Engineering the 2D Hole Gas on Diamond for Carbon-Based Electronics

Abstract

Despite being a bona-fide bulk insulator, diamond develops an intriguing two-dimensional (2D) p-type surface conductivity when its surface is terminated by hydrogen and exposed to appropriate surface adsorbate layer such as atmospheric water as a result of the surface transfer doping process. Consequently, the surface of diamond presents a versatile platform for exploiting some of the extraordinary physical and chemical properties of diamond, leading to applications such as chemical/biological sensing and the development of high-power and high-frequency field effect transistors (FETs). In this talk, I will describe our recent work on the surface transfer doping of diamond by transition metal oxides (TMOs). Specifically, I will show that by interfacing diamond with MoO3 or V2O5 a 2D hole conducting layer with metallic transport behaviours arises on diamond. Magnetotransport studies at low temperature reveal phase coherent transport in the 2D channel with a transition from weak localisation to weak antilocalisation as temperature drops, and are analysed in the context of spin-orbit coupling induced by Rashba effect (Figure 1). The obtained spin-orbit interaction is a few folds higher than that in the air-doped channel or ionic liquid gated channel with similar hole densities, suggesting that the local carrier density could in fact be much higher than that obtained by Hall-effect measurements. We also demonstrate that this surface conducting channel can be exploited to build diamond surface electronic devices such as metal-oxide semiconductor FETs (MOSFETs). Lastly, the prospects for constructing novel quantum devices on diamond surface by making use of this highly tunable 2D conducting layer on diamond are also explored.