Vacancy defects in thin-film La0.5Sr0.5CoO3−δ observed by positron annihilation

Abstract

Vacancy-related defects in laser ablated thin films of the conducting metal–oxide La0.5Sr0.5CoO3−δ were detected using a variable-energy positron beam. The nonstoichiometry, δ, was altered by varying the oxygen partial pressure within the deposition chamber present during cooling. Conductivity measurements confirmed the change in oxygen content. Increased positron trapping at vacancy defects was observed with increasing nonstoichiometry. It is proposed that vacancy clusters were present in the film cooled in 10−5 Torr oxygen.