Particle densities and non-equilibrium in a low-pressure argon plasma jet

Abstract

Plasma diagnostic techniques have been employed to determine particle densities and temperatures in a low-pressure argon plasma jet generated by a cascade arc. These measurements allow characterization of the extent to which the plasma jet deviates from thermodynamic equilibrium and provide a basis for predicting how reactive gases will interact with the excited and ionized species in the plasma jet. It was found that the distribution of atomic states in the plasma jet is not adequately described by either local thermodynamic equilibrium ( L TE) or partial local thermodynamic equilibrium (pLTE), and the jet was optically thick for 3p~4s transitions across the jet radius. Excited argon neutrals outnumber ions by a large ratio,and dominate subsequent dissociation/excitation phenomena. The rate of methane destruction in the plasma jet shows that estimates for particle densities, temperature, and jet velocity are self-consistent.

The competitive ablation and polymerization (CAP) principle and the plasma sensitivity of elements in plasma polymerization and treatment

“…OES revealed that the plasma torch created by a low-temperature cascade arc consists mainly of metastable species of Ar when Ar is used as the plasma gas. 7,8 When an organic vapor is injected into the beam of Ar metastable species, the cascade arc torch (CAT) of Ar, plasma polymerization occurs. When the torch is directed at an organic polymer surface, plasma treatment of the surface occurs.…”

Deposition behavior in a low-temperature cascade arc torch (CAT) polymerization process

“…3,5 It can be assumed that the ratio of excited species (energy carriers) to the unexcited carrier gas is proportional to the power input given by W. This assumption can be expressed in eqs. (4) and (5), as follows.…”

“…Film thickness was recorded every 15-30 s during the first 5 min of a deposition and then at 1-min intervals until a constant deposition rate was obtained. A film density of 1.0 g/cm 3 was estimated from ellipsometry and thickness monitor data and did not vary by more than Ϯ0.1 g/cm 3 over the range of conditions evaluated. This estimated density was required to obtain thickness monitor data in units of Å/s and for estimating the total mass deposition rate.…”

“…2 In comparison with conventional plasma polymerization processes, however, cascade arc torch (CAT) polymerization is a very different process in that its activation and deactivation processes are temporally (and to some extent spatially) separated. [3][4][5] When a discharge power is applied to the system, the plasma of carrier gas (usually argon) is produced in the cascade arc column and expands into a vacuum chamber where monomers are dissociated and ionized by the argon plasma, and the deactivation of the reactive species occurs at a certain position along the axial direction of the argon plasma jet. In such a system, energy input into the cascade arc causes only the formation of the argon plasma, while the generation of the reactive species of monomers is induced directly by the argon plasma rather than by the electric power applied to the arc column.…”

Internal stress in plasma polymer films prepared by cascade arc torch polymerization

“…In the CAT polymerization process, the speed of an argon atom coming out of the cascade arc nozzle is estimated to be above the speed of sound. 10 This high-speed gas torch can be utilized to atomize liquid monomers and plasma polymerize them. The objective of this research is to reduce the internal stress of plasma polymer films by employing liquid monomers with particular molecular structure and high molecular weight for CAT polymerization.…”