Nucleation and Growth of Nanoscale to Microscale Cylindrical Pits in Highly-ordered Pyrolytic Graphite upon Hyperthermal Atomic Oxygen Exposure

The erosion of highly-ordered pyrolytic graphite (HOPG) caused by exposure to hyperthermal atomic oe p) atoms was explored. Profilometry has revealed that the overall erosion yield is linear with respect to increasing atomic oxygen exposure at a constant sample temperature of 373 K. Atomic force microscopy (AFM) was employed to image the eroded material that contains numerous nanoscale to microscale cylindrical etch pits. As there is also a linear relationship between the etch pit diameter and atomic oxygen fluence, it is proposed that the largest cylinders are nucleated at or near the topmost sheet of the original graphite material. There is a large distribution of depths for cylinders of a chosen diameter. This suggests that the chemical and physical nature of the nucleation event plays a key role in the final depth of the etch pit.