Abstract. This paper studies in experiment and theory the breakdown of argon, nitrogen, air and oxygen in a uniform dc electric field at different discharge gaps L, discharge tube radii R and cathode materials. At arbitrary geometric dimensions of the cylindrical discharge vessel and cathode materials the ratio of the breakdown electric field value to the gas pressure p at the minimum of the breakdown curves is shown to remain constant, (E dc /p) min ≈ constant. A modified breakdown law for the low-pressure dc dischargeThat is, the breakdown voltage U dc is shown to depend not only on the product pL, but also on the ratio L/R. A method is presented enabling one to predict a dc breakdown curve in the cylindrical discharge vessel possessing arbitrary L and R values from the measured data on the dc breakdown.

Abstract. This paper reports the results of the detailed and comprehensive experimental and theoretical treatment of the rf gas breakdown. We give the measured breakdown curves of the low-pressure rf discharge in argon, hydrogen and air in a broad range of gas pressures and interelectrode distances. The different processes of generation and loss of charged particles participating in the rf gas breakdown are discussed. We suggest to distinguish the following sections on the rf discharge breakdown curves: multi-pactor, Paschen, diffusion-drift and emission-free ones. The analytic gas breakdown criterion of the combined (rf plus weak dc electric field) discharge taking into account the anisotropy of electron diffusion in the electric field is obtained. A novel method for determining the electron-drift velocity from the measured rf breakdown curves is suggested. The electron-drift velocity data in argon, hydrogen and air obtained with this technique in the range E /p ≈ 50-2000 V cm −1 Torr −1 are given and compared with those got by conventional means.

This paper reviews measured and theoretical data relating to the low-pressure discharge breakdown in DC and uniform RF fields and their combination. The original results on determination of molecular constants of various gases from breakdown curves obtained by the authors are given. We have investigated the effect of the DC electric field on the RF breakdown pattern. In particular the influence of the DC electric field on the ambiguity region of the RF discharge breakdown curves has been determined. Breakdown equations in combined fields have been derived and comparison has been made between these equations and measured data. Simple analytical criteria for gas breakdown for a wide range of parameters have been given.

We report measurements of the breakdown curves for low-pressure rf capacitive discharges in nitrogen, hydrogen, argon, oxygen and ammonia. The electron drift velocity in these gases was deduced, as a function of reduced electric field, from the low-pressure turning points of the breakdown curves. The equation for rf breakdown proposed by Kihara (1952 Rev. Mod. Phys. 24 52) allows the position of both the turning point and the breakdown curve minimum to be calculated from the transport properties of each gas. Therefore we propose a new technique to determine the electron drift velocity from the position of the rf breakdown curve minima. We have determined the drift velocity in the range E/p = 52-1324 V cm −1 Torr −1 for nitrogen, E/p = 33-720 V cm −1 Torr −1 for argon, E/p = 32-713 V cm −1 Torr −1 for ammonia, E/p = 32-550 V cm −1 Torr −1 for hydrogen and E/p = 69-1673 V cm −1 Torr −1 for oxygen.

We report the recorded current-voltage characteristics of a RF capacitive discharge in oxygen. Low-frequency oscillations of the plasma potential in a kilohertz frequency range are observed to accompany the transition of the discharge from a weak-(a-) to a strong-current (g-) regime in the low-pressure range. The weak-current regime of the RF capacitive discharge is observed within the pressure range limited not only from the medium pressure side but also from the lower-pressure one. Electron temperature and plasma density are registered with a probe technique. r

In this paper we report the values of the electron-drift velocity in CF 4 and SF 6 within the range E/p ≈ 200-1000 V cm −1 Torr −1 . We have used the recorded coordinates of the turning point on the breakdown curves of the rf capacitive discharge. We have also formulated the main requirements to the experimental device for correct recording of the breakdown curves of the low-pressure rf capacitive discharge. Our data are in good agreement with those of other authors who have used different approaches. We have also obtained the results on the electron-drift-velocity values within the E/p region where no other techniques are applicable. Our findings are also supported by numerical simulation data obtained with the application of a conventional Bolsig code.

This paper shows that the rf capacitive discharge in NF 3 and SiH 4 can burn in three possible modes: weak-current α-mode, strong-current γ -mode and dissociative δ -mode. This new dissociative δ-mode is characterized by a high dissociation degree of gas molecules (actually up to 100% in NF 3 and up to 70% in SiH 4 ), higher resistivity and a large discharge current. On increasing rf voltage first we may observe a weak-current α-mode (at low NF 3 pressure the α-mode is absent). At rather high rf voltage when a sufficiently large number of high energy electrons appear in the discharge, an intense dissociation of gas molecules via electron impact begins, and the discharge experiences a transition to the dissociative δ-mode. The dissociation products of NF 3 and SiH 4 molecules possess lower ionization potentials, and they form an easily ionized admixture to the main gas. At higher rf voltages when near-electrode sheaths are broken down, the discharge experiences a transition to the strong-current γ -mode.

This paper demonstrates that the similarity law for the rf gas breakdown has the form U rf = ψ(p • L, L/R, f • L)(where U rf is the rf breakdown voltage, p is the gas pressure, L and R are the length and diameter of the discharge tube, respectively, f is the frequency of the rf electric field). It means that two rf breakdown curves registered for narrow inter-electrode gaps or in geometrically similar tubes and depicted in the U rf (p • L) graph will coincide only when the condition f • L = const is met. This similarity law follows from the rf gas breakdown equation and it is well supported by the results of measurements.