B. Besold’s research while affiliated with University of Konstanz and other places

The angular dependence of the emission yields of electrons and positrons emitted from radioactive probes implanted into single crystals was first investigated by Uggerhøj.1 The channeling effect of electrons, emitted from substantial lattice sites, is responsible for enhanced emission yields in the directions of crystal axes or planes. Positrons, on the other hand, show pronounced channeling peaks, if emitted from interstitial sites and blocking dips, if emitted from substantial lattice sites as shown for a ‹110› direction in a 112m In implanted Mo crystal (Fig. 1). In an early paper2 Uggerhøj and Andersen suggested that this effect may be used as a method for the localization of foreign atoms in single crystals. From the emission yields observed for different low index crystal directions, the lattice site occupancy of the emitter atoms can be determined.

Channeling and blocking effects of electrons and positrons emitted from ion-implanted radioactive In dopants in silicon have been utilized for lattice location of In in parts-per-million concentrations. A majority of In atoms occupies substitutional sites after implantation at room temperature. Defect recovery, which is observed after annealing at 700 K, increases the channeling effects. These results corroborate conclusions from previous Mössbauer studies on the same system under identical implantation conditions. The nature of the damage cascades of the individual implanted impurity probe atoms is discussed.

Channeling and blocking effects of electrons and positrons emitted from ion-implanted radioactive In dopants in silicon have been utilized for lattice location of In in parts-per-million concentrations. A majority of In atoms occupies substitutional sites after implantation at room temperature. Defect recovery, which is observed after annealing at 700 K, increases the channeling effects. These results corroborate conclusions from previous Mössbauer studies on the same system under identical implantation conditions. The nature of the damage cascades of the individual implanted impurity probe atoms is discussed.

The ISOLDE facility at CERN has been utilized for ion implantations of radioactive In isotopes into Cu single crystals for impurity lattice-location studies by means of the channeling effects of emitted charged particles. Conversion electrons with energies around 0.2MeV (112In, 114In), electrons from beta--decays with energies up to 2 MeV (114In, 119In) and positrons (112In) were employed for the channeling measurements. These experiments demonstrate the possibility of combining channeling and Mössbauer effect measurements using 119In under identical experimental conditions.