Growth and Defect Formation in Graphene

Abstract

In this work, few-layer graphene (FLG) was grown from SiC(0001) with temperature,
growth time and cooling rate as variables. Samples were characterised by
Scanning Tunnelling Microscopy (STM), Low Energy Electron Diraction (LEED),
Auger Electron Spectroscopy (AES) and Raman Spectroscopy (RS) to determine
graphene quality. The information obtained from these techniques was then used to
determine optimal conditions for growing graphene from SiC(0001). Contamination
on graphene lms is also discussed and a facile method for the removal of large scale
metal contaminant layers from the surface is described.
To study adhesion of FLG to a substrate, a continuum energy model was developed
to obtain the adhesion energy via the measurement of pleat defects by STM. This
model was applied to graphene grown from SiC(0001) and its adhesion energy was
found to be signicantly larger than the those measured for graphene on other substrates.
Variation of pleat defects on graphene grown from SiC(0001) with dierent
growth parameters was also studied by STM. The factors that aect the dimensions
and concentration of pleats were determined and discussed in relation to the quality
of the lm. Further investigation was conducted on the stability of pleat defects
under STM imaging, with the presence of contamination and defects found to have
a signicant eect in reducing the dragging of pleats by the probe tip.
A comparative study of the dynamics of extrinsic defects on FLG and graphite
is also presented in this work. Samples were bombarded with 0.2 keV Ar+ ions,
heated to dierent temperatures and studied with STM. The concentration, mobility,
agglomeration and alignment of defects was examined and mechanisms suggested
for the behaviour observed. The Local Density of States (LDOS) at defect sites of
both graphite and FLG were studied by Scanning Tunnelling Spectroscopy (STS)
to determine if signicant dierences in electronic structure due to defects were
observed between the two systems.
Preliminary experiments to optimise the growth of graphene on Cu substrates by
-wall" and -wall" methods have been performed, to determine whether
cold-wall growth presents a viable alternative to hot-wall for the production of high
quality graphene. Graphene was grown by both methods using dierent growth
periods to determine the optimal growth time for each method. The use of evaporated
Cu on SiO2 as growth substrates is also discussed. Samples produced by
both methods were studied by Scanning Electron Microscopy (SEM) to determine
their quality. Electron Back-Scatter Diraction (EBSD) measurements were also
performed on samples produced by both methods to determine the extent to which
Cu grain orientation aects the growth of graphene.