The hillock formation on the basal planes of graphite due to ion interaction

Abstract

Highly oriented graphite materials were modified by the introduction of foreign species, i.e. doped by iron and implanted by energetic ions. On irradiated surfaces, hillocks were observed and assessed using STM. An increase in atomic weight of the implanted energetic ions led to an increase in area of the damaged surface of graphite and a low RRR value indicated a high density of hillocks in iron-doped graphite. The formation of hillocks is based on the displacement of carbon atoms in graphite basal planes: cascade collision due to implanted ions and protuberances created along the carbon layers by diffusion of species due to iron doping. The heat treatment of the irradiated graphite led to an increase in height of the pre-existing hillocks by diffusion of the trapped atoms towards the surface. The heat treatment of iron-doped graphite at 2800°C allowed the increase in hillock number due to the diffusion of trapped atoms along the graphite layers.