Influence of structural defects toward the nickel-catalyzed etching behaviors of synthetic diamond

Diamond is an attractive material for next-generation wide-bandgap devices, while the top-down processing is very challenging due to its stable chemical and physical properties. Although the metal-catalyzed diamond etching process is quite promising to fabricate different atomic-flat surface structures, a clear understanding on the influence of various defects on the catalytic behaviors is so far missing. Here, metal-catalyzed (nickel (Ni), as the prototype) etching process of the synthetic diamond is investigated by electron microscopy. Our quasi in-situ observations showed that the Ni-catalyzed diamond etching behavior is lattice plane-dependent and the Ni nanoparticles (NPs) prefer to slide along the 110 orientations on the {111} surface. Moreover, the size, density and depth of the etching pits can be effectively modulated by the boron-doping level. The lateral movement of Ni NPs can be restricted by the planar defects, resulting in a larger etching rate along the twin planes/stacking faults. The grain boundaries of diamond were observed to act as a fast diamond-to-graphite transformation route. These results provide deep insights into the understanding of the role of defects in metal-catalyzed diamond etching, and could act as the basement of controllable etching in the diamond-based semiconductor industry.