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Photochemical Reduction and Oxidation Reactions on Barium Titanate Surfaces

Published online by Cambridge University Press:  21 March 2011

Jennifer L. Giocondi  and
Gregory S. Rohrer
Jennifer L. Giocondi
Affiliation:
Department of Materials Science and Engineering, Carnegie Mellon UniversityPittsburgh, Pennsylvania 15213-3890
Gregory S. Rohrer
Affiliation:
Department of Materials Science and Engineering, Carnegie Mellon UniversityPittsburgh, Pennsylvania 15213-3890
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Abstract

The influence of the ferroelectric domain structure of BaTiO3 on the photochemical reactions that occur on its surface has been examined using atomic force microscopy. Both the photochemical reduction of aqueous silver cations and the oxidation of steric acid thin films were studied. During reduction, silver selectively deposits on the surface in patterns determined by the ferroelectric domain structure. Based on the analysis of domain polarization in single crystals, we find that the photochemical reduction reaction occurs preferentially on the positive ends of the dipoles. The most likely explanation for this phenomenon is that when the static dipolar field is oriented with the positive end of the dipole on the surface, photogenerated electrons are driven to the solid-liquid interface where they reduce metal cations. The oxidation of steric acid films, on the other hand, is not spatially selective. During oxidation, the films dissipate uniformly as they are converted to CO2 and H2O. In this case, we conclude that the oxidation occurs indirectly. Photogenerated holes create hydroxyl radicals which can migrate on the surface before reacting with the steric acid molecules.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 654: Symposia AA – Structure-Property Relationships of Oxide Surfaces & Interfaces , 2000 , AA7.4.1
Copyright
Copyright © Materials Research Society 2001

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