Stability and diffusion of Hg implanted YBa2Cu3O6+x

Abstract

The radioactive isotope 197m Hg was implanted at 60 keV with low¯uences (10 13 ions/cm 2 ) into YBa 2 Cu 3 O 6x (YBCO) superconducting thin ®lms at ISOLDE/CERN. We report on the Hg dynamics and stability inside the YBCO lattice as a function of annealing temperature up to 890 K in a vacuum or O 2 atmosphere. The perturbed angular correlation (PAC) technique was used for probing the Hg behavior at the atomic scale, while by monitoring the sampleÕs activity in situ the Hg outdiusion was studied. We found that Hg ions occupy unique lattice sites and that Hg should be bound to two apical oxygens. Hg diusion occurs only for annealing temperatures above 653 K, in vacuum. The Hg migration energy was estimated to be E M 1.58 0.15 eV. Ó