Vertical nanodiamond dominated sheets possessing both high capacitance and high n-type Hall mobility

It is very difficult to prepare vertical nanodiamond (VND) dominated sheets compared with vertical graphene (VG) sheets. Here, we describe the preparation of VNDs by phase transformation from Ta-loaded VGs via argon/oxygen plasma treatment with varied oxygen percentage. As the oxygen percentage increases to 5%, the height of VGs decreases, accompanied by high capacitance and low Hall mobility. When the oxygen percentage increases to 10%, the VGs transform to nanocrystalline diamond (NCD) grains with trans-polyacetylene (TPA) contents in grain boundaries increasing significantly. These VNDs exhibit both high capacitance (1452 μF cm^-2) and n-type Hall mobility (846 cm²V^-1s^-1). With the oxygen percentage increasing to 20%, NCD grains grow larger and the TPA content reduces, while the capacitance decreases considerably, but Hall mobility remaining high, suggesting that the performance improvement results from the synergistic effect of NCDs and TPA. These exhibit significant applications of VNDs in energy storage, high performance sensors, high-frequency and high-power electronic devices.