Description:
This thesis describes a study of subsurface magnetic impurities using low-temperature scanning tunnelling spectroscopy. Single Cobalt and Iron impurities have been prepared up to 15 ML below atomically flat single crystal surfaces of Cu(100) and Cu(111), respectively. In the first part the influence of the Copper band structure on the observed oscillations in the local density of states at the surface is discussed. It is shown that due to the non-spherical Fermi-surface of Copper the electrons propagate only in narrowly confined directions. This results in strongly anisotropic and long-range oscillation patterns. We present a simple model that uses the conduction electrons Green function, obtained from band structure calculations, and an adjustable scattering phase-shift of the impurity to reproduce the observed patterns in good agreement with the experimental data. In the second part the influence of the Kondo-effect on the local density of states in the vicinity of the impurity is discussed. This effect leads to a screening of the impurity spin by the conduction band electrons and to a many-body resonance in the single particle spectral density of the localized d-orbital near the Fermi-Energy ...