cells.

We all know "Moore's Law" and predict that the size of semiconductor devices will become smaller and smaller. However, when the device size is as small as several hundred and several tens of atoms, the material is not the original crystal, and its electronic properties are no longer the same. Therefore, people usually predict that Moore's Law will face the end. However, the atomic structure of graphene is very stable, and it remains stable even with only one hexagon. Therefore, graphene has the potential to make true nano-components, even single-electron triodes. Reducing component size means that more components can be fabricated on the same size chip, increasing chip complexity and reducing cost. More importantly, reducing component size also increases speed and power consumption, therefore, graphene is likely to play an important role in future electronic products.

Chemically, ultra-thin graphene has an unrivalled surface area and is therefore highly reactive. It can replace some of the current applications of graphite to provide superior performance. It also hopes to play a role in the future of energy technology as a material for storing hydrogen. The mechanical strength and toughness of graphene are also amazing and much stronger than steel. Therefore, composite materials made with it are also promising.

In addition to the importance of the research work, the 2010 Physics Awards were the first to be awarded to a winner of the “IgNobelPrize”. It turns out that Gamma Laboratories has a tradition of "Friday Evening Project", which is to use one-tenth of the time to do something that is interesting but not necessarily fruitful, or that is not necessarily important. Once he suspended the frog in a strong magnetic field to demonstrate the diamagnetic effect. This fun experiment not only won him the 2000 Nobel Prize, but was also used as a classroom presentation. The work of graphene is not only from the same person, but also from the "Friday Evening Project" research form!

In other words, the invention of graphene is also very accidental. Perhaps because of the whim, they asked a graduate student to try to mechanically separate the single-layer atomic film from the graphite, and the result failed. As it happens, some people in the group know how to clean the graphite surface with tape: the tape can stick a thin layer of material on the graphite. So they thought, if you repeatedly separate this layer of material with tape, can't it get thinner and thinner, and finally get only one layer of atoms? Of course, this is a random operation, and the result must be a pile of fragments of varying thickness, while a single layer of graphene is hidden.

However, the question is: How to find the product of this single layer? At such scales, the only way to measure thickness is atomic force microscopy (AFM). This microscope scans the surface of the sample with a probe with an atomic-scale tip while maintaining a constant small distance from the sample. This movement of the probe depicts the thickness curve of the material. But because of the precision mechanical scanning, this imaging method is slow and has a small field of view. It is incompetent to look for graphene in a "haystack" style. This requires other microscopic techniques to match. First, they use an optical microscope. Very thin graphite fragments are transparent and are not visible under normal conditions. However, when the fragments are placed on a silicon wafer substrate coated with a layer of silicon dioxide, those films affect the interference of light and change the color of the image. So these films can be observed with an optical microscope. Of course, this method can only observe thicker films, very thin, and only one or several layers of atoms are still invisible. This requires another microscope: a scanning electron microscope (SEM). This type of electron microscope can see films of various thicknesses, but cannot accurately measure the thickness of the film. The images of the two microscopes are mutually confirmed. Anything that cannot be seen by the optical microscope and can be seen by the electron microscope is a very thin film. By observing these areas with an atomic force microscope, a single layer of graphene can be found. It can be seen that this search process requires "joint operations" of three microscopes. And this research room has exactly the conditions for this joint operation. Fortunately, it was only afterwards that the silicon substrate they used happened to have a suitable thickness of silicon dioxide. If the thickness changes a little, you won't see those graphite fragments.

But to win the Nobel Prize, luck alone is not enough. Graphene has been made, and it is not easy to attract interest from the scientific community, because this is not a hot topic. Sure enough, their original paper was twice rejected by Nature. But the authors did not give up. In just over a year, they published a series of interesting experimental results that prove that graphene is a very promising field of research. This has attracted thousands of physicists to put down the task at hand to study graphene, which has brought about rapid growth in this field.

We often say that success requires "time, place, and harmony." For the discovery of graphene, "time of day" is very unfavorable. Although people have predicted theoretically the existence and various properties of graphene, no one has successfully made graphene. There are even thermodynamic theory predictions that the two-dimensional crystal structure is unstable. So only a few research groups in the world were paying attention to this topic. If the Gem team applies for funding for graphene research, it will almost certainly be rejected. And their success comes from “the location”: their labs happen to have the equipment and technology to make and test. More importantly, "human harmony": their researchers have an open mind and persistent enthusiasm! This example also proves that good research does not necessarily require large sums of money and a large team. The pattern of “unintentional willows” is not outdated even in the mature physical sciences. In the corporate world, there is an 80-20 R&D model that allows employees to spend 20% of their time on any project of their own interest. The most famous example of success is Google. The “Friday Night” tradition of Gamma Laboratories is similar.

Therefore, the 2010 Nobel Prize in Physics not only recognized a significant scientific research achievement, but also recognized a unique scientific research method. I believe that this award will leave a unique mark on the history of Nobel.

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