Work Function of Cathode Emitter Materials Obtained by Ab-initio Quantum Mechanical Modeling

Abstract

The work function of a material is a very important figure of merit in determining the material's applicability as an efficient electron emitter. Consequently, the work function of a variety of materials utilized in both thermionic and field-assisted cathodes for electron emission was investigated computationally using ab-initio quantum mechanical modeling methods based on the density functional theory (DFT) approach (Hohenberg and Kohm, 1964). This approach enables the detailed and self-consistent treatment of a system utilizing quantum mechanical principles and yields accurate information pertaining to its electronic properties. Of particular interest are cesium-iodide (CsI) coated carbon-based cathodes (Shiffler et al., 2004), which comprise a very promising class of cold field emitters capable of operating at low global electric fields. However, the exact origin of their enhanced emission properties is not clear, and a better understanding is necessary for further improvement and optimization of this technology. We apply ab-initio quantum mechanical modeling for understanding the origin of the fundamental emission mechanisms of this material system