IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Nanotubes: Science and Applications Topical Conference Wednesday Sessions
       Session NT-WeM

Paper NT-WeM7
Development of N-type Carbon Nanotube Transistors and Fabrication of the First Nanotube Logic Circuits

Wednesday, October 31, 2001, 10:20 am, Room 133

Session: Nanotubes: Nanoelectronics
Presenter: V. Derycke, IBM T.J. Watson Research Center
Authors: V. Derycke, IBM T.J. Watson Research Center
R. Martel, IBM T.J. Watson Research Center
Ph. Avouris, IBM T.J. Watson Research Center
Correspondent: Click to Email
Single carbon nanotubes can be used as the active channel in field effect transistors (FETs).@footnote 1,2@ Without any special treatment, the obtained FETs are always P-type: the current carriers are holes and the devices are off for positive gate bias. Here we show that this transistor behavior is due to a strong pinning of the Fermi level at the valence band of the semiconducting nanotubes and the presence of a large Schottky barrier for electron injection into the device. The fabrication of N-type FETs has recently been achieved by doping the device with an electron donor such as potassium.@footnote 3@ We introduce a novel approach of converting SWNT-based P-FETs into N-FETs without the use of dopands. The technique relies on the control of the electrostatic barriers and the modification of the contacts. By a specific treatment of the device we can position the Fermi level at any position within the band gap in a controlled manner and therefore modify the character of the device. For intermediate modification, the Fermi level lies in the middle of the band gap and the device shows both hole and electron conduction at negative and positive gate biases respectively. In completely converted devices, the Fermi level is pinned at the conduction band edge and the resulting FET is fully N-type. Using our ability to prepare both P- and N-type transistors we were able to fabricate the first nanotube-based integrated logic circuit, a "NOT" gate (voltage inverter). Inverters using K-doped tubes were also fabricated. We will compare the voltage inverters made by the two techniques. @FootnoteText@ @footnote 1@ S. J. Tans, A. R. M. Verschueren, and C. Dekker, Nature (London) 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@ M. Bockrath, J. Hone, A. Zettl, P.L. McEuen, A.G. Rinzler and Richard E. Smalley, Phys. Rev. B 61, R10606 (2000).