Metal ion and oxygen vacancies in bulk and thin film La1-xSrxCoO3

Positron-lifetime and depth-resolved Doppler-broadening spectroscopy were used to investigate vacancies formed in bulk and laser ablated thin film La1-xSrxCoO3. In bulk samples, metal ion vacancies, which are most likely situated in the La sublattice, show a lifetime of 219 ps and a Doppler-broadening S parameter 1.06 times higher than the bulk. The metal-ion vacancy concentration increases with increasing Sr content. For x>~0.3, oxygen vacancies are detected, yielding a positron lifetime of 149 ps, only 10 ps longer than the bulk lifetime; the S parameter is 4% higher than for the bulk. For a given Sr concentration the films show a higher defect density than the bulk samples. The introduction of oxygen vacancy related defects is observed for increasing Sr doping concentration for both film and bulk samples. In films these defects probably consist of larger clusters and/or form complexes with metal ion vacancies.