| Issue |
Europhys. Lett.
Volume 39, Number 2, July II 1997
|
|
|---|---|---|
| Page(s) | 159 - 164 | |
| Section | Condensed matter: structure, thermal and mechanical properties | |
| DOI | https://doi.org/10.1209/epl/i1997-00329-2 | |
| Published online | 01 September 2002 | |
Scanning tunneling spectroscopy of rare-earth metals: Gadolinium on yttrium
Physikalisches Institut, Universität Karlsruhe - 76128 Karlsruhe, Germany
Received:
10
March
1997
Accepted:
16
June
1997
Scanning tunneling microscopy images of ultrathin Gd
films on Y(0001) show a strong chemical
contrast depending on the tunneling voltage.
For small voltages the tunneling spectra for Gd
reveal pronounced features which are
attributed to occupied and unoccupied electronic surface
states as found previously in photoemission
experiments. These Gd surface states give rise
to a large tunneling current
and the image contrast between Gd and
Y is enhanced by a factor of two because low-energy surface
states are absent in Y.
On the other hand, for a high positive bias
of 
the contrast is reversed due to
tunneling into unoccupied Y electronic states
presumably originating from the Y 5d band. The corresponding
current increase with respect to Gd exceeds the current
increase induced by a monolayer step.
PACS: 61.16.Ch – Scanning probe microscopy: scanning tunneling, atomic force, scanning optical, magnetic force, etc / 71.20.Eh – Rare earth metals and alloys / 73.20.At – Surface states, band structure, electron density of states
© EDP Sciences, 1997
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