Date of Award
1995
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
The main thrust of this thesis concerns studies of the electronic structure of Au-Ag bimetallic materials, both in bulk alloys and in metallic overlayers on Ru(001). First, a series of bulk Au-Ag alloys: Au{dollar}\rm\sb{lcub}0.75{rcub}Ag\sb{lcub}0.25{rcub},\ Au\sb{lcub}0.67{rcub}Ag\sb{lcub}0.33{rcub},\ Au\sb{lcub}0.50{rcub}Ag\sb{lcub}0.50{rcub},\ Au\sb{lcub}0.25{rcub}Ag\sb{lcub}0.95{rcub},\ and\ Au\sb{lcub}0.05{rcub}Ag\sb{lcub}0.95{rcub}{dollar} has been studied using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and X-ray absorption near-edge structure (XANES). It is found that in alloys with {dollar}>{dollar}50% atomic Au, the alloy d-band width narrows little relative to that of pure Au; however at 50% (and less) atomic Au concentration, the widths of the Au-Ag alloy d-band are much smaller than that of Au. What emerges from these observations is a picture in which dilution as well as the relative energy positions of the Au and Ag d-band components, relative to the Fermi level, play a subtle but crucial role in determining the overall d-band width of dilute Au-Ag alloys. X-ray absorption near-edge structure measurements indicate 5d charge depletion at the Au site and an increase in 4d charge at the Ag site, for both concentrated and dilute Au-Ag alloys. This observation, together with Au 4f and Ag 3d X-ray photoemission core-level data, shows that Au gains non-d conduction charge and loses d charge while Ag gains d charge and loses non-d charge. Moreover, the net charge flow is negligibly small in accordance with the principle of electroneutrality. Next, photoemission spectroscopy with synchrotron radiation has been used to study the Au 4f and Ag 3d core-level binding-energy shifts and the valence-band behaviour of Au and Ag overlayers on Ru(001). These results are compared with the bulk Au-Ag measurements to see if and under what conditions two-dimensional (2-D) alloy formation takes place and if there are any differences between the electronic structure of the bulk and surface alloys. It is found that the order of deposition, annealing temperature, and the ruthenium substrate all play an important role in Au-Ag surface alloying on Ru(001).
Recommended Citation
Bzowski, Arthur, "Electronic Structure Of Gold-silver Bimetallics" (1995). Digitized Theses. 2486.
https://ir.lib.uwo.ca/digitizedtheses/2486