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Title: LEED studies of some adsorption systems on the (100) and (110) surfaces of nickel
Author: Onuferko, Julia H.
ISNI:       0000 0001 3459 3121
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1978
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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 1⁄2% 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.
Supervisor: Not available Sponsor: Science Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics ; QD Chemistry