TY - JOUR
T1 - Structure, defects, and impurities at the rutile TiO2(0 1 1)-(2 × 1) surface
T2 - A scanning tunneling microscopy study
AU - Dulub, Olga
AU - Valentin, Cristiana Di
AU - Selloni, Annabella
AU - Diebold, Ulrike
N1 - Funding Information:
The authors thank T.J. Beck, Jimi Burst, and Matthias Batzill for assistance with taking XPS and UPS data, XueQing Gong for help with the theoretical STM image, and T.E. Madey for useful discussions. Support by the National Science Foundation (CHE-010908) and the Department of Energy (DE-TG02-05ER15702) is gratefully acknowledged.
PY - 2006/10/1
Y1 - 2006/10/1
N2 - 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.
AB - 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.
KW - Domain boundaries
KW - Scanning tunneling microscopy
KW - Segregation
KW - Surface defects
KW - Titanium oxide
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U2 - 10.1016/j.susc.2006.06.042
DO - 10.1016/j.susc.2006.06.042
M3 - Article
AN - SCOPUS:33749066530
SN - 0039-6028
VL - 600
SP - 4407
EP - 4417
JO - Surface Science
JF - Surface Science
IS - 19
ER -