Interface*

Charge transfer at complex oxide interfaces can give rise to a rich variety of exotic two-dimensional phenomena. Recently, an antiferromagnetic to nonmagnetic transition was reported at the LaTiO₃/LaFeO₃ interface based on the observation of Ti and Fe valence change by X-ray photoelectron spectroscopy. Nonetheless, a direct spatially resolved measurement with atomic resolution to support the charge transfer truly happens at the interface is lacking. Here, we investigate the valence variations of Ti and Fe at the LaTiO₃/LaFeO₃ interface by a combination of molecular beam epitaxy and aberration corrected scanning transmission electron microscopy. We demonstrate that the charge transfer from Ti to Fe occurs near the interface accompanied by minor cation intermixing, and the charge transfer depth is two unit cells. Our work provides a spatially resolved observation of charge transfer at this interface, and lends significant credence to charge transfer designs in functional oxide interfaces.