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

Positron-lifetime and depth-resolved Doppler-broadening spectroscopy were u sed to investigate vacancies formed in bulk and laser ablated thin film La1 -xSrxCoO3. In bulk samples, metal ion vacancies, which are most likely situ ated in the La sublattice, show a lifetime of 219 ps and a Doppler-broadeni ng S parameter 1.06 times higher than the bulk. The metal-ion vacancy conce ntration increases with increasing Sr content. For x greater than or equal to 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 def ect density than the bulk samples. The introduction of oxygen vacancy relat ed defects is observed for increasing Sr doping concentration for both film and bulk samples. In films these defects probably consist of larger cluste rs and/or form complexes with metal ion vacancies. [S0163-1829(99)03519-5].