In situ AES study of damaging process of graphite surface under energetic ion bombardment

Abstract

In order to investigate the behavior of hydrogen implanted in graphite and the role of hydrogen both in damaging and annealing processes, we have performed an in situ AES analysis of graphite under hydrogen or inert gas (He or Ar) ion bombardment as well as under annealing. The results are summarized as follows. Damaging processes introduced by either H, He or Ar ion bombardment are found to be quite similar to each other, depending only on the lattice displacement effect, and both the electronic excitation effect and the chemical effect of implanted hydrogen are hardly seen in C-KLL AES spectra as well as laser Raman spectra. Considering the large enhancement of hydrogen retention in neutron irradiated graphites, it is very likely that hydrogen is trapped at preexisting damage sites, though it is hardly possible to distinguish a CH bond and a CC single bond in the present AES analysis. A certain difference does appear in the annealing between hydrogen implanted graphite and a helium implanted one. These results make us to conclude that hydrogen is trapped with a chemical bond to carbon atoms even at higher temperatures.