Date of Award
Doctor of Philosophy (PhD)
Engineering and Technology
Karl H. Schoenbach
Hani E. Elsayed-Ali
Microhollow cathode discharges are non-thermal discharges of such small sizes that thermalization of the electrons is prevented. By reducing the diameter of the cathode opening in these discharge geometries to values on the order of 100 $\mu$m we were able to operate discharges in argon and xenon in a direct current mode up to atmospheric pressure. The large concentration of high electrons, in combination with high pressures favors three body processes such as excimer formation. This was confirmed by experiments in xenon and argon where emission of excimer radiation at 172 nm and 130 nm, respectively, was observed when the pressure was increased beyond 50 Torr. The intensity of excimer radiation in xenon excimer emitters was found to have a maximum at 400 Torr. At this pressure, the VUV radiant flux of a single discharge operating at currents greater than 2 mA and a forward voltage of 220 V reaches values between 6% and 9% of the input electrical power. These are values, which are comparable to those achieved in barrier discharge excimer lamps. Results of a simple rate equation model indicate that even higher efficiencies (40%) might be achievable. The VUV intensity scales linearly with discharge current, which makes analog control of the excimer emission with semiconductor devices possible.
The possibility to form arrays of these discharges will allow the generation of dc-flat panel excimer lamps with radiant emittances exceeding 60 W/cm2. Applications for such lamps are lighting, flat panel displays, optical surface processing, pollution control and many others.
"Microhollow Cathode Discharge Excimer Lamps"
(1998). Doctor of Philosophy (PhD), Dissertation, Engineering and Technology, Old Dominion University, DOI: 10.25777/sq0g-rx89