Coherent Topotactic Interface between Corundum and Rutile Structures

There is a growing interest in epitaxial interfaces between nonisostructural transition-metal oxides that might exhibit interfacial correlated-electron effects. In this study, we show at the atomic scale that a fully coherent and very stable interface between rutile-type TiO ₂ and corundum-type Ti ₂ O ₃ , namely (100) _{TiO 2} //(1120) _{Ti 2 O 3} , is formed through a topotactic transition. A two-dimensional electron gas is generated at the interface through electron transfer from Ti ₂ O ₃ to TiO ₂ . In addition, the existence of Ti interstitials close to the interface indicates that the topotactic transition occurs via the migration of cations, instead of oxygen as suggested previously. Employing the topotaxy between oxides of different crystal structures offers rich choices to construct coherent interfaces.