Particle-in-cell Monte Carlo modeling of Langmuir probes in an Ar plasma

Abstract

The Langmuir-probe diagnostic of a plasma is studied using a particle-in-cell Monte Carlo model. The electron-density, temperature, and potential profiles are determined for a probe immersed in an Ar plasma. The model is verified using the low-pressure results of Sternovsky et al. [J. Appl. Phys. 94, 1374 (2003)]. It was proved that the ion to electron temperature ratio may not be constant in the sheath–presheath region.

Ion‐Neutral Collision Effects in Langmuir Probe Theory

“…For these reasons, an accurate collisional model is necessary. Previous works have used a constant collision frequency [16], a constant mean free path [6][7][8] or a simple partition of cross section between isotropic momentum transfer and backscattering charge transfer [17]. Our collision technique is self-consistent and it has confirmed good agreement with experimental drift velocities.…”

“…3(b) where ion and electron density as a function of radial position are shown for various gas pressures. The increase of the ion density close to the probe is an effect reported also by Cenian et al [17]. We can also see the decrease of the ion density for larger collisionality.…”

Measurement of sheath thickness at a floating potential

“…[18][19][20] Kinetic studies on plasma collected by electrostatic probes have been also conducted. [21][22][23][24][25][26] However, there have been a few experimental results for the measurement of the sheath thickness. 11,27 In this paper, we present a method to measure the sheath thickness by using a floating harmonics method and a wave cutoff method.…”

Current status of microplasma research

“…In an example, a thin probe of about 10 µm diameter fabricated by an ion milling technique was used in a PDP-like microdischarge [34]. For the analysis of the current-voltage characteristics, however, a proper correction must be made for the compensation of the collision effects by using, for example the Monte Carlo simulation [35]. Only for derivation of n e , a method using the Stark broadening of spectral lines can be used conventionally.…”