Browsing by Subject "physics, applied"

Now showing 1 - 5 of 5
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    A method for atomic force microscopy cantilever stiffness calibration under heavy fluid loading
    (2009) Kennedy, Scott J; Cole, Daniel G; Clark, Robert L
    This work presents a method for force calibration of rectangular atomic force microscopy (AFM) microcantilevers under heavy fluid loading. Theoretical modeling of the thermal response of microcantilevers is discussed including a fluid-structure interaction model of the cantilever-fluid system that incorporates the results of the fluctuation-dissipation theorem. This model is curve fit to the measured thermal response of a cantilever in de-ionized water and a cost function is used to quantify the difference between the theoretical model and measured data. The curve fit is performed in a way that restricts the search space to parameters that reflect heavy fluid loading conditions. The resulting fitting parameters are used to calibrate the cantilever. For comparison, cantilevers are calibrated using Sader's method in air and the thermal noise method in both air and water. For a set of eight cantilevers ranging in stiffness from 0.050 to 5.8 N/m, the maximum difference between Sader's calibration performed in air and the new method performed in water was 9.4%. A set of three cantilevers that violate the aspect ratio assumption associated with the fluid loading model (length-to-width ratios less than 3.5) ranged in stiffness from 0.85 to 4.7 N/m and yielded differences as high as 17.8%. (C) 2009 American Institute of Physics. [doi:10.1063/1.3263907]
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    Negative refraction in three-dimensional point-dipolelike polaritonic crystals
    (2010) Rose, A; Kempa, K
    We propose two practical realizations of the point-dipole crystal, shown previously to be capable of negative refraction and other metamaterial and plasmonic properties. These are: an array of highly polarizable spheres, and the complementary array of spherical cavities in a highly polarizable medium. We study light propagation through these polaritonic crystals and show that they are capable of negative refraction, and can be constructed from available materials for experimental demonstrations at both microwave and optical frequencies. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3500323]
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    Nonstoichiometry of LixCu2O2+delta single crystal and its relation to magnetic ordering
    (2010) Yeh, KW; Huang, TW; Ke, CT; Wu, PM; Zhao, L; Chao, WH; Lee, YC; Chen, CL; Wu, MK
    We report the first systematic study on the nonstoichiometry of Li/Cu ionic ratios x and oxygen defect concentrations delta in LixCu2O2+delta solid solution. Nonstoichiometric crystals with intentional Li-deficient (x=0.97) or Li-excessive (x=1.06) concentrations were prepared by slow-cooling and floating-zone methods. By applying different oxygen pressures during growth, different magnitudes of oxygen defects were obtained, revealing varied magnetic and electrical properties. Our results strongly suggest that Li/Cu and oxygen nonstoichiometry in these crystals are responsible for the varied temperatures of helimagnetic ordering. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483244]
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    Optimal composition of europium gallium oxide thin films for device applications
    (2010) Wellenius, P; Smith, ER; Leboeuf, SM; Everitt, HO; Muth, JF
    Europium gallium oxide (EuxGa1-x)(2)O-3 thin films were deposited on sapphire substrates by pulsed laser deposition with varying Eu content from x=2.4 to 20 mol %. The optical and physical effects of high europium concentration on these thin films were studied using photoluminescence (PL) spectroscopy, x-ray diffraction (XRD), and Rutherford backscattering spectrometry. PL spectra demonstrate that emission due to the D-5(0) to F-7(J) transitions in Eu3+ grows linearly with Eu content up to 10 mol %. Time-resolved PL indicates decay parameters remain similar for films with up to 10 mol % Eu. At 20 mol %, however, PL intensity decreases substantially and PL decay accelerates, indicative of parasitic energy transfer processes. XRD shows films to be polycrystalline and beta-phase for low Eu compositions. Increasing Eu content beyond 5 mol % does not continue to modify the film structure and thus, changes in PL spectra and decay cannot be attributed to structural changes in the host. These data indicate the optimal doping for optoelectronic devices based on (EuxGa1-x)(2)O-3 thin films is between 5 and 10 mol %. (C) 2010 American Institute of Physics. [doi:10.1063/1.3319670]
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    Parametric analysis of the strain-dependent behavior of a metamaterial electric resonator
    (2010) Arritt, B; Adomanis, B; Khraishi, T; Smith, D
    In this paper, we describe the strain-dependent behavior of an electric-LC (ELC) resonator unit cell, commonly used in metamaterial designs. We leverage analytic expression to understand the way strain manifests itself in a change in electromagnetic (EM) response. We verify the simplified physical models using full-wave simulations and generalize the trends to accommodate the strain profile for any arbitrary plane-stress loading scenario. (C) 2010 American Institute of Physics. [doi:10.1063/1.3507892]