Wide band gap materials for field emission devices

An analysis of wide band gap materials from the point of view of their application in cold emission devices is presented, and criteria of material choice for device application are discussed. Not only material but also technological parameters are taken into consideration. Among the material parameters, the following were found to be the most important; electron affinity, dielectric constant, thermal conductivity, melting point, chemical and physical robustness. The major technological parameter is compatibility of the material deposition process with commercially available facilities and other steps of cathode fabrication. It was shown that wide band gap materials are most effective for emission if deposited on sharp conductive tips. Experimental results from diamond, AlN, $c$-BN, and $SiO2$ field emitters are presented and some possible mechanisms explaining their $I–V$ characteristics are discussed.