Effects of nanoparticles on properties of the ionization region in a magnetron plasma

Abstract Effects of nanoparticles (NPs) on properties of the ionization region (IR) of a gas aggregation source (GAS) plasma and the properties of the sheath near the target are investigated using a global (volume averaged) model. The case where the GAS is operating in argon with copper target is considered. It is shown that with increasing the nanoparticle charge density, taking place at an increase of the NP size or the NP density, the densities of thermal electrons and argon ions slightly decrease, while the temperature of thermal electrons becomes larger. The voltage drop in the IR increases when the NP charge density becomes larger, to increase the power transferred to thermal electrons at an enhancement of the power losses in collisions with NPs and argon and copper atoms. For a fixed voltage applied to the target, the increase of the voltage drop in the IR is accompanied by a decrease of the voltage drop in the sheath near the target and, consequently, by a decrease of the sheath size, voltage drop in the sheath, energies with which ions bombard the target, sputtering yields and, as a result, by decreasing the densities of copper ions and copper atoms. It is shown that the absolute value of the charge of negatively charged NPs increases with increasing the NP density because of the growth of thermal electron temperature. Comparing the rates describing the deposition of copper ions and copper atoms on NPs, it is found that the growth of relatively large NPs (⩾10 nm) in the IR is due to the deposition of Cu ions on the surface of NPs, not Cu atoms. The results of our simulations are in good agreement with the available experimental data on the effect of NPs on magnetron plasma properties.