Surface loss probability of atomic hydrogen for different electrode cover materials investigated in H2-Ar low-pressure plasmas

In an inductively-coupled H2-Ar plasma at a total pressure of 1.5 Pa the influence of the electrode cover material on selected line intensities of H, H2, and Ar are determined by optical emission spectroscopy and actinometry for the electrode cover materials stainless steel, copper, tungsten, Macorr, and aluminum. Hydrogen dissociation degrees for the considered conditions are determined experimentally from the measured emission intensity ratios. The surface loss probability βH of atomic hydrogen is correlated with the measured line intensities and βH values are determined for the considered materials. Without the knowledge of the atomic hydrogen temperature, βH cannot be determined exactly. However, ratios of βH values for different surface materials are in first order approximation independent of the atomic hydrogen temperature. Our results show that βH of copper is equal to the value of stainless steel, βH of Macor r and tungsten is about 2 times smaller and βH of aluminum about 5 times smaller compared with stainless steel. The latter ratio is in reasonable agreement with literature. The influence of the atomic hydrogen temperature TH on the absolute value is thoroughly discussed. For our assumption of TH = 600 K we determine a βH for stainless steel of 0.39± 0.13.