Abstract:
This research focuses on the study of the impurities in low-strain high pressure,
high temperature (HPHT) synthetic diamonds. The dominant characterisation
methods are synchrotron-based x-ray techniques, supported by
other conventional laboratory techniques. The research identifies the role
of defects in generating long-range strain. A software programme based on
the dynamical theory of x-ray diffraction has specially been developed to
quantify the local changes in the lattice parameter and the local lattice inclinations
(combined as the “effective misorientation” or local Bragg angle
change). In recent measurements, the strain sensitivity of the (quantitative)
x-ray plane-wave monochromatic topography was increased to the level of
10−8. This level of sensitivity was achieved using the double crystal technique
with successively higher order reflections and correspondingly, higher
energy x-rays. This is a level which has never previously been accessed for
diamond.
Preliminary results for this research have already contributed immensely to
driving a technological development of a new range of diamond-based x-ray
optical elements for modern third and fourth-generation x-ray sources like
synchrotron storage rings and Free Electron Lasers (FEL), where industry
(industrial diamond growers) and end-users (the synchrotrons of the world)
participate collaboratively in a research and development programme.
Description:
MSc., Faculty of Science, University of the Witwatersrand, 2011
