AVS 50th International Symposium
    Processing at the Nanoscale Thursday Sessions
       Session PN-ThA

Paper PN-ThA9
Nanoscale Fabrication and Characterization of Chemically Modified Silicon Surfaces Using Conductive Atomic Force Microscopy in Liquids

Thursday, November 6, 2003, 4:40 pm, Room 317

Session: Molecular Monolayers
Presenter: C.R. Kinser, Northwestern University
Authors: C.R. Kinser, Northwestern University
D.E. Kramer, Northwestern University
M.W. Such, Northwestern University
P. Bertin, Northwestern University
H. Jin, Northwestern University
S.T. Nguyen, Northwestern University
M.J. Bedyzk, Northwestern University
M.C. Hersam, Northwestern University
Correspondent: Click to Email
Self-assembled monolayers of terminal alkenes on hydrogen passivated silicon provide an attractive route for covalent organic functionalization of silicon surfaces. This talk addresses two important experimental issues that improve the applicability of these surfaces for potential device applications: (1) Means of verifying the conformation of terminal reactive groups; (2) Strategies for patterning these monolayers down to the nanometer length scale. The first issue is addressed using X-ray reflectivity and X-ray standing wave techniques at the monolayer level. X-ray characterization of a bromine tagged analog of ethyl-undecylenate on Si(111) show that the monolayer coverage is 0.59 and the bromine lies 14.6 Å above the silicon surface. This data illustrates that the molecule is reacted to the surface via the terminal alkene, thus presenting the bromine functionality for post-chemistry. In this manner, the effectiveness of subsequent chemical reactions on functionalized silicon surfaces can be efficiently forecasted. The remainder of the talk describes a novel strategy for nanopatterning monolayers on hydrogen passivated silicon directly from the liquid phase. In Liquid Phase Nanolithography, hydrogen desorption is induced by applying a bias across a conductive atomic force microscope tip-sample junction submerged in an organic solvent. Appropriately chosen molecules suspended in the solvent directly chemisorb on the depassivated lines. We will present results for patterning neat undecylenic acid methyl ester on H:Si(111) with 50 nm spatial resolution using this technique and suggest approaches for utilizing this scheme to fabricate biomedical nanosensors.