A review of surface functionalisation of diamond for thermionic emission applications

Surface functionalisation of diamond can produce negative electron affinity (NEA), where the conduction band lies higher in energy than the vacuum level. Hydrogen termination is well-known to produce NEA on diamond but can be removed by temperatures above similar to 700 degrees C, making it unsuitable for diamond-based thermionic applications, where high temperatures are converted into electricity via an electron emission process. In this review article we give an overview of thermionic emission, describe the potential applications of diamond-based thermionic energy converters, then review the different surface termination schemes that can provide a diamond surface with NEA. We discuss the relative merits of the different NEA surfaces that have been developed both computationally and experimentally as alternative cathode materials for thermionic devices. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Surface functionalisation of diamond can produce negative electron affinity (NEA), where the hydrogen termination, a well-known producer of NEA, can be removed by high temperatures above 700 degrees C. The review article provides an overview of thermionic emission, potential applications of diamond-based thermionic energy converters, and different surface termination schemes for NEA on diamond. Discussion on the relative merits of various NEA surfaces developed computationally and experimentally for thermionic devices is also included.