| dc.description.abstract | Carbon nanotubes are an exciting new material with exemplary mechanical and
electronic properties. Carbon nanotubes can be either metallic or semiconducting; either
type has properties which rival conventional materials. The one-dimensional electronic
nature of these materials leads to extreme sensitivity to the local energy landscape, a
desirable property for a sensing element.
Production of carbon nanotubes currently has no method of growing nanotubes
with a speci c electronic property, any di erentiation occurs through processing a
heterogenous ensemble. Recently, networks of carbon nanotubes have shown attractive
properties for electronic applications. The self-selecting current path has properties
averaged from the ensemble of nanotubes providing repeatability in addition to
exibility
and transparency.
This thesis is a study of the transport properties of thin and thick networks of
single-walled carbon nanotubes and their electrical response to oxygen adsorption in
both a simple resistive geometry and as the gate layer in a nanotube-metal-oxide-silicon
capacitor. The thickness of network was found to determine the electrical characteristics
of the network ensemble, thin networks displaying semiconducting transport
characteristics, thick networks becoming more metallic. The response of the nanotube
networks to oxygen exposure was found to be dependent on UV treatment. UV-desorbed
networks exhibited an increased conductance upon oxygen-exposure, adsorbed networks
exhibited a decrease in conductance upon further oxygen-exposure. Thinner, more
semiconducting nanotube networks exhibited a greater change in conductance upon
oxygen exposure. The nanotube-metal-oxide-semiconductor capacitor also showed a
greater change in
at-band capacitance for thin nanotube networks. The capacitance of
the nanotube device at the nanotube network
at-band voltage is shown to be in
uenced
by both oxygen and nitrogen gases. The origin of the behaviour of the
at-band voltage
is attempted to be understood and future work is suggested.
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