Structure, defects, and impurities at the rutile TiO2(0 1 1)-(2 × 1) surface: A scanning tunneling microscopy study

Olga Dulub, Cristiana Di Valentin, Annabella Selloni, Ulrike Diebold

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The titanium dioxide rutile (0 1 1) (equivalent to (1 0 1)) surface reconstructs to a stable (2 × 1) structure upon sputtering and annealing in ultrahigh vacuum. A previously proposed model (T.J. Beck, A. Klust, M. Batzill, U. Diebold, C. Di Valentin, A. Selloni, Phys. Rev. Lett. 93 (2004) 036104/1) containing onefold coordinated oxygen atoms (titanyl groups, Ti{double bond, long}O) is supported by Scanning Tunneling Microscopy (STM) measurements. These Ti{double bond, long}O sites are imaged bright in empty-states STM. A few percent of these terminal oxygen atoms are missing at vacuum-annealed surfaces of bulk-reduced samples. These O vacancies are imaged as dark spots. Their number density depends on the reduction state of the bulk. Double vacancies are the most commonly observed defect configuration; single vacancies and vacancies involving several O atoms are present as well. Formation of oxygen vacancies can be suppressed by annealing a sputtered surface first in vacuum and then in oxygen; annealing a sputtered surface in oxygen results in surface restructuring and a (3 × 1) phase. Anti-phase domain boundaries in the (2 × 1) structure are active adsorption sites. Segregation of calcium impurities from the bulk results in an ordered overlayer that exhibits domains with a centered (2 × 1) periodicity in STM.

Original languageEnglish (US)
Pages (from-to)4407-4417
Number of pages11
JournalSurface Science
Issue number19
StatePublished - Oct 1 2006

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry


  • Domain boundaries
  • Scanning tunneling microscopy
  • Segregation
  • Surface defects
  • Titanium oxide


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