Loading...
Please wait, while we are loading the content...
Similar Documents
Potential distribution around a charged dust grain in an electronegative plasma
| Content Provider | Semantic Scholar |
|---|---|
| Author | Shukla, Padma Kant Stenflo, Lennart |
| Copyright Year | 2010 |
| Abstract | The potential distribution around a charged dust grain in an electronegative plasma is obtained by using the appropriate dielectric susceptibilities for the Boltzmann distributed electrons and negative ions, and for the inertial positive ions that are streaming from the bulk plasma into the electronegative plasma sheath. The existence of oscillatory ion wakefields is shown. Positive ions are trapped/focused in the ion wakefields, and subsequently the negative dust particles are attracted to each other, forming ordered dust structures. It is well known that a stationary test charge is shielded in plasmas, and that the near-field potential follows the Debye–Hückel–Yukawa law [1]. Furthermore, it has been shown [2–4] that the far-field potential of a moving test charge in a collisionless electron-ion plasma decreases as the inverse cube of the distance r from the test charge. On the other hand, the far-field potential in a collisional electron-ion plasma [5–8] decays as r−2. When neutral dust grains are immersed in an electropositive plasma, they usually get negatively charged [9,10] due to the high mobility of the electrons that reach the dust grain surface. Several authors [11–13] have investigated the potential around a charged dust grain in a dusty plasma whose constituents are electrons, positive ions and negative dust grains. Besides, the Debye–Hückel–Yukawa potential, there appear long-range oscillatory wakefields [12, 13] due to collective interactions between the test charge and the dust ion-acoustic [14] and dust acoustic [15] waves in dusty plasmas with equilibrium drifts of the ions and the dust grains. Since oscillatory wakefields have both positive and negative potential distributions, the background positive ions are trapped/focused in the negative part of the oscillatory wake potential. It turns out that negative dust grains are attracted to each other as they are glued by positive ions. The underlying physics of this scenario is similar to that † Also at the Scottish Universities of Physics Alliance (SUPA), Department of Physics, University of Strathclyde, Glasgow, Scotland G4 ONG, UK; Grupo de Lasers e Plasmas, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, 1049-001 Lisbon, Portugal; Department of Physics, Ume̊a University, SE-90187 Ume̊a, Sweden. ‡ Also at the Department of Physics, Ume̊a University, SE-90187 Ume̊a, Sweden. 674 P. K. Shukla and L. Stenflo of the Cooper pairing of electrons in superconductors, where phonons do the job of gluing electrons in lattices. However, in industrial plasmas, negative ion-containing plasmas (known as the electronegative plasmas [16, 17]) have been extensively used in dry etching and plasma-enhanced thin-film deposition processing. In electronegative plasmas, the charge state of a dust particle is greatly affected by the presence of negative ions [19–22]. Electronegative plasmas are composed of electrons, positive inertial ions, and a fraction of negative ions, which typically follow the Boltzmann density distribution [23–25] in the electrostatic potential. In this Letter, we present an investigation of the potential distribution around a charged dust grain in an electronegative plasma sheath [23]. Such an investigation is of significant interest with regard to creating soft condensed materials in plasma-processing technologies [18]. The electrostatic potential around a test dust particle (with charge Q) moving with a constant velocity vt is [2] φ(R, t) = Q 2π2 lim →0 ∫ dk exp(ik · r − k) k2D(k,−k · vt) , (1) where r = R − vtt, D(k, ω = −k · vt) is the dielectric constant of the electronegative plasma, and k is the wave vector of the low-frequency ion oscillations in the electrostatic potential. Following Montgomery et al. [2], the term lim →0 exp(− k) has been included to ensure proper convergence of the integrals. The dielectric constant of an electronegative plasma with Boltzmann distributed electrons and negative ions, as well as inertial positive ions and static charged dust grains for |k · vt| kVTe,T− reads D(k,−k · vt) = 1 + χe + χ− + χ+, (2) where VTj = (kBTj/mj) 1/2 is the thermal speed of the particle species j (j equals e for electrons, − for negative ions and + for positive ions). The dielectric susceptibilities for our purposes are |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://liu.diva-portal.org/smash/get/diva2:359870/FULLTEXT01.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Acoustic cryptanalysis Charge (electrical) Chromosome Condensation Cube Dosage Form Disease susceptibility Dry etching Electron Electrons Equilibrium Expanded memory High-κ dielectric Hückel method Interaction Ions Montgomery modular multiplication Neural oscillation Order (action) Phonon Physical vapor deposition Plasma Active Plasma display Restricted Boltzmann machine Stationary process Universities Velocity (software development) |
| Content Type | Text |
| Resource Type | Article |
