Abstract
Abstract Building on our previous study in argon gas, we extend our approach to helium and neon capacitively coupled plasmas, which allows the effective secondary-electron emission coefficient (SEEC, γ ) to be determined in-situ under discharge operation. The method relies on the γ -dependence of the DC self-bias voltage, which arises due to the electrical asymmetry effect (EAE). The EAE is induced by applying two consecutive radio-frequency harmonics with a variable phase angle to excite the discharge. Experimental measurements of the DC self-bias voltage are complemented by particle-in-cell/Monte Carlo collisions simulations. A sequence of SEEC values is used in the simulations, and the actual γ is determined by matching the computed DC self-bias to the experimental value. Applying this method at a driving frequency of 4 MHz, we obtain effective γ values of 0.105 and 0.165 for helium at 120 Pa and 240 Pa, respectively, and 0.072 and 0.103 for neon at 80 Pa and 160 Pa, respectively, with an estimated uncertainty of ±0.01.