Low-energy D⁺ and H⁺ ion irradiation effects on highly oriented pyrolytic graphite

We have investigated the low-energy (100 eV) D⁺ and H ⁺ ion irradiation effects on the structural and chemical properties of highly oriented pyrolytic graphite (HOPG). Structural disorder due to the ion irradiation was identified by the Raman spectroscopy, the D⁺ irradiation giving rise to greater structural disorder than the H⁺ irradiation. Only sp² bonding was identified in the X-ray photoemission spectroscopy of the D⁺-irradiated HOPG, indicating no change in the surface chemical structure. The H⁺ irradiation, on the other hand, gave rise to sp³ bonding and π - π * transition, the sp³ bonding increasing with increasing irradiation dose. It is thus shown that the chemical properties of the HOPG surface may be sensitively modified by the low-energy H⁺ ion irradiation, but not by the low-energy D⁺ ion irradiation.