Electrostatic field measurements and band flattening during electron-transfer processes at single-crystal TiO[sub 2] electrodes by electric field-induced optical second harmonic generation

Journal Article · Thu May 05 00:00:00 EDT 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100069a022· OSTI ID:7169781

Lantz, J M; Corn, R M ^[1]

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1. Univ. of Wisconsin, Madison, WI (United States)

Optical second harmonic generation (SHG) is employed as a local, time-resolved measurement of the electrostatic fields at the surface of single-crystal TiO[sub 2] electrodes in contact with aqueous electrolyte solutions. The interfacial SHG at a fundamental wavelength of 584 nm is dominated by the electric field-induced second harmonic (EFISH) response from the first 20 nm of the space charge layer at the surface of the semiconductor. A substantial decrease in the amount of SHG from the electrode while under potentiostatic control is observed upon illumination of the surface with UV light (320 nm) whose energy is above the bandgap for TiO[sub 2] (3.0 eV or 410 nm). Comparisons of the drop in SHG upon UV illumination with photovoltage measurements for TiO[sub 2] electrodes at open circuit verify that this decrease is due to a reduction in the strength of the electrostatic fields ([open quotes]band flattening[close quotes]) within the space charge region upon UV illumination. The EFISH response from the surface decreases with increasing power of the UV illumination, corresponding to a band flattening of up to 70% for the highest power densities. Upon termination of the UV illumination, a slow (10-12 s) rise time is observed for the return of the surface SHG to its normal levels. 50 refs., 8 figs.

• OSTI ID: 7169781
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 98:18; ISSN 0022-3654
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE
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PHOTOCURRENTS
PHOTOELECTROCHEMICAL CELLS
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RADIATIONS
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