title: Characterization of surface metallic states in SrTiO3 by means of aberration corrected electron microscopy.
abstract: An unusual conducting surface state can be produced in SrTiO3 substrates by irradiation with Argon ions from a plasma source, at low energy and high doses. The effects of irradiation are analyzed here by atomic force microscopy (AFM) and aberration corrected scanning transmission electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS). Depth sensitive studies demonstrate the existence of a heavily damaged surface layer and an oxygen vacancy rich layer immediately underneath, both induced during the irradiation process. We find a clear dependence of the Ti oxidation state with the depth, with a very intense Ti(3+) component near the surface. Oxygen vacancies act as n-type doping by releasing electrons into the lattice and producing an insulator-to-metal transition, which explains the unusual metallic behavior of these samples.
authors.affiliation: GFMC, Departamento. Física Aplicada III, Universidad Complutense de Madrid, 28040 Madrid, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Sánchez-Santolino
authors.forename: J
authors.initials: J
authors.lastname: Tornos
authors.forename: F Y
authors.initials: FY
authors.lastname: Bruno
authors.forename: F A
authors.initials: FA
authors.lastname: Cuellar
authors.forename: C
authors.initials: C
authors.lastname: Leon
authors.forename: J
authors.initials: J
authors.lastname: Santamaría
authors.forename: S J
authors.initials: SJ
authors.lastname: Pennycook
authors.forename: M
authors.initials: M
authors.lastname: Varela