Photoelectron Energy Spreads and Emission Properties of Some Organic Thin Films

Abstract

Photoelectric emission is of current interest for its applications to microscopy as well as for its possible use as an electron source for integrated circuit lithography, particle accelerators, x-ray sources, and free electron lasers. These diverse applications share a common requirement for electron sources of relatively high brightness. A significant difficulty to be overcome results from the fact that available light sources have photon energies too low to induce photoelectron emission from the materials of most interest. In particular, surfaces which emit electrons under illumination by visible or near ultraviolet light are limited to a small number of materials based on highly reactive metals. To explore a possible alternative, we have investigated the emission of electrons from organic compounds possessing an intermediate electron energy level which assists the emission process through multiphoton absorption. The energy spreads of electrons emitted from these surfaces are important because beam spreading and aberrations in an instrument can depend on the energy distribution. Here we describe transverse energy measurements of photoelectrons from thin films of 2,2‘-binaphthyl on silicon and copper substrates. This coating material was chosen because of its high two-photon quantum yield.