Friday, December 19, 2008

Klitzing's Vision of Carbon as the Material of the Future

Nature chose carbon as the material sustaining the life-blood in the earth. Scientists also envision carbon as the material for the future technologies. Klitzing in his talk on June 30, 2008 elucidated these points by highlighting the potentials of carbon based electronics. Diamond, carbon nanotube (CNT) and graphene all are made of same carbon atoms, their properties vary enormously. In the first part, he explained different types of carbon nanotube field effect transistors (CNTFET), such as vertical CNTFET, high aspect ratio nanostick networks etc as well as growth techniques of CNT. However, the preparation of graphene samples happened to be the most interesting information to me. Graphene are one atomic thick layer of carbons and there is still to be an ecient method for synthesizing graphenes. Klitzing explained the scotch tape method of graphene separation, which nothing else but just the separation of a graphene layer from a sample of graphite flake by attaching flake to a scotch-tape. Apart from the interest in graphene from the point of view of technology, graphenes are wonderful one dimensional system to observe different relativistic phenomena such as mass less Dirac Fermions.

The evening discussion session with Klitzing was a very interesting one. As I asked him about his projections on silicon being replaced by carbon nanotubes as the functional material for electronics, Klitzing became skeptical about the prospects of CNT for electronics. CNT devices has to be of orders of magnitude better performance than silicon for that. But there might be few off-stream applications for CNT, for example, as VLSI interconnects. He also shared the events that ensued after his discovery of quantum Hall effect. As he submitted a paper reporting his discovery of this effect to a journal, it got rejected. Afterwards, he happened to meet the editor of this journal in a conference and explained him in details all the discoveries. The editor was convinced and his paper got accepted. Such a great discovery was largely unanticipated in solid state physics in the 1970s . His discovery led to a fundamental connection between electrical resistance and the fundamental constants and is used worldwide for accurate calibration of resistances. It also led to a new determination of the fine structure constant. The 'von Klitzing constant', RK = 25812.807 ohm is named after him. Did he guess that he is going to get Nobel Prize? He indeed did. After this discovery, he was invited to give talks all over the world. And he joked saying that, the Nobel committee spent more money to investigate the impact of this discovery than the prize money.

He explained the role of fundamental physical constants as the basis for defining measurement units independently from space and time. Based on the physical constant, such as, h or G, the fundamental units of measurement are going to be redefined in 2011. His discovery is going to play a pivotal role in redefining the measurement units. He elucidated the relation between the measurement of mass and h. His suggestions for prospective researchers was like this, 'try to find the bumps on the curves.' A good researcher has a good feeling about which effects are vital for understanding the bumps on the curves and which ones to ignore. Being a pure experimentalist, he reiterated the necessity to be in contact with solid state theoreticians and vice versa too. Designs experiments cleverly is an important trait of a good experimentalist, he said. But being at the right place at the right time is the essential ingredient for ground breaking discoveries and inventions. He concluded by saying that in the 1970s the stage was set for his discovery; if he had not discovered quantum Hall effect, someone else would surely had done it soon.

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