Optical and electrical characterization of an atmospheric pressure microplasma jet for Ar/CH{sub 4} and Ar/C{sub 2}H{sub 2} mixtures

Journal Article · Tue May 15 00:00:00 EDT 2007 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2714646· OSTI ID:20982881

Yanguas-Gil, A; Focke, K; Benedikt, J; Keudell, A von ^[1]

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1. Arbeitsgruppe Reaktive Plasmen, Fakultaet fuer Physik und Astronomie, Ruhr Universitaet Bochum, Universitaetsstrasse 150, 44780 Bochum (Germany)

A rf microplasma jet working at atmospheric pressure has been characterized for Ar, He, and Ar/CH{sub 4} and Ar/C{sub 2}H{sub 2} mixtures. The microdischarge has a coaxial configuration, with a gap between the inner and outer electrodes of 250 {mu}m. The main flow runs through the gap of the coaxial structure, while the reactive gases are inserted through a capillary as inner electrode. The discharge is excited using a rf of 13.56 MHz, and rms voltages around 200-250 V and rms currents of 0.4-0.6 A are obtained. Electron densities around 8x10{sup 20} m{sup -3} and gas temperatures lower than 400 K have been measured using optical emission spectroscopy for main flows of 3 slm and inner capillary flows of 160 SCCM. By adjusting the flows, the flow pattern prevents the mixing of the reactive species with the ambient air in the discharge region, so that no traces of air are found even when the microplasma is operated in an open atmosphere. This is shown in Ar/CH{sub 4} and Ar/C{sub 2}H{sub 2} plasmas, where no CO and CN species are present and the optical emission spectroscopy spectra are mainly dominated by CH and C{sub 2} bands. The ratio of these two species follows different trends with the amount of precursor for Ar/CH{sub 4} and Ar/C{sub 2}H{sub 2} mixtures, showing the presence of distinct chemistries in each of them. In Ar/C{sub 2}H{sub 2} plasmas, CH{sub x} species are produced mainly by electron impact dissociation of C{sub 2}H{sub 2} molecules, and the CH{sub x}/C{sub 2}H{sub x} ratio is independent of the precursor amount. In Ar/CH{sub 4} mixtures, C{sub 2}H{sub x} species are formed mainly by recombination of CH{sub x} species through three-body reactions, so that the CH{sub x}/C{sub 2}H{sub x} ratio depends on the amount of CH{sub 4} present in the mixture. All these properties make our microplasma design of great interest for applications such as thin film growth or surface treatment.

• OSTI ID: 20982881
• Journal Information: Journal of Applied Physics, Vol. 101, Issue 10; Other Information: DOI: 10.1063/1.2714646; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ARGON
ATMOSPHERIC PRESSURE
CAPILLARY FLOW
CARBON MONOXIDE
CRYSTAL GROWTH
ELECTRIC POTENTIAL
ELECTRON DENSITY
ELECTRON TEMPERATURE
EMISSION SPECTROSCOPY
HELIUM
HIGH-FREQUENCY DISCHARGES
METHANE
PLASMA
PLASMA DENSITY
PLASMA DIAGNOSTICS
PLASMA JETS
RECOMBINATION
SCANNING LIGHT MICROSCOPY
SURFACE TREATMENTS
THIN FILMS