On the origin of metallic conductivity at the interface of LaAlO3/SrTiO3

► Metallic interfaces are observed when insulating amorphous films of LaAlO3, La2O3, or Al2O3 are deposited on crystalline SrTiO3 substrates by pulsed laser deposition, whereas the deposition of amorphous LSMO films results in an insulating interface. ► The interfacial conductivity of the SrTiO3-based hetero-structures with amorphous over-layers shows strong dependences on both film thickness and oxygen pressure during film growth. ► The occurrence of metallic interfaces in these complex oxide hetero-structures is probably due to redox reactions at the STO substrate surface.