Oxygen and sulphur adsorption on cylindrical crystals of copper and nickel : an Auger electron spectroscopy study

• Main Author: Armitage, Alistair Fullerton
• Published: University of Warwick 1982
• Subjects: 530.41; QC Physics
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.345355

The research reported in this thesis is concerned with the adsorption (and segregation) of oxygen and sulphur to copper and nickel surfaces. Auger electron spectroscopy (a highly surface-specific technique,) has been used to provide quantitative measurements of the constituents at various metal surfaces. The segregation of impurities to polycrystalline nickel surfaces is reported first. The competition for surface sites between carbon and sulphur was observed to occur in a different manner on different grains. The equivalence of segregation and adsorption was demonstrated for sulphur on nickel. The polycrystalline samples presented only a limited range of surfaces for examination. Work on a hemispherical nickel crystal (which presented all possible orientations for examination) was limited by experimental difficulties in determining the exact surface orientation being sampled at any instant. The largest part of the research reported in this thesis was on cylindrical crystals of copper and nickel. By careful choice of the cylinder axis, a sample could be cut with a surface structure that varied in a well-controlled manner. The adsorption of oxygen on copper turned out to be strongly dependent on the copper surface structure. The initial rate of chemisorption varied linearly with the step density. In contrast, the chemisorption of oxygen on nickel was not greatly affected by variations in the surface structure. However, at higher exposures of oxygen, an oxide film developed at a rate that did depend on the surface structure of the sample. The adsorption of sulphur from a beam of molecules proceeded quite differently. On a copper cylinder a bulk sulphide grew in a manner that did not seem to be influenced by the substrate surface structure. On nickel, the initial adsorption of sulphur did vary slightly with surface structure, but the later growth of a bulk sulphide did not.