AVS 49th International Symposium
    Nanometer Structures Wednesday Sessions
       Session NS+EL-WeA

Paper NS+EL-WeA5
Photoinduced Anisotropy of Second-Harmonic Generation from Azobenzene-Modified Alkylsiloxane Monolayers

Wednesday, November 6, 2002, 3:20 pm, Room C-207

Session: Nanolithography & Self Assembly
Presenter: T.E. Furtak, Colorado School of Mines
Authors: Y.W. Yi, Colorado School of Mines
T.E. Furtak, Colorado School of Mines
M.J. Farrow, University of Colorado
D.M. Walba, University of Colorado
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Non-contact alignment of substrates in liquid crystal displays offers the advantage of reduced contamination and minimal surface charging. This approach also provides a means of reversible alignment after a device has been assembled. With this objective we have synthesized self-assembled monolayers based on dimethylaminoazobenzene units covalently attached to a glass surface by means of a short alkylsiloxane anchor (azo-SAM). The resulting architecture favors an orientation in which the axis of the azobenzene group should be nearly parallel to the surface with an isotropic azimuthal distribution. Under illumination with polarized UV light the trans-cis isomerization and subsequent relaxation serves to wiggle the molecule into an orientation perpendicular to the UV optical field. We have tested this scenario using optical second harmonic generation. We are able to identify a surface order parameter that characterizes the photoalignment of the azobenzene group. These data correlate with the recently reported behavior of nematic liquid crystal cells containing one substrate treated with the same azo-SAM.@footnote 1@ This work is supported by NSF MRSEC grant DMR-9809555. @FootnoteText@ @footnote 1@"Liquid Crystal Alignment by Photo-Buffing Azo-SAMs", G. Fang, N. A. Clark, J. E. Mcclennan, M. Farrow, D. Walba, March Meeting of the American Physical Society, Indianapolis (3/20/20002).