  The conductance confined at the interface of complex oxide heterostructures
provides new opportunities to explore nanoelectronic as well as nanoionic
devices. Herein we show that metallic interfaces can be realized in
SrTiO3-based heterostructures with various insulating overlayers of amorphous
LaAlO3, SrTiO3 and yttria-stabilized zirconia films. On the other hand, samples
of amorphous La7/8Sr1/8MnO3 films on SrTiO3 substrates remain insulating. The
interfacial conductivity results from the formation of oxygen vacancies near
the interface, suggesting that the redox reactions on the surface of SrTiO3
substrates play an important role.
