Pressure Dependence of Plasma Polymerization of Methane at Constant W / FM

The pressure dependence of the deposition rate of plasma polymerization is investigated at a given energy input level W / FM to examine the variation of reactive species concentration at the deposition site. The variation is due to the shift of the glow properties caused by the change of the system pressure. At shorter interelectrode distance, the deposition rate first increases, then decreases linearly after passing a peak value. The initial increase gets weaker with wider interelectrode distance, and at a wide enough interelectrode distance, no initial increase is observed: The deposition rate decreases linearly with the increasing system pressure. These results indicate that the distribution of reactive species in the glow cannot be assumed to be uniform.