Hot electron cascades in the scanning tunneling microscope

The nonequilibrium distribution of electrons at the junction of a scanning tunneling microscope is investigated by detecting photons with energies hν>eV, where V is the bias voltage. Electrons are found at energies exceeding the Fermi level by almost $eV$. While their distribution deviates from a Fermi-Dirac function it is consistent with a model of hot electrons and holes that diffuse in energy and real space.