Miniaturized non-thermal atmospheric pressure plasma jet—characterization of self-organized regimes

Abstract

The study reports for the first time on self-organization effects in a radio frequency (RF) plasma generated with a miniaturized non-thermal atmospheric pressure plasma jet. The source is configured as a capacitively coupled RF jet (27.2 MHz) with two outer ring electrodes around a quartz capillary (d = 4.0 mm) between which a gas mixture flows at typical rates of 0.05-5 slm. The application background of this source is the deposition of thin films with a PECVD process. Therefore, thin film producing agents can be added in small quantities downstream the active discharge region. Commonly, the timeresolved observation of the discharge development reveals that the discharge consists of distinct discharge filaments that appear stochastically and evolve alongside the wall of the capillary. This stochastic mode can be easily found under most situations. However, under special conditions, a quasi-laminar flow is established and a controlled number of equidistant filaments develop which form fixed discrete rotating patterns (locked mode). In this paper, a systematic study is performed using Ar as process gas to define the range of existence of the locked mode. The temporal discharge behaviour is studied by performing a low frequency analysis on the optical emission of the plasma. RF power, gas flow rate and electrode distance are interpreted as scaling parameters that are responsible for the self-organization in the non-thermal atmospheric pressure plasma jet. The appearance of the different discharge regimes is described on a phenomenological basis and the collective behavior of the discharge filaments is explained based on the thermal interference of the discharge channels with the gas flow inside the capillary.

Tetrakis(trimethylsilyloxy)silane for nanostructured SiO2-like films deposited by PECVD at atmospheric pressure

“…The accuracy of the TTMS flow rates given in Table 1 is estimated as 10%. The RF power (27.12 MHz, DTG2710, Dressler) supplied to the plasma was 6 or 15 W. This, along with the given flow ensures a source operation in a distinctive discharge mode with four azimuthally rotating discharge filaments dubbed Locked Mode 4 (LM4) and described in detail in [23]. Here, the time needed to deposit a film is longer: 15 min for one experiment.…”

Laser schlieren deflectometry for temperature analysis of filamentary non-thermal atmospheric pressure plasma

“…The systematic overview of distinguished regimes has been published in Ref. 25. The filamentary structure of the plasma jet represents a common attribute of this kind of discharges.…”

“…25 The discharge regime of the plasma source is suitable for the task because of a symmetric patterning and regular steady dynamics of the filaments. Plasma parameters and conditions of this jet have been already characterized in a recently published study, 7 which presents a comparative base for the results of laser schlieren deflectometry (LSD) analysis.…”

Modulation-Induced Filament Tearing in Microwave Atmospheric Plasma Jet

“…1(a) and (c) shows that at certain instants the discharge is still filamentary. The filaments tend to wind around the inner wall of the capillary, which is typical for locked modes described in [2] and [3]. Vice versa, Fig.…”

“…This problem can be overcome by adding molecular admixture, which promotes diffusive, non-contracted character of the plasma. Recently [2], [3], it was found that filamentary nature, typical for the argon jet, can be easily affected by small variations in experimental conditions, namely power and gas flow. In this way, the plasma inhomogeneity can be partly compensated by an optimization of temporal delocalization of the filament(s).…”