Date on Master's Thesis/Doctoral Dissertation

12-2012

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Electrical and Computer Engineering

Committee Chair

Harnett, Cindy K.

Author's Keywords

CVD; carbon nanotubes; sensors; graphere

Subject

Nanotubes; Carbon; Gas detectors

Abstract

The discovery of carbon nanotubes and subsequently graphene has led to an interest in carbon materials as sensing elements due to their unique properties. Graphene is a 2-dimensional material that has a large surface area that can be exposed to surface adsorbates from a target gas. This enables studies on the interaction of gas molecules with the graphene surface and subsequent changes in its properties. Graphene also exhibits high conductivity and low noise and has low crystal defects. Due to its high electron mobility at room temperature, graphene exhibits high sensitivity (in tune of detecting ppm) which is a required trait in environmental and industrial sensing applications, making graphene a good candidate for sensors. Several models of sensors based on graphene as sensing element have been put forth previously based on high-resolution lithographic techniques and for individual electrode attachment to the sensing film with e-beam lithography. These techniques can produce small numbers of devices that explore the limits of molecular scale sensing, but the methods are currently impractical for large scale production of low cost sensors. The work presented here counters this labor-intensive process and puts forth a practical lowcost sensor. Graphene sheets grown using chemical vapor deposition are transferred onto an acrylic chip designed for gas sensing. The working principle of the sensor is the electrical conductivity change exhibited by the graphene when molecules adsorb onto the material while the sensor chip is exposed to the target gas in a controlled environment. We present our graphene based sensor with the focus on designing small, cost effective and reliable sensors with high sensitivity towards the target gas, detailing the assembly of graphene/acrylic based devices, their characterization and investigation of their performance as resistive chemical sensors using different substrates as graphene supports.

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