Plasma polymerization by magnetron glow discharge. I. Effect of magnetic field on breakdown of monomers in low pressure

Abstract

The breakdown voltage Vb of glow discharge of an organic monomer generally decreases as the system pressure decreases; however, below a certain threshold pressure, the breakdown voltage increases with decreasing system pressure. In the pressure range below 100 mTorr, the breakdown voltage generally increases as a linear function of 1/p, where p is the system pressure of the reactor. In this region, glow discharge without magnetic enhancement often yields unstable discharge, which is associated with a very steep slope of a line in the Vb vs 1/p plot. The similar plots for glow discharges of non-polymer-forming gases, such as He, Ar, and O2, do not follow the simple linear relationship, but a more or less linear increase is followed by a plateau. Effects of magnetic field on the breakdown phenomena were investigated by using planar parallel electrodes with circular arrangement of permanent magnets. Three different electrode systems with slightly different magnetic field profiles were used to investigate the effects of magnetic field intensity and its profile in the interelectrode space. The increasing intensity of magnetic field generally reduces the slope of Vb vs 1/p and produces more stable glow discharge in the lower pressure region where stable glow discharge cannot be created without magnetic enhancement.