AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS3-TuA

Paper SS3-TuA7
Investigation of the Adsorption of Acetic Acid on Ge(100)-2x1

Tuesday, November 4, 2003, 4:00 pm, Room 328

Session: Organic Functionalization of Semiconductor Surfaces
Presenter: J.A. Van Deventer, Stanford University
Authors: J.A. Van Deventer, Stanford University
M.A. Filler, Stanford University
S.F. Bent, Stanford University
Correspondent: Click to Email
The modification of group-IV semiconductor surfaces has been an active area of research over the past several years because a greater understanding of semiconductor surface reactivity may lead to applications in nanopatterning, biological recognition, and molecular electronics. In the present work, we investigate the reaction of acetic acid and related isotopes on Ge(100)-2x1 at 300K using infrared spectroscopy and density functional theory. This reactive system is noteworthy because it combines the carbonyl and alcohol functional groups studied in previous investigations into one bifunctional molecule, allowing competition and selectivity to be studied in detail. IR spectroscopy following chemisorption of acetic acid shows a strong absorption at 1664 cm@super -1@ in the @nu@(C=O) region and two large peaks at 1962 and 1925 cm@super -1@ in the @nu@(Ge-H) region. We attribute these features to intradimer and interdimer O-H dissociation products. DFT calculations suggest that these O-H dissociation products are likely to occur through one of two oxygen dative-bonded states. Interestingly, the more stable dative-bonded precursor state is the result of a stabilized ring formed by electron donation from the nucleophilic dimer atom to the nearby hydroxyl hydrogen atom of the adsorbed molecule. The kinetic barrier to reaction of this pathway is calculated to be 3.09 kcal/mol above the dative-bonded state, leading to a final product that lies 39.52 kcal/mol below the vacuum level. The O-H dissociation product is both kinetically and thermodynamically favorable compared to the other pathways, such as @alpha@-CH dissociation and [2+2] C=O, available to the molecule.