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The Structure of Hematite (Alpha-Fe(2)O(3)) (001) Surfaces in Aqueous Media: Scanning Tunneling Microscopy and Resonant Tunneling Calculations of Coexisting O and Fe Terminations
Geochimica Et Cosmochimica Acta
  • Carrick Eggleston, University of Wyoming
  • A. G. Stack
  • K. M. Rosso
  • S. R. Higgins
  • A. M. Bice
  • S. W. Boese
  • R. D. Pribyl
  • J. J. Nichols
Document Type
Article
Publication Date
3-1-2003
Disciplines
Abstract

The iron oxide-water interface is of interest not only in geochemical and environmental processes, but also in fields ranging from corrosion to photocatalysis. The structure of alpha-Fe2O3 (001) surfaces is not fully understood, and questions have arisen recently concerning different terminations of (001) terraces; a so-called Fe-termination is expected, but under some conditions an O-termination may also be possible. Ultra-high vacuum (UHV) scanning tunneling microscope (STM) studies report evidence for an O-termination in coexistence with an Fe-termination, but other studies find no evidence for an O-termination. Molecular mechanics studies suggest that an O-termination should be possible in an aqueous environment. An O-termination could result from dissolution; if Fe atoms were to dissolve from an Fe-termination, an O-termination would presumably result (and vice-versa). We imaged hematite (001) surfaces in air and aqueous solution using STM. To aid interpretation of the images, we use a resonant tunneling model (RTM) parameterized using ab initio calculations. Our STM and RTM results are consistent with mixed O- and Fe-terminated (001) surfaces. For acid-etched surfaces we find evidence for a periodic (with wavelength of 2.2 +/- 0.2 nm) arrangement of nominal O- and Fe-terminated domains. Two different borders between domains should occur, one in which the Fe-termination is high relative to the O-termination, and the reverse. The different domain borders have significantly different heights, consistent with RTM calculations. This agreement allows us to conclude that the Fe-termination is topographically high on most terraces. Surface domains are observed in aqueous solutions at the atomic scale, and appear to be very unreactive on tens-of-seconds time scales at pH 1. Copyright (C) 2003 Elsevier Science Ltd.

DOI
10.1016/S0016-7037(02)01200-0
Citation Information
Carrick Eggleston, A. G. Stack, K. M. Rosso, S. R. Higgins, et al.. "The Structure of Hematite (Alpha-Fe(2)O(3)) (001) Surfaces in Aqueous Media: Scanning Tunneling Microscopy and Resonant Tunneling Calculations of Coexisting O and Fe Terminations" Geochimica Et Cosmochimica Acta Vol. 67 Iss. 5 (2003) p. 985 - 1000
Available at: http://works.bepress.com/carrick_eggleston/6/