Thermionic electron emission from low work-function phosphorus doped diamond films

Franz A M Koeck, Robert Nemanich, Andrada Lazea, Ken Haenen

Research output: Contribution to journalArticlepeer-review

113 Scopus citations


Thermionic electron emitters are a key component in applications ranging from travelling wave tubes for communications, space propulsion and direct energy conversion. As the conventional approach based on metallic emitters requires high operating temperatures the negative electron affinity (NEA) characteristic of diamond surfaces in conjunction with suitable donors would allow an electronic structure corresponding to a low effective work function. We have thus prepared phosphorus-doped polycrystalline diamond films on metallic substrates by plasma assisted chemical vapor deposition where an NEA surface characteristics was induced by exposure of the film surface to a hydrogen plasma. Thermionic electron emission measurements in an UHV environment were conducted with respect to the Richardson-Dushman relation observing an emission current at temperatures < 375 °C. Measurements were terminated at 765 °C without significant reduction in the electron emission current indicating a stable hydrogen passivation of the diamond surface. A fit of the emission data to the Richardson equation allowed for the extraction of emission parameters where the value of the materials work function was evaluated to 0.9 eV. This value could well be the lowest measured work function of any known material.

Original languageEnglish (US)
Pages (from-to)789-791
Number of pages3
JournalDiamond and Related Materials
Issue number5-8
StatePublished - May 2009


  • chemical vapor deposition
  • diamond
  • doping
  • phosphorus

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Chemistry
  • Mechanical Engineering
  • Materials Chemistry
  • Electrical and Electronic Engineering


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