Solution Processable Carbon-Based Electronics
Author(s)
Ball, James Michael
Type
Thesis
Abstract
Fabricating electronic devices using solution-based processing methods opens up a broad
range of potential applications that are inaccessible to conventional semiconductor fabrication
technologies. The chemically diverse family of carbon-based materials are suitable for
this purpose with almost limitless possibilities for molecular tailoring. The present work
is a study of some of the materials for and device physics of field-effect transistors based
on solution processable layers. Each aspect of this work is chosen to address a current
difficulty in the development solution-processable carbon-based electronics.
For portable and battery-powered applications, low-power circuits are required. This
can be achieved by using a complementary logic circuit architecture (that requires both
electron and hole transporting semiconductors) where the discrete devices operate at low
voltages. Practically, this requires a high capacitance gate dielectric which is compatible
with solution processing of a range of semiconductor materials. One family of molecules
suitable for this purpose are self-assembling phosphonic acids that can form molecular
monolayers. In the present study, molecular tailoring of this family of molecules is investigated
as a route towards improving the compatibility of these dielectrics with solution
processed semiconductors.
One of the difficulties with utilising a complementary logic circuit architecture is the
requirement of a suitable electron transporting semiconductor. This semiconductor must
be solution-processable, exhibit a high electron mobility and be stable against degradation
upon atmospheric exposure. Although many p-channel semiconductors fulfil these
requirements, equivalent performance in many families of n-channel semiconductors remains
challenging. In the present study, the use of fullerenes, a widely used family of
semiconductors, is explored for implementation as an n-channel material in field-effect
transistors. Their electronic structure is controlled by chemical tailoring of each molecule
and the impact of this parameter variation on the air-stability of these fullerenes is assessed.
Graphene, potentially one of the most important materials for future electronics, is
currently impractical to prepare over large areas. Chemical derivation routes are sought
which allow processing of graphene from solution. One of the most important routes
is solution phase exfoliation of graphene oxide followed by thermal or chemical reduction.
Unfortunately this introduces a high density of defects within the final graphene
layer which ultimately limits the charge-carrier mobility. Here, a milder oxidation with
surfactant-assisted solution phase exfoliation is investigated as a route to improving the
quality of graphene films following reduction. The electronic properties of thin- films of
these chemically-derived graphene layers are explored as the active layer in field-effect
transistors.
range of potential applications that are inaccessible to conventional semiconductor fabrication
technologies. The chemically diverse family of carbon-based materials are suitable for
this purpose with almost limitless possibilities for molecular tailoring. The present work
is a study of some of the materials for and device physics of field-effect transistors based
on solution processable layers. Each aspect of this work is chosen to address a current
difficulty in the development solution-processable carbon-based electronics.
For portable and battery-powered applications, low-power circuits are required. This
can be achieved by using a complementary logic circuit architecture (that requires both
electron and hole transporting semiconductors) where the discrete devices operate at low
voltages. Practically, this requires a high capacitance gate dielectric which is compatible
with solution processing of a range of semiconductor materials. One family of molecules
suitable for this purpose are self-assembling phosphonic acids that can form molecular
monolayers. In the present study, molecular tailoring of this family of molecules is investigated
as a route towards improving the compatibility of these dielectrics with solution
processed semiconductors.
One of the difficulties with utilising a complementary logic circuit architecture is the
requirement of a suitable electron transporting semiconductor. This semiconductor must
be solution-processable, exhibit a high electron mobility and be stable against degradation
upon atmospheric exposure. Although many p-channel semiconductors fulfil these
requirements, equivalent performance in many families of n-channel semiconductors remains
challenging. In the present study, the use of fullerenes, a widely used family of
semiconductors, is explored for implementation as an n-channel material in field-effect
transistors. Their electronic structure is controlled by chemical tailoring of each molecule
and the impact of this parameter variation on the air-stability of these fullerenes is assessed.
Graphene, potentially one of the most important materials for future electronics, is
currently impractical to prepare over large areas. Chemical derivation routes are sought
which allow processing of graphene from solution. One of the most important routes
is solution phase exfoliation of graphene oxide followed by thermal or chemical reduction.
Unfortunately this introduces a high density of defects within the final graphene
layer which ultimately limits the charge-carrier mobility. Here, a milder oxidation with
surfactant-assisted solution phase exfoliation is investigated as a route to improving the
quality of graphene films following reduction. The electronic properties of thin- films of
these chemically-derived graphene layers are explored as the active layer in field-effect
transistors.
Date Issued
2011-01
Date Awarded
2011-04
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Anthopoulos, Thomas
Bradley, Donal
Sponsor
EPSRC
Creator
Ball, James Michael
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)