Effect of the plasma excitation power on the properties of SiOxCyHz films deposited on AISI 304 steel

Abstract

Films were produced on stainless-steel substrates by radiofrequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) of mixtures containing 70% hexamethyldisiloxane, 20% oxygen and 10% argon. While the plasma excitation power was varied from 15 to 75 W, the deposition time and total gas pressure were kept constant at 1800 s and 8.0 Pa, respectively. The influences of the plasma power on the plasma kinetics and the ion bombardment of the growing film are discussed. Film composition and chemical structure were determined using X-ray photoelectron-and infrared reflectance-absorbance spectroscopy, respectively. Profilometry was used to measure the thicknesses of the resulting layers. The root mean square roughness was evaluated from surface topographic profiles acquired by atomic force microscopy. Scanning electron microscopy and energy dispersive spectroscopy were employed to evaluate the morphology and elemental composition of the coatings. Electrochemical impedance spectroscopy and potentiodynamic polarization tests were used to derive the corrosion resistance of the samples to a saline solution. Substantial changes in the material structure and progressive increases in film thickness were observed with increasing applied power. The resulting material was an organosilicon layer composed of Si\ \O backbones surrounded by methyl groups, very similar to conventional polydimethylsiloxane. Increases in the proportions of Si\ \O and methylsilyl groups in the structure were observed at greater plasma excitation powers, indicating densification of the structure owing to greater ion bombardment. The surface morphology and roughness were also dependent on the treatment power. Independently of the deposition conditions, application of the film increased the corrosion resistance of the stainless steel. A 10,000-fold elevation in the total system resistance under electrochemical testing was achieved for the film prepared with the greatest ion bombardment intensity. Film thickness was observed to be a key parameter but the coating structure had a major effect on this result.

Surface characteristics and optical properties of plasma deposited films on indirect aesthetic restorative dental materials

“…For the coated groups, XPS analyses showed chemical differences between both plasma-enhanced chemical vapor deposition-deposited coatings, in which PAr results displayed a high carbon (C) content (approaching 50%), followed by silicon (Si) (~30%) and (~25%) of oxygen (O). This finding is also in accordance with other reports, which present similar XPS results of HMDSO/Ar [70] and HMDS/O 2 /Ar dilutions [71] and match the composition of conventional polydimethylsiloxane [72,73].…”

Thin Film Deposition by Atmospheric Pressure Dielectric Barrier Discharges Containing Eugenol: Discharge and Coating Characterizations

“…It should be also observed that the substrate temperature influences the adsorption of non-excited and fragmented molecules or slightly fragmented precursors during the film growing process. Such rising and decaying of the film thickness with the applied voltage are in good agreement with the absorption intensity of the functional groups shown by the FTIR spectrum [ 36 , 54 ].…”

“…However, over a certain intensity, two competing factors occur in the polymerization process, the increase in the substrate temperature and the plasma ablation, which leads to the reduction of the film thickness. The films at higher field intensity are thinner and denser with a high degree of cross-linkage [ 36 , 54 ]. It should be also observed that the substrate temperature influences the adsorption of non-excited and fragmented molecules or slightly fragmented precursors during the film growing process.…”

Role of the Plasma Activation Degree on Densification of Organosilicon Films

“…Thin films produced from organosilicons are normally characterized by high electrical resistance and optical transparency, in the visible region of the electromagnetic spectrum, enabling them for applications in microelectronics and integrated optics [1,2]. Furthermore, the combination of transparency, flexibility and moderate permeability to gas/vapor of such films favors a number of applications including encapsulation of organic electronic devices [3,4], improvement of packages performance (food, electrical devices, drugs) [5], reduction of water absorption and degradation [6,7], and protection of metal surfaces against corrosion [8,9]. The rotation of methyl groups may result in low surface tension materials, which are suitable for coating of fabrics [10,11], dental devices [12] and biocompatible [13] and anti-bio fouling surfaces [1,14].…”