AVS 52nd International Symposium
    Surface Science Thursday Sessions
       Session SS2-ThM

Paper SS2-ThM4
Layer-by-Layer Growth on Ge(100) via Spontaneous Chemical Reaction

Thursday, November 3, 2005, 9:20 am, Room 202

Session: Functionalization of Semiconductor Surfaces
Presenter: A. Kim, Korea Advanced Institute of Science and Technology (KAIST), Korea
Authors: A. Kim, Korea Advanced Institute of Science and Technology (KAIST), Korea
M.A. Filler, Stanford University
S.F. Bent, Stanford University
S. Kim, KAIST, Korea
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We have demonstrated the layer-by-layer growth, via a urea coupling reaction between two bifunctional molecules, ethylene diamine and 1,4-phenylene diisocyanate, to form an ultrathin film on Ge(100)-2´1 at room temperature under vacuum conditions.@footnote 1@ The initial adsorption and subsequent growth of each layer was studied with multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy.  Ethylene diamine reacts with Ge(100)-2x1 to produce a surface-bound amine group which is available for additional reaction. Subsequent exposure of 1,4 phenylene diisocyanate leads to a spontaneous urea coupling reaction between the surface-bound amine and highly reactive isocyanate functional group. Three bands at 1665, 1512, and 1306 cm-1 are characteristic of a urea linkage and provide evidence of the coupling reaction.  The coupling procedure can be repeated in a binary fashion to create covalently bound ultrathin films at room temperature and, in the present work, we demonstrate the successful growth of four layers.  In addition, we have found that an initial exposure of 1,4-phenylene diisocyanate to Ge(100)-2x1 produces an isocyanate-functionalized surface which, upon exposure to ethylene diamine, also forms urea linkages.  This layer-by-layer deposition method provides a strategy with which to design and produce precisely tailored organic materials. @FootnoteText@ @footnote 1@ Kim, A.; Filler, M. A.; Kim, S.; Bent, S. F.; J. AM. CHEM. SOC. 2005, 127, 6123-6132