Preferential {100} etching of boron-doped diamond electrodes and diamond particles by CO2 activation

The etching behavior of polycrystalline boron-doped diamond (BDD) electrodes and diamond particles with gaseous CO2 at 800 and 900°C was investigated by field-emission scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. Polycrystalline BDD (800ppm), composed of a mixture of cubic {100} and triangular {111} orientated planes, was used so as to pursue the possibility of preferential etching by high temperature CO2 treatment. Nanometer sized pits were observed on the {100} planes while no change was observable for the {111} planes when the activation temperature was 800°C. The difference in the etching behavior by CO2 with regard to the different planes was clarified using diamond particles and comparing with steam activation. The results demonstrate that CO2 activation leads to preferential {100} etching, whereas steam-activation results in preferential {111} etching.