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    Investigating Defects in the Sensing Mechanism of Carbon Nanotube Field-Effect Transistors

    Cover for Investigating Defects in the Sensing Mechanism of Carbon Nanotube Field-Effect Transistors
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    View/Open: Hankins_georgetown_0076D_14166.pdf (5.4MB) Bookview

    Creator
    Hankins, Andrew
    Advisor
    Paranjape, Makarand
    ORCID
    0000-0002-0068-425X
    Abstract
    In nanotechnology, understanding the effect of interfaces and defects becomes critically
     
    important in determining a material’s properties and device performance. It is well known that
     
    one-dimensional and two-dimensional materials exhibit excellent physical, electrical, thermal,
     
    and optical properties, making them highly desirable for a wide array of applications. However,
     
    their low dimensionality also means they can be heavily affected by defects in the material and
     
    the interfaces they form with other materials commonly used in semiconductor device
     
    fabrication. Carbon nanotubes are one such material that is often used in sensing applications.
     
    The best and most commonly used device configuration for carbon nanotube-based sensors is the
     
    field-effect transistor. To fabricate a carbon nanotube field-effect transistor, metal contact
     
    electrodes must be deposited on either side of a semiconducting carbon nanotube. The resulting
     
    interface between the metal and the nanotube form a Schottky barrier, which can have an
     
    important role in establishing transistor characteristics. Modifications to this interface by the
     
    environment can modulate the barrier and produce a commensurate change in the overall
     
    performance of the device. Transistor operation may also be modified by the presence of defects
     
    in the carbon nanotube structure. The role of defects and the interplay between the Schottky
     
    barrier at the interface and the defects present in the carbon nanotube represent critical areas of
     
    interest when studying sensors based on carbon nanotube field-effect transistors. Therefore, the
     
    iv
     
    purpose of this study is to explore how defects in carbon nanotubes can affect the sensing
     
    mechanism, and to assess its relative importance when compared with modulations of the
     
    Schottky barrier in carbon nanotube field-effect transistor-based sensors. To explore this effect,
     
    carbon nanotube field-effect transistors have been fabricated as gas sensors, specifically to detect
     
    ammonia (an electron donor) and nitrogen dioxide (an electron acceptor). Gas exposure
     
    measurements were performed on near pristine (low defect) nanotube devices and compared with
     
    highly-defective nanotube devices. By utilizing selective passivation of critical device areas to
     
    isolate the sensing mechanism, results show that the presence of defects has a critical role in the
     
    sensing mechanism of carbon nanotube field-effect transistor gas sensors. Results also suggest a
     
    resolution to the long-standing debate over the sensing mechanism of these devices. These
     
    results represent an important step toward understanding the effect of both interfaces and defects
     
    for carbon nanotube sensor development and adds a critical piece of understanding necessary for
     
    the development of future nanoscale sensors.
     
    Description
    Ph.D.
    Permanent Link
    http://hdl.handle.net/10822/1055016
    Date Published
    2019
    Subject
    Carbon Nanotubes; Chemical Sensing; Defects; Field-Effect Transistor; Passivation; Sensing Mechanism; Solid state physics; Condensed matter; Nanoscience; Physics; Condensed matter physics; Nanoscience; Physics;
    Type
    thesis
    Publisher
    Georgetown University
    Extent
    159 leaves
    Collections
    • Graduate Theses and Dissertations - Physics
    Metadata
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    • Cover for Mechanism of Gas Sensing in Carbon Nanotube Field Effect Transistors

      Mechanism of Gas Sensing in Carbon Nanotube Field Effect Transistors 

      Dube, Isha (Georgetown University, 2014)
      Gas sensors based on carbon nanotubes in the field effect transistor configuration have exhibited impressive sensitivities compared to the existing technologies. However, the lack of an understanding of the gas sensing ...
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    Georgetown University Seal
    ©2009 - 2023 Georgetown University Library
    37th & O Streets NW
    Washington DC 20057-1174
    202.687.7385
    digitalscholarship@georgetown.edu
    Accessibility