Spatial correlation of photo-induced and thermionic electron emission from low work function diamond films

Nils Neugebohrn, Tianyin Sun, Franz A M Koeck, Gary G. Hembree, Robert Nemanich, Thomas Schmidt, Jens Falta

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Hydrogen terminated, nitrogen doped diamond thin films have been the focus of recent research for application in thermionic energy conversion devices and possibly in solar cells. Nitrogen doped diamond films can attain negative electron affinity (NEA) through treatment with hydrogen plasma, which also produces a very low work function surface. Photoemission and thermionic emission spectroscopy measurements confirm a work function of approximately 2 eV for such films. The research presented here includes results from imaging these thin films with photo-electron emission microscopy (PEEM) and thermionic electron emission microscopy (ThEEM), in addition to spectroscopic studies using ultraviolet photoelectron spectroscopy (UPS). From the images it can be concluded that the photo- and thermionic emission are spatially uniform and do not originate from different isolated emission sites. This observation holds true up to the highest resolution and for all temperatures investigated (300-800 K). While relatively uniform, the emission is found to be influenced by the surface morphology and film microstructure. The spatial intensity distributions of the PEEM and ThEEM images are very similar, as reflected by the structure present in both of these images. This observation indicates that both emission processes are enabled by the low work function of the film.

Original languageEnglish (US)
Pages (from-to)12-16
Number of pages5
JournalDiamond and Related Materials
Volume40
DOIs
StatePublished - 2013

Fingerprint

thermionic emission
Electron emission
Diamond films
diamond films
electron emission
Microscopic examination
microscopy
Thermionic emission
Hydrogen
Nitrogen
Ultraviolet photoelectron spectroscopy
negative electron affinity
nitrogen
Thin films
Electron affinity
thermionics
ultraviolet spectroscopy
Emission spectroscopy
energy conversion
Photoemission

Keywords

  • Doped diamond
  • Electron emission
  • PEEM
  • Thermionic emission

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry
  • Electrical and Electronic Engineering
  • Mechanical Engineering
  • Physics and Astronomy(all)
  • Chemistry(all)

Cite this

Spatial correlation of photo-induced and thermionic electron emission from low work function diamond films. / Neugebohrn, Nils; Sun, Tianyin; Koeck, Franz A M; Hembree, Gary G.; Nemanich, Robert; Schmidt, Thomas; Falta, Jens.

In: Diamond and Related Materials, Vol. 40, 2013, p. 12-16.

Research output: Contribution to journalArticle

Neugebohrn, Nils ; Sun, Tianyin ; Koeck, Franz A M ; Hembree, Gary G. ; Nemanich, Robert ; Schmidt, Thomas ; Falta, Jens. / Spatial correlation of photo-induced and thermionic electron emission from low work function diamond films. In: Diamond and Related Materials. 2013 ; Vol. 40. pp. 12-16.
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AU - Neugebohrn, Nils

AU - Sun, Tianyin

AU - Koeck, Franz A M

AU - Hembree, Gary G.

AU - Nemanich, Robert

AU - Schmidt, Thomas

AU - Falta, Jens

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N2 - Hydrogen terminated, nitrogen doped diamond thin films have been the focus of recent research for application in thermionic energy conversion devices and possibly in solar cells. Nitrogen doped diamond films can attain negative electron affinity (NEA) through treatment with hydrogen plasma, which also produces a very low work function surface. Photoemission and thermionic emission spectroscopy measurements confirm a work function of approximately 2 eV for such films. The research presented here includes results from imaging these thin films with photo-electron emission microscopy (PEEM) and thermionic electron emission microscopy (ThEEM), in addition to spectroscopic studies using ultraviolet photoelectron spectroscopy (UPS). From the images it can be concluded that the photo- and thermionic emission are spatially uniform and do not originate from different isolated emission sites. This observation holds true up to the highest resolution and for all temperatures investigated (300-800 K). While relatively uniform, the emission is found to be influenced by the surface morphology and film microstructure. The spatial intensity distributions of the PEEM and ThEEM images are very similar, as reflected by the structure present in both of these images. This observation indicates that both emission processes are enabled by the low work function of the film.

AB - Hydrogen terminated, nitrogen doped diamond thin films have been the focus of recent research for application in thermionic energy conversion devices and possibly in solar cells. Nitrogen doped diamond films can attain negative electron affinity (NEA) through treatment with hydrogen plasma, which also produces a very low work function surface. Photoemission and thermionic emission spectroscopy measurements confirm a work function of approximately 2 eV for such films. The research presented here includes results from imaging these thin films with photo-electron emission microscopy (PEEM) and thermionic electron emission microscopy (ThEEM), in addition to spectroscopic studies using ultraviolet photoelectron spectroscopy (UPS). From the images it can be concluded that the photo- and thermionic emission are spatially uniform and do not originate from different isolated emission sites. This observation holds true up to the highest resolution and for all temperatures investigated (300-800 K). While relatively uniform, the emission is found to be influenced by the surface morphology and film microstructure. The spatial intensity distributions of the PEEM and ThEEM images are very similar, as reflected by the structure present in both of these images. This observation indicates that both emission processes are enabled by the low work function of the film.

KW - Doped diamond

KW - Electron emission

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