AVS 52nd International Symposium
    Nanometer-Scale Science and Technology Wednesday Sessions
       Session NS-WeA

Paper NS-WeA7
Chemically Engineering the Motion of Individual Molecules on the Si(100)-2x1 Surface: a Scanning Tunneling Microscopy Study

Wednesday, November 2, 2005, 4:00 pm, Room 210

Session: Nanopatterning and Manipulation
Presenter: R. Basu, Northwestern University
Authors: R. Basu, Northwestern University
J.D. Tovar, Northwestern University
M.C. Hersam, Northwestern University
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Room temperature ultra-high vacuum (UHV) scanning tunneling microscopy (STM) is used to study a unique bond-breaking mediated motion of individual organic molecules on the clean Si(100)-2x1 surface. Specifically 4-methoxystyrene molecules are observed to undergo switching between two cycloaddition conformations mediated by pivotal motion about one Si-C bond. Styrene molecules, on the other hand, do not undergo such lateral translations, thus suggesting that the rotational degree of freedom of the methoxy group is responsible for the apparent motion of 4-methoxystyrene. To test this hypothesis, the rotational degree of freedom of the methoxy group was suppressed by synthesizing an analog molecule (5-vinyl-2,3-dihydrobenzofuran) where the methoxy group is covalently linked back to the aromatic ring. UHV STM imaging of 5-vinyl-2,3-dihydrobenzofuran on clean Si(100)-2x1 indeed confirms the suppression of molecular motion. This study suggests that the motion of organosilicon adsorbates can be controlled by chemically engineering their intramolecular degrees of freedom.