Nanostructuring the graphite basal plane by focused ion beam patterning and oxygenetching

Abstract

Ga+ focused ion beam (FIB) patterning was used to structure highly oriented pyrolytic graphitesurfaces with square, periodic arrays of amorphous carbon defects (mesh sizes:300 nm–2 µm). Controlled oxygen etching of these arrays leads to matrices of uniform, orientationallyaligned, nm-sized, hexagonal holes. The properties of the resulting hole assembly (hole depthsand lateral hole dimensions) have been investigated by means of atomic force microscopy,scanning electron microscopy and FIB sectioning. The hole dimensions and uniformity bothdepend on the FIB parameters and etching conditions. Etching temperatures from 500 to700 °C were applied. Initialetch rates of up to 106 C s−1 per individual hole were observed when using oxygen pressures of 200 mbar. For an etch temperatureof 590 °C the rate of etching of individual holes was found to depend measurably on the inter-holeseparation. This confirms that the associated reaction kinetics is mediated by the finitediffusion length of reactive oxygen species along the graphite basal plane. Prolongedetching results in hole–hole contact and generation of mesa arrays of controllable size andshape.