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Breakdown Phenomena in Water Vapor Microdischarges

100%

Radmilović-Radjenović M., Radjenović B., Savić M.

issue 5

752-755

The gas breakdown at the large gap sizes is reasonably well understood. However, the breakdown phenomenon in microgaps is still not sufficiently explored. The high electric fields realized in small gaps combined with the lowering of the potential barrier, seen by the electrons in the cathode as ion approaches lead to ion-enhanced field emission leading to deviations from the standard Paschen law. In this paper, semi-empirical expressions for the breakdown voltage based on the fitting of numerical solutions of the DC breakdown criteria in microdsicharges have been derived. In the standard breakdown criteria the secondary emission coefficient that incorporates the enhancement of the secondary electron emission has been included. The obtained expressions can be used for determination the pressure and the gap dependence of the breakdown field strength in the water vapor, separately.

Transport Coefficients For Electrons in Mixtures CF_4/Ar/O_2 and CF, CF_2 or CF_3 Radicals

88%

Nikitović Ž., Stojanović V., Radmilović-Radjenović M.

Acta Physica Polonica A

2011

vol. 120

issue 2

289-291

Transport coefficients for electrons in mixtures of CF_{4} with Ar and O_{2} for ratios of the electric field to the gas number density E/N from 1 Td to 1000 Td (1Td=10^{-21} V m^2) are presented. The analysis of non-conservative collisions revealed a range of the reduced electric field E/N where electron attachment introduced by radicals significantly changes electron kinetics obtained for mixtures without dissociation of CF_{4} gas. The results obtained by using a simple, Two Term solutions for Boltzmann's equation are verified by Monte Carlo simulations. It was found that three body attachments for oxygen is not significant for pressures that are standard in plasma etching equipment i.e. below 1 Torr. Furthermore, the attachment to CF, CF_{2} and CF_{3} at low mean energies is significant, several orders of magnitude. At the same time the mean energy and energy distribution functions for the given E/N are the same as in unperturbed gas mixture. The large changes of the attachment rate are sufficient to change the nature of plasmas and turn them into ion-ion plasmas with very few electrons for realistic abundances.

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2 Acta Physica Polonica A

1 2011

1 2010

2 Radmilović-Radjenović M.

1 Nikitović Ž.

1 Radjenović B.

1 Savić M.

1 Stojanović V.

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Breakdown Phenomena in Water Vapor Microdischarges

Transport Coefficients For Electrons in Mixtures CF_4/Ar/O_2 and CF, CF_2 or CF_3 Radicals