Nano-crystalline diamond electrodes with cap layer decorated by gold particles

We describe the electrochemical characteristics of a nano-crystalline diamond (NCD) electrode with a thin (∼ 60 nm) low-doped cap layer on a highly boron-doped diamond contact layer, where the grain boundary areas of the surface are decorated by gold particles by electroplating. The presence of the surface cap layer leads to a reduced background current compared to the highly doped NCD electrodes. At the same time, the electrical resistance to the gold particles via grain boundary defects of the cap layer does not limit the activity of the particles in 0.1 M H2SO4 electrolyte. The equivalent circuit of the decorated cap-layer electrodes is discussed using the results of electrochemical impedance spectroscopy and data on gold–diamond Schottky diodes fabricated on identical NCD layers. This equivalent circuit can be reduced to a low number of key elements, which could be useful for optimizing such electrodes for high sensitivity/low noise applications.