Sheath formation criterion in collisional electronegative warm plasma

Dhawan, Rajat; Malik, Hitendra K.

doi:10.1016/j.vacuum.2020.109354

Cited by 17 publications

(6 citation statements)

References 37 publications

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“…Equations (10) and (13) are coupled differential equations which will be solved with the help of appropriate numerical methods. In this paper, we have adopted the Runge-Kutta (RK) method of fourth-order.…”

Section: Boundary Conditions and Modified Bohm's Criterionmentioning

confidence: 99%

“…Such a thin layer is termed as sheath that plays a momentous role in analyzing the plasma-surface interactions [8]. The investigation of sheath characteristics in different plasma systems has been carried out by several researchers [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. The sheath characteristics have been found to show a distinct nature, when negative ions are introduced in the system [23,[29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

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Modelling of electronegative collisional warm plasma for plasma-surface interaction process

Dhawan

Malik

2021

Plasma Sci. Technol.

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An electronegative collisional plasma having warm and massive positive ions, non-extensive distributed electrons and Boltzmann distributed negative ions is modelled for the plasma-surface interaction process that is used for the surface nitriding. Specifically the sheath formation is evaluated through the Bohm’s criterion, which is found to be modified, and the variation of the sheath thickness and profiles of the density of plasma species and the net space charge density in the sheath region in addition to the electric potential. The effect of ion temperature, non-extensivity and collisional parameter is examined in greater detail considering the collisional cross-section to obey power-law dependency on the positive ion velocity. The positive ions are found to enter in the sheath region at lower velocities in the collisional plasma compared to the case of collision-less plasma; this velocity sees minuscule reduction with increasing non-extensivity. The increasing ion temperature and collisional parameter lead to the formation of sheath with smaller thickness.

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Section: Boundary Conditions and Modified Bohm's Criterionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modelling of electronegative collisional warm plasma for plasma-surface interaction process

Dhawan

Malik

2021

Plasma Sci. Technol.

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“…In previous studies on the properties of the magnetized sheath, the stress tensor in the ion motion equations is often neglected, meaning that the influence of stress on ion motion is not considered [14][15][16][17]. Some studies only consider the effects of thermal pressure and external fields [18][19][20][21][22][23][24][25][26][27]. Generally, when ions enter the sheath, their velocity rapidly increases to several times the ion sound speed under the influence of the electric field.…”

Section: Introductionmentioning

confidence: 99%

Effect of ion stress on properties of magnetized plasma sheath

CHEN 陈,

CUI 崔,

GAO 高

et al. 2024

Plasma Sci. Technol.

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In the plasma sheath, there is a significant gradient in ion velocity, resulting in strong stress on ions treated as a fluid. This aspect has often been neglected in previous sheath studies. This study is based on the Braginskii plasma transport theory and establishes a 1D3V sheath fluid model that takes into account the ion stress effect. Under the assumption that ions undergo both electric and diamagnetic drift in the presheath region, self-consistent boundary conditions, including the ion Bohm velocity, are derived based on the property of the Sagdeev pseudopotential. Furthermore, assuming that the electron velocity at the wall follows a truncated Maxwellian distribution, the wall floating potential is calculated, leading to a more accurate sheath thickness estimation. The results show that ion stress significantly reduces the sheath thickness, enhances ion Bohm velocity, wall floating potential, and ion flux at the wall. It hinders the acceleration of ions within the sheath, leading to notable alterations in the particle density profiles within the sheath. Further research indicates that in ion stress, bulk viscous stress has the greatest impact on sheath properties.

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“…For the last several decades, plasma sheath problems have been extensively analysed using kinetic [1][2][3][4][5][6][7][8][9][10][11] and fluid [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] models. Tonks and Langmuir [1] were the first to consider the sheath in gas discharges, with cold ions and hot electrons, and solved the mystery of higher ion velocity in the sheath than the respective thermal velocity in the bulk plasma.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Dhawan and coworkers analysed the sheath formation with different conditions in warm electronegative plasmas using a fluid description. [12][13][14][15][16][17] The fluid and numerical description of supersonic ion flow at sheath entrance were discussed in Refs. [18][19][20][21], but kinetic analysis of a sheath with supersonic ion flow is very rare.…”

Section: Introductionmentioning

confidence: 99%

Plasma sheath in the presence of warm ions

Din

Adnan

Khan

2023

Contributions to Plasma Physics

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The numerical solution of a warm ion sheath for an electrode/wall in contact with a low‐density isotropic plasma is analysed for sonic and supersonic flow of ions at the sheath entrance. For this, we consider half Maxwellian electron and water bag ion velocity distribution functions at the sheath edge. The generalized kinetic Bohm criterion is used to calculate the average ion velocity at the sheath edge. A relation between electrode/wall floating potential, sheath edge potential, and ion temperature is derived from the floating electrode/wall condition. The numerical solution of potential profiles for sonic and supersonic ions is calculated with varying ion temperature at different values of sheath edge potential. The results show that for sonic ions, the sheath solution merges smoothly into presehath solution, but for supersonic ions, we have density gradients, which increase with increasing ion temperature.

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Sheath formation criterion in collisional electronegative warm plasma

Cited by 17 publications

References 37 publications

Modelling of electronegative collisional warm plasma for plasma-surface interaction process

Modelling of electronegative collisional warm plasma for plasma-surface interaction process

Effect of ion stress on properties of magnetized plasma sheath

Plasma sheath in the presence of warm ions

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