Bulletin of the American Physical Society
2018 Annual Meeting of the APS Four Corners Section
Volume 63, Number 16
Friday–Saturday, October 12–13, 2018; University of Utah, Salt Lake City, Utah
Session L03: CMP + Materials 9: Plasmonics/Heterostructures/Electron Yield Measurements |
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Chair: Sheng-Ting Hung, JILA Room: JFB 103 |
Saturday, October 13, 2018 11:20AM - 11:44AM |
L03.00001: Unraveling temperature-dependent photocarrier dynamics using plasmonic effects of metal nanoparticles Invited Speaker: Terefe Getaneh Habteyes In this presentation, first the optical properties of metal nanoparticles will be discussed with a particular emphasis on localized surface plasmon resonances, which is defined as collective oscillation of conductive electrons induced by electromagnetic radiation of certain frequency. Since the dimensions of the nanoparticles is less than 100 nm, the surface field is confined to size scales much smaller than the wavelength of the incident radiation, resulting in a local field that is several orders of magnitude larger than the excitation field. The local field can further be enhanced and squeezed down to volume of single cubic nanometer by coupling the resonant plasmonic nanoparticles. These plasmonic properties have been exploited for various applications including for single molecule detection, biosensing and photothermal cancer therapy as well as for enhancing the efficiency of optoelectronic devices. In this presentation, examples of high resolution near-field images of surface plasmon modes obtained using apertureless near-field scanning optical microscope will be discussed. The application of plasmonic effects for enhancing photocarrier generation in semiconductors and understanding the carrier dynamics will be discussed based on our very recent results on InGaAs/GaAs quantum well. |
Saturday, October 13, 2018 11:44AM - 11:56AM |
L03.00002: An Analysis of Historical Secondary Electron Yield Measurements for Copper Phil Lundgreen, John R Dennison Secondary Electron Yield (SEY) is a critical material property that has had many different values reported in scientific literature for specific elements and compounds. SEY gauges the number of emitted electrons per incident electron and is a basic material property that is of critical importance for many physics-based applications. A study has been conducted on copper to identify the relative importance and origins of variations of SEY vs. incident energy curves. Variations may result from or be attributed to: bulk composition and impurities, surface modification (including roughness, oxidation, and contamination); sample modification (including thermal annealing and ion sputtering); sample charging; instrumentation effects (including collector efficiency and stray fields); and absolute calibrations techniques. Agreement between the various curves for copper found in the literature, is underwhelming, with a variation of ~60% observed. These results support the need to develop a detailed database of electron yield curves that include, where available, pertinent materials and background information for each study. |
Saturday, October 13, 2018 11:56AM - 12:08PM |
L03.00003: Electron Yield Measurements of a Carbon-composite Material Matthew L Robertson, Justin E Christensen, Gregory Wilson, John R Dennison Electron irradiation experiments were conducted to investigate the electron yield and emission properties of an epoxy/carbon-fiber composite material. The structure consists of alternating layers of a carbon fiber weave in an epoxy matrix. We discuss how this nanoscale structure made of both conducting and insulating components with dimensions on the order of electron penetration depths influences the electron yield and emission properties of the material. Secondary, backscatter and emission energy spectra measurements were made in an ultrahigh vacuum electron emission test chamber, with electron beam energies ranging from 15 eV to 30000 eV. Related structural and charging properties have also been investigated by scanning electron microscopy and cathodoluminescence. The emission properties of the composite material are modeled using a nonlinear combination of the two base materials. In various combinations along with effects of surface roughness and morphology. |
Saturday, October 13, 2018 12:08PM - 12:20PM |
L03.00004: Electron Yield Measurements of Multilayer Conductive Materials Gregory Wilson, Matthew L Robertson, Jordan Lee, JR Dennison The electron yield (EY), defined as the number of electrons emitted over electrons incident from a sample undergoing energetic electron bombardment, provides a fundamental way to study the interaction of incident electrons with constituent electrons in a material. Electron emission from even simple layered materials with thicknesses on the order of electron penetration depths is a complex problem involving electron transport, electron-electron interactions, and energy transfer processes. To understand how the EY is affected by thin layer structures, SEY, BSEY, and electron emission spectra were measured for two multilayer sample sets. The first sample set had highly ordered pyrolytic graphite substrates with gold sputtered coatings ranging from 1 nm to 100 nm thick. The second sample set had high purity gold substrates with graphitic amorphous carbon foils ranging from 0.5 nm to 500 nm adhered to the surface. The measured yield curves were complex functions of incident energy and coating thickness. The models proposed here necessitate the consideration of the origins of emitted electrons, the nature of elastic and inelastic collisions, and the energy dependent range of electrons. |
Saturday, October 13, 2018 12:20PM - 12:32PM |
L03.00005: Characterization of Electron Yield Suppression with Carbon Nanotube Forest Grown on Silicon Substrates Brian D Wood, Justin E Christensen, Jordan Lee, Gregory Wilson, JR Dennison, T.-C. Shen Total, secondary and backscatter electron yield, along with emission energy spectra data, were taken of 3 carbon nanotube forests (CNTFs) with beam energies between 15-30,000 eV. Forests morphology, which vary in relative density, and height between 20-40 μm, were controlled by varying growth parameters. Due to their inherent microstructure and low-Z composition, CNTF’s can be used to reduce the electron yield of a base material by acting as a convoluted layer recapturing the substrate’s emitted electrons. Data analysis of a bare annealed substrate, with and without the deposited aluminum, allowed use of a multi-layered yield model to dissect the constituent contributions to the sample’s yield as a whole. Measured energy spectra of emitted electrons help determine the forest’s effectiveness at attenuating the yield, and over what energy range density and height are more influential. It is shown the forest reduces the overall yield of the substrate, substantially in the lower energy regime. At higher energies, the substrate’s yield dominates over the CNTF suppression due to their sparse packing density, and height. Treating the forest simply as a layered modification of a substrate predicts lower yield in the lower energy range, but under predicts suppression at higher energies. |
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