Optical Emission Spectroscopy Applied to Plasma Magnetron Sputtering Metallic Deposition Onto Liquid at Low Pressure

ABSTRACT

This dedicated optical emission spectroscopy (OES) study aims to improve the understanding of low‐pressure sputtering onto liquids used for the production of nanoparticle (NPs) suspensions. In this work, ruthenium (Ru) nanoparticles are synthesized in polyethylene glycol contained in a glass vial positioned outside the deposition reactor. The successful application of OES at the plasma‐liquid interface enabled the determination of several key parameters. The gas temperature exceeding 660 K was measured using two different approaches, namely Doppler broadening and the analysis of the OH()(0‐0) rotational spectra. Such values of temperature inherently enhance the PEG evaporation, which is consistent with the decrease in the energy of hydrogen species to () eV above the liquid surface. This value was obtained from the analysis of the line profile and the so‐called excessive Doppler broadening. Furthermore, the electric field above the plasma‐liquid interface was determined to be () V/cm through measurements of the Stark shift of the Ar line at 541.047 nm. Finally, by investigating the electric field, the plasma‐liquid chemistry, and the dynamic properties of the surface, this study provides new insights that contribute to a better understanding of this physical synthesis technique.