Annealing studies combined with low temperature emission Mossbauer spectroscopy of short-lived parent isotopes: Determination of local Debye-Waller factors

An extension of the online implantation chamber used for emission Mossbauer Spectroscopy (eMS) at ISOLDE/CERN that allows for quick removal of samples for offline low temperature studies is briefly described. We demonstrate how online eMS data obtained during implantation at temperatures between 300 K and 650 K of short-lived parent isotopes combined with rapid cooling and offline eMS measurements during the decay of the parent isotope can give detailed information on the binding properties of the Mossbauer probe in the lattice. This approach has been applied to study the properties of Sn impurities in ZnO following implantation of In-119 (T-1/2 = 2.4 min). Sn in the 4+ and 2+ charge states is observed. Above T > 600 K, Sn2+ is observed and is ascribed to Sn on regular Zn sites, while Sn2+ detected at T < 600 K is due to Sn in local amorphous regions. A new annealing stage is reported at T approximate to 550 K, characterized by changes in the Sn4+ emission profile, and is attributed to the annihilation of close Frenkel pairs.