Date of Award
Doctor of Philosophy
Patricia A. Thiel
Adsorbates such as sulfur and oxygen can strongly affect metal transport on coinage metal surfaces. It has been proposed that the formation of metal-additive complexes aid in the enhancement of metal island coarsening. Our focus is solely on additive sulfur. We examined the interactions between sulfur and three different coinage metal surfaces at a very low temperature (5K) and low sulfur coverages to determine if M-S complexes formed under specific conditions. Our primary experimental technique is scanning tunneling microscopy (STM). The three surface studied were Ag(100), Ag(110), and Cu(110). On Ag(100) and Cu(110), only sulfur atoms were present at all experimental coverages. S atoms and linear independent AgS2 complexes were observed on the Ag(110) surface depending on the sulfur coverage. MS2 is a common motif observed in other coinage metal-sulfur complexes, and this is the first time that a MS2 complex has been directly observed isolated. Extensive DFT analysis supports the experimental observations.
We have found that sulfur accelerates the coarsening of Au islands on Au(111) at room temperature (300K) under 0.31 ML S. The enhancement in the Au island decay rate was an order of magnitude, which is less of an enhancement compared to the Cu(111) and Ag(111) systems. A stabilization of the Au islands occurred at a higher sulfur coverage (0.56 ML), where the surface was covered by an 2D Au-S phase.
In this dissertation, we describe work in which we have expanded the understanding of M-S complexes, and the role they play in mass transport. We believe this data will provide a better understanding of sulfur coinage metal interactions.
Peter Michael Spurgeon
Spurgeon, Peter Michael, "Investigations of sulfur-silver interactions and mass transport on silver and gold surfaces" (2019). Graduate Theses and Dissertations. 17788.