A STM study of the effects of the ion incident angle and energy on surface damage induced by Ar + bombardment of HOPG

Abstract

Scanning tunnelling microscopy has been used to study the surface damage induced by ion bombardment of highly ordered pyrolytic graphite (HOPG). Ar ions with energies in the range from 0.5 to 3 keV were used to bombard HOPG surfaces at different angles of incidence. A low fluence ( < 2 × 10 12 ions cm 2 ) was used to enable characterisation of single ion impacts on surfaces. It is shown that each ion impact creates a small protrusion on the HOPG surface whose average volume increases as the ion energy and the incident angle to the surface decreases in the range investigated. Statistical distributions of protrusion diameter and height are given for comparison, as well as the average diameter and height. The origin of these features on the surfaces is discussed. It is suggested that thermal spikes created by the ion in the near surface region may play a very important role in producing this surface damage.