The minimum voltage required to break down a discharge V brk has long been known to be a strong function of the product of the neutral gas pressure and the electrode separation ͑pd͒. This paper investigates the dependence of V brk on pd in radio-frequency ͑rf͒ systems using experimental, computational and analytic techniques. Experimental measurements of V brk in an argon discharge are made for pressures in the range 1-500 mTorr and electrode separations of 2-20 cm. A particle-in-cell simulation is used to investigate a similar pd range and examine the effect of the secondary emission coefficient on the rf breakdown curve, particularly at low pd values. A zerodimensional global ͑volume averaged͒ model is also developed to compare with experimental and simulated measurements of breakdown.
Breakdown in low pressure radio frequency (rf) plasmas is investigated with particle-in-cell simulations in a model gas based on argon. A one dimensional model with a realistic rf wave form is used in a range of pressures between 1 and 50 mTorr. Dynamic scaling and electron generated secondaries are introduced in order to simulate breakdown realistically, and it is possible to follow the discharge development from a few initial electrons to the steady state plasma with ne ∼109 cm−3. The results confirm that breakdown is controlled by the resonant multiplication of secondary electrons known as the multipactor. For the pressures investigated, however, ionization is the main source of new charges and a model based on a typical electron trajectory is introduced to account for the growth in the number of electrons in the discharge gap. The model is in good agreement with the simulation results.
A one dimensional ͑1D͒ particle-in-cell ͑PIC͒ computer simulation has been used in conjunction with a small experimental plasma reactor, to investigate the effects of pulsing on a low pressure, capacitively coupled, rf argon plasma. In particular this article investigates the time-constants involved in the development and evolution of the bias voltage in asymmetric reactor geometry. Surprisingly, the charging time for the blocking capacitor does not occur on electron time scales, but is influenced primarily by the ambipolar drift of ions to the earthed electrode. It is shown that following plasma breakdown there is a net current flow in the system which charges the blocking capacitor in the external matching circuit and produces the bias voltage. Both the PIC simulation and the experimental measurements show that a net current flow is produced by a delay in the onset of the electron current to the earthed electrode, which is correlated to the charging time of the capacitor. From the simulation it can be seen that during this period the plasma potential in the center of the discharge is higher than one would expect, preventing electrons from reaching the earthed electrode.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.