Synthesis of nanoclusters and quasy one-dimensional structures in glow discharge at T ≈ 2 K

The present article considers the phenomena observed in ultracold multimodal dusty plasma generated in the glow discharge cooled with superfluid helium. It was shown that intense sputtering of the clay insert due to focused beams of low energy electrons and ions produces a total flow ∼100 ng s⁻¹ of sputtered materials at the power released in the discharge less than 0.1 W at T ⩽ 2 K. The synthesis rates for nanoclusters (∼10 ng s⁻¹) and filaments (∼1 ng s⁻¹) were estimated for the first time. Fast growth of quasy one-dimensional structures, the filaments with high aspect ratio, ∼100, in ultracold plasma was explained by self-assembly of polarizable materials in strongly inhomogeneous electric fields. The intense broadband emission stimulated by laser excitation of the filaments synthesized was assigned to carbon quantum dots, domains enriched with carbon. The key parameters of the nanocluster cloud were determined for the first time. The nanocluster concentration was estimated as high as 10¹²÷10¹³ nanocluster/m³. Charging of nanoclusters in plasma produced a stable uprising nanocluster flow (∼10⁸ cluster/s) driven by external electrostatic field and observable due to laser light scattering on dust acoustic waves developed within the flow. Temporal variations of the nanocluster concentration caused changes of the interparticle distance in the dusty plasma structure composed of CeO₂ particles. It was found that the particles trapped in the structure had the mean size of about 2 μm and much narrower size distribution in comparison with the very broad initial distribution. (paper)