Experimental study of electron transport in mesoscopic carbon based nanostructures
In this thesis we have studied experimentally electronic transport in mesoscopic
hybrid polypyrrole-gold devices and single multiwalled carbon nanotube
devices.
A novel fabrication technique for mesoscopic conducting hybrid polymer-gold
films has been developed. The hybrid polymer-gold films have been fabricated by
electrochemical deposition of polypyrrole on a gold nanoisland layer. Temperature
dependence of conductance show that the dominant transport mechanism in the
polypyrrole-gold films is variable range hopping in the temperature range from 20
K to 300 K. At very low temperature strong nonlinearities in the field dependent
conductance are observed. The field dependence follows a phenomenological model
that is different from conventional field dependent transport theories probably due
to the presence of gold islands embedded in polymer.
Further, we have explored size and temperature dependences of basic electrical
properties of intermediate sized multiwalled carbon nanotubes in a diameter
range, 3 to 10 nm, which has not been systematically explored previously. In particular,
we have observed in gate controlled conductance measurements, transport
gaps which become more pronounced with decreasing temperature. Many transport
features are found to scale with channel length and diameter of the nanotube
devices. These include onstate and offstate resistances, on/off ratios, as well as periodicities
of Coulombic oscillations. The kind of scaling behaviours observed are
a manifestation of both diameter dependent intrinsic bandgaps and localization effects.
However, some deviations from the scaling and complex transport gaps have
also been observed which may be due to chiralities and possible interwall effects.
...
Publisher
University of JyväskyläISBN
978-951-39-4723-1ISSN Search the Publication Forum
0075-465XKeywords
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