Investigation of defects in diamond implanted with N-O molecular ions
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Date
2020
Authors
Matindi, Tresor Balembo
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Abstract
The incorporation of shallow n-type dopants in diamond is one of the major challenges for its electronic
applications. n-Type behavior in diamond has been observed for substitutional phosphorus
and nitrogen, with activation energies of approximately 0.62 eV and 1.7 eV respectively. Both
nitrogen and phosphorus are deep lying substitutional impurity states in diamond. It has been
theoretically demonstrated that the substitution of the N-O molecule into the diamond lattice
forms a stable defect in the band gap and in the negatively charged state induces a shallow defect
below the conduction band edge which may lead to n-type conductivity.
In this project, surface characterization and optical spectroscopy were carried out to investigate
the nature and behavior of the defects induced by the implantation of N-O ions into type IIa Chemical Vapor Deposition (CVD) diamond samples. Photoluminescence peaks attributed to
N-O complexes were observed at 293.3 nm, 297.3 nm, 305.9 nm, 309.8 nm, 314.4 nm for the
sample which was implanted with N-O molecular ions and annealed at 600 C. The mechanism
of electronic transitions leading to emission of photoluminescence of these peaks is proposed.
In addition, a peak at 533 nm was observed on the cathodoluminescence spectrum of the same
sample and was tentatively attributed to a radiative recombination of a shallow n-type defect
and a deep lying p-type defect in the middle of the band gap, associated to vacancy-related
states. The results presented extends the knowledge on defects leading to shallow n-type dopants
in diamond. We believe that this thesis creates a paradigm for future studies on the search
for alternative suitable shallow dopants, which is the sine qua non for potential application of
diamond-based electronic devices
Description
A thesis submitted to the Faculty of Science, in fulfilment of the requirements for the degree of Doctor of Philosophy, University of the Witwatersrand, Johannesburg