Bound states at impurities in a two-dimensional metalE. 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 layer grown on the Si(111) surface, which behaves as a quasi-two-dimensional (2D) metal. From scanning tunneling spectroscopy measurements at T = 45, 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