Person:
Graham, Samuel

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Start date: 2000 × End date: 2009 × Author: King, William P. ×

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Now showing 1 - 5 of 5
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    Thermal metrology of silicon microstructures using Raman spectroscopy
    (Georgia Institute of Technology, 2007-06) Abel, Mark R. ; Wright, Tanya L. ; King, William P. ; Graham, Samuel
    Thermal metrology of an electrically active silicon heated atomic force microscope cantilever and doped polysilicon microbeams was performed using Raman spectroscopy. The temperature dependence of the Stokes Raman peak location and the Stokes to anti-Stokes intensity ratio calibrated the measurements, and it was possible to assess both temperature and thermal stress behavior with resolution near 1µm. The devices can exceed 400 C with the required power depending upon thermal boundary conditions. Comparing the Stokes shift method to the intensity ratio technique, non-negligible errors in devices with mechanically fixed boundary conditions compared to freely standing structures arise due to thermally induced stress. Experimental values were compared with a finite element model, and were within 9% of the thermal response and 5% of the electrical response across the entire range measured.
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    Thermal conduction from microcantilever heaters in partial vacuum
    (Georgia Institute of Technology, 2007-01-01) Lee, Jung Chul ; Wright, Tanya L. ; Abel, Mark R. ; Sunden, Erik Oscar ; Marchenkov, Alexei ; Graham, Samuel ; King, William P.
    This paper reports the thermal and electrical characteristics of a heated microcantilever in air and helium over a wide range of pressures. The cantilever heater size modulates thermal conductance between the cantilever and its gaseous surroundings; and the Knudsen number, Kn characterizes this thermal conductance. When Kn<1, thermal transport from the cantilever heater depends on gas pressure, and when Kn>1, thermal transport from the cantilever heater remains constant. This measurement of thermal conductance around Kn = 1 could aid the design and analysis of Pirani sensors and other microscale thermal sensors and actuators.
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    Microwave assisted patterning of vertically aligned carbon nanotubes onto polymer substrates
    (Georgia Institute of Technology, 2006-07) Sunden, Erik Oscar ; Moon, Jack K. ; Wong, C. P. ; King, William P. ; Graham, Samuel
    This paper presents a low pressure hot embossing method for transferring patterns of vertically aligned carbon nanotubes into thermoplastic substrates. The procedure utilizes the synthesis of carbon nanotubes in discrete patterns on silicon substrates through the vapor liquid solid growth mechanism. The nanotube pattern and silicon stamp is placed on top of a polycarbonate film and locally heated above the glass transition temperature using microwave processing. The weight of the silicon substrate presses the nanotubes into the polycarbonate, resulting in the complete transfer of vertically aligned patterns. The technique is a rapid processing method, which could be used to integrate aligned nanomaterials with MEMS and flexible electronics that are fabricated on a wide range of thermoplastic polymer materials.
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    Nanomaterial transfer using hot embossing for flexible electronic devices
    (Georgia Institute of Technology, 2006-02-26) Allen, Ashante ; Sunden, Erik Oscar ; Cannon, Andrew ; Graham, Samuel ; King, William P.
    We demonstrate hot embossing to pattern carbon nanotubes (CNTs) on flexible substrates. Patterns of CNTs grown on both microtextured and flat silicon templates were transferred into polymer substrates, with good replication of both the CNT patterns and surface relief features. The transferred CNTs formed a highly entangled network with electrical resistance of 1 kΩ–9 MΩ, depending on growth and embossing conditions. The electrical properties showed a strong sensitivity to both light and temperature. This dry transfer process shows promise for high throughput manufacturing of nanomaterial-based flexible electronic devices.
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    Room-temperature chemical vapor deposition and mass detection on a heated atomic force microscope cantilever
    (Georgia Institute of Technology, 2006-01) Sunden, Erik Oscar ; Wright, Tanya L. ; Lee, Jung Chul ; King, William P. ; Graham, Samuel
    This letter reports the localized room-temperature chemical vapor deposition of carbon nanotubes (CNTs) onto an atomic force microscope cantilever having an integrated heater, using the cantilever self-heating to provide temperatures required for CNT growth. Precise temperature calibration of the cantilever was possible and the CNTs were synthesized at a cantilever heater temperature of 800 °C in reactive gases at room temperature. Scanning electron microscopy confirmed the CNTs were vertically aligned and highly localized to only the heater area of the cantilever. The cantilever mechanical resonance decreased from 119.10 kHz to 118.23 kHz upon CNT growth, and then returned to 119.09 kHz following cantilever cleaning, indicating a CNT mass of 1.4×10 ⁻¹⁴ kg. This technique for highly local growth and measurement of deposited CNTs creates new opportunities for interfacing nanomaterials with microstructures.