Lattice sites of implanted Na in GaN and AlN in comparison to other light alkalis and alkaline earths


The lattice location of ion implanted radioactive Na-24 (t(1/2)=14.96h) in GaN and AlN was determined using the emission channeling technique at the ISOLDE/CERN facility. In the room temperature as-implanted state in both GaN and AlN, the majority of the sodium atoms are found on interstitial sites near the octahedral position, with a minority on cation Ga or Al substitutional sites. Following annealing at 800-900 degrees C, the interstitial fraction is reduced while the substitutional incorporation increases. Our results thus further establish the amphoteric character of Na in GaN and AlN, in analogy to other light alkali Li and alkaline earths Be and Mg. The site changes upon annealing are attributed to the onset of migration of interstitial Na, for which an activation energy of 2.2-3.4eV is estimated in GaN and 2.0-3.1eV in AlN, and its subsequent capture by cation vacancies resulting from the implantation. A comparison of the lattice site change behavior of Li, Be, Na, and Mg shows that the onset of interstitial migration correlates with the ionic radii of these elements. Published under license by AIP Publishing.



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Wahl, U; David-Bosne, E; Amorim, LM; Costa, ARG; De Vries, B; Correia, JG; da Silva, MR; Pereira, LMC; Vantomme, A



We thank M. Kappers from the University of Cambridge for growing GaN sample #1 and O. Briot from the University of Montpellier for growing the AlN sample. We acknowledge the beam time provided by the ISOLDE Collaboration. This work was funded by the Portuguese Foundation for Science and Technology (FCT) through Project No. CERN-FIS-PAR-0005-2017 and the Strategic Project No. UID/Multi/04349/2019, by the FWO Vlaanderen, and the KU Leuven Research Fund (No. SF/18/008). The ISOLDE beam times were supported by the European Commission through the Horizon 2020 Program (Grant No. 654002 ENSAR2).

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