Deformation of $sp^2$ graphitic nanostructure by irradiation with highly charged ion

I will discuss possibility of structural deformation of graphitic $sp^2$ network by irradiation of highly charged ions. Meguro {\it et al.}, [Appl. Phys. Lett..{\bf 79}, 3866 (2001)] reported indication of nano-diamond formation on graphite surface when it is irradiated by Ar$^{+8}$ ions with incident kinetic energy of 400 eV. The nano-diamond structure was suggested from STS and IR spectrum taken after irradiation showing energy gap of 6 eV and C-C stretching with the frequency of 1360 cm$^{-1}$. This structural change was considered to be induced by injection of holes from highly charged ion (Ar$^{+8}$) while role the kinetic energy of Ar ion was thought to be marginal. Electron-ion dynamics simulation combined to the time-dependent density functional theory [O. Sugino, Y. Miyamoto. Phys Rev B{\bf 59}, 2579 (1999), {\it ibid}, Phys. Rev. B{\bf 66}, 088901(E) (2002)] has been performed to examine the mechanisms of the structural change. This simulation has found that the role of incident kinetic energy of Ar$^{+8}$ and subsequent cooling mechanisms also play crucial role in determining the structural change. More details will be presented and discussed in my talk.