Onuferko, Julia H. (1978) LEED studies of some adsorption systems on the (100) and (110) surfaces of nickel. PhD thesis, University of Warwick.

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Abstract

A LEED study of the Ni(100) and Ni(110) surfaces has been performed using analysis of intensity-energy ( I-V ) spectra.

Spectra have been obtained for the clean surfaces and compare favourably with previously available data. Extensive data have been obtained for the Ni(110)(1x2)H and Ni(100)(2x2)C-p4g systems.

Qualitative adsorption studies were undertaken to investigate adsorption conditions and electron beam effects in relation to acquiring reliable I-V spectra. These include the adsorption of hydrogen and ethylene on both surfaces.

Ni(110)(1x2)H spectra compare well with previous work. A model involving pairwise distortion of the top layer of nickel atoms gives reasonable agreement between this experiment and theoretical calculations of other workers.

Symmetry requirements for the Ni(100)(2x2)C-p4g structure have led to the postulation of a model involving distortions of the nickel substrate atoms. The expansion thus caused is consistent with certain peak shifts in I-V spectra. Full dynamical calculations have been performed for various combinations o; distortions and carbon positions. Encouraging agreement is obtained for such a model with carbon atoms situated in 4-fold hollows, 0.1 Å above the nickel layer.

In addition to this, I-V data from the clean surfaces and the Ni(110) (1x2 )H and Ni(100)(2x2) C-p4g surfaces were used for Constant Momentum Transfer Averaging. The clean Ni(100) surface averages compare well with previous work. Ni(110) surface averages do not indicate the probable 5% surface layer contraction, and the 8 ½% contraction proposed by dynamical theory is not seen for the Ni(110)(1x2)H surface averages. Averages obtained from the Ni(100)(2x2)C-p4g surface do contain features indicative of top layer expansion; however, many multiple scattering features main and peak shapes cannot be explained by purely kinematical arguments.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Nickel -- Surfaces, Nickel -- Absorption and adsorption, Adsorption, Nickel -- Spectra
Official Date:	December 1978
Dates:	Date Event December 1978 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Woodruff, D. P.
Sponsors:	Science Research Council (Great Britain)
Extent:	vii, 100 leaves : illustrations, charts
Language:	eng

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