Ar/HMDSO/O₂ Fed Atmospheric Pressure DBDs: Thin Film Deposition and GC‐MS Investigation of By‐Products

Abstract

The thin film deposition in DBDs fed with Ar/HMDSO/O2 mixtures was studied by comparing the FT‐IR spectra of the deposits with the GC‐MS analyses of the exhaust gas. Under the experimental conditions investigated, oxygen addition does not enhance the activation of the monomer while it highly influences the chemical composition and structure of the deposited coating as well as the quali‐quantitative distribution of by‐products in the exhaust. Without oxygen addition a coating with high monomer structure retention is obtained and the exhaust contains several by‐products such as silanes, silanols, and linear and cyclic siloxanes. The dimethylsiloxane unit seems to be the most important building block of oligomers. Oxygen addition to the feed is responsible for an intense reduction of the organic character of the coating as well as for a steep decrease, below the quantification limit, of the concentration of all by‐products except silanols. Some evidences induce to claim that the silanol groups contained in the deposits are formed through heterogeneous (plasma‐surface) reactions.

GC‐MS Investigation of Organosilicon and Fluorocarbon Fed Plasmas

“…GC-MS can improve the understanding of the plasma chemistry in PE-CVD processes, since it allows the evaluation of the precursor reactivity, the qualitative and eventually quantitative determination of stable byproducts formed by plasma activation [7][8][9][10][11]. The employment of this diagnostic technique strictly requires the optimization of a suitable exhaust sampling procedure, which generally utilizes a discrete sampling system, such as a sampling bag or a liquid nitrogen (LN2) cold trap.…”

“…The employment of this diagnostic technique strictly requires the optimization of a suitable exhaust sampling procedure, which generally utilizes a discrete sampling system, such as a sampling bag or a liquid nitrogen (LN2) cold trap. In the first case the sampled gas is simply taken with a gastight syringe from the bag and analyzed by GC-MS, while with the LN2 trap before the analysis the collected species are dissolved in a suitable solvent [7][8][9][10][11]. Of course the sampling bag is not convenient for species with low volatility, while the LN2 trap procedure does not work with high volatile compounds.…”

“…We recently focused our efforts on gaschromatography with mass spectrometric detection (GC-MS), a very powerful gas phase indirect diagnostic technique of both low pressure and atmospheric pressure cold plasmas [7][8][9]. GC-MS can improve the understanding of the plasma chemistry in PE-CVD processes, since it allows the evaluation of the precursor reactivity, the qualitative and eventually quantitative determination of stable byproducts formed by plasma activation [7][8][9][10][11].…”

Effect of methane on the conversion of HFC-134a in a dielectric barrier discharge non-equilibrium plasma reactor

“…Filamentary discharge is scattered while the diffuse discharge is uniform and the uniformity of the diffuse discharge results in higher level of activation of reactants compared to their activation in a scattered filamentary discharge [41]. Therefore, the transition of filamentary to homogeneous glow discharge in the present study enhances the activation of CF 3 CH 2 F and CH 4 in plasma and results in a higher level of conversion.…”

Infrared gas phase study on plasma-polymer interactions in high-current diffuse dielectric barrier discharge

“…11 Quantitative measurements of the reactive species on their ground or excited states were carried out by different spectroscopic methods such as optical emission spectroscopy (OES), laser induced fluorescence (LIF) measurement, mass spectroscopy (MS), and ultraviolet (UV) and infrared (IR) absorption spectroscopy. [12][13][14][15][16][17][18][19][20][21][22][23] Using an ex-situ Fourier-transform infrared (FTIR), Pipa et al studied the composition of stable molecules from an atmospheric-pressure plasma jet (APPJ) operating in an argon-air mixture. 22 The NO production shows a good agreement with other measurements by emission spectroscopy 24 while additional C-related molecules were attributed to plasma contact with the plastic holder of the APPJ.…”