Hot electron tunneling in femtosecond laser-assisted scanning tunneling microscopy

The combination of scanning tunneling microscopy with femtosecond laser spectroscopy yields simultaneously ultimate spatial and temporal resolution. One possibility to realize this combination is the direct excitation of the tunnel junction in a pump–probe configuration and the detection of a tunnel current component that depends nonlinearly on the laser intensity. The laser-induced signal is expected to be very small, therefore a suitable sample material and a modulation technique is required. In measurements on a GaP(100) surface evidence for tunneling of hot electrons is obtained giving the possibility for local time-resolved tunneling spectroscopy.