THESIS
2014
xv, 97 pages : illustrations (some color) ; 30 cm
Abstract
As one of the allotropes of carbon, graphene, a two-dimensional single atomic layer of graphite,
is considered as a promising material for future nano-electronic devices due to its excellence in
electrical properties. Since its emergence in 2004, graphene has attracted much interest for its great
potential in replacing silicon in modern electronic industry.
This thesis focuses on graphene with disorders. By covering graphene with metal electrode,
disorders, which are metal atoms, are introduced in graphene. Therefore, modification has been
made in conventional sample fabrication of graphene device for capacitance measurement in order
to ensure metal-covered graphene. Furthermore, the application of hexagonal boron nitride and
pick-up dry transfer technique lay the foundation fo...[
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As one of the allotropes of carbon, graphene, a two-dimensional single atomic layer of graphite,
is considered as a promising material for future nano-electronic devices due to its excellence in
electrical properties. Since its emergence in 2004, graphene has attracted much interest for its great
potential in replacing silicon in modern electronic industry.
This thesis focuses on graphene with disorders. By covering graphene with metal electrode,
disorders, which are metal atoms, are introduced in graphene. Therefore, modification has been
made in conventional sample fabrication of graphene device for capacitance measurement in order
to ensure metal-covered graphene. Furthermore, the application of hexagonal boron nitride and
pick-up dry transfer technique lay the foundation for graphene in high quality and cleanness and
the negative influence of PMMA and SiO
2 has been eliminated.
A capacitance bridge system has been proposed, in which the out-of-balance signal reflects the
capacitance of the device under test. Results show enhanced performance for capacitance bridge over commercial LCR meter.
Properties of metal-covered graphene have been investigated through capacitance measurement.
Yttrium-covered samples show broken ambipolar property resulting from perturbed electronic
structure of graphene. We attribute this unusual phenomenon to the strong bonding between
graphene carbon atoms and yttrium atoms. In the meanwhile, niobium-covered samples display
intact ambipolar properties and the amount of doping is in good agreement with theoretical mismatch
in work function. Although the binding energy between graphene carbon atom and niobium
atom is less than that between graphene carbon atom and yttrium atom, the weak bonding between
graphene and niobium atom induces resonant states in graphene. The evolution and competition
with Landau level is in good consistence with previous work concerning resonant impurities in
graphene. What’s more, this resonant states induced by niobium atom is weaker than those in
previous works since resonant states in our samples are easily destroyed by temperature.
Possible future work is proposed. Sputter would realize more controllable amount of metal
atom impurities and the interaction between graphene and other metals should be interesting.
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