Monoenergetic and Directed Electron Emission from a Large-Bandgap Organic Insulator with Negative Electron Affinity

Spectra of low-energy electrons inelastically back-scattered from hexatriacontane films contain a component of almost monoenergetic electrons (energy spread ∼ k B T ) directed preferentially perpendicular to the film surface. This emission is due to electrons having relaxed down to the conduction band edge by multiple scattering. A theoretical model for the emission of such thermalized electrons shows that both, the negative electron affinity of the order A = -0.5 eV and the electronic anisotropy of the hexatriacontane are the key elements necessary to describe the emission directionality.