Photofield emission spectroscopy and surface density of states

A novel procedure for the investigation of optical excitations on the metal surface by the photofield emission method is reviewed. A separation procedure of thermocurrent, accompanying the measured photocurrent, induced by the chopped light beam, is described. A differentiation of the true photocurrent curve allows one to obtain an energy distribution of photoelectrons. For the (0 0 0 1) face of Ti, it exhibits very small and densely spaced maxima, confirmed by theory as surface resonances. The dependence of the density on the thickness of the Ti crystal, grown by evaporation of Ti on the W field emitter surface, was verified experimentally. The possibility of observing surface resonances on a microcrystal of a homogeneous field emitter is discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.