Surface Amorphous Oxides Induced Electron Transfer into Complex Oxide Heterointerfaces

Complex oxide heterointerfaces are interesting because they host many exotic emergent phenomena and have potential for unconventional oxide electronics. Crucial to explore these phenomena and applications is controlling electron transfer. In the past, this has been difficult to achieve in many heterointerfaces such as LaAlO3/SrTiO3 fabricated on SrO-terminated SrTiO3, while a great success has been made in LaAlO3/SrTiO3 fabricated on TiO2-terminated SrTiO3. Here, a variety of (both TiO2- and SrO-terminated) SrTiO3-based heterostructures (not limited to LaAlO3/SrTiO3) are capped with different kinds of amorphous oxides prepared at room temperature. It is found that more than 10(14) cm(-2) electrons can be induced into heterointerfaces that are originally either conducting or insulating. By a thorough examination of various combinations between different heterostructues and different amorphous oxides, it is concluded that the observed effect is dominated by electron transfer from surface amorphous oxides into complex oxide heterointerfaces.