The aim of this research was to develop the sensitive diagnostic method of Time
Differential Perturbed Angular Distributions (TDPAD) using implanted fluorine (10F)
as the nuclear probe, and apply it to defect and impurity studies of diamond crystals,
by detecting the internal electric field gradient (efg) at the imparity sites. Defects and
impurities can substantially determine and modify the electrical and physical properties
of materials. Such studies lead to theoretical advances and new materials. Diamond
presents a unique system in which to perform these studies. The related Muon Spin
Rotation (MSR) technique, which detects the local magnetic field at the muon residence
sites, was also used to study the behaviour of the implanted hydrogen-like impurity.
The l0F is recoil implanted into the diamond by a 4 MeV pulsed proton beam
from an accelerator. The parameters describing the local efg (magnitude, asymmetry,
distribution and orientation) at the residence sites of the implanted 10F probes are
measured by detecting the perturbed Tf-ray angular distribution from the 19F deexcitation.
The efg reflects the local microscopic structure and dynamic processes.
Measurements were performed as a function of crystallographic orientation, diamond
type (naturally present defects and impurities) and temperature. Studies were also
made of other carbon allotropes.
The accelerator pulsing facilities were improved by the stabilization of the chopper
and the development of a buncher. Theoretical model functions were developed for the
analysis of data for non-axially symmetric efg’s in cubic single crystals.
Essentially two different residence sites for 19F probe ions in diamond and its
allotropes were found. The first (principal) site has a quadrupole coupling frequency of
« 60 MHz, and is well defined with near axial symmetry for the efg. The second (diffuse)
site, has a lower coupling frequency, also near axial symmetry but a large spread in the
efg. The efg Ls oriented along a crystallographic direction in both sites. The
measured degree of polycrystal'inity of the natural diamond lattice corresponded to
certain defects and impurities in diamond
