electron gas at the oxide interface*

The discovered revolutionary class of polar oxide heterostructures holds tremendous promise for exploiting the physical properties of the novel 2DEG formed at the oxide/oxide interface. SrTiO₃ is a widely used substrate for the growth of other functional oxide thin films. The reactivity of the substrate with respect to the film during deposition, particularly with regard to redox reactions, has typically been glossed over. We have recently demonstrated by depositing a variety of metals and measuring the in situ core level spectra of both the metal and SrTiO₃ that, depending on the oxide formation energy and work function of the metal, there will be an interfacial layer of oxygen-deficient SrTiO₃ at the interface with the top oxide film. I will focus on the integrated highly spin-split ferromagnetic semiconductor EuO onto perovskite SrTiO₃ (001). A careful deposition of Eu metal by molecular beam epitaxy resulted in EuO growth via oxygen out-diffusion from SrTiO₃. This in turn leaves behind a highly conductive interfacial layer through generation of oxygen vacancies. Below the Curie temperature of 70 K of EuO, this spin-polarized two-dimensional t_2g electron gas at the EuO/SrTiO₃ interface displays very large positive linear magnetoresistance.