Adsorption of D(H) atoms on Ar ion bombarded (0001) graphite surfaces

Adsorption of thermal (2000K) D (H) atoms on HOPG surfaces prior to and after bombardment with 500eV Ar ions was studied with thermal desorption and vibrational spectroscopies. Ion bombardment of HOPG generates vacancy (VD, displaced surface C atoms) and interstitial (ID, Ar captured between 1st and 2nd C plane) defects. These defects remove the ability of the surface to adsorb D like on virgin HOPG surfaces and to form C-gr-D bonds. After a dose of 0.1 Ar per C surface atom, D adsorption is markedly suppressed. Annealing of bombarded surfaces at 1350K, connected with desorption of trapped Ar and removal of ID, recovers a large fraction of the adsorption capacity for D. Therefore, the long range stress in the surface plane introduced by ID must be responsible for a significant fraction of D adsorption blocking. It is suggested that ID prevent reconstruction of the C surface which is required for the formation of C-gr=D bonds. For ion doses above 0.5 Ar/Q adsorption of D on the surface is negligible. After annealing at 1350K, D can be adsorbed in quantities comparable to the virgin HOPG surface, however forming C-D bonds which are similar to those observed in hydrogenated amorphous carbon instead of those which are normally formed on HOPG. Instationary etching via release of deuterocarbon species occurs primarily in the C-1 and C-2 channels. It is only observed at bombarded HOPG prior to annealing and probably due to the presence of isolated C-1 and C-2 species on the surface generated upon VD formation. (C) 2004 Elsevier B.V. All rights reserved.