Over the last few years carbon nanotubes (CNs) have attracted an increasing interest as building blocks for electronics applications. While metallic nanotubes are considered as interconnects in integrated circuits, semiconducting tubes are evaluated as field-effect transistor (FET) components. Since the first CNFET operation has been demonstrated in 1998,@footnote 1,2@ device performance has been significantly improved.@footnote 3,4,5@ Among other things it has been shown that CNFETs operate in the ballistic regime even at room-temperature, provided that not too large drain and gate voltages are applied and that their channel length does not exceed a couple of hundred nanometers.@footnote 6,7,8@ One of the more unexpected findings in the context of CNFETs was that they cannot be described within a conventional MOSFET model. The most critical observation has been that carbon nanotube transistors in fact behave as Schottky barrier devices.@footnote 9,10@ It was found that switching in nanometer size semiconductors, such as carbon nanotubes, contacted with source/drain metal electrodes is determined entirely by the metal/semiconductor interfaces and their field-dependence, provided that transport in the semiconductor is ballistic. Making use of this particular type of nanotube property, we have been able to gain important insights into the topic of multi-mode transport in CNFETs@footnote 11@ and, most importantly, have recently successfully fabricated the first band-to-band tunneling CNFET with a much more abrupt switching behavior than can be obtained with any conventional transistor approach.@footnote 12@
@FootnoteText@
@footnote 1@ S.J. Tans A. Verschueren, and C. Dekker, Nature 393, 49 (1998). @footnote 2@ R. Martel T. Schmidt, H.R. Shea, T. Hertel, and Ph. Avouris, Appl. Phys. Lett. 73, 2447 (1998).@footnote 3@ A. Bachtold, P. Hadley, T. Nakanishi, and C. Dekker, Science 294, 1317 (2001).@footnote 4@ A. Javey, H. Kim, M. Brink, Q. Wang, A. Ural, J. Guo, P. McIntyre, P. McEuen, M. Lundstrom, and H. Dai, Nature Materials 1, 241 (2002).@footnote 5@ S. Wind, J. Appenzeller, R. Martel, V. Derycke, and Ph. Avouris, Appl. Phys. Lett. 80, 3817 (2002).@footnote 6@ M. Fuhrer, H. Park, and P.L. McEuen, IEEE Trans. on Nanotech. 1, 78 (2002).@footnote 7@ A. Javey, J. Guo, Q. Wang, M. Lundstrom, and H. Dai, Nature 424, 654 (2003).@footnote 8@ S. Wind, J. Appenzeller, Ph. Avouris, Phys. Rev. Lett. 91, 058301 (2003).@footnote 9@ S. Heinze, J. Tersoff, R. Martel, V. Derycke, J. Appenzeller, and Ph. Avouris, Phys. Rev. Lett. 89, 106801 (2002).@footnote 10@ J. Appenzeller, J. Knoch, V. Derycke, R. Martel, S. Wind, and Ph. Avouris, Phys. Rev. Lett. 89, 126801 (2002).@footnote 11@ J. Appenzeller, J. Knoch, M. Radosavljevic, and Ph. Avouris, Phys. Rev. Lett. 92, 226802 (2004).@footnote 12@ J. Appenzeller, Y.-M. Lin, J. Knoch, and Ph. Avouris, Phys. Rev. Lett. 93, 196805 (2004).