| AVS 57th International Symposium & Exhibition | |
| Energy Frontiers Topical Conference | Thursday Sessions |
| Session EN-ThP |
| Session: | Energy Frontiers Topical Conference Poster Session |
| Presenter: | M. Zumer, Jozef Stefan Institute, Slovenia |
| Authors: | M. Zumer, Jozef Stefan Institute, Slovenia V. Nemanic, Jozef Stefan Institute, Slovenia B. Zajec, Jozef Stefan Institute, Slovenia R.J. Nemanich, Arizona State University F.A.M. Koeck, Arizona State University |
| Correspondent: | Click to Email |
Nitrogen doped, hydrogen terminated diamond films have shown a work function of less than 1.5 eV and thermionic electron emission has been detected at temperatures as low as 300 °C . This report explores the influence of hydrogen and deuterium gas on the electron emission using a triode setup with an applied electric field that ranges from low values to 4 MV/m . The extracting grid and phosphor screen were set to the same potential. The hydrogen terminated, nitrogen doped diamond films were deposited on 25 mm diameter molybdenum substrates by microwave plasma assisted chemical vapour deposition. The process involves a nucleation layer, nitrogen doped layer and surface termination which were all optimized to enhance the emission. The thermionic electron emission from 300 to 500 °C was quite intense. A typical average emission current density at 500 °C was of the order of 2E-6A/cm2 at a base pressure of the order of 10-7 mbar. The emission was relatively stable exhibiting only a weak tendency to decrease with time. The emission was relatively uniform across the surface as opposed to the intense emission sites often observed in field emission. When hydrogen was leaked into the chamber, the emission current density increased by greater than an order of magnitude as the pressure was increased from UHV to 10-5 mbar. Results indicated that atomic hydrogen generated by a nearby Bayard-Alpert ionization gauge induced the effect . An identical leak rate of deuterium causes a similar but less intense increase of the emission current. At both cases, the initial value of the thermionic emission was restored by establishing again the UHV. The question of whether the hydrogen (deuterium) improves the surface through bonding and forming a NEA or whether it assists in the charge transfer process is assessed. These results should guide the development of an efficient thermionic cell for direct conversion of heat to electricity.