Charged-species profiles in electronegative radio-frequency plasmas

Journal Article · Tue Feb 28 23:00:00 EST 1995 · Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics; (United States)

DOI:https://doi.org/10.1103/PhysRevE.51.2436· OSTI ID:6448908

Vender, D; Stoffels, W W; Stoffels, E; Kroesen, G M.W.; de Hoog, F J ^[1]

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1. Department of Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

The negative ion density profile in a low pressure oxygen rf plasma has been measured by a photodetachment technique. At an rf power of 10 W and a neutral pressure of 10 mTorr, a parabolic negative ion density profile is obtained with a peak density of 8[times]10[sup 15] m[sup [minus]3] and a maximum ratio of negative ion to electron densities [ital n][sub [minus]]/[ital n][sub [ital e]][approx]18. Under these conditions, the most abundant positive ion, determined by ion mass spectrometry, is O[sub 2][sup +] with O[sup +] being less than 10% of the positive ion density. The most abundant negative ion is O[sup [minus]] with O[sub 2][sup [minus]] and O[sub 3][sup [minus]] being less than 20% of the total negative charge density. The maximum in the density profile of negative ions shifts closer to the powered rf electrode as the pressure is increased in the asymmetric system. Comparison of the results to theory indicates that the asymmetry follows from an enhancement of the ionization rate near the powered electrode sheath. The parabolic profile is also obtained in CCl[sub 2]F[sub 2] at low pressure. Simulations and measurements show a rapid drop in ion density near the sheath that may be related to the recently discussed stratification'' phenomenon in electronegative plasmas.

• OSTI ID: 6448908
• Journal Information: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics; (United States), Journal Name: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics; (United States) Vol. 51:3; ISSN PLEEE8; ISSN 1063-651X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700330* -- Plasma Kinetics
Transport
& Impurities-- (1992-)
ANIONS
CHARGE STATES
CHARGED PARTICLES
DISTRIBUTION
ELECTRIC DISCHARGES
ELECTROMAGNETIC RADIATION
ELEMENTS
HIGH-FREQUENCY DISCHARGES
ION DENSITY
IONS
MEDIUM VACUUM
NONMETALS
OXYGEN
PLASMA DIAGNOSTICS
PLASMA SHEATH
RADIATIONS
RADIOWAVE RADIATION
SPATIAL DISTRIBUTION