Carbon overgrowths and ion beam modification studies of FCC crystals by ion implantation
Date
2008-06-26T07:04:42Z
Authors
Naidoo, Shunmugam Ramsamy
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Abstract
At the onset of this study, the work presented in Chapter 3 of this thesis was the
primary focus. The work was motivated by JF Prins where he observed the formation
of diamond layers on copper followed by C+ implantation into copper. This initial
result suggested that it may be possible to generate single crystal diamond layers on
single crystal copper. Subsequent efforts to reproduce this result failed. A unique
end station was developed where a number of parameters could be altered during
the implantation process. A series of carbon ion implantations were carried out on
copper and copper-nickel (FCC) single crystals in this end station. The layers were
characterised using initially Auger Electron Spectroscopy (AES), Low Energy Electron
Diffraction (LEED) and later Raman Spectroscopy. During the early period of this
study, the surface science equipment at the then Wits-Schonland Research Institute
for Nuclear Sciences, was constantly giving problems. The time constraints on waiting
for funds to be made available to repair the equipment, urged me to pursue alternative
research endeavours and the results of this research is presented in chapter 4 and 5.
The initial work will be investigated further in the future. Details of the end station
are presented and the initial results of carbon layers generated in this end station are
presented.
In chapter 4, a study of C+ implantation into a type IIa (FCC single crystal) diamond
using the cold implantation rapid annealing (CIRA) technique is reported. The Raman
spectrum was recorded as a function of annealing temperature and C+ ion dose. De-
fect peaks at 1450, 1498 and 1638 cm−1 appear in the Raman spectra, which have been
previously considered to be unique to MeV implantation. The maximum energy of
implantation used in this study was 170 keV. The peaks were monitored as a function
of annealing temperature and ion dose. The annealing behaviour of the peaks were
similar to those observed in the MeV implantation experiments. It is thus concluded
that the defects that give rise to these peaks are related to the point-defect interac-
tions that occur within the implantation regime and not to the implantation energy.
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Understanding the nature of the defects that arise during the implantation annealing
process, allows one to manipulate the implantation-annealing cycle, so as to generate
defect structures that are useful in the fabrication of an active device in a diamond
substrate. This is shown in chapter 5.
A p-type (type IIb, FCC crystal) diamond was implanted with either carbon or phos-
phorus ions using the cold implantation rapid annealing (CIRA) process. In each case,
the energies and doses were chosen such that upon annealing, the implanted layer
would act as an n-type electrode. The electroluminescence (EL) emitted from these
carbon and phosphorus junctions, when biased in the forward direction, was compared
as functions of annealing and diode temperatures. Typical luminescence bands such as
those observed in cathodoluminescence (CL), in particular blue band A (2.90 eV) and
green band (2.40 eV) were observed. Two bands centred around 2.06 and 4.0 eV were
also observed for both the carbon and phosphorus junctions, while a band at 4.45 eV
appeared only in the phosphorus implanted junction. This was the first time that the
4.45 eV band was observed in an electroluminescent junction.
Description
Keywords
ion implantation, copper crystals