In and ex situ optical spectroscopy of HCI-bombarded solid surfaces

We have observed Raman scattering from highly oriented pyrolytic graphite (HOPG) surfaces after irradiation with highly charged ions (HCIs) as ex situ spectroscopy. HCIs having various potential energies from 5 keV for Ar16+ to 99 keV for Xe50+ were normally incident onto HOPG surfaces with the same collision velocities (5 × 105 m/s). In all spectra at fluence of 1 × 1011 ions/cm2, disorder induced peaks (D peak) appeared around 1580 cm−1 in addition to narrower peaks (G peak) which were also observed unirradiated HOPG at 1358 cm−1. Relative intensities of the D peak with respect to the G peak increase gradually as increasing potential energies of the HCIs. This shows obviously the effect of potential energy deposition on structural deformation of HOPG.