Metal-insulator transition in boron-ion implanted type IIa diamond.
Date
2000
Authors
Tshepe, Tshakane
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
High purity natural type Il a diamond specimens were used in this study. Conducting
layers in the surfaces of these diamonds were generated using low-ion dose multiple
implantation-annealing steps. The implantation energies and the ion-doses were spread
evenly to intermix the point-defects, thereby increasing the probability of interstitialvacancy
recombinations and promoting dopant-interstitial-vacancy combination resulting
in activated dopant sites in the implanted layers. The process used to prepare our samples
is known as cold-implantation-rapid-annealing (CIRA). Carbon-ion and boron-ion
implantation was used to prepare the diamond specimens, and de-conductivity measurements
in the temperature range of 1.5-300 K were made following each CIRA sequence.
An electrical conductivity crossover from the Mott variable range hopping (VRH)
to the Efros-Shklovskii VRH conduction was observed when the temperature of insulating
samples was lowered. The conductivity crossover temperature Tcross decreases with
increasing concentration of the boron-ion dose in the implanted layers, indicating the narrowing
of the Coulomb gap in the single-particle density of states near the Fermi energy. (Abbreviation abstract)
Description
A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg,
in fulfillment of the requirements for the degree of Doctor of Philosophy.
Keywords
Metal-insulator transitions., Transition metals., Ion implantation.