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Now showing items 1 - 16 of 1065

  • NOVEL METHODS OF PREPARING NANODEVICES

    The present invention relates to novel nano- and micro-electromechanical devices and novel methods of preparing them. In one aspect, the invention includes methods of preparing a nanodevice. In certain embodiments, the methods comprise coating a polymer layer with a first at least one thin solid material layer using atomic layer deposition (ALD), thus forming an ALD-generated layer. In other embodiments, the methods comprise patterning the first at least one thin solid material layer to form a nanodevice. In yet other embodiments, the methods comprise releasing the nanodevice from the polymer layer.
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  • Hemispherical micro-resonators from atomic layer deposition

    Gray, Jason M.   Houlton, John P.   Gertsch, Jonas C.   Brown, Joseph J.   Rogers, Charles T.   George, Steven M.   Bright, Victor M.  

    Hemispherical shell micro-resonators may be used as gyroscopes to potentially enable precision inertial navigation and guidance at low cost and size. Such devices require a high degree of symmetry and large quality factors (Q). Fabricating the devices from atomic layer deposition (ALD) facilitates symmetry through ALD's high conformality and low surface roughness. To maximize Q, the shells' geometry is optimized using finite element method (FEM) studies to reduce thermoelastic dissipation and anchor loss. The shells are fabricated by etching hemispherical molds in Si (1 1 1) substrates with a 2:7:1 volumetric ratio of hydrofluoric:nitric:acetic acids, and conformally coating and patterning the molds with ALD Al2O3. The Al2O3 shells are then released from the surrounding Si substrate with an SF6 plasma. The resulting shells typically have radii around 50 mu m and thicknesses close to 50 nm. The shells are highly symmetric, with radial deviations between 0.22 and 0.49%, and robust enough to be driven on resonance at amplitudes 10 x their thickness, sufficient to visualize the resonance mode shapes in an SEM. Resonance frequencies are around 60 kHz, with Q values between 1000 and 2000. This Q is lower than the 10(6) predicted by FEM, implying that Q is being limited by unmodeled sources of energy loss, most likely from surface effects or material defects.
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  • Ultra-thin 3D Nano-Devices from Atomic Layer Deposition on Polyimide

    Eigenfeld, Nathan T.   Gray, Jason M.   Brown, Joseph J.   Skidmore, George D.   George, Steven M.   Bright, Victor M.  

    A new nanofabrication process for nano/micro-devices through the combination of inorganic nanomaterials from atomic layer deposition (ALD) on 3-dimensional organic polyimide substrates is developed. The first suspended ALD structures with multiple patterned suspended levels on the order of 10 nm are fabricated and results surrounding the mechanical stability of ultra-thin suspended structures are discussed.
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  • Low-frequency noise in gallium nitride nanowire mechanical resonators

    Gray, Jason M.   Bertness, Kris A.   Sanford, Norman A.   Rogers, Charles T.  

    We report on the low-frequency 1/f (flicker) parameter noise displayed by the resonance frequency of doubly clamped c-axis gallium nitride nanowire (NW) mechanical resonators. The resonators are electrostatically driven and their mechanical response is electronically detected via NW piezoresistance. With an applied dc voltage bias, a NW driven near its mechanical resonance generates a dc and Lorentzian rf current that both display 1/f noise. The rf current noise is proportional to the square of the derivative of the Lorentzian lineshape with a magnitude highly dependent on NW dc bias voltage conditions, consistent with a model wherein noise in the NW's electrical impedance leads to temperature noise from local Joule heating, which in turn generates resonance frequency noise via thermal expansion and the temperature-dependent Young's modulus. An example device with a 27.8 MHz resonance frequency experiences an approximate resonance frequency shift of -1.4 Hz/nW. The resonance frequency noise increases as the square of the bias voltage, indicating specific operating conditions that optimize the signal-to-noise ratio in proposed NW sensors.
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  • Low-frequency noise in gallium nitride nanowire mechanical resonators

    Gray, Jason M.   Bertness, Kris A.   Sanford, Norman A.   Rogers, Charles T.  

    We report on the low-frequency 1/f (flicker) parameter noise displayed by the resonance frequency of doubly clamped c-axis gallium nitride nanowire (NW) mechanical resonators. The resonators are electrostatically driven and their mechanical response is electronically detected via NW piezoresistance. With an applied dc voltage bias, a NW driven near its mechanical resonance generates a dc and Lorentzian rf current that both display 1/f noise. The rf current noise is proportional to the square of the derivative of the Lorentzian lineshape with a magnitude highly dependent on NW dc bias voltage conditions, consistent with a model wherein noise in the NW's electrical impedance leads to temperature noise from local Joule heating, which in turn generates resonance frequency noise via thermal expansion and the temperature-dependent Young's modulus. An example device with a 27.8 MHz resonance frequency experiences an approximate resonance frequency shift of -1.4 Hz/nW. The resonance frequency noise increases as the square of the bias voltage, indicating specific operating conditions that optimize the signal-to-noise ratio in proposed NW sensors. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769445]
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  • Gallium nitride nanowire electromechanical resonators with piezoresistive readout

    Gray, Jason M.   Rogers, Charles T.   Bertness, Kris A.   Sanford, Norman A.  

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  • Gallium nitride nanowire electromechanical resonators with piezoresistive readout

    Gray, Jason M.   Rogers, Charles T.   Bertness, Kris A.   Sanford, Norman A.  

    The authors report on the fabrication, piezoresistive readout, and frequency response of doubly clamped c-axis gallium nitride nanowire (NW) resonators that show mechanical quality factors exceeding 10 000. The devices are fabricated using a combination of lithographic patterning and dielectrophoresis to suspend NWs across 10 mu m gaps. An electrostatic gate induces NW vibration, which is electronically detected via NW piezoresistance. The naturally occurring range of NW diameters results in lowest beam resonances in the range of 9-36 MHz, consistent with a Young's modulus of roughly 300 GPa. Mechanical quality factors, Q, as high as 26 000 under vacuum at 8 K are observed. Selective variation of NW temperature by local joule heating while maintaining cold mechanical clamps demonstrates the dominant role of the polycrystalline metallic end clamps in the room-temperature mechanical dissipation. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3622326]
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  • Indigenous Passages to Cuba, 1515-1900 - by Yaremko, Jason M.

    Stone, Erin W.  

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  • Jason M. Pobjoy, The Child in International Refugee Law

    Brittle   Ruth  

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  • Indigenous Passages to Cuba, 1515–1900 by Jason M. Yaremko

    Altman, Ida  

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  • The Child in International Refugee Law , written by Jason M. Pobjoy

    Crawley, Heaven  

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  • , by Block, D., Gray, J., & Holborow, M.

    Prerna Bakshi  

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  • Parallels of Gray in E. M. Forster's HOWARDS END

    Brown Smith, Julie  

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  • Parallels of Gray in E. M. Forster\"s HOWARDS END

    Brown Smith   Julie  

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  • Jason M. Colby. Orca: How We Came to Know and Love the Ocean’s Greatest Predator.

    Brown, Jen Corrinne  

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  • Social Work Theories and Methods, by Gray, M., & Webb, S. A.

    Kebede, Wassie  

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