Date of Award
Master of Science
Patricia A Thiel
This thesis explores the conditions that lead to the encapsulation of metal nanoparticles at the surface of graphite. For intercalation to occur in graphite there are two criteria that need to be met: (1) defects need to be introduced into the material and (2) the sample needs to be heated during deposition of the metal. The defects are believed to be the active portals by which metal nanoparticles enter the graphite galleries. The research presented uses varying sputtering conditions such as the time, ion, and energy to introduce defects into commercially available highly oriented pyrolytic graphite (HOPG) before ruthenium deposition to investigate the role defect creation has in the encapsulation of metal islands.
The goal of this research is to explore defect creation using different sputtering conditions to better understand the conditions that elicit active portals and optimize the method for encapsulation of metal islands, specifically ruthenium. Ultra-high vacuum (UHV) techniques such as electron beam heating, physical vapor deposition, scanning tunneling microscopy (STM), and X-Ray photoelectron spectroscopy (XPS) are utilized to help create and characterize the defects and encapsulated ruthenium islands.
The data presented suggests three key characteristics of the sputtering and deposition process: (1) when the portal density is sufficient to achieve an equilibrium of ruthenium atoms on top of the graphite surface and in the galleries an increase in portals has no impact; (2) ions used for sputtering have an ideal kinetic energy associated with creating the desired quantities of defects, a deviation in energy could increase or decrease the reflection/transmission that occurs during sputtering; (3) paired with literature previously published, the data presented suggests di-vacancies are the minimum portal size required for intercalation of metals ions.
Michael William Manley
Manley, Michael William, "Creation of graphite surface defects via ion bombardment: The origin of active portals and their role in encapsulation of metal nanoparticles" (2020). Graduate Theses and Dissertations. 17875.