Enabling diamond surface electronics through surface transfer doping

Diamond, being a bona-fide insulator, supports a surprising two-dimensional (2D) p-type surface conducting layer when its surface is both hydrogen-terminated and covered with a thin water layer (by exposure to air). The spontaneous charge exchanged between diamond and the atmospheric adsorbates dissolved in the water layer, a process known as surface transfer doping, gives rise to diamond surface conductivity. This can be exploited in building diamond surface electronic devices such as high-frequency high-power diamond field-effect transistors (FETs) and biosensors.

Using high electron affinity organic molecules, such as C60F48and F4-TCNQ, and transition metal oxides such as MoO3 as alternative solid-state surface acceptors to replace the volatile water layer, we demonstrate surface transfer doping of diamond with great efficiency and superior thermal stability.

We are now working on the integration of these novel surface acceptors into diamond device architectures to develop high-performance diamond RF power FETs with superior stability and power handling.

Apart from the device application, we are also interested in exploring the quantum transport behaviour, such as spin-orbit interaction, weak localisation (WL) and weak anti-localisation (WAL), and superconductivity, afforded by the 2D hole system on diamond surface. This work has important implications for the development of novel spintronic devices and Josephson junction devices based on diamond. This research is undertaken in collaboration with Dr Chris Pakes.