Measurement of Hydrogen Radical Density and Its Impact on Reduction of Copper Oxide in Atmospheric-Pressure Remote Plasma Using H₂and Ar Mixture Gases

A 60 Hz alternating current excited atmospheric-pressure plasma with an ultrahigh electron density of over 10 16 cm -3 employing H 2 /Ar [ p (H 2 )/ p (H 2 +Ar) 1–3%] gases was used to reduce copper oxides on copper. The remote plasma reduced CuO and Cu 2 O at room temperature. The ground-state hydrogen (H) radical density in the atmospheric-pressure plasma was measured by vacuum ultraviolet absorption spectroscopy using a micro hollow cathode lamp. The ratio of reduction of amount of CuO flux to the H radical flux was determined from the measured H radical density and gas temperature.