AVS 46th International Symposium
    Topical Conference on Emerging Opportunities and Issues in Nanotubes and Nanoelectronics Thursday Sessions
       Session NT+NS+EM+MS-ThA

Paper NT+NS+EM+MS-ThA7
Gear-like Rolling Motion of Carbon Nanotubes on HOPG

Thursday, October 28, 1999, 4:00 pm, Room 6C

Session: Nanotubes: Functionalization and Metrology
Presenter: M.R. Falvo, University of North Carolina, Chapel Hill
Authors: M.R. Falvo, University of North Carolina, Chapel Hill
J. Steele, University of North Carolina, Chapel Hill
A. Buldum, University of North Carolina, Chapel Hill
D. Schall, North Carolina State University
R.M. Taylor II, University of North Carolina, Chapel Hill
D.W. Brenner, North Carolina State University
J. Lu, University of North Carolina, Chapel Hill
R. Superfine, University of North Carolina, Chapel Hill
Correspondent: Click to Email
Though much work has been done in recent years in exploring nanometer and atomic scale sliding friction, little experimental or theoretical work has been done on rolling and its relation to sliding at this scale. We will present lateral force microscope investigations of frictional phenomena of multiwall carbon nanotubes (MWCNTs) on highly oriented pyrolytic graphite (HOPG), that include all the rigid body motions: sliding, rotating in-plane, and rolling. Using an advanced manipulation interface for AFMs, the nanoManipulator, we study these friction phenomena through sophisticated manipulation experiments where lateral forces are monitored during manipulations. We have manipulated MWCNTs into a state of atomic registry between the lattice of the tube and underlying substrate. Out of atomic registry the friction is smooth and uniform. As the CNT is rotated in the plane of the substrate, three discrete atomically registered orientations are observed marked by a 3-10 fold increase in the lateral force required to remove them from these orientations. Results of molecular statics calculations for this system show that the potential energy as a function of in-plane rotation angle has three deep minima spaced sixty degrees apart corresponding to atomic lattice registry. When the CNT locks into atomic registry, there is a transition from an in-plane rotational motion to a stick-slip rolling motion. Rather than being perfectly cylindrical, our lateral force data during rolling indicate that the CNT may be faceted (polygonal cross section). MS calculations indicate that faceting is to be expected for MWCNT depending on diameter and wall thickness. The calculated friction expected for rolling a faceted MWCNT agrees well with experimental lateral force data. Molecular dynamics calculations will be shown that lend insight into the energy loss mechanisms for both the sliding and rolling case. This work is supported by the NIH (NCRR), NSF, ONR (MURI), and ARO (DURIP).