Surface loss probabilities of H and N radicals on different materials in afterglow plasmas employing H₂ and N₂ mixture gases

Surface loss probabilities of hydrogen (H) and nitrogen (N) radicals on different wall materials in H₂/N₂ mixture plasmas have been investigated by employing vacuum ultraviolet (VUV) absorption spectroscopy with a high pressure microdischarge hollow cathode lamp as a light source. The surface loss probability of a radical was calculated by using the lifetime obtained from the decay curve of the radical density in afterglow plasmas. The surface loss probabilities on different walls in the H₂/N₂ mixture plasmas were higher than those in a pure H₂ or N₂ plasma. The behaviors of species such as ions and VUV photons as a function of the gas mixture ratio were measured to investigate those influences on plasma-surface interactions. In addition, changes on the surface exposed to the plasma were analyzed by x-ray photoelectron spectroscopy. Quantitative measurements of surface loss probabilities of radicals on various wall materials are expected to be crucially important in achieving good understanding of the interaction between the surface and the plasma.