Profiling of High-Pressure DC Microdischarge for excimer emission.*

UV excimer emission from microdischarges is of enormous interest, with numerous publications in this area.  Microdischarges have been shown to have increased excimer UV emission at higher pressures up to 1 atm.  The higher pressure operation is desirable due to higher plasma density and stronger excimer emission. This work focuses on the micro discharges operating in the 1–2 atm. the range for a possibly stronger UV emission. 

The microfabricated device uses a planar micro discharge configuration with a thick electroplated copper film as the electrode material. This device shows stable operation at higher pressures due to good heat transfer from the thick copper. Devices utilizing thin-film copper are seen to arc very easily and thus unstable. In this study, electrode gaps are varied from 25µm to 50µm.  The devices tend to arc if the current is not limited, but by using appropriate biasing, we observe that it is possible to maintain stable glow discharges in Argon in the pressure range of 1-2 atm.  (The 2 atm limitation comes from the test setup, not the plasma so operation at higher pressures is possible). For a 50 µm spacing device, the breakdown voltage varies linearly between 400 V at 1atm and 480 V at 2 atm. The glow is less diffuse as the pressure increases, but the plasma impedance remains the same (~120 KΩ) even at higher pressure. UV-VIS spectra taken with an ocean-optics HR4000 spectrometer show glow discharge characteristics with strong emission from the usual Argon lines. VUV characterization is ongoing.