Transport of Hot Electrons in Thin Gold Films

Considerable interest has been expressed of late concerning the transparency of thin metal films to electrons with energies of a few electron volts above the Fermi level.(1-4) In the present experiments, information concerning the mean free path for loss of energy in gold is determined directly from measurements of electron transport. The technique used is that of tunnel emission(3,4) in which electrons are caused to tunnel from a metal substrate through a thin insulating layer into a thin metal electrode through which a certain number pass into a vacuum where they are collected. Measurement of the relative number transmitted through the thin metal layer as a function of the thickness of the layer yields a direct measurement of the energy mean free path.