Local deposition of SiO_xplasma polymer films by a miniaturized atmospheric pressure plasma jet (APPJ)

Abstract

An atmospheric plasma jet (APPJ, 27.17 MHz, Ar with 1% HMDSO) has been studied for the deposition of thin silicon-organic films. Jet geometries are attractive for local surface treatment or for conformal covering of 3D forms, e.g. inner walls of wells, trenches or cavities, because they are not confined by electrodes and their dimensions can be varied from several centimetres down to the sub-millimetre region. Deposition experiments have been performed on flat polymer and glass samples with a deposition rate of 0.25-23 nm s −1 . The knowledge of the static deposition profile of the plasma source (footprint) is essential to allow for a controlled deposition with the source moving relative to the substrate. By adjusting the plasma parameters (RF power and gas flow) to the geometry (i.e. electrode configuration, tube diameter, relative tube position, substrate distance) the footprint can be shaped from a ring form reflecting the tube dimension to a parabolic profile. Next to the conventional stochastic mode of operation we observe a characteristic locked mode-reported here for the first time for an RF-APPJ which can improve the film deposition process distinctively. The experimental results of the local film distribution agree well with an analytical model of the deposition kinetics. The film properties have been evaluated (profilometry, XPS, FT-IR spectroscopy and SEM) for different deposition conditions and substrate distance. The FT-IR spectra demonstrate dominating SiO absorption bands, thus providing an indication for the prevailing (inorganic) SiO x character of the films. HMDSO molecules disintegrate to a sufficient degree as proved by the absence of CH 2 absorption in the spectra. XPS measurements confirm the local dependence with a slightly increased organic character a few millimetres away from the maximum in the deposition profile. The substrate distance and the source direction both seem relevant and require consideration during coating of 3D objects.

Hydrophobic coatings deposited with an atmospheric pressure microplasma jet

“…The jet has to be driven with higher working gas flows compared to the former work [7] , and moderate to high powers to achieve these operational conditions. The discharge then develops three spatially relatively immobile filaments, which are in contact with the substrate and give the impression of constricted, high current 'hot' filaments with a high plasma density.…”

Time resolved optical emission spectroscopy in power modulated atmospheric pressure plasma jet

“…), plasma enhanced chemical vapour deposition (PECVD) of thin films, plasma decontamination of toxic compounds, and recently in biomedical application and plasma medicine [1][2][3][4][5][6]. The dielectric barrier discharges (DBD) [1,2] and atmospheric pressure plasma jets (APPJ) [7] belong to the most successful designs.…”

“…Moreover, the flow regime of plasma jet can enhance the delivery of active species from the active plasma zone to the treated sample. In comparison to the other atmospheric pressure plasma sources the treated surface could be then placed farther [4,8].…”

Chemical Composition of SiOx Films Deposited by an Atmospheric Pressure Plasma Jet (APPJ)

“…[4,5] The films are deposited using the recently observed homogenized plasma mode (locked mode) which is characterized by regularly ordered and moving discharge filaments. [6] It could be shown that this discharge mode in conjunction with a symmetric mixing of the vaporized precursor with the surrounding cylindrically rotating plasma at the outlet of the capillary leads to a significantly enhanced homogeneity of the profile and chemical composition of the deposited films as compared to a plasma jet with irregular discharge filaments. [6] SiO x films with exceptionally low carbon content and a high degree of cross-linkage could be deposited using OMCTS [octamethylcyclotetrasiloxane, Si 4 8 ].…”

“…[6] It could be shown that this discharge mode in conjunction with a symmetric mixing of the vaporized precursor with the surrounding cylindrically rotating plasma at the outlet of the capillary leads to a significantly enhanced homogeneity of the profile and chemical composition of the deposited films as compared to a plasma jet with irregular discharge filaments. [6] SiO x films with exceptionally low carbon content and a high degree of cross-linkage could be deposited using OMCTS [octamethylcyclotetrasiloxane, Si 4 8 ]. An experimental study on the influence of the O 2 versus OMCTS concentration on the chemical composition of the films and their radial gradients over the static deposition profile is carried out by means of XPS and ATR-FTIR.…”