Coulomb explosion potential sputtering induced by slow highly charged ion impact

We have observed secondary ion emission from a hydrogen-terminated Si(111) 1 × 1 surface and a native SiO 2 thin film on the Si substrate ( SiO 2 ∕ Si ) irradiated with slow ( v ion < v Bohr ) iodine highly charged ions (HCIs) in a wide range of charge state q from q = 15 up to 50. The yields of secondary ions evaluated from time-of-flight mass spectra showed rapid increases with q of the projectile. The relation of the yields to the potential energy of HCIs is discussed in terms of the Coulomb explosion model. It was found that the simultaneous emission of multiple Si + ions occurs in an event of a single high- q HCI impact onto the SiO 2 ∕ Si .