Gas breakdown in an atmospheric pressure radio-frequency capacitive plasma source

Abstract

Gas breakdown is studied in an atmospheric pressure rf capacitive plasma source developed for materials applications. At a rf frequency of 13.56 MHz, breakdown voltage is largely a function of the product of the pressure and the discharge gap spacing, approximating the Paschen curve. However, breakdown voltage varies substantially with rf frequency due to a change in the electron loss mechanism. A large increase in breakdown voltage is observed when argon, oxygen, or nitrogen is added to helium despite their lower ionization potential. Discussion is given for optimal breakdown conditions at atmospheric pressure.

Three modes in a radio frequency atmospheric pressure glow discharge

“…The rising V -I characteristic is also typical of that of most reported rf APGD experiments. [12][13][14][15][16][17][18][19][20] This abnormal glow phase ended at point D at which sheath breakdown was triggered and the breakdown event lasted from D to F. During this transition period, the plasma underwent a voltage reduction of 43% and a current increment of 72%. If multiple sheath breakdowns were allowed to occur in succession, via a recovery phase between two adjacent breakdowns, later breakdown events could result in current reduction rather than current increment.…”

“…Our study suggests that similar to the ␣ mode these two additional modes have a diffuse and uniform appearance with the ionized gas at near room temperature and that the ␣ mode, hitherto considered as the only rf APGD mode, is essentially an abnormal glow mode. So rf APGD have a much wider operation range than previously believed [12][13][14][15][16][17][18][19][20] and this greater operation range allows rf APGD to be flexibly operated for many applications. To provide further insights into these three modes, we study their mode transition mechanism also.…”

“…From a practical standpoint, rf APGDs are attractive because of their low breakdown voltage. 12 Over the past 3 years some of their plasma properties have been investigated including emission spectrum, 13,14 vibrational and rotational temperature, 12,15,16 densities of excited species, 17 and charged particles, 18 and plasma dynamics. 12,19 Yet many more aspects of their fundamental characteristics remain to be unraveled, observed and characterized before a full understanding is achieved.…”

Mode transition in radio-frequency atmospheric argon discharges with and without dielectric barriers

“…While this can be addressed by using helium as the working gas, it is desirable to realize APGD applications with less expensive gases such as argon and nitrogen. 4 Using radio-frequency ͑rf͒ excitation at which gas breakdown voltage is low 5 and plasma stability is robust, 6 large-area Ar rf APGDs have been achieved with unconventional electrodes such as microstructured electrodes, 7 multiple electrodes, 8 and microslot electrodes. 9 Recently, dielectric insulation of electrodes is also found beneficial.…”

Atmospheric-pressure diffuse dielectric barrier discharges in Ar/O2gas mixture using 200 kHz/13.56 MHz dual frequency excitation

“…In this study, the first breakdown of the plasma cannot be obtained by the single RF voltage, an additional LF voltage must be supplied in order to produce a stable RF discharge. According to the literature, the amplitude of electron oscillation A can be estimated [44,52]:…”