Positron lifetime and depth-resolved Doppler-broadening spectroscopy were used to investigate the vacancies which formed in bulk and laser-ablated thin film samples. In bulk samples, metal ion vacancies (which were most likely to be situated in the La sub-lattice) had a lifetime of 219ps and a Doppler-broadening S-parameter which was 1.06 times higher than that for the bulk. The metal-ion vacancy concentration increased with increasing Sr content. When the La:Sr ratio was 70:30, O vacancies were detected; with a positron lifetime of 149ps. This was 10ps longer than the bulk lifetime. The S-parameter was 4% higher than that for the bulk. For a given Sr concentration, the films exhibited a higher defect density than that of bulk samples. The introduction of O vacancy-related defects was observed, with increasing Sr-doping concentration, for both film and bulk samples. In films, these defects were assumed to consist of larger clusters and/or to form complexes with metal-ion vacancies.

Metal Ion and Oxygen Vacancies in Bulk and Thin Film La1-xSrxCoO3. T.Friessnegg, S.Madhukar, B.Nielsen, A.R.Moodenbaugh, S.Aggarwal, D.J.Keeble, E.H.Poindexter, P.Mascher, R.Ramesh: Physical Review B, 1999, 59[20], 13365-9