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Please use this identifier to cite or link to this item: http://hdl.handle.net/10119/9829

Title: Discovery of deep and shallow trap states from step structures of rutile TiO_2 vicinal surfaces by second harmonic and sum frequency generation spectroscopy
Authors: Takahashi, Hiroaki
Watanabe, Ryosuke
Miyauchi, Yoshihiro
Mizutani, Goro
Keywords: titanium dioxide
TiO2
SHG
step bunching
photocatalysis
Issue Date: 2011-04-15
Publisher: American Institute of Physics
Magazine name: Journal of Chemical Physics
Volume: 134
Number: 15
Start page: 154704-1
End page: 154704-13
DOI: 10.1063/1.3578178
Abstract: In this report, local electronic structures of steps and terraces on rutile TiO_2 single crystal faces were studied by second harmonic and sum frequency generation (SHG/SFG) spectroscopy. We attained selective measurement of the local electronic states of the step bunches formed on the vicinal (17 18 1) and (15 13 0) surfaces using a recently developed step-selective probing technique. The electronic structures of the flat (110)-(1×1) (the terrace face of the vicinal surfaces) and (011)-(2×1) surfaces were also discussed. The SHG/SFG spectra showed that step structures are mainly responsible for the formation of trap states, since significant resonances from the trap states were observed only from the vicinal surfaces. We detected deep hole trap (DHT) states and shallow electron trap (SET) states selectively from the step bunches on the vicinal surfaces. Detailed analysis of the SHG/SFG spectra showed that the DHT and SET states are more likely to be induced at the top edges of the step bunches than on their hillsides. Unlike the SET states, the DHT states were observed only at the step bunches parallel to [1  1] [equivalent to the step bunches formed on the (17 18 1) surface]. Photocatalytic activity for each TiO_2 sample was also measured through methylene blue photodegradation reactions and was found to follow the sequence: (110) < (17 18 1) < (15 13 0) < (011), indicating that steps along [0 0 1] are more reactive than steps along [1 1^-  1]. This result implies that the presence of the DHT states observed from the step bunches parallel to [1  1] did not effectively contribute to the methylene blue photodegradation reactions.
Rights: Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Hiroaki Takahashi, Ryosuke Watanabe, Yoshihiro Miyauchi, and Goro Mizutani, Journal of Chemical Physics, 134(15), 154704 (2011) and may be found at http://link.aip.org/link/doi/10.1063/1.3578178
URI: http://hdl.handle.net/10119/9829
Material Type: publisher
Appears in Collections:c10-1. 雑誌掲載論文 (Journal Articles)

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