What Determines the Lifetime of Photoexcited Carriers on TiO2 Surfaces?

Kenichi Ozawa, Susumu Yamamoto, Ryu Yukawa, Roya Liu, Masato Emori, Koki Inoue, Taku Higuchi, Hiroshi Sakama, Kazuhiko Mase, Iwao Matsuda

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


Pump-probe time-resolved X-ray photoelectron spectroscopy measurements have been carried out to comparatively assess the relaxation process of the photoexcited states on pristine and Ar+-sputtered TiO2(110) surfaces and a TiO2(011)-2 × 1 surface, on which the accumulation-type space charge layers are developed. Ultraviolet laser irradiation induces a surface photovoltage (SPV) of around 0.1 eV. The SPV relaxation time on pristine TiO2(110) is determined to be approximately 100 ns and is doubled on the sputtered surface. In contrast, a much shorter time of 1 ns is observed on TiO2(011)-2 × 1. The difference in the relaxation time on the two TiO2(110) surfaces is explained by differences in the O vacancy density on the surface as well as the barrier height of the surface potential for the photoexcited holes. A large hole capture cross section of a state characteristic of TiO2(011)-2 × 1 is, on the other hand, responsible for the fast SPV relaxation on this surface.

Original languageEnglish
Pages (from-to)29283-29289
Number of pages7
JournalJournal of Physical Chemistry C
Issue number51
Publication statusPublished - 2016 Dec 29
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films


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