Distinct behavior of localized and delocalized carriers in anatase TiO2 (001) during reaction with O2

Chiara Bigi, Zhenkun Tang, Gian Marco Pierantozzi, Pasquale Orgiani, Pranab Kumar Das, Jun Fujii, Ivana Vobornik, Tommaso Pincelli, Alessandro Troglia, Tien Lin Lee, Regina Ciancio, Goran Drazic, Alberto Verdini, Anna Regoutz, Phil D.C. King, Deepnarayan Biswas, Giorgio Rossi, Giancarlo Panaccione, Annabella Selloni

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Abstract

Two-dimensional (2D) metallic states induced by oxygen vacancies (VOs) at oxide surfaces and interfaces provide opportunities for the development of advanced applications, but the ability to control the behavior of these states is still limited. We used angle resolved photoelectron spectroscopy combined with density-functional theory (DFT) to study the reactivity of VO-induced states at the (001) surface of anatase TiO2, where both 2D metallic and deeper lying in-gap states (IGs) are observed. The 2D and IG states exhibit remarkably different evolutions when the surface is exposed to molecular O2: while IGs are almost completely quenched, the metallic states are only weakly affected. DFT calculations indeed show that the IGs originate from surface VOs and remain localized at the surface, where they can promptly react with O2. In contrast, the metallic states originate from subsurface vacancies whose migration to the surface for recombination with O2 is kinetically hindered on anatase TiO2 (001), thus making them much less sensitive to oxygen dosing.

Original languageEnglish (US)
Article number025801
JournalPhysical Review Materials
Volume4
Issue number2
DOIs
StatePublished - Feb 28 2020

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)

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    Bigi, C., Tang, Z., Pierantozzi, G. M., Orgiani, P., Das, P. K., Fujii, J., Vobornik, I., Pincelli, T., Troglia, A., Lee, T. L., Ciancio, R., Drazic, G., Verdini, A., Regoutz, A., King, P. D. C., Biswas, D., Rossi, G., Panaccione, G., & Selloni, A. (2020). Distinct behavior of localized and delocalized carriers in anatase TiO2 (001) during reaction with O2. Physical Review Materials, 4(2), [025801]. https://doi.org/10.1103/PhysRevMaterials.4.025801