Melting of Oxygen Vacancy Order at Oxide-Heterostructure Interface.

Modifications in oxygen coordination environments in heterostructures consisting of dissimilar oxides often emerge and lead to unusual properties of the constituent materials. Although lots of attention has been paid to slight modifications in the rigid oxygen octahedra of perovskite-based heterointerfaces, revealing the modification behaviors of the oxygen coordination environments in the heterostructures containing oxides with oxygen vacancies have been challenging. Here, we show that a significant modification in the oxygen coordination environments-melting of oxygen vacancy order-is induced at the heterointerface between SrFeO (SFO) and DyScO (DSO). When an oxygen-deficient perovskite (brownmillerite structure) SrFeO film grows epitaxially on a perovskite DyScO substrate, both FeO octahedra and FeO tetrahedra in the (101)-oriented SrFeO thin film connect to ScO octahedra in DyScO. As a consequence of accommodating a structural mismatch, the alternately ordered arrangement of oxygen vacancies is significantly disturbed and reconstructed in the 2 nm thick heterointerface region. The stabilized heterointerface structure consists of Fe octahedra with an oxygen vacancy disorder. The melting of the oxygen vacancy order, which in bulk SrFeO occurs at 1103 K, is induced at the present heterointerface at ambient temperatures.