Bulletin of the American Physical Society
Joint Meeting of the Four Corners and Texas Sections of the American Physical Society
Volume 61, Number 15
Friday–Saturday, October 21–22, 2016; Las Cruces, New Mexico
Session H2: Nanosciences |
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Chair: Vladimir Drachev, University of North Texas Room: Ballroom 2 |
Saturday, October 22, 2016 9:36AM - 10:00AM |
H2.00001: Modifying carbon surfaces and thin films to tune chemical and optical properties Invited Speaker: Anna Zaniewski Diamond and graphene are carbon-based materials with remarkable electronic, chemical and optical properties. In this talk, we present a variety of techniques for surface and thin film modifications which result in tuning the properties of graphene and diamond. The first is UV laser modification of conductive nanocrystalline diamond thin films, which results in localized optical bleaching and reduced electrical conductivity. Second, we will discuss the electroless reduction of solution-based metal ions for nanoparticle deposition on graphene transferred to a variety of substrates. We find that the metal ions are spontaneously reduced on a wide variety of graphene substrates, and the substrates play a large role in graphene chemistry. This substrate dependence affects not only wet chemistry, but also plasma-based material deposition; in this light, we discuss results of plasma enhanced atomic layer deposition (PEALD) of dielectrics on graphene. Future experiments of photochemistry on carbon surfaces will also be discussed. [Preview Abstract] |
Saturday, October 22, 2016 10:00AM - 10:12AM |
H2.00002: Maximizing Magnetic Domain Densities in 60Å Co/Pt Thin Film Lauren Hindman, Brittni Newbold, Berg Dodson, Karine Chesnel In Co/Pt thin films, magnetic domains are present perpendicular to the plane of the sample. These domains can be found in different forms ranging from maze like structure to a spotted or bubbly form. The domain morphologies can change in response to an external magnetic field. To study these responses, we have been imaging the domains at varying field strengths. My work specifically focused on Co/Pt multilayers with 60 Å of Cobalt. A Vibrating Sample Magnetometer (VSM) was used to apply a field to a 60 Å Co/Pt thin film and obtain data on its hysteresis. Magnetic force microscopy (MFM) then imaged the domains at remanence, or without a magnetic field present. By statistically analyzing the images, we were able to find the field that resulted in the highest density of domains. This density was significantly greater than at other fields. Easy production of high density morphologies could lead to advances in data storage. [Preview Abstract] |
Saturday, October 22, 2016 10:12AM - 10:24AM |
H2.00003: Effect of Crystal Orientation Upon the Surface Energy of Native Oxides on Si(100) and Si(111) as Measured by Three Liquid Contact Angle Analysis (3LCAA) R.T. Van Haren, E. Ocampo Landeros, M.T. Bade, A.O. Martinez, Y.W. Pershad, S.M. Suhartono, R.P. Francis, N. Herbots, S.D. Whaley, R.J. Culbertson, H.L. Thinakaran, A.P. Krishnan The surface energy $\gamma^{\mathrm{T}}$ of native oxides on Si(100) and (111) is measured via Three Liquid Contact Angle Analysis (3LCAA) to detect crystal orientation effects. Low surface roughness of Si wafers lowers $\gamma^{\mathrm{T}}$ via low density of dangling bonds, so $\gamma ^{\mathrm{T}}$ scales with chemical reactivity freely from topography [1]. 3LCAA based on the Van Oss theory measures $\gamma^{\mathrm{T}}$ via surface interactions with molecular dipoles (Lifshitz-Van der Waals), labeled $\gamma^{\mathrm{LW}}$, with electron donors, $\gamma ^{\mathrm{+}}$, and acceptors, $\gamma^{\mathrm{-}}$. Surface energy components $\gamma^{\mathrm{LW}}$, $\gamma^{\mathrm{+}}$, and $\gamma ^{\mathrm{-}}$ give insights into optimizing $\gamma^{\mathrm{T}}$ for hermetic NanoBonding\texttrademark in sensors [1], to extend lifetime and reliability in saline environments from days to years via matching electronegativity in cross-bonding pairs.$^{\mathrm{\thinspace }}$3LCAA with 18 M$\Omega $ Deionized water, glycerine, and $\alpha $-bromonaphthalene in a Class 100 hood and the Sessile Drop method yield for native SiO2/Si(111) $\gamma^{\mathrm{T}} \quad =$ 56.7$+$/-2 mJ/m$^{\mathrm{2}}$, and $\gamma ^{\mathrm{T}} \quad =$ 49.7$+$/-2 mJ/m$^{\mathrm{2}}$ on Si(100), a 13{\%} difference. Since Si(111) surface atomic density is 12{\%} larger than Si(100), 3LCAA finds that $\gamma^{\mathrm{T}}$ scales with surface atomic density. [1] US9018077, granted 2015, \textit{Herbots et al} [Preview Abstract] |
Saturday, October 22, 2016 10:24AM - 10:36AM |
H2.00004: Surface Energies of Native Oxides on Si(100), Si(111) and GaAs(100) via Three Liquid Contact Angle Analysis (3LCAA) Correlation with Composition by Ion Beam Analysis (IBA) E. Ocampo Landeros, S.M. Suhartono, R.T. Van Haren, R.P. Francis, Y.W. Pershad, M.T. Bade, E.W. Davis, A.O. Martinez, N. Herbots, S.D. Whaley, R.J. Culbertson, K.L Kavanagh Surface energies, $\gamma^{T}$, of native oxides of Si(100) [1], Si(111) and GaAs(100) are measured via contact angles of sessile drops of three liquids (3 Liquid Contact Angle Analysis, or 3LCAA) and correlated with surface composition via ion beam scattering. 3LCAA, based on Van Oss' theory, computes $\gamma^{T}$ from Lifshitz-Van der Waals interactions with molecules, $\gamma^{LW}$, electron donors, $\gamma^{+}$, and acceptors $\gamma^{-}$. Varying $\gamma^{LW}$, $\gamma^{+}$, and $\gamma^{-}$ helps optimize $\gamma^{T}$ and increase lifetime and reliability in hermetic NanoBonding$^{TM}$ [2], in integrated sensors and solar cells. Liquids used for 3CLAA are 18M$\Omega $ DI water, glycerin, and $\alpha $-bromo-naphthalene in a Class 100 flow hood. Oygen coverage is measured via the 3.038 $\pm$ 0.01 MeV nuclear resonance $^{16}$O ($\alpha $, $\alpha ) \quad^{16}$O.$\gamma^{T}$ is found 57 $\pm$ 2 mJ/m$^{2\, }$for Si(111), which is hydrophilic, 50 $\pm$ 2 mJ/m$^{2\, }$ for Si(100) and 35 $\pm$ 3 mJ/m$^{2\, }$GaAs(100), which are hydrophobic. Thus, native oxides on GaAs(100) are significantly more hydrophobic (33{\%}) than on Si(100). [1] A.L. Brimhall et al\textit{, Bull. of the APS}, Vol. 60, (2015) [2] US9018077, (2015), Herbots et al [Preview Abstract] |
Saturday, October 22, 2016 10:36AM - 10:48AM |
H2.00005: Optical and magnetic properties of cobalt nanoparticles fabricated by high temperature reduction of cobalt salt Hari Bhatta, Ali Aliev, Vladimir Drachev Magnetic nanoparticles have attracted great amount of enthusiasm among scientists from various fields because of their technological applications include data storage, magnetic fluids, catalysis and biomedical applications include magnetic resonance imaging (MRI), drug delivery, gene cloning, and hyperthermia for cancer therapy. The cobalt nanoparticles were fabricated by the method of high temperature reduction of cobalt salt using trioctylphosphine as a surfactant, oleic acid as a stabilizer, and lithium triethylborohydride as a reducing reagent. The formation of cobalt nanoparticles was confirmed by Energy-dispersive X-ray spectroscopy (EDX) analysis. Transmission electron micrographs show the formation of spherical cobalt nanoparticles having average particle size 8.7 nm. As synthesized cobalt nanoparticles showed the high quality plasmon resonance at 275 nm. Time dependent study showed the cobalt nanoparticles dispersed in hexane are stable in the solution. The magnetic measurements show the superparamagnetic behavior of cobalt nanoparticles with blocking temperature corresponding to mixture of fcc and hcp structures. [Preview Abstract] |
Saturday, October 22, 2016 10:48AM - 11:00AM |
H2.00006: Spatially Resolved Biosensing with Graphene Nanodisk Arrays Lauren Zundel, Alejandro Manjavacas Graphene nanostructures have emerged as ideal platforms to design optical biosensors thanks to their ability to support strong and narrow resonances in the infrared part of the spectrum. These resonances, known as surface plasmons, arise from the collective oscillations of their conduction electrons and, contrarily to the case of conventional plasmonic materials, can be tuned by changing the doping level of the nanostructure via, for instance, electrostatic gating. Here, we propose to use these extraordinary properties to design an optical biosensor with spatial resolution. The proposed device consists of a set of 1-micron square pixels, each of them composed of an array of graphene nanodisks. By carefully engineering the size and the distribution of the nanodisks we can tune all pixels to support a plasmonic resonance at the same frequency and with equal intensity, but for different values of doping. Then, by modifying the doping level of the whole system we can select which pixel is on resonance, and therefore we can detect the presence and the location of the molecules with a spatial resolution well below the diffraction limit. The concept of spatially resolved biosensing proposed here opens a new avenue for the design of plasmonic biosensors with improved capabilities. [Preview Abstract] |
Saturday, October 22, 2016 11:00AM - 11:12AM |
H2.00007: Ferritin-encapsulated PbS quantum dots for use in Dye Sensitized Solar Cells Kameron Hansen, Cameron Olsen, Ryan Peterson, Alessandro Perego, John Colton, Richard Watt Lead ll Sulfide (PbS) is an intrinsic semiconductor with direct band-gap in the IR range, and thus is an attractive candidate for use as a photon-absorber in dye-sensitized solar cells. However, PbS quantum dots inside the mesoporous TiO$_{\mathrm{2}}$ layer have been known to be unstable and suffer from severe clustering. We experiment encapsulating PbS QD in native protein ferritin with the goal of improving the stability and spatial homogeneity of PbS$+$TiO$_{\mathrm{2}}$'s photovoltaic response. We build off reported colloidal chemistry methods to synthesize PbS QD inside ferritin, and we provide detailed characterization of the resulting quantum dots' quality, size, and optical properties. Specifically, inductively coupled plasma mass-spectroscopy is used to measure lead concentrations, Bradford protein assay to measure protein concentration, photoluminescence and optical absorption spectroscopy to measure band-gap energies, and HRTEM to measure core diameters. Our results show no significant difference between the aerobic and anaerobic synthesis methods. DSSCs are fabricated using PbS-FTN as the dye, and an overall efficiency of 0.19 percent is achieved. [Preview Abstract] |
Saturday, October 22, 2016 11:12AM - 11:24AM |
H2.00008: Superconducting Nuclear Recoil Sensor for Directional Dark Matter Detection Ann Junghans, Nina Weisse-Bernstein, Kevin Baldwin, Randy Lafler, Nguyen Phan, Dinesh Loomba, Markus Hehlen The Universe consists of 72{\%} dark energy, 23{\%} dark matter and only 5{\%} of ordinary matter. One of the greatest challenges of the scientific community is to understand the nature of dark matter. Current models suggest that dark matter is made up of slowly moving, weakly interacting massive particles (WIMPs). But detecting WIMPs is challenging, as their expected signals are small and rare compared to the large background that can mimic the signal. The largest and most robust unique signature that sets them apart from other particles is the day-night variation of the directionality of dark matter on Earth. This modulation could be observed with a direction-sensitive detector and hence, would provide an unambiguous signature for the galactic origin of WIMPs. There are many studies underway to attempt to detect WIMPs both directly and indirectly, but solid-state WIMP detectors are widely unexplored although they would present many advantages to prevalent detectors that use large volumes of low pressure gas. We present first results of a novel multi-layered architecture, in which WIMPs would interact primarily with solid layers to produce nuclear recoils that then induce measureable voltage pulses in adjacent superconductor layers, in response to exposure to a range of sources. [Preview Abstract] |
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