Atomic Force Microscopic and Raman Investigation of Boron-Doped Diamond Nanowire Electrodes and Their Activity toward Oxygen Reduction

(Graph Presented) Reactive ion etching of diamond interfaces using oxygen plasma is a widely used approach for the formation of diamond nanowires. In this paper, we highlight the influence of the doping level of the etched diamond substrate on the density of the resulting nanowires. Heavily boron-doped diamond interfaces result in very dense diamond nanowires, while etching of low boron-doped diamond substrates results in sparsely formed nanostructures, as boron dopant atoms in the diamond act as masks during the etching process. In pursuit of a better understanding of doping and plasma etching effects, we demonstrated by performing Raman imaging on single diamond nanowires that the etching process leads to a dedoping of the wire tip and a partial transformation of diamond to sp² carbon. The etching process does not, however, alter the initial diamond feature of the rest of the nanowire. Finally, the activity of the different diamond nanowires toward oxygen reduction in alkaline solution was investigated. Interestingly, high boron-doped diamond nanowire interfaces reduce oxygen at a relatively lower potential of -0.3 V vs Ag/AgCl despite the boron dedoping at the tip of the wires.