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

Abstract

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 10 12 ÷10 13 nanocluster/m 3 . Charging of nanoclusters in plasma produced a stable uprising nanocluster flow (∼10 8 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 CeO 2 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.

Ion confinement efficiency and ionization balance in a complex DC discharge plasma

“…This coefficient indicates how much more heat is released in the discharge plasma without microparticles in comparison with the complex plasma upon maintaining equal ion density. The relative overheating coefficient η Q is useful, first of all, for technologies and processes at low and cryogenic temperatures, when heating is undesirable [24][25][26][27][28]. As was demonstrated in [18], at low discharge currents (I < 1 mA) a gain in the relative heating is quite large (η Q > 10), but it disappears with increasing the discharge current.…”

Oxygen atoms and nitrogen molecules as spectroscopic probes for the temperature determination in non-equilibrium cryogenic helium plasma jets

“…A cryoplasma is a plasma generated under experimental conditions which can be controlled continuously over a wide range of temperature below 100 K. In non-equilibrium plasmas the electron temperature (T e 10 4 K) is usually much higher than the plasma gas temperature (T g 100 K). Non-equilibrium cryoplasmas are promising for some advanced technologies, such as the cryoetching of sub-20 nm features and ultra low-k materials used as interlayer dielectrics in modern microchips [1,2], ashing of photoresists [3], synthesis of polymeric nanoclusters and quasi one-dimensional structures [4]. The plasma gas temperature is one of the key parameters in cryoplasma chemistry [5][6][7].…”

“…Only one exception for cryogenic plasmas has been reported in the literature for the He 2 excimer solvated in the liquid helium [20]: the lowest allowed rotational quantum state of the d 3 Σ u + state was exclusively populated. The presence of impurities in helium gas changes the emission spectra observed in different plasmas initiated by radiofrequency (RF), dielectric barrier discharge, corona, and direct current discharges or by highly energetic particles [4,6,[21][22][23][24][25][26][27]. Lowering the temperature of the helium gas usually causes decreasing of the impurity emission intensities accompanied by increasing of the emission intensity from the helium atoms and molecules [6,22].…”

Determination and control of ion parameters in complex plasma of a DC discharge

“…Lowtemperature ion traps have found promising applications in the study of fundamental processes in quantum physics [8] and quantum information processing [9]. In a low-temperature DC discharge, dust clouds of various topologies and compositions can form, including low-dimensional structures [4,10] such as clusters [11][12][13]. These clusters can localize ions with higher density in a plasma region (whose size is comparable with that of the cluster) with high precision.…”