AVS 53rd International Symposium
    Surface Science Thursday Sessions
       Session SS-ThP

Paper SS-ThP15
Tuning the Exchange Reaction between a Self-Assembled Monolayer and Other Molecules by Electron Irradiation

Thursday, November 16, 2006, 5:30 pm, Room 3rd Floor Lobby

Session: Surface Science Poster Session
Presenter: N. Ballav, Universität Heidelberg, Germany
Authors: N. Ballav, Universität Heidelberg, Germany
A. Shaporenko, Universität Heidelberg, Germany
M. Zharnikov, Universität Heidelberg, Germany
Correspondent: Click to Email
The molecules comprising a self-assembled monolayer (SAM) may exchange gradually when exposed to solutions containing other molecules, which are capable to build a SAM on the given substrate. This replacement offers a route to generate a new organic surface on a substrate already supporting a SAM. The rate and extent of replacement depend on a number of parameters, including the identity of the molecular chain, chain length, degree of order, and topography/roughness of the substrate. Taking SAMs of non-substituted and @omega@-substituted alkanethiolates (AT) as test systems, we studied the effect of an additional factor - electron or X-ray irradiation. We show that, in view of the exchange process, such a treatment is especially effective at a relatively low irradiation dosage, below 1 mC/cm@super 2@. Staying under this limit and varying the dosage, we were able to change the rate and extent of the exchange reaction continuously and to a noticeable extent. In particular, in the case of a non-substituted AT SAM and -OH and -COOH substituted alkanethiols in the solution, the rate of the exchange reaction could be increased by an order of the magnitude, and about 60-70% of the primary SAM molecules could be substituted after a preliminary irradiation (it was less than 10% without the irradiation). The suggested combination of e-beam patterning and substitution reaction can be used for the fabrication of molecular gradients of any particular form with the resolution down to several nanometers.