T. Bitzer et al., Sodium-induced ordering of the benzoate species on Si(100)-2 x 1: a combined HREELS, XPS and NEXAFS study, SURF SCI, 458(1-3), 2000, pp. 173-184
The structure of benzoate on Na/Si(100)-2 x 1 has been studied by high reso
lution electron energy loss spectroscopy, X-ray photoelectron spectroscopy
and near edge X-ray adsorption fine structure spectroscopy. At room tempera
ture, benzoic acid (C6H5-COOH) chemisorbs on Na/Si(100)-2 x 1 through a cle
avage of the OH bond in the carboxylic group. The benzoate molecules formed
are bonded exclusively to the sodium atoms in a bidentate coordination, in
which the oxygen atoms are equivalent. At room temperature, benzoate satur
ation on Na/Si(100)-2 x 1 is reached at a coverage of one benzoate species
for each Na atom or silicon dimer. At this coverage, the molecules are tilt
ed in polar direction by 62 degrees+/-4 degrees to the surface plane and az
imuthally rotated by 41 degrees+/-4 degrees with respect to the [01 (1) und
er bar] surface azimuth. We propose an adsorbate structure, in which the be
nzoate molecules are oriented parallel to each other in densely packed rows
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