Surface density of states and field emission

Abstract

The relation between the total energy distribution of electrons field emitted from metals and the surface density of states is analyzed in general terms. Numerical reslts on the total energy distribution of field-emitted electrons from the (100) and (110) planes of tungsten obtained previously by the authors and extended here to a wider energy region are interpreted in terms of surface density-of-states effects. It is shown in particular that the peak in the total energy distribution from the (100) plane at 0.29 eV below the Fermi level is due to virtual surface states which give rise to enhanced tunneling at that energy. For the (100) plane of tungsten virtual surface states are shown to exist in an energy region extending from 0.20 to 0.95 eV below the Fermi level, but only the states at 0.29 eV below ${E}_{F}$ give rise to peaks in the total energy distribution of the emitted electrons. Another broad peak in the total energy distribution from the (100) plane observed at about 1.3 eV below the Fermi level is also reproduced by our calculation. This peak is the cumulative effect of a number of factors which cannot be disentangled in a simple way, but is not a result of surface states.