Nanowire charging in collisionless plasma

Shahravan, Anaram; Lucas, C.; Matsoukas, Themis

doi:10.1063/1.3483300

Cited by 5 publications

(6 citation statements)

References 27 publications

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“…The manner in which these results apply to the overall theoretical framework of nonspherical particle charging in general depends on the compactness of the particle geometries 17 , 38 and the flow regime of the charging species 40 . Our results are of fundamental importance in complex plasmas 3 – 11 , 38 , 40 , aerosol science, 21 – 26 and astrophysics 14 – 19 , as well as in numerous applications.…”

Section: Discussionmentioning

confidence: 75%

“…The charge of clustered particles seems heavily dependent on their morphology, which in turn impacts the particles’ accretion process 17 . In aerosol science, extensive experimental and computational research is reported on the charging of nonspherical particles at atmospheric pressures 21 – 26 , since particle charge is of vital importance in determining particle size in differential mobility analyzers.…”

Section: Introductionmentioning

confidence: 99%

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Charge of clustered microparticles measured in spatial plasma afterglows follows the smallest enclosing sphere model

et al. 2021

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The plasma-induced charge of non-spherical microparticles is a crucial parameter in complex plasma physics, aerosol science and astrophysics. Yet, the literature describes this charge by two competing models, neither of which has been experimentally verified or refuted. Here we offer experimental proof that the charge on a two-particle cluster (doublet) in the spatial afterglow of a low-pressure plasma equals the charge that would be obtained by the smallest enclosing sphere and that it should therefore not be based on its geometrical capacitance but rather on the capacitance of its smallest enclosing sphere. To support this conclusion, the size, mass and charge of single particles (singlets) and doublets are measured with high precision. The measured ratio between the plasma-afterglow-induced charges on doublets and singlets is compared to both models and shows perfect agreement with the predicted ratio using the capacitance of the smallest enclosing sphere, while being significantly dissimilar to the predicted ratio based on the particle’s geometrical capacitance.

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Section: Discussionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Charge of clustered microparticles measured in spatial plasma afterglows follows the smallest enclosing sphere model

et al. 2021

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“…more detailed short range potential interactions than the models employed here), charge exchange upon collision, and exchange of momentum and energy upon collision. Also not examined were aspherical particles and aggregates [23,[51][52][53]; this will require consideration of alignment and rotation in flow, as well as an appropriate drag coefficient [54]. Finally, many instances the dilute approximation is not valid, and multi-body particle interactions (particularly electrostatic) will need to be considered in future collision modeling efforts.…”

Section: Discussionmentioning

confidence: 99%

“…In aerosols and dusty plasmas, oppositely charged particles rapidly aggregate (collide and bind) with one another, while the charging of particles to sufficiently high levels of the same polarity stabilizes them against aggregation [16][17][18][19][20]. Given the importance of charged particle collisions in particleladen flows, numerous efforts have been devoted to developing accurate collision rate models for charged particles [21][22][23]. Many of these efforts consider the combined influences of electrostatic potential interactions and thermal energy on particle motion, such that the number of collisions per unit volume per unit time (R ij ) between particles of type i (size, charge level) and type j can be calculated as: (1) where n i and n j are the number concentrations of particles of type i and type j, respectively, and k ij is the collision rate coefficient.…”

Section: Introductionmentioning

confidence: 99%

Collision rate coefficient for charged dust grains in the presence of linear shear

Hui

Hogan

2017

Phys. Rev. E

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Like and oppositely charged particles or dust grains in linear shear flows are often driven to collide with one another by fluid and/or electrostatic forces, which can strongly influence particle-size distribution evolution. In gaseous media, collisions in shear are further complicated because particle inertia can influence differential motion. Expressions for the collision rate coefficient have not been developed previously which simultaneously account for the influences of linear shear, particle inertia, and electrostatic interactions. Here, we determine the collision rate coefficient accounting for the aforementioned effects by determining the collision area, i.e., the area of the plane perpendicular to the shear flow defining the relative initial locations of particles which will collide with one another. Integration of the particle flux over this area yields the collision rate. Collision rate calculations are parametrized as an enhancement factor, i.e., the ratio of the collision rate considering potential interactions and inertia to the traditional collision rate considering laminar shear only. For particles of constant surface charge density, the enhancement factor is found dependent only on the Stokes number (quantifying particle inertia), the electrostatic energy to shear energy ratio, and the ratio of colliding particle radii. Enhancement factors are determined for Stokes numbers in the 0-10 range and energy ratios up to 5. Calculations show that the influences of both electrostatic interactions and inertia are significant; for inertialess (St=0) equal-sized and oppositely charged particles, we find that even at energy ratios as low as 0.2, enhancement factors are in excess of 2. For the same situation but like-charged particles, enhancement factors fall below 0.5. Increasing the Stokes number acts to mitigate the influence of electrostatic potentials for both like and oppositely charged particles; i.e., inertia reduces the enhancement factor for oppositely charged particles and increases it for like-charged particles. Uniquely, at elevated Stokes numbers with attractive potentials we find collisionless "pockets" within the collision area, which are regions completely bounded by the collision area but within which collisions do not occur. Regression equations to results are provided, enabling calculation of the enhancement factor as a function of energy ratio and Stokes number. In total, this study both leads to insight into the collision dynamics of finite-inertia, charged particles in shear flows, and provides a means to simply calculate the particle-particle collision rate coefficient.

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“…This shift can be explained by the charging effect of the plasma. [31][32][33][34] Charging by the plasma takes place in only seconds, where chemical/electrochemical charging can take several minutes 24 to hours. 27 This method allows real-time monitoring of the charging effect induced by low-pressure plasmas and could be utilized for photonics applications based on the LSPR shift.…”

mentioning

confidence: 99%

Shifts in plasmon resonance due to charging of a nanodisk array in argon plasma

Lapsley

Shahravan

Hao

et al. 2012

Applied Physics Letters

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A method for generating charge-induced plasmonic shifts, using argon plasma to charge nanoparticle arrays, is presented. Particles develop a negative charge, due to enhanced collisions with high-temperature electrons, in low-temperature plasmas. The negative charge generated causes a blue shift in the localized surface plasmon resonance. The dynamics of the shift were recorded and discussed. This effect could be used as a real-time method for studying the dynamics for charging in plasma. Plasmonics deals with optically excited, oscillations of electrons at the interface between a metal and a dielectric, 1 and this phenomenon has driven the development of many optical devices. 2-9 Surface plasmons excited in metal structures, confined at the nanoscale in three dimensions (i.e., nanoparticles, nanodisks, etc.), are known as localized surface plasmons. At certain wavelengths, maximum coupling from electromagnetic waves to localized surface plasmons can be achieved and these are known as the localized surface plasmon resonances (LSPRs) of the structure. LSPRs of metal nanostructures depend on properties such as the size, 10,11 shape, 12-14 metal material, 15 surrounding dielectric material, [16][17][18][19][20][21][22] and the charge of the metal. [23][24][25][26][27][28][29][30] Active plasmonic devices can be realized by externally tuning the LSPR of nanostructures. Previously, chemical/electrochemical charging was used to actively tune the LSPR of arrays of both silver 24,25,30 and gold 23,26,27,29 nanostructures; however, this process is relatively slow. In this study, a rapid shift in the LSPR of an array of gold nanodisks was induced by surrounding the particles with a low-temperature argon plasma. This shift can be explained by the charging effect of the plasma. [31][32][33][34] Charging by the plasma takes place in only seconds, where chemical/electrochemical charging can take several minutes 24 to hours. 27 This method allows real-time monitoring of the charging effect induced by low-pressure plasmas and could be utilized for photonics applications based on the LSPR shift.In the experiment, the optical extinction spectrum of an array of gold nanodisks was measured while generating plasma. An array of gold nanodisks (diameters of 120 nm, thicknesses of 30 nm, and a periodicity of 300 nm) was fabricated on glass via electron-beam lithography. 35 A custom vacuum chamber was designed to include two flat, parallel windows to allow transmission of a probe light (Fig. 1(a)). The nanodisk array was placed inside the vacuum chamber where it was attached to one of the flat windows. The probe light, ejected from the input optical fiber and collimated by a lens, traveled through the vacuum chamber and the sample. The output light was collected by the output lens/optical fiber and delivered to an optical spectrometer. A vacuum system was used to evacuate the chamber to a base pressure of 150 mTorr. Argon was introduced into the chamber using a mass flow controller. The argon gas was introduced at a flow rate of 6 SCCM ...

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Nanowire charging in collisionless plasma

Cited by 5 publications

References 27 publications

Charge of clustered microparticles measured in spatial plasma afterglows follows the smallest enclosing sphere model

Charge of clustered microparticles measured in spatial plasma afterglows follows the smallest enclosing sphere model

Collision rate coefficient for charged dust grains in the presence of linear shear

Shifts in plasmon resonance due to charging of a nanodisk array in argon plasma

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