Using negative electron affinity diamond emitters to mitigate space charge in vacuum thermionic energy conversion devices

J. R. Smith, G. L. Bilbro, Robert Nemanich

Research output: Contribution to journalArticle

12 Scopus citations


A negative electron affinity (NEA) diamond surface is employed as an emitter electrode in a vacuum thermionic energy conversion device in order to mitigate the negative space charge effect. The motive diagram of an NEA device operating at the virtual saturation point is compared to a similar device with a conventional emitter material operating in the space charge limited regime in order to understand how NEA mitigates space charge. Output current characteristics are calculated for various NEA values, and the results are compared to an ideal (no space charge) model. Increasing the value of the NEA causes the output current characteristic to approach that of the ideal model. Motive diagrams for various values of NEA are calculated and used to explain this phenomenon. It is shown that an NEA device can achieve a maximum output power density equal to the maximum output power density of a similar ideal device.

Original languageEnglish (US)
Pages (from-to)2082-2085
Number of pages4
JournalDiamond and Related Materials
Issue number11-12 SPEC. ISS.
Publication statusPublished - Nov 2006
Externally publishedYes



  • Device modeling
  • Diamond crystal
  • Negative electron affinity
  • Thermionic energy conversion

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry
  • Surfaces, Coatings and Films
  • Surfaces and Interfaces

Cite this