A thesis submitted to the Faculty of Science, University of the
Witwatersrand, Johannesburg, in fulfilment of the requirements for the
degree of Doctor of Philosophy.
Johannesburg, June, 2013 / Diamond with its outstanding and unique physical properties offers the opportunity
to be used as semiconductor material in future device technologies. Promising ap-
plications are, among others, high speed and high-power electronic devices working
under extreme conditions, such as high temperature and harsh chemical environments.
With respect to electronic applications, a controlled doping of the material is neces-
sary which is preferably done by ion implantation. The ion implantation technique
allows incorporation of foreign atoms at de¯ned depths and with controlled spatial
distribution which is not achievable with other methods. However, the ion implanta-
tion process is always connected with the formation of defects which compensate and
trap charge carriers thus degrading the electrical behaviour. It is therefore essential
to understand the nature of defects produced under various implantation conditions.
In this respect, this study involves the investigation of the nature of the radiation
damage produced during the multi-implantation of carbon ions in synthetic high-
pressure, high-temperature (HPHT) type Ib diamond spread over a range of energies
from 50 to 150 keV and °uences, using the cold-implantation-rapid-annealing (CIRA)
routine. Single energy implantation of carbon ions in synthetic HPHT (type Ib), at
room temperature, was also performed. Both ion milling and FIB (Focused Ion
Beam) milling were used to prepare thin specimen for transmission electron micro-
scope (TEM) analysis.
The unimplanted, implanted and annealed samples were characterized using trans-
mission electron microscopy based techniques and Raman spectroscopy.
ii
iii
In unimplanted type Ia natural diamond, a high density of platelets, exhibiting the
typical contrast of both edge-on and inclined platelets on f100g planes was found.
As-implanted HPHT type Ib diamond, implanted with single energy of 150 keV car-
bon ions and °uence of 7£1015 ions cm¡2 revealed an amorphous diamond layer of
about 80 nm in thickness while, for low °uence implantations, the damaged diamond
retained its crystallinity after annealing at 1600 K. In addition, damaged diamond
transformed into disordered carbon comprising regions with bent (002) graphitic
fringes and regions of amorphous carbon when high °uence, i.e., one above the amor-
phization/graphitisation threshold were used followed by rapid thermal annealing at
1600 K. Furthermore, the interface between the implanted and annealed layer and
the diamond substrate at the end of the range, showed diamond crystallites, inter-
spersed between regions of amorphous carbon and partially graphitized carbon. This
indicates that solid phase epitaxial recrystallization regrowth in diamond does not
occur.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/13350 |
| Date | 06 January 2014 |
| Creators | Nshingabigwi, Emmanuel Korawinga |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf |
Page generated in 0.014 seconds