Duncan, David A. (2012) Adsorbate structure determination using energy scanned photoelectron diffraction. PhD thesis, University of Warwick.

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Abstract

Energy-scanned photoelectron diffraction was used to determine the local adsorption
site of several molecular species on well defined single crystal surfaces.
Cytosine and uracil on Cu(110) were found to adsorb with their molecular
planes perpendicular to the surface and mostly aligned along the close packed [110]
direction. Both molecules were found to adsorb through their constituent oxygen
atom(s) and a deprotonated nitrogen atom. The associated Cu-O and Cu-N bond
lengths were found to be 1.94 (+0.06/-0.04)Å and 1.94 (+0.07 / -0.03) Å, respectively,
for cytosine and 1.96 ± 0.04 / 1.93 ± 0.04 Å and 1.96 ± 0.04 Å, respectively, for
uracil.
The mono- and bi- tartrate phases of tartaric acid on Cu(110) were found to
adsorb via deprotonated carboxylic acid groups with the oxygen atoms in different
near-atop sites. The associated Cu-O bond lengths were found to be 1.92 ± 0.08 Å
/ 1.93 ± 0.06 Å and 1.93 – 1.97 ± 0.06 – 0.09 Å respectively.
Glycine on Cu(111) was found to adsorb via both its nitrogen and oxygen
constituent atoms, though three competing models were found for the local adsorption
site of the oxygen atoms. The nitrogen atom was found to adsorb in a near-atop site
with an associated Cu-N bond length of 2.02 ± 0.03 Å. The oxygen adsorption site
was found to at least have some near-atop characteristics, with the near-atop site
having an associated Cu-O bond length of 2.00 – 2.02 ± 0.04 – 0.07 Å.
Reanalysis of the C 1s PhD data of the hydrocarbon remnant from the decomposition
of furan on Pd(111) found that the lowest energy model predicted by DFT
does not occur, at least in large quantities, on the surface. The most likely structure
was found to be CH–C–CH2.
On the Ru(0001) surface, dehydrogenation of methanol was not observed in
the temperature range around 150 K, with no evidence for the strong modulations in
the O 1s PhD spectra predicted for a methoxy species.
A reexamination of water adsorption of the rutile TiO2(110) surface found that
water does, at least partially, dissociate on the perfect surface as well as at defect
sites – in contrast to previously published experimental results. The associated Ti-O
bond lengths for the resulting atop and bridging hydroxyl species were found to be
1.85 ± 0.08 Å and 1.94 ±0.07 Å respectively.
Finally vanadyl phthalocyanine was found to adsorb upright (with the oxygen
atom further from the surface than the vanadium atom) on the Au(111) surface. The
V=O bond length was found to be 1.60 ± 0.04 Å.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics
Library of Congress Subject Headings (LCSH):	Crystals -- Surfaces, Crystals -- Absorption and adsorption
Official Date:	March 2012
Dates:	Date Event March 2012 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Woodruff, D. P.
Extent:	xv, 164 leaves : ill., charts
Language:	eng

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