Lattice sites of ion-implanted Cu atoms in diamond

Radioactive 67Cu atoms were accelerated to 60 keV at the online isotope separator ISOLDE at CERN, and implanted into a type IIa natural diamond sample to a dose of 2x1012 cm-2. The channeling of β--particles and conversion electrons emitted in the decay of 67Cu and 67Zn*, respectively, were monitored about the three major axial directions with a two-dimensional position-sensitive detector. The electron emission channeling data were collected from the room-temperature-implanted sample and after annealing at 1200 K. The observed channeling patterns were fitted with simulations based on the many beam formalism of electron motion through a crystal lattice. In the as-implanted sample, 25% of the Cu atoms were located a mean, isotropic displacement of 0.25(5) A from substitutional sites, and the remainder, fR=75%, at sites that gave an isotropic emission yield. Annealing at 1200 K results in enhanced axial and planar channeling effects. The fits to the data yield either a fraction f1=45(5)% of Cu atoms located 0.24(4) A from substitutional sites and fR=57%, or a fraction f1=10(2)% at substitutional sites, a fraction f2=50(5)% at mean isotropic displacement of 0.5 A from substitutional sites, and a 'random' fraction fR=40%