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Far-infrared bands in plasmonic metal-insulator-metal absorbers optimized for long wave infrared
Title
Far-infrared bands in plasmonic metal-insulator-metal absorbers optimized for long wave infrared.
Creator
Evans, Rachel, Peale, Robert, Ishigami, Masahiro, Lyakh, Arkadiy, University of Central Florida
Abstract / Description
Metal(-)insulator(-)metal (MIM) resonant absorbers comprise a conducting ground plane, a thin dielectric, and thin separated metal top-surface structures. Long-wave infrared (LWIR) fundamental absorptions are experimentally shown to be optimized for a ratio of dielectric thickness to top-structure dimension t/l (>) 0.08. The fundamental resonance wavelength is predicted by different analytic standing-wave theories to be ~2nl, where n is the dielectric refractive index. Thus, for the...
Show moreMetal(-)insulator(-)metal (MIM) resonant absorbers comprise a conducting ground plane, a thin dielectric, and thin separated metal top-surface structures. Long-wave infrared (LWIR) fundamental absorptions are experimentally shown to be optimized for a ratio of dielectric thickness to top-structure dimension t/l (>) 0.08. The fundamental resonance wavelength is predicted by different analytic standing-wave theories to be ~2nl, where n is the dielectric refractive index. Thus, for the dielectrics SiO2, AlN, and TiO2, l values of a few microns give fundamentals in the 8-12 micron LWIR wavelength region. Agreement of observed fundamental resonance wavelength with theory is better for t/l (>) ~0.2. Harmonics at shorter wavelengths are always observed, but we show that there are additional resonances in the far-infrared 20-50 micron wavelength range, well beyond the predicted fundamental. These appear to be due to dispersion. They may impact selectivity in spectral sensing applications.
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Date Issued
2018
Identifier
CFE0007176, ucf:52267
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007176
Experimental confirmation of ballistic nanofriction and quasiparticle interference in Dirac materials.
Title
Experimental confirmation of ballistic nanofriction and quasiparticle interference in Dirac materials.
Creator
Lodge, Michael, Ishigami, Masahiro, Kaden, William, Schelling, Patrick, Del Barco, Enrique, Roy, Tania, University of Central Florida
Abstract / Description
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...
Show moreThis 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-dependenceof quasiparticle interference patterns at the surface of zirconium silicon sulfide (ZrSiS), a topological nodal line semimetal whose charge carrier quasiparticles possess a pseudospin degree offreedom. 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 inthe 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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Date Issued
2018
Identifier
CFE0007218, ucf:52222
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007218