Time-Resolved Analysis of the Electron Temperature in RF Magnetron Discharges with a Pulsed Gas Injection

Abstract

Pulsed gas injection in a plasma can affect many fundamentals, including electron heating and losses. The case of an asymmetric RF magnetron plasma with a pulsed argon injection is analyzed by optical emission spectroscopy of argon 2p-to-1s transitions coupled with collisional-radiative modeling. For a fully detailed population model of argon 2p levels accounting for direct and stepwise electron-impact excitation in optically thick conditions, a rapid decrease in the electron temperature, Te, is observed during each gas injection with the sudden pressure rise. The opposite trend, with unrealistic Te values before and after each pulse, is observed for analysis based on simple corona models, thus emphasizing the importance of stepwise excitation processes and radiation trapping. Time-resolved electron temperature variations are directly linked to the operating parameters of the pulsed gas injection, in particular the injection frequency. Based on the complete set of data, it is shown that the instantaneous electron temperature monotonously decreases with increasing pressure, with values consistent with those expected for plasmas in which charged species are produced by electron-impact ionization of ground state argon atoms and lost by diffusion and recombination on plasma reactor walls.

Direct Liquid Reactor-Injector of Nanoparticles: A Safer-by-Design Aerosol Injection for Nanocomposite Thin-Film Deposition Adapted to Various Plasma-Assisted Processes

“…Figure 4a depicts the temporal evolution profile of the power injected in the discharge during a single DLRI pulse (red curve): the injected power decreased down to 30 W within 200-300 ms, until it reached the set value of 100 W just before the injection of the subsequent pulse. Part of this temporal variation is linked to the sudden pressure rise due to the pulsed operation of the DLRI (Figure 4b) [50]. However, this slow return to equilibrium also implied a temporal response of the plasma to the presence of droplets and/or nanoparticles in the plasma volume.…”

Pulsed-aerosol assisted low-pressure plasma for thin film deposition

“…the transfer of power into the gas down to P inj,pulse ≈2 W [38]. However, in contrast with argon plasmas where the plasma parameters mainly reacted to the strong variation of neutral species [45], Fig. 4.b shows that the injected power does not reach the maximal value P inj,0 ≈ 100 W for more than few s after the pulse and stays at an intermediate state around 87 W. It can be attributed to the presence of liquid droplets con ned in the plasma volume.…”

Helium line emission spectroscopy to measure plasma parameters using modeling and machine learning in low-temperature plasmas

“…Based on CR model calculations, line intensity ratios (LIRs) have long been utilized to determine n e and T e . Argon (Ar) gas is commonly used in nonfusion low-temperature plasmas, and Ar I CR models have been developed to gain insight into Ar plasmas [38][39][40][41][42][43][44][45][46][47]. For instance, six pairs of Ar I LIRs were examined for the determination of n e and T e in comparison with those measured using a double probe as a function of the RF input power in helicon discharge plasmas [44].…”