A study of TiO2(110) and the effects of potassium and palladium deposition
A study of TiO2(110) and the effects of potassium and palladium deposition
A TiO2(110) crystal was characterised using LEED, surface resistance measurements and ellipsometry. The facile loss of oxygen atoms from the surface were evident frem the LEED, showing a reconstructed surface. Upon mild heating, oxygen loss led to a crystallographic shear plane forming. The altered environment of the titanium atoms led to an empty electronic level within the band gap which was optically probed by ellipsometry. The deposition of potassium on TiO2(110) showed the formation of a c(2x2) overlayer. Large perturbations in Delta and PROB*LEM were observed in the monolayer and are interpreted as charge transfer from the potassim atoms to the TiO2 surface. The optical excitation across the band gap is altered by filling of the conduction band states by the charge transfer from potassium. As the film thickness increased the change of the surface roughness was monitored via a change in the plasmon and surface plasmon peak magnitudes. Palladium was found to grow epitaxially in a layer by layer (FM) growth mode at 300K. The cause of this epitaxial relationship is though to be the corrugation of the (110) plane, orientating one of the three high symmetry directions of the Pd(111) film along the substrate < 110> direction. Unlike the case of potassium, ellipsometry and AES showed no interaction between the palladium atoms and TiO2. CO was found to adsorb on Pd(110) in a PROB*LEM structure as found for CO on Pd(111). Heating both palladium and potassim films on TiO2 caused the atoms to agglomerate into islands. In the case of palladium the minimum size of these islands was 100nm, as determined by electron microscopy.
University of Southampton
1991
Nicholson, Graeme Peter
(1991)
A study of TiO2(110) and the effects of potassium and palladium deposition.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
A TiO2(110) crystal was characterised using LEED, surface resistance measurements and ellipsometry. The facile loss of oxygen atoms from the surface were evident frem the LEED, showing a reconstructed surface. Upon mild heating, oxygen loss led to a crystallographic shear plane forming. The altered environment of the titanium atoms led to an empty electronic level within the band gap which was optically probed by ellipsometry. The deposition of potassium on TiO2(110) showed the formation of a c(2x2) overlayer. Large perturbations in Delta and PROB*LEM were observed in the monolayer and are interpreted as charge transfer from the potassim atoms to the TiO2 surface. The optical excitation across the band gap is altered by filling of the conduction band states by the charge transfer from potassium. As the film thickness increased the change of the surface roughness was monitored via a change in the plasmon and surface plasmon peak magnitudes. Palladium was found to grow epitaxially in a layer by layer (FM) growth mode at 300K. The cause of this epitaxial relationship is though to be the corrugation of the (110) plane, orientating one of the three high symmetry directions of the Pd(111) film along the substrate < 110> direction. Unlike the case of potassium, ellipsometry and AES showed no interaction between the palladium atoms and TiO2. CO was found to adsorb on Pd(110) in a PROB*LEM structure as found for CO on Pd(111). Heating both palladium and potassim films on TiO2 caused the atoms to agglomerate into islands. In the case of palladium the minimum size of these islands was 100nm, as determined by electron microscopy.
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Published date: 1991
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Local EPrints ID: 460586
URI: http://eprints.soton.ac.uk/id/eprint/460586
PURE UUID: d3c51979-23c2-49e4-91bc-9e0e928545f0
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Date deposited: 04 Jul 2022 18:24
Last modified: 04 Jul 2022 18:24
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Author:
Graeme Peter Nicholson
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