Electronic Transport in Semi-conducting Carbon Nanotube Transistor Devices
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Recent demonstrations of high performance carbon nanotube field-effect transistors (CNFETs) highlight their potential for a future nanotube-based electronics. Besides being just a nanometer in diameter, carbon nanotubes offer intrinsic advantages if compared with silicon that are responsible for their outstanding properties. Their one-dimensional character is advantageous for a low scattering probability and consequently a high on-current in a transistor device. Electrons and holes behave similarly in CNs, enabling a complementary metal-oxide semiconductor (CMOS) like technology with n-type and p-type transistors. Since chemical bonds in case of carbon nanotubes are completely satisfied, problems with dangling bonds, as at any silicon surface, do not exist. This implies that carbon nanotubes can be more easily combined with various gate dielectrics, e.g. high-k dielectrics for an improved gate control. And last, the fact that metallic as well as semiconducting carbon nanotubes can be fabricated may lead to an all nanotube-based electronics with metallic tubes acting as interconnects and semiconducting tubes being used as active device regions.
All of the above aspects of nanotubes have been experimentally verified. Investigating the physics of scaled CNFETs however revealed also a number of other - rather unexpected - properties of nanotube-based devices. The most important and far-reaching observation recently made is that CNFETs are indeed Schottky barrier devices. This has important implications for their scaling behavior as well as their performance limits. In my presentation I will focus in particular on this aspect of carbon nanotube transistors and discuss a number of our most recent experimental data and simulations.
J. Appenzeller received the M.S. and Ph.D. degrees in physics from the Technical University of Aachen, Germany in 1991 and 1995. His Ph.D. dissertation investigated quantum transport phenomena in low dimensional systems based on III/V heterostructures. He worked for one year as a Research Scientist in the Research Center in Juelich, Germany before he became an Assistant Professor with the Technical University of Aachen in 1996. During his professorship he explored mesoscopic electron transport in different materials including carbon nanotubes and superconductor/semiconductor-hybride devices. From 1998 to 1999, he was with the Massachusetts Institute of Technology, Cambridge, as a Visiting Scientists, exploring the ultimate scaling limits of silicon MOSFET devices. Since 2001, he has been with the IBM T.J. Watson Research Center, Yorktown, NY, as a Research Staff Member mainly involved in the investigation of the potential of carbon nanotubes for a future nanoelectronics.
Researchers should cite this work as follows:
POTR 234, Purdue University, West Lafayette, IN