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Slow Surface Charge Trapping Kinetics on Irradiated TiO_2

Szczepankiewicz, Steven H. and Moss, John A. and Hoffmann, Michael R. (2002) Slow Surface Charge Trapping Kinetics on Irradiated TiO_2. Journal of Physical Chemistry B, 106 (11). pp. 2922-2927. ISSN 1520-6106. doi:10.1021/jp004244h.

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Free and trapped charge carriers in polycrystalline TiO_2 following band gap irradiation are characterized by diffuse reflectance IR spectroscopy (DRIFTS). A spectrum-wide absorption signal proportional to λ^(1.7) (λ = wavelength/μm) indicates the presence of free conduction band electrons coupled with acoustic phonons in the lattice. Free electrons appear to decay according to saturation kinetics. The fitted parameters indicate a limited number of trapping states. The concentration of these states appears to be diminished by sequential UV treatments. The free carrier decay lifetime is lengthened as the samples are dehydrated, which suggests an excited-state relaxation event during electron trapping. Photogenerated free electrons are comparable to conduction band electrons injected from surface-bound chromophores, and the lifetime of these electrons can be extended across several orders of magnitude. A broad IR absorption peak centered at 3380 cm^(-1) is attributed to an electronic transition from an occupied surface electron trap 0.42 eV below the conduction band.

Item Type:Article
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Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 2002 American Chemical Society. Received: November 17, 2000; In Final Form: November 8, 2001. Publication Date (Web): February 20, 2002. This work was funded by NSF and by DARPA through the Northrup-Grumman Corp.
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Defense Advanced Research Projects Agency (DARPA)UNSPECIFIED
Northrop-Grumman CorporationUNSPECIFIED
Issue or Number:11
Record Number:CaltechAUTHORS:20150807-092336352
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Official Citation:Slow Surface Charge Trappi Kinetics on Irradiated TiO2 Steven H. Szczepankiewicz, John A. Moss, and Michael R. Hoffmann The Journal of Physical Chemistry B 2002 106 (11), 2922-2927 DOI: 10.1021/jp004244h
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59307
Deposited By: Ruth Sustaita
Deposited On:07 Aug 2015 18:35
Last Modified:10 Nov 2021 22:18

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