VACANCY DEFECTS IN THIN-FILM LA0.5SR0.5COO3-DELTA OBSERVED BY POSITRON-ANNIHILATION

Vacancy-related defects in laser ablated thin films of the conducting metal-oxide La0.5Sr0.5CoO3-delta were detected using a variable-energy positron beam. The nonstoichiometry, delta, was altered by varying th e oxygen partial pressure within the deposition chamber present during cooling, Conductivity measurements confirmed the change in oxygen con tent. Increased positron trapping at vacancy defects was observed with increasing nonstoichiometry. It is proposed that vacancy clusters wer e present in the film cooled in 10(-5) Torr oxygen. (C) 1998 American Institute of Physics.