Glow discharges species

Figure C2.18.3. Relationship between ion-assisted etching and directionality in plasma etching, (a) Demonstration of the synergy between ion bombardment and reactive species during ion-assisted etching, (b) Ions incident on an etched feature. This situation prevails in glow discharges when the feature dimensions are much less than the plasma sheath thickness. Reproduced from [35]...

Vapor—vapor reactions (14,16,17) are responsible for the majority of ceramic powders produced by vapor-phase synthesis. This process iavolves heating two or more vapor species which react to form the desired product powder. Reactant gases can be heated ia a resistance furnace, ia a glow discharge plasma at reduced pressure, or by a laser beam. Titania [13463-67-7] Ti02, siUca, siUcon carbide, and siUcon nitride, Si N, are among some of the technologically important ceramic powders produced by vapor—vapor reactions. 

The fugitive species SO was first identified by its ultraviolet spectrum in 1929 but it is thermodynamically unstable and decomposes completely in the gas phase in less than I s. It is formed by reduction of SOn with sulfur vapour in a glow discharge and its spectroscopic properties... 

Mass spectrometric studies of the ionic species which arrive at the cathode of both glow and corona discharges yield useful information regarding ion-molecule reactions which occur within these systems. Glow discharges have been used to study endothermic reactions, and their usefulness and limitations have been demonstrated by studies of the dissociative charge transfer reactions Ar+ + N2 N+ + N + Ar N2+ + N2 N+ + N + N2 N2+ + 02 0+ + O + N2. Exo-... 

Mass spectrometer studies of oxidant additions to fluoro- and chlorocarbon gases have demonstrated that the relative reactivity of atoms with unsaturate species in a glow discharge follows the sequence F -- O > Cl > Br (41), Of course, the most reactive species present will preferentially undergo saturation reactions that reduce polymer formation and that may increase halogen atom concentration. Ultimately, determination of the relative reactivity of the plasma species allows prediction of the primary atomic etchants in a plasma of specific composition. 

After removal of the native aluminum oxide layer, molecular chlorine (CI2) can etch pure, clean aluminum without a plasma (84,52), Indeed, CI2 may be the primary etchant species for aluminum in a glow discharge, perhaps due to a higher concentration of CI2 than chlorine atoms in the discharge (74). 

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