Plasma Chemical Reactions on Solid Surfaces

Abstract

In this paper we report two chemical reactions which occur on solid wall surface under the influence of an ECR plasma with low gas pressure (<10^-2Pa).
One reaction is ammonia synthesis by the use of an H₂-N₂ mixture plasma. The system is not in equilibrium state. When the solid wall surface is used as a catalyst, a very high selectivity and also a high yield are obtained. The yield is about 70 times higher than that expected for usual systems in thermodynamically equilibrium state.
Another one is erosion of carbides by a hydrogen plasma. A chemical sputtering of carbon atoms in carbides is found when they are irradiated by a hydrogen plasma. The threshold values in hydrogen ion energy for the chemical sputtering are found to be 130 eV for TiC and 80 eV for SiC. These results show that the glow discharge cleaning gives a change in the composition of the first wall of fusion devices (ion energy∼10² eV), but the ECR discharge cleaning does not (ion energy<10 eV).