Unexpected Precipitates In Conjunction With Layer-By-Layer Growth In Mn-Enriched La2/3sr1/3mno3 Thin Films

In recent years, layer-by-layer heteroepitaxy has become a versatile tool for depositing novel materials not accessible in bulk form. While it is possible to control the mono layer sequence on an atomic scale with the help of sophisticated analysis techniques, not all important features of the thin film growth are detectable. We report on a detailed analysis of layer-by-layer deposited Mn-enriched La2/3Sr1/3MnO3 thin films using various, complementary experimental techniques. Our results show that, contrary to the expectations from the growth parameters and initial characterization, the films did not grow as atomic planes but segregated into layers of La2/3Sr1/3MnO3 with additional embedded precipitant crystals. We attribute this separation to a Volmer-Weber island-like growth of Mn3O4 crystals within layers of La2/3Sr1/3MnO3 due to increased surface tension inhibiting La and Sr oxides from sticking to nucleated Mn3O4 surfaces during the growth at high temperatures.