Study of the metal-electrolyte interface by in situ photoemission

by David Eugene Grider

Institution: Iowa State University
Year: 1980
Keywords: Physics; Solid state physics; Condensed Matter Physics
Record ID: 1511630
Full text PDF: http://lib.dr.iastate.edu/rtd/6787



In situ photoemission (IPE) was used to study the boundaries between 0.5 M H(,2)SO(,4) and single crystals of Cu and Au. Correlating structure in the electronic states of these metals with features in the photoelectron quantum yield (photoelectrons/photon), it was possible to specify the energy of certain photoelectrons prior to transmission through the solid-liquid interface. Using this energy specification, the sensitivity of IPE to the structure of the interfacial region was found to be enhanced;The electrolyte level is located in energy near the final states for direct interband transitions near L in Au. By varying the direct interband contribution to the quantum yield through a work function modulation technique, V(,0) was found to be located at 3.28 eV above the Fermi level of Au at a potential of 0.0 V(,NHE). Exploiting knowledge of electron momentum restrictions and the polarization dependence of optical matrix elements, a feature in the ratio of the p-polorized to s-polarized photoelectron quantum yield from Cu (111) was correlated to the onset of transitions to Bloch-like final states at approximately 4.1 eV. By making use of this feature in the yield ratio, it was possible to monitor the quality of the interface using both clean and adsorbate (thiourea, Br('-), I('-), tetrabutylammonium, pyridine) covered Cu surfaces. It was found that the major effect of adsorption of halide ions and thiourea molecules could be attributed to a partial relaxation of the conservation of electron momentum parallel to the surface during the emission process.