Thermionic field electron emission from graphite-based nanomaterials

Abstract

Thermionic and field electron emissions governed by Richardson–Dushman and Fowler–Nordheim equations, respectively, normally coexist under typical experimental conditions. However, some carbon-based cathodes demonstrate deviations of temperature dependencies of the current–voltage characteristics from those predicted by these equations. The nature of deviations cannot be ascribed to insufficient variations of work function or surface topology, which result from temperature variations. In this work, the temperature dependencies of the electron emission characteristics were experimentally investigated for the nanographite film cathodes obtained by a chemical vapor deposition method. It was found that self-consistent explanation of the experimental observations of the thermionic and field electron emissions from the nanocarbon cathodes may be given by taking into account the temperature dependence of free carrier density.