This Electronics Seminar Topic deals with the followingIntroduction
The remarkable properties of carbon nanotubes may allow them to play a crucial role in the relentless drive towards miniaturization at the nanometre scale.
Nanotechnology is predicted to spark a series of industrial revolutions in the next two decades that will transform our lives to a far greater extent than silicon microelectronics did in the 20th century. Carbon nanotubes could play a pivotal role in this upcoming revolution if their remarkable electrical and mechanical properties can be exploited.
Since the first measurements were made in 1997, these rolled up sheets of graphite have captured the imagination of researchers around the world. Progress in understanding the basic physics and chemistry of nanotubes has advanced at a phenomenal rate – and shows no signs of slowing.
Carbon nanotubes can be considered as a single sheet of graphite rolled in the form of a tube, though it is not actually made by rolling one. They were first observed by a Japanese scientist Sumio Iijima in the early part of the 1990’s. The tubes that consist of a single layer of graphite is termed as ‘Single walled nanotubes’ and the ‘Multi-walled tubes are those consisting of more than a single layer in the form of concentric cylinders.
Both these types have their respective fields of applications in the industry and the scientific scenario. Nanotubes have an impressive list of attributes. They can behave like metals or semiconductors, can conduct electricity better than copper, can transmit heat better than diamond, and they rank among the strongest materials known – not bad for structures that are just a few nanometres across. Several decades from now we may see integrated circuits with components and wires made from nanotubes, and maybe even buildings that can snap back into shape after an earthquake.
Electronic Structure of nanotubes.
The remarkable electrical properties of single wall carbon nanotubes stem from the unusual electronic structure of “graphene”- the 2-D material from which they are made. (Graphene is simply a single atomic layer of graphite.). The band structure of graphene is not same as that of a metal or a semiconductor. Instead it is in between these two extremes. In most directions, electrons moving at the Fermi energy are backscattered by atoms in the lattice whereas in some others they don’t. Graphene therefore can be considered as a semi-metal, since it is metallic in these special directions and semi-conducting in the others. Thus a nanotube can be either a metal or a semiconductor, depending on how the tube is rolled up.
Whereas the multiwall nanotubes were tens of nanometres across, the typical diameter of a single-wall nanotube was just one or two nanometres. The past decade has seen an explosion of research into both types of nanotube. The multi walled carbon nanotubes should behave slightly different to their single walled relatives due to the interaction of the adjacent layers. Though various theories can be incorporated, many of them may not hold true for such microscopic materials.
Nanotubes as one dimensional metals
Solid –state devices in which electrons are confined to two-dimensional planes have provided some of the exciting scientific and technological breakthroughs of the past many decades. However, 1-D systems are also proving to be very exciting. Studies of quasi 1-D systems, such as conducting polymers , study of ballistic systems, electron waveguides and many other fields that may transform the face of electronics fall into this category. The 1-d systems on which these phenomena can be studied have been limited by the fact that they are inherently complex to make. What has been lacking is the perfect model system for exploring one dimensional transport – a 1-d conductor that is cheap and easy to make. , can be individually manipulated and measured, and has little structural disorder. Single walled carbon nanotubes fit this bill remarkably well.
Nanotubes are ideal systems for studying the transport of electrons in one dimension, and have commercial potential as nanoscale wires, transistors and sensors. For many years, studies of quasi-one-dimensional systems, such as conducting polymers, have provided a fascinating insight into the nature of electronic instabilities in one dimension. In addition, 1-D devices such as “electron waveguides” – in which electrons propagate through a narrow channel of material – have been created. Experiments on these devices have shown, for example, that the conductance of “ballistic” 1-D systems – in which electrons travel the length of the channel without being scattered – is quantized in units of the charge on the electron squared divided by the Planck constant.
Click Here To Download Full Seminar
Related Posts:
Tags: Electronic Applications of carbon Nano Tubes, Electronics Seminar Topics, engineering topics, Latest Seminar topics, Seminar topics
good topics send more figures and ppt.
