15:45 〜 16:00
▲ [17p-A408-11] Epitaxial growth of oxygen vacancy ordered n=3 Ruddlesden-Popper Sr4Co3O9
キーワード：Oxygen vacancy ordering, Layered perovskites, Strongly correlated oxides
Layered perovskite compounds are an important material series that serve a variety of applications. Among them, Ruddlesden-Popper (RP) phase with the general formula of An+1BnO3n+1 is the most representative structure. Due to the very complex spin state of cobalt, many interesting physical and chemistry properties are reported in RP cobaltites as well. The epitaxial thin film Sr2CoO4 shows the first case of 2D magnetism and check-board Co2+/Co3+ is found in La1.5Sr0.5CoO4 single crystal. However, unlike other well reported RP phase titanates, nickelates etc., the n ≥ 3 RP cobaltite is much less reported, since the synthesis of n ≥ 3 RP cobaltite becomes difficult.
In this work, n = 3 RP cobaltite single crystal thin film with oxygen vacancy ordering, i.e. a layered-brownmillerite, is synthesized on LaAlO3 (100) substrate for the first time. The oxygen-vacancy-ordering is clearly identified by STEM and the theoretically predicted atomic model of Sr4Co3O9 has good agreement with experimental observations. Inspired from our recent work of strain-mediated material growth energy landscape, the LaAlO3 may create a local energy minimum for this layered perovskite and avoids the growth of stable hexagonal Sr4Co3O9 due to huge mismatch between cubic and hexagonal lattices. This work could be a good example of strain-mediated energy landscape of material synthesis, which could not only influence the anion-vacancy-ordering as reported, but also stabilize the structure which is difficult to obtain by direct sintering. Besides, by doping this material, 2D behavior or enhanced thermoelectric performance can be expected.
In this work, n = 3 RP cobaltite single crystal thin film with oxygen vacancy ordering, i.e. a layered-brownmillerite, is synthesized on LaAlO3 (100) substrate for the first time. The oxygen-vacancy-ordering is clearly identified by STEM and the theoretically predicted atomic model of Sr4Co3O9 has good agreement with experimental observations. Inspired from our recent work of strain-mediated material growth energy landscape, the LaAlO3 may create a local energy minimum for this layered perovskite and avoids the growth of stable hexagonal Sr4Co3O9 due to huge mismatch between cubic and hexagonal lattices. This work could be a good example of strain-mediated energy landscape of material synthesis, which could not only influence the anion-vacancy-ordering as reported, but also stabilize the structure which is difficult to obtain by direct sintering. Besides, by doping this material, 2D behavior or enhanced thermoelectric performance can be expected.