Bohm criterion for the collisional sheath

Valentini, H.-B.

doi:10.1063/1.871736

Cited by 74 publications

(40 citation statements)

References 13 publications

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“…A nonvanishing electric field strength and, additionally, a small space charge density are taken into account at the sheath edge. The foregoing results 8 …”

Section: ͑1͒mentioning

confidence: 99%

Response to ‘‘Comment on ‘Bohm criterion for the collisional sheath’ ’’ [Phys. Plasmas 3, 1459 (1996)]

Valentini

1996

Physics of Plasmas

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A plasma sheath concept including both the collisionless and collisional sheaths is explained. References to results of this concept are given. The plasma sheath concept used by Riemann and Meyer in their comment is not relevant for the thick collisional sheath and leads to conclusions which are in obvious contrast to relevant numerical results. Thus, the general remarks of the comment on the paper by Valentini [Phys. Plasmas 3, 1459 (1996)] are not relevant. The criticisms of a few details are justified. A slight quantitative modification of the previous results has been obtained (H.-B. Valentini, submitted to Phys. Plasmas).

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“…A nonvanishing electric field strength and, additionally, a small space charge density are taken into account at the sheath edge. The foregoing results 8 …”

Section: ͑1͒mentioning

confidence: 99%

Response to ‘‘Comment on ‘Bohm criterion for the collisional sheath’ ’’ [Phys. Plasmas 3, 1459 (1996)]

Valentini

1996

Physics of Plasmas

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“…To answer this question, Valentini 3 presented an analysis accounting for space charges and collisions and derived a modified Bohm criterion. This analysis, however, is wrong and could serve to increase persisting misunderstandings of the plasma-sheath concept.…”

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confidence: 99%

Comment on ‘‘Bohm criterion for the collisional sheath’’ [Phys. Plasmas 3, 1459 (1996)]

Riemann

Meyer

1996

Physics of Plasmas

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“…For collisional plasmas, the definition of the sheath boundary is ambiguous [5], [21]- [23]. When is is small according to Riemann [5], the Bohm criterion is still good for the sheath boundary.…”

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confidence: 99%

Sheath thickness evaluation for collisionless or weakly collisional bounded plasmas

Wang

Wendt

1999

IEEE Trans. Plasma Sci.

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Abstract-The widely used Child-Langmuir law for sheath thickness evaluation in semi-infinite collisionless plasmas makes the assumptions of quasi-neutrality (n e = n i ) and zero electric field intensity E = 0 at the sheath edge, as well as applying the Bohm criterion for ions entering the sheath. However, through a whole region fluid model, Poisson's equation has been solved numerically for the steady-state solution through the sheath and presheath without these assumptions. With the sheath edge defined, as in the Child-Langmuir law, at the place where the ion velocity is equal to the Bohm velocity, the sheath thickness of a bounded collisionless or weakly collisional plasma has been found with this model in some cases to be much larger than that obtained with the Child-Langmuir Law. The sheath thickness discrepancy is significant under conditions found in low pressure high density plasma (HDP) tools for plasma processing. Results presented indicate that the sheath thickness is very sensitive to the electric field and space charge density at the sheath edge. The electric field and space charge density can be successfully estimated by an intermediate scale matching method [1]-[5], and are used to derive a modified expression for the potential in the sheath that can be solved numerically for sheath thickness. With these results, the matching problem, arising when sheath and plasma are modeled separately, can be overcome.

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Bohm criterion for the collisional sheath

Cited by 74 publications

References 13 publications

Response to ‘‘Comment on ‘Bohm criterion for the collisional sheath’ ’’ [Phys. Plasmas 3, 1459 (1996)]

Response to ‘‘Comment on ‘Bohm criterion for the collisional sheath’ ’’ [Phys. Plasmas 3, 1459 (1996)]

Comment on ‘‘Bohm criterion for the collisional sheath’’ [Phys. Plasmas 3, 1459 (1996)]

Sheath thickness evaluation for collisionless or weakly collisional bounded plasmas

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