We have studied the lattice location of implanted nickel in silicon, for different doping types (n, n + and p + ). By means of on-line emission channeling, 65 Ni was identified on three different sites of the diamond lattice: ideal substitutional sites, displaced bond-center towards substitutional sites (near-BC) and displaced tetrahedral interstitial towards anti-bonding sites (near-T). We suggest that the large majority of the observed lattice sites are not related to the isolated form of Ni but rather to its trapping into vacancy-related defects produced during the implantation. While near-BC sites are prominent after annealing up to 300-500• C, near-T sites are preferred after 500-600• C anneals. Long-range diffusion starts at 600-700• C. We show evidence of Ni diffusion towards the surface and its further trapping on near-T sites at the R p /2 region, providing a clear picture of the microscopic mechanism of Ni gettering by vacancy-type defects. The high thermal stability of near-BC sites in n + -type Si, and its importance for the understanding of P-diffusion gettering are also discussed.

The lattice site location of radioactive 27Mg implanted in AlN was determined by means of emission channeling. The majority of the 27Mg was found to substitute for Al, yet significant fractions (up to 33%) were also identified close to the octahedral interstitial site. The activation energy for interstitial Mg diffusion is estimated to be between 1.1 eV and 1.7 eV. Substitutional Mg is shown to occupy ideal Al sites within a 0.1 Å experimental uncertainty. We discuss the absence of significant displacements from ideal Al sites, in the context of the current debate, on Mg doped nitride semiconductors.

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We have investigated the lattice location of implanted transition metal (TM) 56 Mn, 59 Fe and 65 Ni ions in undoped single-crystalline cubic 3C-SiC by means of the emission channeling technique using radioactive isotopes produced at the CERN-ISOLDE facility. We find that in the room temperature as-implanted state, most Mn, Fe and Ni atoms occupy carbon-coordinated tetrahedral interstitial sites (T C). Smaller TM fractions were also found on Si substitutional (S Si) sites. The TM atoms partially disappear from ideal-T C positions during annealing at temperatures between 500 °C and 700 °C, which is accompanied by an increase in the TM fraction occupying both S Si sites and random sites. An explanation is given according to what is known about the annealing mechanisms of silicon vacancies in silicon carbide. The origin of the observed lattice sites and their changes with thermal annealing are discussed and compared to the case of Si, highlighting the feature that the interstitial migration of TMs in SiC is much slower than in Si.

We determined the lattice location of Mn in ferromagnetic (Ga,Mn)As using the electron emission channeling technique. We show that interstitial Mn occupies the tetrahedral site with As nearest neighbors (T As ) both before and after thermal annealing at 200 °C, whereas the occupancy of the tetrahedral site with Ga nearest neighbors (T Ga ) is negligible. T As is therefore the energetically favorable site for interstitial Mn in isolated form as well as when forming complexes with substitutional Mn. These results shed new light on the long standing controversy regarding T As versus T Ga occupancy of interstitial Mn in (Ga,Mn)As.[http://dx.doi.org/10.1063/1.4905556] a lino.pereira@fys.kuleuven.be (Ga,Mn)As has become the model system, in which to explore the physics of carrier-mediated ferromagnetism in semiconductors and the associated spintronic phenomena. 1,2In particular, as the most widely studied dilute magnetic semiconductor (DMS), (Ga,Mn)As is the perfect example of how the magnetic behavior of DMS materials is strongly influenced by local structure. In typical high Curie temperature (T C ) (Ga,Mn)As thin films (several % Mn regime), the majority of the Mn atoms substitute for Ga (Mn s ), while a minority fraction (several % of all Mn) occupies interstitial sites (Mn i ).3,4 Mn s provides both the localized magnetic moment and the itinerant hole that mediates the magnetic coupling, whereas Mn i has a twofold compensating effect: (i) magnetically, as Mn i -Mn s pairs couple antiferromagnetically and (ii) electrically, since double donor Mn i compensates Mn s acceptors.3 For a given Mn s concentration, Mn i therefore determines the hole concentration, the Fermi level and the effective Mn s concentration (of non-compensated Mn s moments), all of which define the magneto-electronic behavior of (Ga,Mn)As. The existence of such a crucial role of Mn i is clearly reflected in the effect of the Mn i concentration on the two relevant figures of merit: T C and magnetization. 3−5 Despite this central role in the understanding of (Ga,Mn)As, and, consequently, of Mn-doped III-V DMS materials, interstitial Mn is far from being a well understood defect. The presence of Mn i in ferromagnetic (Ga,Mn)As was first reported based on ion channeling measurements. 6Although consistent with Mn i occupying tetrahedral (T) interstitial sites, the measurements did not allow to discriminate between the two nonequivalent T sites: coordinated by four Ga atoms (T Ga ) or by four As atoms (T As ). Transmission electron microscopy measurements using the (002) diffracted beam indicated that Mn i predominantly occupies the T As site.7 X-ray absorption fine structure (XAFS) techniques were later applied, suggesting T Ga occupancy (e.g., Refs. 8 and 9). However, XAFS is not well suited to distinguish neighboring elements with similar atomic numbers, as is the case for Ga and As, especially in such cases of multi-site occupancy (substitutional and interstitial), where the site to be identified is in fact the minority one (interstitial). In pi...