GC‐MS Investigation of Hexamethyldisiloxane–Oxygen Fed Cold Plasmas: Low Pressure Versus Atmospheric Pressure Operation

Abstract

This study deals with the investigation by means of gas chromatography‐mass spectrometry (GC‐MS) of the exhaust gas of an rf low pressure (LP) glow discharge and of an atmospheric pressure (AP) FDBD fed with hexamethyldisiloxane (HMDSO), O2, and Ar. The influence of feed composition on monomer depletion and on the qualitative–quantitative distribution of stable by‐products formed by recombination of plasma intermediates is investigated. Without O2 addition to the feed almost comparable values of HMDSO depletion are observed both at low and AP. Oxygen addition does not influence the monomer depletion at LP while it induces a slight decrease of the depletion at AP. Whatever the working pressure, O2 controls the overall chemistry of the plasma, since it influences the concentration of by‐products (e.g., silanes, silanols, linear, and cyclic methylsiloxanes). At AP evidences of the importance of methyl abstraction from HMDSO molecule have been obtained, while at LP the prevalence of Si–O bond rupture, of fragmentation, and oligomerization reactions is observed. The comparison of results from the GC‐MS investigation of the exhaust gas with FT‐IR spectra of the deposited coatings allows to enhance hypotheses on the formation of silanols in the gas phase and in the deposit.

Wettability and surface microstructure of polyamide 6 coated with SiOXCYHZ films

“…The production of low molecular weight fragments, such as CH x groups, is expected to increase with the oxygen proportion in the plasma [23]. These species can be reactivated by the plasma and deposited on the surface, enhancing the concentration of polymerizing species and contributing with the preservation of organics in the structure [15,27]. Aside from oxidation reactions, oligomerization of species, considered as homogeneous reactions, can also take place inducing powder in the plasma phase.…”

“…The high reactivity and concentration of neutral and charged species formed upon the HMDSO breakage, induce multiple step reactions, resulting in large species of high molecular weight (macromolecules) which remains in the plasma until they sit on the surface by the action of gravitational or electrostatic forces [27]. Blanchard et al [15] proposed different routes for the HMDSO fragmentation during the deposition of organosilicon films.…”

Corrosion resistance of 2024 aluminum alloy coated with plasma deposited a-C:H:Si:O films

“…The deposition kinetics is based on the HMDSO fragmentation and multiple step reactions in the plasma phase, providing precursors for film formation 7 . When O 2 is added to the vapor of HMDSO (HMDSO/O 2 ), organic constituents are scavenged from the films, increasing the inorganic character (SiO 2 -like) 5,10 of the structure.…”

“…Organosilicon to oxide films can be deposited by PECVD from hexamethyldisiloxane, HMDSO 5,[7][8][9] . The deposition kinetics is based on the HMDSO fragmentation and multiple step reactions in the plasma phase, providing precursors for film formation 7 .…”

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.…”