Anisotropy of synthetic diamond in catalytic etching using iron powder

•Synthetic diamond crystallites were etched using iron without requiring hydrogen.•The effect of temperature on the etching behaviour was demonstrated.•The anisotropy of etching on different crystal planes was investigated.•The extent of etching on diamond surface was examined quantitatively.•A schematic model for diamond etching by iron is being proposed. This paper demonstrated a novel technique for catalytic etching of synthetic diamond crystallites using iron (Fe) powder without flowing gas. The effect of temperature on the etching behaviour on different crystal planes of diamond was investigated. The surface morphology and surface roughness of the processed diamond were examined by scanning electron microscope (SEM) and laser-probe surface profiling. In addition, the material composition of the Fe-treated diamond was characterized using micro-Raman spectroscopy and the distribution of chemical elements and structural changes on Fe-loaded diamond surfaces were analyzed by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. Results showed that at the same temperature the {100} plane was etched faster than the {111} plane, and that the etching rate of both {100} and {111} plane increased with temperature. The etch pits on {100} plane were reversed pyramid with flat {111} walls, while the etch holes on {111} plane were characterized with flat bottom. It was also demonstrated that graphitization of diamond and subsequent carbon diffusion in molten iron were two main factors resulting in the removal of carbon from the diamond surface.