The MeV implantation of Au ions into (100), followed by annealing, was used to form Au nanoparticles having modified optical properties. Variable-energy positron spectroscopy showed that clusters of two Mg and two O vacancies were attached to the Au nanoparticle surfaces within the projected range. It was also found that clusters of two Mg and two O vacancies were created at depths less than the projected range and extended into regions beyond it due to the damage which was introduced by knock-on collisions.

Vacancy Clusters on Surfaces of Au Nanoparticles Embedded in MgO. J.Xu, A.P.Mills, A.Ueda, D.O.Henderson, R.Suzuki, S.Ishibashi: Physical Review Letters, 1999, 83[22], 4586-9