Aerosol–Surface Interactions in Low-Pressure Misty Plasma Deposition of Nanocomposite Thin Films

Abstract

Low-pressure misty plasma processes, in which liquid suspensions of nanoparticles are sprayed into low-pressure plasma, are promising candidates for the synthesis of nanocomposite thin films. Clusters of agglomerated nanoparticles forming on the samples during plasma deposition constitute the main challenge to overcome. In this work, injections of colloidal solutions are first carried out in a misty plasma reactor to highlight the diversity in size and morphology of the agglomeration patterns depending on plasma operating conditions. Then, the plasma-specific aerosol–surface interactions are investigated in a second reactor dedicated to in-plasma surface analysis. It is shown that a high substrate temperature (with respect to the liquid's boiling temperature) helps in distributing the nanoparticles more uniformly by triggering Leidenfrost-like boiling when the droplets reach the substrate. Results also hint at a potential plasma-induced selection in the size of the droplets, where the smallest droplets (< 10 µm) would be electrostatically filtered out by the plasma sheath.