Effects of post-deposition heat treatment and hydrogenation on electrical conductivity of nanodiamond films

Effects of post-deposition hydrogenation on electrical conductivity of intrinsic and nitrogen doped nanodiamonds have been characterized. Nanodiamond films were deposited by means of microwave plasma assisted chemical vapor deposition in gas mixtures of methane and argon with little or without hydrogen additives. For nitrogen doped nanodiamonds, nitrogen gas of varied flow rates was added to the gas mixture of methane and argon as a dopant. Electrical conductivity of as-grown nanodiamond films was measured by either (i) directly measuring the conductivity of a metal/nanodiamond/metal sandwich test structure or (ii) applying an electrical current through two terminals of a van der Pauw test structure while measuring the voltage across the other two terminals on corners of a nanodiamond film that was deposited on an electrically insulating surface of a substrate. The same measurement was repeated after subjecting the nanodiamond to a heat treatment and later repeated again after exposing the nanodiamond to hydrogen plasma. Effects of the heat treatment and the plasma hydrogenation on electrical conductivity of nanodiamond are reported and discussed.