Electronic properties of surface conducting hydrogen-terminated diamond

Submission note: A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the Department of Physics, School of Engineering and Mathematical Sciences, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora.

The present work details a series of investigations primarily focused on the surface conductivity that arises at the hydrogen-terminated diamond surface. The goal is to understand the surface transfer doping process between the diamond and acceptor overlayer, and also the electronic behaviour of the accumulation layer that forms below the diamond surface. The significant research milestones presented are: An angle-resolved photoemission study of hydrogen-terminated [100] diamond to determine the bulk valence band dispersion of diamond and subsequently determine a one-band carrier effective mass. In-situ simultaneous photoemission, Kelvin probe and electrical measurements to study the response of surface conducting diamond to doping with C60F48. This determines a ‘universal’ curve to describe band bending as a function of accumulated holes, and the formation of an interface dipole that is directly dependent on the amount of transferred charge. High-resolution surface sensitive photoemission spectroscopy reveals C60F48 molecules on the hydrogen-terminated diamond surface have two distinct charge states. These charge states correspond to molecules that participate in charge transfer and those that do not. Quantitative analysis of the ratio of these charge states has led to the development of a model that explains the charge transfer process in diamond. This model has been applied to angle-resolved photoemission data of epitaxial graphene grown on Silicon Carbide doped with C60F48 to successfully the explain the observed behaviour. Finally, we report on the observation of weak localization and weak anti-localization effects in surface conducting diamond at low temperature. This not only conclusively proves the two-dimensional nature of the hole gas in surface conducting diamond, but also reveals the presence of strong spin-orbit interaction at the surface of hydrogen-terminated diamond that could lead to new devices incorporating spin manipulation. The results chapters in this thesis are comprised of a collection of published journal articles.