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 environmentsmelting
of oxygen vacancy orderis induced at the heterointerface between
SrFeO2.5 (SFO) and DyScO3 (DSO). When an oxygen-deficient
perovskite (brownmillerite structure) SrFeO2.5 film grows
epitaxially on a perovskite DyScO3 substrate, both FeO6 octahedra and FeO4 tetrahedra in the (101)-oriented
SrFeO2.5 thin film connect to ScO6 octahedra
in DyScO3. 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 Fe3+ octahedra with an oxygen vacancy disorder. The melting of
the oxygen vacancy order, which in bulk SrFeO2.5 occurs
at 1103 K, is induced at the present heterointerface at ambient temperatures.