Greifswald 2024 – scientific programme

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P: Fachverband Plasmaphysik

P 8: Complex Plasmas and Dusty Plasmas I

P 8.5: Talk

Tuesday, February 27, 2024, 12:15–12:30, WW 1: HS

Surface modification and core-shell structure of MF particles in the plasma sheath — •Sören Wohlfahrt, Franziska Reiser, and Dietmar Block — Kiel University, Kiel, Germany

Complex (dusty) plasmas consist if micrometer sized particles in addition to the typical plasma species of ions, electrons and neutrals. Dependent on the particle material, they show a distinct plasma-particle interaction that leads to a modification of the particles surface and even a decrease of the particle size in a process commonly referred to as 'etching'. In case of the widely used melamine formaldehyde (MF) particles, there is a strong connection between the surface reactivity and the etch process itself, which can be explained in the framework of an increasingly roughened surface shell and an unmodified particle core. We use a polarization resolved light scattering technique based on Lorentz-Mie theory to investigate the size and size evolution of single MF-particles in the plasma sheath. Our scattering-model assumes a coated sphere, which is analogous to a core-shell structure. Thus, the optical properties of the particle surface become directly accessible in the experiment. We will present time resolved measurements of single MF particles whose core is unaffected by the etch process, while the shell shows a steep increase in the imaginary part of the refractive index. Although the shell is only 100 nm thick (< 5% of particle size), this increase has a significant influence on the overall scattering- and absorption cross section of the particle and affects the particle dynamics as well.

Keywords: plasma-particle interaction; particle surface modification; mie-scattering