Extended scaling and Paschen law for micro-sized radiofrequency plasma breakdown

Abstract

The single particle motion analysis and particle-in-cell merged with Monte Carlo collision (PIC/MCC) simulations are compared to explain substantial breakdown voltage reduction for helium microwave discharge above a critical frequency corresponding to the transition from the drift-dominant to the diffusion-dominant electron loss regime. The single particle analysis suggests that the transition frequency is proportional to the product ofp m and ( )where p is the neutral gas pressure, d is the gap distance, and m is a numerical parameter, which is confirmed by the PIC simulation. In the low-frequency or drift-dominant regime, i.e., -g regime, the secondary electron emission induced by ion drift motion is the key parameter for determining the breakdown voltage. The fluid analysis including the secondary emission coefficient, g, induces the extended Paschen law that implies the breakdown voltage is determined by pd, f p, g, and d R where f is the frequency of the radio or microwave frequency source, and R is the diameter of electrode. The extended Paschen law reproduces the same scaling law for the transition frequency and is confirmed by the independent PIC and fluid simulations.

Generation of energetic electrons in pulsed microwave plasmas

“…Thus, the electron kinetic energy is examined rather than temperature. The PIC simulation results would be different from fluidor global simulations where the Maxwellian energy distribution is assumed and the kinetic effects are ignored.…”

“…It is found that the pulsed microwave DBD plasma sustained by the same driving voltage ( V) produces as much energetic electrons as in the bare electrode case. This is due to the characteristics of the ‐mode plasma which is rarely affected by . On the other hand, the DC pulse requires higher than 550 V to break down the gas and higher than 260 V to sustain the plasma.…”

“…Although various microplasma devices have been developed, operated by different power sources such as DC, DC pulse, radio‐frequency, and microwave, it is not clear whether such devices are optimized for efficient generation of energetic electrons. Recent simulation studies on the scaling law of gas breakdown transition between and ‐mode for noble gases (helium and argon) suggest that the operating pressure, electrode geometry, and driving frequency can be optimized to produce capacitively coupled plasma (CCP) with low voltage and small ion flux damage. For example, at the atmospheric pressure (760 Torr) and the driving frequency 2.45 GHz, PIC simulations showed that the breakdown mode transition for helium plasma occurs at about 100 μm.…”

Study of the Effect of the Field Emission on the Breakdown Voltage Characteristic of Direct Current Nitrogen Microdischarges

“…It was found that the onset of field emission in direct current microdischarges with gap sizes of the order of a few µm can lead to the breakdown at voltages far less than predicted by the standard scaling law. Deviations from the standard scaling law observed in microgaps can be described and explained by the quantum mechanical theory of field emission from metals [13][14][15][16][17][18]. * corresponding author; e-mail: marija@ipb.ac.rs…”

Gas breakdown and its scaling law in microgaps with multiple concentric cathode protrusions

“…As is known, scaling laws are essential in understanding breakdown processes at different conditions and predicting discharge properties on different scales. [21][22][23]34,[49][50][51][52][53][54][55] The breakdown scaling law based on Townsend theory is usually investigated in cases with plane-parallel gaps when the electric field is uniform. 56,57 Previous studies indicate that Townsend theory is still valid in microdischarges unless the field emission plays a role.…”