Carbon Nanotubes: Properties And Applications - A Brief Review

As per Moore's law, transistor density of an integrated circuit doubles in every two years. In order to meet the density and sustain the IC, scaling of MOSFET transistors is carried out continuously. When the gate length of MOSFET reached nanometre regime, effects of parametric variations and leakage current, have become pronounced and substantially affected the I-V characteristics of MOSFETs. In order to meet the challenges of nanoscale CMOS, research work is being carried on nanodevices, like Carbon Nanotube Field Effect Transistor (CNFET), Resonant Tunneling Diode (RTD), the Single Electron Transistor (SET), and the Spin transistor (SPINFET). MOSFET like CNFETs proved to be the best devices to work with for highperformance VLSI because of its high-speed, lower shortchannel effect, higher sub-threshold slope, and lowpower operation than Si-MOSFET [2-4], [6], [9], [11], [12]. The operation principle and structure of CNFET are almost similar to CMOS, and hence the design infrastructure of this technology can be utilized, together with its fabrication process. The major difference between CNFETs and MOSFETs is that the CNFET channel is formed by CNTs instead of silicon, which facilitates a higher drive current density, due to higher current carrier mobility in CNTs compared to Si-MOSFET. The aim of this paper is to bring into light some basic concepts of this emerging technology like its structure, properties, and applications. In 1993, Ijima of NEC Japan discovered carbon nanotubes, while studying the surface of graphite electrode in an electric arc discharge. They are actually allotrope of carbon possessing unique electrical, mechanical and thermal properties because of which they have wide applications in field-emission displays, nano composite materials, nanosensors, and nanoelectronics [6], [9], [11], [12]. Carbon nanotubes exist in two forms: (i) Single Wall Carbon Nanotube (SWCNT) and (ii) Multiwall Carbon Nanotube (MWCNT). SWCNT shown in Figure 1 are normally capped at the ends and can be visualized as a layer of graphite rolled into a smooth cylinder. SWCNTs are superior than MWCNTs but they are costlier. MWCNT shown in Figure 2 appears like a coaxial assembly of SWCNTs. Diameter of MWCNT ranges from 5-50 nm and the inter layer spacing is 3.4 Å. MWCNTs can be manufactured easily in large quantities. The structure of MWCNT is complex and their unique properties may get