AVS 49th International Symposium
    Nanotubes: Science and Applications Topical Conference Tuesday Sessions
       Session NT-TuP

Paper NT-TuP4
Experimental and Theoretical Studies on the Gas Adsorption of Multi Walled Carbon Nanotubes Thin Films

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Poster Session
Presenter: S. Picozzi, INFM, Univ. L'Aquila, Italy
Authors: S. Picozzi, INFM, Univ. L'Aquila, Italy
L. Lozzi, INFM, Univ. L'Aquila, Italy
S. Santucci, INFM, Univ. L'Aquila, Italy
L. Valentini, Univ. Perugia, Italy
I. Armentano, Univ. Perugia, Italy
J.M. Kenny, Univ. Perugia, Italy
A. Pecchia, Univ. Tor Vergata, Italy
A. Di Carlo, Univ. Tor Vergata, Italy
P. Lugli, Univ. Tor Vergata, Italy
B. Delley, Paul Scherrer Institut, Switzerland
Correspondent: Click to Email
The special geometry and unique properties of carbon nanotubes (CNT) offer relevant potential applications.@footnote 1@ In particular, the effects of environment gases (such as O2, NO2, NH3) on the electronic and transport properties of carbon nanotubes have recently attracted great interests.@footnote 2,3@ To date, the reported theoretical gas sensing studies have been based either on isolated single wall carbon nanotubes (SWNTs) or on SWNT mats. In the present work multi-wall carbon nanotubes (MWNTs) deposited by plasma enhanced chemical vapor deposition have been investigated as resistive gas sensors towards NO2. Experimental findings revealed the chemisorption of oxidizer gas upon the surface of the MWNTs, suggesting that p-type semiconductor behavior is present. The possibility of modulating the electronic properties of nanotubes using adsorption of gas molecules is investigated using first-principles density functional calculations. Transport characteristics are calculated using non-equilibrium Green's functions. The simulations account for the reaction dynamics between the CNT and the adsorbing gas,thus allowing the determination of the preferred adsorption site as well as the calculation of the current flowing along the nanotube as a function of time. The charge transport is dominated by the hopping mechanism across a bundle of several nanotubes. For this reason the influence that the adsorbed molecules have on the hopping rate between adjacent nanotubes has been also investigated. The results elucidate the mechanisms of adsorption and doping of CNTs and its influence on their conduction properties. @FootnoteText@ @footnote 1@ M.S.Dresselhaus, G. Dresselhaus and P.C.Eklund, "Science of Fullerenes and Carbon Nanotubes" (Academic, New York, 1996). @footnote 2@ J. Kong, N.R. Franklin, C. Zhou, M.G.Chapline, S. Peng, K. Cho and H. Dai, Science 287, 622 (2000).@footnote 3@ P.G. Collins, K. Bradley, M. Ishigami and A. Zettl, Science 287, 1801 (2000).