Polymerizable Species Created in Jet Stream of Luminous Gas

The existence of the dissociation glow in DC discharge strongly suggests that the creation of chemically reactive species in LCVD involves different mechanism than those in the electron impact ionization. However, in DC discharge, electron impact and ion impact reactions cannot be eliminated. Low-pressure cascade arc torch (LPCAT) provides a unique opportunity to investigate the formation of chemically reactive species with minimal influence of ions and electrons. That is, the creation of chemically reactive species from an organic molecule by the luminous 

When plasma polymerization is carried out in a flow system, in which glow covers the entire cross-section of reactor with respect to the direction of monomer flow, the monomer molecules coming into the reactor first encounter the luminous gas phase. It is very unlikely that the molecules pass through the luminous gas phase without interacting with it and reach the relatively narrow zone in which IG or DG, located near the electrode surface, occurs. Therefore, the mode of activation that occurs in LPCAT without the influence of ionization is important in terms of the creation of chemically reactive species in LCVD. The creation of reactive species by the luminous gas is the mechanism considered here. 

In cascade arc plasma polymerization, a monomer (or monomers) is introduced in the expansion chamber. Because of an extremely high velocity of gas injected from a small nozzle (e.g., 3 mm in diameter), the second gas injected into the expansion chamber in vacuum cannot migrate into the cascade arc generator. Thus, the activation of Ar in the cascade arc generator and deactivation of the excited neutral species of Ar in the expansion chamber, which activate the monomer introduced in the expansion chamber, are totally decoupled. LPCAT plasma polymerization occurs under such a spatially and temporally decoupled activation/ deactivation system. 

The ionization of Ar by high-energy electron, e, occurs in the cascade arc generator. 

At the same time, the creation of excited neutrals by the high-energy electron e impact also occurs in the generator. 

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