|dc.contributor.author||Amos, Terri Emma||
|dc.description.abstract||Materials in nuclear reactors and satellites experience continually damaging
radiation which leads to their degradation over time. Currently, a materials
safe working lifetime within these environments is estimated with a large, costly,
safety margin. The work of this thesis aims to improve the usefulness of an optical
technique known as reflection anisotropy spectroscopy (RAS), which once fully
characterised could allow materials to be actively monitored in such environments.
The intrinsic optical anisotropy of the Cu(110) surface has been exploited to study
nanoscale kinetics of ion bombarded surfaces. Within the Cu(110) RA spectrum
the 2.1eV peak is particularly sensitive to surface defects and largely unaffected
by the bulk of the substrate. Using the Poelsema-Comsa model (which assumes
defects scatter surface electronic states within a patch centred on the defect) it
can be demonstrated that at finite temperatures the decay of the 2.1eV peak
contains information relating to the diffusion of surface defects. A kinetic Monte
Carlo simulation has been created to model the destruction of this peak and
allows further understanding of the diffusion processes involved.
The decay of the 2.1eV peak with ion bombardment has been successfully modelled
for a range of temperatures using experimental RAS data for comparison.
Through a novel way of analysing RAS data, it has been shown that the total
scattering cross section per ion impact decreases with bombardment time, which
it is believed to be due to surface diffusion. This could give a novel way of
measuring surface diffusion directly from RAS measurements.
Clustering of ion induced surface defects has been analysed and the results found
are consistent with STM images of the same surface obtained 30 minutes after
bombardment. While molecular dynamics calculations have previously attempted
to predict the surface topology and defect clustering nanoseconds after impact,
using a kinetic Monte Carlo simulation improves on this, demonstrating that
diffusion on long time scales (currently inaccessible using molecular dynamics
calculations) play an important role in predicting nano-surface topology.
2.1eV peak recovery after surface damage by ion bombardment was also
investigated. The peak was found to recover at finite temperatures, which is also
seen in experimental data. It was concluded that the surface diffusivity values in
the literature are too high and a new value for diffusivity has been calculated by
comparing simulation and experimental data.||en
|dc.contributor.sponsor||Engineering and Physical Sciences Research Council (EPSRC)||en
|dc.publisher||The University of Edinburgh||en
|dc.subject||reflection anisotropy spectroscopy||en
|dc.subject||kinetic Monte Carlo||en
|dc.title||Modelling nanoscale kinetics of radiation damaged surfaces||en
|dc.type||Thesis or Dissertation||en
|dc.type.qualificationname||PhD Doctor of Philosophy||en