Characterization of cleaved surfaces of metallic bronzes.

Herve Guyot 1Hafid Balaska 1,4Enesto Placidi 3Nunzio Motta 2

1. CNRS-LEPES, BP 166 X, Grenoble 38042, France
2. Universita di Roma Tre, Roma, Italy
3. Universita di Roma 'Tor Vergata', Roma 00133, Italy
4. Universite de Skikda, BP 26, Skikda, Algeria

Abstract

Several monophosphate tungsten bronzes are metallic ternary oxides with layered crystallographic structures and exhibit specific physical properties resulting from to the anisotropy of their structures. The P4W8O32 bronze shows two phase transitions to charge density wave states, which are related to the quasi two-dimensionality of this metallic oxide. The low-dimensionality of this bronze has been evidenced by transport properties and by measurements of the Fermi surface and the band structure [1,2]. These measurements were performed on (001) surfaces cleaved in UHV. We have characterized these clean surfaces electron diffraction and STM imaging. The LEED patterns of (001) surfaces show at room temperature several Bragg spots reflecting a long range periodicity, that is in good agreement with the three dimensional crystallographic structure. The local investigation of (001) surfaces evidences different periodicities, which are interpreted as the presence of (001) and stepped (021) facets. The first orientation corresponds to the planes parallel to the layers, while the second orientation corresponds to the high density planes of the WO6 layers. These facets appear to be relaxed 1x1 surfaces.

[1] A. Mascaraque, L. Roca, J. Avila, S. Drouard, H. Guyot, and M. C. Asensio, PRB 66, 115104 (2002).
[2] L. Roca, A. Mascaraque, J. Avila, S. Drouard, H. Guyot, M. C. Asensio, PRB 69, 075114 (2004).

 

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Presentation: oral at E-MRS Fall Meeting 2004, Symposium I, by Herve Guyot
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-29 14:59
Revised:   2009-06-08 12:55