Measurement of the absolute CF₂concentration in a dielectric barrier discharge running in argon/fluorocarbon mixtures

Abstract

The role of different CFx-radicals in plasma polymerization in fluorocarbon mixtures has not been determined yet. Therefore spectroscopic investigations of dielectric barrier discharges (DBDs) in argon/fluorocarbon mixtures at atmospheric pressure were conducted with the focus on measurement of the concentration of CFx-radicals. The following diagnostic procedures were applied: FTIR absorption spectroscopy to diagnose stable compounds in the discharge, optical emission spectroscopy of the DBD in the UV and visible range and measurement of the CF2 concentration by UV absorption spectroscopy. The DBD was running in argon with the following admixtures: CF4, C2F6, C2H2F4, C3F8, C3HF7, c-C4F8. The relative concentration of the CF3-radical and the absolute concentration of CF2 in Ar/fluorocarbon mixtures were measured by emission spectroscopy and by absorption and emission spectroscopy, respectively. Emission and absorption spectroscopy were performed simultaneously in combination with electrical measurements of the discharge characteristics. The influence of small amounts of hydrogen or oxygen added to the argon/fluorocarbon mixtures was investigated.

Plasma enhanced CVD of fluorocarbon films by low-pressure dielectric barrier discharge

“…Compared to filament discharges at atmospheric pressure, the low-pressure glow-like discharges contribute to the deposition of FC films with very smooth surfaces. Vinogradov et al found dusty-like particles with their sizes in the range of 0.1-1 μm for FC films deposited at atmospheric pressure [17,18]. Dusty-like particles can be produced due to strong filament discharges at atmospheric pressure.…”

“…The gas spacing between the electrodes can be varied in the range of 0.1 mm to several mm. DBDs have been used to deposit fluorocarbon films at atmospheric pressure [17,18]. However, plenty of dust-like particles on the surface have been observed.…”

Thin film deposition and surface modification with atmospheric pressure dielectric barrier discharges

“…Vinogradov et al [40,41] investigated the deposition of fluorocarbon films in filamentary DBDs fed with different fluorocarbons, e.g. CF 4 , C 2 F 6 , C 2 H 2 F 4 , C 3 F 8 , C 3 HF 7 and c-C 4 F 8 , in mixture with Ar; an in situ investigation of the plasma phase was performed by means of UV absorption spectroscopy, Fourier transform infrared (FT-IR) absorption spectroscopy, and optical emission spectroscopy.…”

Optical diagnostics in dielectric barrier discharges at atmospheric pressure

“…Analysis of the intensity ratios between SPS and CH(A), and between FNS and CH(A), has instead shown that CH(A) excitation is not achieved by electron impact on CH but by dissociative excitation of CH 4 . In particular, in N 2 -CH 4 and in He-CH 4 , respectively: e + CH 4 → CH(A) + products (9) He(2 3 S) + CH 4 → CH(A) + products (10) Summing up the whole of these experiences, we conclude that the mixed discharge/post-discharge regime of a DBD, and the generally low average electron density, results in emission spectra that are far from being dominated by electron impact on the corresponding ground state. The relationship between the emission and the corresponding radical is then not at all straightforward, and sometimes even nonexistent.…”

“…Non-emitting species measurement must be achieved by other techniques. Classical absorption (nontime-resolved) was applied to the detection of NO, NO 2 , NO 3 , N 2 O 5 , and O 3 in [8] and of CF 2 in [9], and two-photon LIF to the measurement of oxygen atoms in [10] and nitrogen atoms in [11]. We have explored this realm, touching many of the issues described above by a multidiagnostic approach with time-resolved optical diagnostics, applied to common DBD devices.…”