A positron annihilation study was carried out with the aim of determining the nature of the native defects in these structures. The positron lifetimes were measured at room temperature, and a long component was found which depended upon the type of cation. Theoretical calculations were made of the bulk lifetime in these materials, and for several types of vacancy-like defect. On the basis of the experimental and theoretical results, the native defects were tentatively identified as being cation-vacancy complexes.

N.De Diego, F.Plazaola, J.Del Río, M.T.Santos, E.Diéguez: Journal of Physics - Condensed Matter, 1996, 8[9], 1301-6