This dissertation is broadly divided into two parts. The first part details the development and usage of an experimental apparatus to measure the dry nanofriction for a well-defined interface at high sliding speeds. I leverage the sensitivity of a quartz crystal microbalance (QCM) to determine the drag coefficient of an ensemble of gold nanocrystals sliding on graphene at speeds up to 11 cm/s. I discuss the theories of velocity-dependent friction, especially at high sliding speeds, and QCM modeling. I also discuss our synthesis protocols for graphene and molybdenum disulfide, as well as our protocol for fabricating a clean, graphene-laminated QCM device and nanocrystal ensemble. The design and fabrication of our QCM oscillator circuit is presented in detail. The quantitatively-measured the drag coefficient is compared against molecular dynamics simulations at both low and high sliding speeds. We show evidence of a predicted ultra-low friction regime and find that the interaction energy between gold nanocrystals and graphene is lower than previously assumed. In the second part of this dissertation, I detail the band structure measurement of a novel semimetal using scanning tunneling microscopy. In particular, I measured the energy-dependence of quasiparticle interference patterns at the surface of zirconium silicon sulfide (ZrSiS), a topological nodal line semimetal whose charge carrier quasiparticles possess a pseudospin degree of freedom. The aims of this study were to (1) discover the shape of the band structure above the Fermi level along a high-symmetry direction, (2) discover the energetic location of the line node in the same high-symmetry direction, and (3) discover the selection rules for k transitions. This study confirms the predicted linearity in E(k) of the band structure above the Fermi level. Additionally, we observe an energy-dependent mechanism for pseudospin scattering. This study also provides the first experimentally-derived estimation of the line node position in E(k).
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Lodge, Michael, "Experimental Confirmation of Ballistic Nanofriction and Quasiparticle Interference in Dirac Materials." (2018). Electronic Theses and Dissertations. 6092.