Issue |
Europhys. Lett.
Volume 63, Number 6, September 2003
|
|
---|---|---|
Page(s) | 867 - 873 | |
Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
DOI | https://doi.org/10.1209/epl/i2003-00601-y | |
Published online | 01 November 2003 |
Formation of the strain-induced electronic superstructure
on the magnetite
surface
SFI Laboratories, Physics Department, Trinity College - Dublin 2, Ireland
Received:
25
March
2003
Accepted:
3
July
2003
We present direct experimental evidence of the formation of a
superstructure on the (111) surface of a magnetite,
single crystal. The superstructure, which has a periodicity of
42
and three-fold symmetry, has been observed by means of STM
and LEED. Under the correct conditions of oxygen pressure and
sample anneal temperature, the superstructure is reproducibly
formed throughout most of the sample surface. Clear atomic
resolution within the superstructure has been achieved. The
characteristics of the superstructure, including its dependency
on the tunnel bias voltage and its atomic-scale periodicity,
suggest that it is an electronic effect rather than a mosaic of
several iron oxide phases. We explain the results in terms of the
formation of giant static polarons, although we notice that other
types of electron-lattice instabilities such as charge density
wave may offer possible explanations. Polarons with dimensions of
many interatomic distances in three-dimensional systems are
unlikely to exist but the situation for two- and one-dimensional
cases is predicted to be different. We suggest three possible
scenarios of instability linking the electron band structure and
lattice distortions in magnetite: either resulting from
reallocation of
and
valence states
between octahedral sites or, alternatively, from reallocation
between octahedral and tetrahedral sites.
PACS: 72.80.Ga – Transition-metal compounds / 68.47.Gh – Oxide surfaces / 71.38.-k – Polarons and electron-phonon interactions
© EDP Sciences, 2003
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