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Surface transfer doping of hydrogen-terminated diamond has been achieved utilising V2O5 as a surface electron accepting material. Contact between the oxide and diamond surface promotes the transfer of electrons from the diamond into the V2O5 as revealed by the synchrotron-based high resolution photoemission spectroscopy. Electrical characterization by Hall measurement performed before and after V2O5 deposition shows an increase in hole carrier concentration in the diamond from 3.0x1012 to 1.8x1013cm2 at room temperature. High temperature Hall measurements performed up to 300 °C in atmosphere reveal greatly enhanced thermal stability of the hole channel produced using V2O5 in comparison with an air-induced surface conduction channel. Transfer doping of hydrogen-terminated diamond using high electron affinity oxides such as V2O5 is a promising approach for achieving thermally stable, high performance diamond based devices in comparison with air-induced surface transfer doping

We report on optimisation of the environmental stability and high temperature operation of surface transfer doping in hydrogen-terminated diamond using MoO3 and V2O5 surface acceptor layers. In-situ annealing of the hydrogenated diamond surface at 400 °C was found to be crucial to enhance long-term doping stability. High temperature sheet resistance measurements up to 300 °C were performed to examine doping thermal stability. Exposure of MoO3 and V2O5 transfer-doped hydrogen-terminated diamond samples up to a temperature of 300 °C in ambient air showed significant and irreversible loss in surface conductivity. Thermal stability was found to improve dramatically however when similar thermal treatment was performed in vacuum or in ambient air when the oxide layers were encapsulated with a protective layer of hydrogen silsesquioxane (HSQ). Inspection of the films by X-ray diffraction revealed greater crystallisation of the MoO3 layers following thermal treatment in ambient air compared to the V2O5 films which appeared to remain amorphous. These results suggest that proper encapsulation and passivation of these oxide materials as surface acceptor layers on hydrogen-terminated diamond is essential to maximise their environmental and thermal stability.

Metal chalcogenides, and doped molybdenum sulfides in particular, have considerable potential as earth-abundant electrocatalysts for the hydrogen evolution reaction.