On the stability of electronic perturbations on a graphite surface produced by low-energy ion bombardment

The stability of the electronic perturbations (EPs) on a graphite surface produced by low-energy argon ion bombardment was investigated. The ion bombardment was performed using an ion irradiation system consisting of a compact microwave ion source directed to the observation site for scanning tunneling microscopy. We measured the change in the number of the EPs upon repetitive ion bombardment and found that the numbers saturated with the ion dose. Similar experiments were made for a carbon ion-bombarded sample, but the number increased in proportion to the ion dose. Long-time observations of the surface after ion bombardment revealed that the number of EPs gradually decreased for the case of argon ion-bombarded sample. The experimental results suggest that desorption of argon may contribute to the decrease of the EP.