Europhys. Lett.
Volume 72, Number 3, November 2005
Page(s) 430 - 436
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 12 October 2005
Europhys. Lett., 72 (3), pp. 430-436 (2005)
DOI: 10.1209/epl/i2005-10263-3

Bound states at impurities in a two-dimensional metal

E. Dupont-Ferrier, P. Mallet, L. Magaud and J. Y. Veuillen

LEPES-CNRS - BP 166, 38042 Grenoble Cedex 9, France

received 27 June 2005; accepted in final form 15 September 2005
published online 12 October 2005

We present an experimental study of the local electronic properties of atomic-size impurities in an $\chem{ErSi_{2}}$ layer grown on the Si(111) surface, which behaves as a quasi-two-dimensional (2D) metal. From scanning tunneling spectroscopy measurements at T = 45$\un{K}$, we show that the silicide 2D state probed on defect-free areas becomes localized at impurities. For two different silicide point-defects, a resonance is found in the conductance spectra, at voltages above the 2D state band edge. This resonance is interpreted as a bound state within a repulsive impurity potential model. Spectroscopy on additional extra-impurities obtained after Co deposition is also reported.

73.20.At - Surface states, band structure, electron density of states.
68.37.Ef - Scanning tunneling microscopy (including chemistry induced with STM).
73.20.Hb - Impurity and defect levels; energy states of adsorbed species.

© EDP Sciences 2005