  Based on a no-equilibrium STM model, we study Kondo resonance on a surface by
self-consistent calculations. The shapes of tunneling spectra are dependent on
the energy range of tunneling electrons. Our results show that both
energy-cutoff and energy-window of tunneling electrons have significant
influence on the shapes of tunneling spectra. If no energy-cutoff is used, the
Kondo resonances in tunneling spectrum are peaks with the same shapes in the
density of state of absorbed magnetic atoms. This is just the prediction of
Tersoff theory. If we use an energy cutoff to remove high-energy lectrons, a
dip structure will modulate the Kondo resonance peak in the tunneling spectrum.
The real shape of Kondo peak is the mixing of the peak and dip, the so-called
Fano line shape. The method of self-consistent non-equilibrium matrix Green
function is discussed in details.
