SiOx Coatings Research Articles

Roll-to-Roll SiOx Synthesis on Polyethylene Terephthalate Film by Atmospheric-Pressure Plasma-Assisted Chemical Vapor Deposition

Silicon oxide (SiOx) coatings are attracting significant attention and are widely used in industrial applications. They can be prepared by plasma-assisted chemical vapor deposition (PACVD). PACVD at atmospheric pressure (AP-PACVD) is often employed to synthesize SiOx coatings, but it has generally not been scaled up to an industrially viable level. In the present work, a SiOx coating was continuously deposited onto a polyethylene terephthalate film using industrial-scale roll-to-roll type AP-PACVD. 1,1,3,3-Tetramethyldisiloxane (TMDSO) and tetraethoxysilane (TEOS) were selected as precursors. The elemental compositions and chemical structures of the SiOx coatings were characterized, and oxygen and water-vapor transmission rates were measured. The SiOx coating using TEOS exhibited better barrier properties than that using TMDSO, corresponding to the high oxygen content, high SiO2 content, and high siloxane network content in the SiOx coating.

Enhanced Corrosion Protection of Printed Circuit Board Electronics using Cold Atmospheric Plasma-Assisted SiOx Coatings.

The miniaturization and widespread deployment of electronic devices across diverse environments have heightened their vulnerability to corrosion, particularly affecting copper traces within printed circuit boards (PCBs). Conventional protective methods, such as conformal coatings, face challenges including the necessity for a critical thickness to ensure effective barrier properties and the requirement for multiple steps of drying and curing to eliminate solvent entrapment within polymer coatings. This study investigates cold atmospheric plasma (CAP) as an innovative technique for directly depositing ultrathin silicon oxide (SiOx) coatings onto copper surfaces to enhance corrosion protection in PCBs. A systematic investigation was undertaken to examine how the scanning speed of the CAP deposition head impacts the film quality and corrosion resistance. The research aims to determine the optimal scanning speed of the CAP deposition head that achieves complete surface coverage while promoting effective cross-linking and minimizing unreacted precursor entrapment, resulting in superior electrical barrier and mechanical properties. The CAP coating process demonstrated the capability of depositing SiOx onto copper surfaces at various thicknesses ranging from 70 to 1110 nm through a single deposition process by simply adjusting the scanning speed of the plasma head (5-75 mm/s). Evaluation of material corrosion barrier characteristics revealed that scanning speeds of 45 mm/s of the plasma deposition head provided an effective coating thickness of 140 nm, exhibiting superior corrosion resistance (30-fold) compared to that of uncoated copper. As a proof of concept, the efficacy of CAP-deposited SiOx coatings was demonstrated by protecting an LED circuit in saltwater and by coating printed circuits for potential agricultural sensor applications. These CAP-deposited coatings offer performance comparable to or superior to traditional conformal polymeric coatings. This research presents CAP-deposited SiOx coatings as a promising approach for effective and scalable corrosion protection in miniaturized electronics.

In-situ formed silicon oxycarbide nanowires into porous SiC(rGO) PDCs enable balanced enhancement of robustness and thermal management

With ongoing development of rocket combustion and hypersonic vehicles, urgent needs are created on thermal structures, protection and thermal insulating materials, particularly balanced enhancement of mechanical and antioxidant properties. Herein, we propose a design strategy to construct continuous in-situ formed SiOC nanowires (SiOCnws)-toughened self-healing SiOx coatings into porous SiC(rGO) PDCs. The key production technique is re-pyrolyzing coassembled flexible precursors/SiC(rGO)p/graphite blends, followed by decarbonization and silica sol impregnation-sintering (SIS) process. Well-distributed hierarchical pores are built to heighten thermal insulation properties by the integrated decarburization of graphite coupled with free carbon. High-yield SiOCnws, with high surface activity, are first cultivated via graphite-assisted vapor-solid (VS) mechanism without transition metal catalysts. They interconnect to form intricate 3D meshwork by graphite-assisted melt-spinning and have good compatibility with ceramic matrix and SiOx coatings by carbothermal reaction. Hierarchically porous SiOCnws/SiC(rGO)40% PDCs after once SIS exhibit favorable thermal conductivity of 0.27 W‧m−1‧K−1 and exceptional high robustness (compressive strength: 39.02 MPa, hardness: 10.27 GPa). Such composites display low reflection loss of −48.14 dB at 11.22 GHz and even good structural stability at about 1300 °C as burned by a butane blowtorch for 3600 s, shedding light on competitive components for uses in thermal protection fields.

Development of a-C:H coatings doped with trimethylsilyl acetate prepared using plasma enhanced chemical vapor deposition

The main aim of the present study was to develop hard a-C:H:SiOx coatings prepared from the unique gaseous mixture of trimethylsilyl acetate (TMSAc) with methane using plasma of RF capacitively coupled glow discharge. Studied coatings were prepared using different methane ratios in TMSAc/CH4 gaseous mixtures ranging from 7.1 % to 85.7 %. Simultaneously, the influence of the power supplied to the discharge (25–100 W) on the properties of resulting coatings was investigated. The presented research work discusses in detail the evolution of chemical composition, mechanical characteristics, and optical properties of resulting coatings depending on variable CH4 ratio and discharge power. Within this study, various materials with the smooth surface structure were achieved. Applying low CH4 ratio and 25 W power led to the formation of soft SiOxCyHz coatings with high content of Si–O and –CH3 groups exhibiting hardness of approx. 0.95 GPa. Gradually increasing the CH4 ratio and discharge power up to the specified limit values (85 % and 100 W, respectively) induced structural changes, resulting in a-C:H:SiOx coatings with a remarkable hardness of 11 GPa and excellent fracture resistance. These attributes are of utmost importance in numerous industrial applications, including anticorrosive coatings, low-friction wear-resistant coatings to prolong the lifetime of car engines, biocompatible coatings, components for plastic molds, as well as parts for optical disc molds and textile machinery.

Deposition of a‐C:H:SiOx Coatings Using Low‐Frequency Inductively Coupled Plasma

This article investigates the plasma‐enhanced chemical vapor deposition of a‐C:H:SiOx coatings in a non‐self‐sustaining arc discharge plasma with a hot cathode in combination with a low‐frequency (200 kHz) inductively coupled plasma. It is shown that increasing the inductor power from 0 to 600 W leads to a twofold increase in the ion current density on the substrate. An increase in ion bombardment intensity results in a 1.3‐fold reduction in the coating's growth rate due to the resputtering phenomenon, a 1.5‐fold reduction in surface roughness, and an improvement in the mechanical properties of the coatings. The hardness of the coating is increased by 9–11%, the plasticity index by 10–17%, and the resistance to plastic deformation by 32–49%.

Stretch‐tolerant PECVD gas barrier coatings for sustainable flexible packaging

AbstractThis study employs X‐ray photoelectron spectroscopy (XPS), thickness measurements, permeation analysis and laser scanning microscopy to analyse the stretch tolerance in dependence of the chemical composition and deposition rates of plasma‐enhanced chemical vapour deposition coatings. SiOx and SiOCH coatings are deposited on polyethylene terephthalate film using a full factorial study design of three parameters (monomer/oxygen mass flow and pulse duration). They exhibit distinct differences, with the monomer mass flow emerging as a critical factor influencing deposition rates and stretch tolerance. SiOCH coatings demonstrate faster growth rates due to higher monomer flow. SiOx coatings exhibit superior barrier performance. Stretch tolerance does not solely correlate with atomic composition, since a SiOx coating with higher‐than‐predicted stretch tolerance was observed.

Improved wear and corrosion resistance of alumina alloy by MAO and PECVD

Aluminum alloys, which are vital in various industries, are susceptible to corrosion and wear. Although the micro-arc oxidation (MAO) method addresses these issues, it introduces microporosity, which undermines the integrity of the alloy. In this study, MAO coatings are enriched via plasma-enhanced chemical vapor deposition (PECVD) using hexamethyldisilane, specifically SiCOx and SiOx. The assessment of the mechanical, tribological, and corrosion-resistant characteristics of these composite coatings reveals substantial enhancements in the aluminum alloy properties post-PECVD treatment. Surface morphology observations highlight the reduced pore size and area of the PECVD-coated surfaces, particularly in SiCOx coatings, which are known for their superior gap-filling properties. Scratch tests demonstrate superior adhesion of SiCOx coatings, showed a higher scratch resistance of approximately 17.8 N compared to 15.9 N for SiOx coatings. The wear rate of the SiCOx coating significantly decreased compared to the MAO coating owing to higher hardness, dropping from 3.57 × 10−5 mm3/N·m to 2.04 × 10−5 mm3/N·m. SiCOx-coated surfaces show higher corrosion potential (−0.0078 V) than MAO-only coating (−0.0212 V), indicating enhanced corrosion resistance. These innovative coatings provide an advanced surface treatment strategy and are suitable for a wide range of industrial applications owing to their enhanced surface attributes.

Near-Plasma Chemical Surface Engineering.

As a new trend in plasma surface engineering, plasma conditions that allow more-defined chemical reactions at the surface are being increasingly investigated. This is achieved by avoiding high energy deposition via ion bombardment during direct plasma exposure (DPE) causing destruction, densification, and a broad variety of chemical reactions. In this work, a novel approach is introduced by placing a polymer mesh with large open area close to the plasma-sheath boundary above the plasma-treated sample, thus enabling near-plasma chemistry (NPC). The mesh size effectively extracts ions, while reactive neutrals, electrons, and photons still reach the sample surface. The beneficial impact of this on the plasma activation of poly (tetrafluoroethylene) (PTFE) to enhance wettability and on the plasma polymerization of siloxanes, combined with the etching of residual hydrocarbons to obtain highly porous SiOx coatings at low temperatures, is discussed. Characterization of the treated samples indicates a predominant chemical modification yielding enhanced film structures and durability.

Structure, mechanical and tribological properties of Ti-doped and Cr-doped a-C:H:SiOx coatings

The work is devoted to the deposition of Ti- and Cr-doped a-C:H:SiOx coatings on WC-8Co substrates using plasma-assisted chemical vapor deposition and magnetron sputtering methods. The structure, surface morphology, mechanical and tribological properties of coatings are investigated depending on the Ti or Cr content. It is shown that only a small concentration of Ti or Cr in coatings improves their mechanical and tribological properties compared to undoped coatings. The addition of 0.8 at.% Ti to the a-C:H:SiOx coating reduces its wear rate by 3 times, and the addition of 3 at.% Cr to the a-C:H:SiOx coating reduces its friction coefficient by 30% and the wear rate by 10 times. According to VDI 3198 standard, the Ti- and Cr-doped a-C:H:SiOx coatings with a low concentration of metals have the adhesive strength quality HF1. At higher metal concentrations, the properties of the coatings deteriorate due to graphitization of the carbon structure.

Robust packaging of printed flexible electronics with functional SiOx coatings via cold atmospheric plasma assisted deposition

The ubiquity of printed flexible electronics (PFEs) spans diverse sectors, from healthcare to automotive, aerospace, agriculture, and consumer electronics, owing to their low cost, lightweight, flexibility, and conformability. However, addressing the critical challenge of ensuring robust packaging to enhance the durability and reliability of PFEs remains imperative. The limitation lies in the functionality of traditional polymer-based dielectric encapsulants, resulting in weak bonding between electrical components on the circuit and the encapsulant. As a consequence, when PFEs are exposed to harsh environmental conditions, water condensation occurs at the interface, leading to device failure. While hybrid multi-layer inorganic and organic encapsulation methods have demonstrated promise in providing robust packaging for electronic devices, the required deposition of inorganic coatings involves complex, time-consuming, and costly processes, rendering them unsuitable for scalable manufacturing of PFE devices. To address this challenge, a novel approach is investigated using cold atmospheric plasma (CAP) technology for the deposition of SiOx coatings as an intermediate layer between the printed circuit and the dielectric encapsulant coating. This effective intermediate layer promotes adhesion and enhances barrier properties of commonly used polymeric coatings in PFE devices. The CAP method enables selective deposition of high-quality and consistent SiOx thin films onto desired substrates under atmospheric conditions. Through a systematic study of CAP deposition conditions, the optimum thickness (∼820 nm) of the SiOx coating was determined, providing the required functionality to enhance barrier properties for corrosion protection of printed circuits while maintaining high mechanical flexibility. A remarkable 105-fold improvement in corrosion protection properties was observed through accelerated corrosion protection tests in saline water with the developed hybrid inorganic–organic coating process, compared to traditional encapsulation without the SiOx intermediate layer. As a proof-of-concept, the improved packaging of printed antennas, typically used in automobile rooftop shark fin applications, is showcased, highlighting the utility of the developed process in creating fully functional PFEs capable of reliable operation in harsh environmental conditions. This research represents a significant advancement towards scalable and cost-effective manufacturing of high-performance and reliable PFEs, introducing new possibilities for a broad range of applications.

Less Energetic Routes for the Production of SiOx Films from Tris(dimethylamino)silane by Plasma Enhanced Atomic Layer Deposition

SiOx films, frequently derived from amino silane precursors, have found several applications with high added value. Although frequently used, the deposition of coatings from Tris(dimethyl amino) silane (TDMAS) has been reported to demand considerable amounts of energy, mainly due to the difficulty of oxidizing such compounds. As is well known, Plasma-enhanced atomic layer deposition (PEALD) is able to improve the oxidation efficiency, even under low processing temperatures. Owing to this, PEALD can be considered a very promising technique for the deposition of SiOx coatings. In this work, the deposition of silicon oxide films using TDMAS at 150 °C has been investigated. The effect of the plasma oxidation time (6 to 18 s) and atmosphere composition (pure O2 or O2 + Ar) on the chemical structure, elemental composition, and chemical bonding state of the films has also been evaluated. Increasing the plasma oxidation time in pure O2 resulted in a larger proportion of retained C (Si-CH3), whereas N was preserved in the structure (Si-N). On the other hand, the formation of SiOx films from TDMAS is favored in shorter oxidation times and O2 + Ar plasmas.

Plasma Deposition to Improve Barrier Performance of Biodegradable and Recyclable Substrates Intended for Food Packaging

The extensive application of biodegradable polymers in the food packaging industries was partially limited due to poor barrier performances. In the present work, we investigated the improvement of oxygen barrier performances by means of the deposition of a few nanometres of SiOx coatings on Poly(butylene succinate) (PBS) films. The coated samples produced by the plasma-enhanced chemical vapor deposition technique were tested in terms of morphology and composition of the surface and barrier properties. Barrier performances studied as a function of SiOx thickness were greatly improved and a reduction of at least 99% was achieved for oxygen transmission rate. In order to reduce the formation of residual stress between PBS substrate and SiOx coatings, a proper buffer layer (silicon organic SiOxCyHz) was used.

Organosilica coating layer prevents aging of a polymer with intrinsic microporosity

AbstractThis study tracks the physical aging behavior of coated and uncoated ultra‐thin poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) films on silicon wafers based on the refractive index using ellipsometry. The measured refractive index directly correlates with the free volume and hence the physical aging progression. Plasma‐enhanced chemical vapor deposition (PECVD) creates coatings with different thicknesses and oxidation degrees onto PTMSP films. Compared to uncoated PTMSP films, the PECVD‐coated films show a reduction of the refractive index increase of more than two orders of magnitude for less than 10 nm thin SiOx coatings. In contrast, SiOCH films show only a minor impact. The results reveal the superior physical aging behavior of PECVD‐coated films compared to untreated PTMSP films.

Tribological Characteristics of a-C:H:Si and a-C:H:SiOx Coatings Tested in Simulated Body Fluid and Protein Environment.

This paper presents the tribological properties of silicon and oxygen incorporated diamond-like carbon coatings tested in simulated body fluid and bovine serum albumin environments. The tests were performed using a ball-on-disc tribometer with an AISI316L steel counterbody. The wear tracks and wear scars were analyzed using optical microscopy and a nanoindenter. The interaction between the coating and the working environment was analyzed by Fourier transform infrared spectroscopy, whereas changes in the chemical structure before and after the tribological tests were compared with the use of Raman spectroscopy. Our study showed that the tribological parameters are governed by the presence of oxygen rather than the changing concentration of silicon. Both of the spectroscopy results confirm this statement, indicating that coatings with low concentrations of silicon and oxygen appear to be better candidates for biological applications in terms of wear resistance.

Kinetics of plasma-assisted chemical vapor deposition combined with inductively excited RF discharge and properties of a-C:H:SiOx coatings

The paper studies the plasma-assisted chemical vapor deposition of a-C:H:SiOx coatings in plasma of non-self-sustained arc discharge with a hot cathode combined with inductively excited radio-frequency (RF) discharge. The a-C:H:SiOx coatings are produced by polyphenyl methylsiloxane (PPMS) dissociation in plasma with and without RF discharge. The optical emission spectroscopy is used to study the PPMS dissociation process. Raman spectroscopy provides the structural investigations of the obtained coatings, while the energy dispersive X-ray spectroscopy is used to analyze the chemical composition. It is shown that the mechanical and tribological properties of a-C:H:SiOx coatings depend on the RF discharge power and the bias voltage amplitude of the substrate. It is demonstrated that substrate bias voltage can be reduced during the coating deposition in combined discharge without significant degradation of its mechanical and tribological properties due to the better dissociation and ionization of PPMS vapor molecules in inductively excited RF discharge.

The Atomic Oxygen Erosion Resistance Effect and Mechanism of the Perhydropolysilazane-Derived SiOx Coating Used on Polymeric Materials in Space Environment.

In this work, the atomic oxygen (AO) erosion-resistance effect and mechanism of the Perhydropolysilazane (PHPS) coating were investigated from the perspective of element distribution in the depth direction. The results revealed that the coating demonstrated good adhesion and intrinsic AO erosion-resistance, which was attributed to the composition gradient formed in the coating. Moreover, the oxygen ratio of the SiOx on top layer of the coating could be elevated during AO exposure, strengthening the Ar ion etching durability of the coating. According to these results, an AO erosion-resistance mechanism model of the PHPS-derived SiOx coating was finally obtained.

Prediction of loss of barrier properties in cracked thin coatings on polymer substrates subjected to tensile strain

Thin brittle coatings on polymer films are a potentially useful material combination for food packaging applications. The brittle coatings inevitably risk cracking when the package is converted. This strain-induced cracking leads to a loss of the key barrier properties. In design of packaging materials, it would be useful to predict the loss of the oxygen transmission rate (OTR) as a function of the applied tensile strain, which are linked by the crack opening and crack spacing in the coating. Previous works have presented a model that predicts the effect of strain on the OTR in the presence of cracks in the coating. This work uses an improved numerical model based on finite element method (FEM) to predict the oxygen permeability more accurately, especially for thin coatings with high crack densities. The numerical predictions show reasonable correspondence with experimental results for SiOx coatings. These results as well as predictions for previously tested metal-oxide coated polymer films show a significant increase in OTR at crack onset, which suggests that efforts should be made to make the coatings more ductile with higher crack onset strains if the barrier performance should be maintained in converted packages. The quantitative link from deformation over the damage state to barrier properties indicate that mechanics could provide a tool to aid the design of improved food packages with retained barrier capacity.

Si3N4 Nanofibrous Aerogel with In Situ Growth of SiOx Coating and Nanowires for Oil/Water Separation and Thermal Insulation.

Nanofibrous aerogels constructed by ceramic fiber components (CNFAs) feature lightweight, compressibility, and high-temperature resistance, which are superior to brittle ceramic aerogels assembled from nanoparticles. Up to now, in order to obtain CNFAs with stable framework and multifunctionality such as hydrophobicity and gas absorption, it is necessary to perform binding and surface modification processes, respectively. However, the microstructure as well as properties of CNFAs are deteriorated by the direct addition of binders and modifiers. To tackle these problems, we introduced a unique low-temperature (100 °C) chemical vapor deposition method (LTCVD) to achieve the cross-linking and hydrophobization of Si3N4 CNFA in only one step. More importantly, during the LTCVD process, SiOx coatings and nanowire arrays were in situ formed via vapor-solid (VS) and vapor-liquid-solid (VLS) mechanisms on the surface and intersection of Si3N4 nanofibers, which cemented the aerogel framework, endowed it with hydrophobicity, and improved its oxidation resistance at high temperature. Compared to most of its counterparts, the Si3N4/SiOx CNFA exhibited better mechanical properties, higher capability of oil/water separation (33-76 g·g-1), lower thermal conductivity (0.0157 W/m·K-1), and superior structural stability in a wide temperature range of -196-1200 °C. This work not only presents an excellent Si3N4/SiOx CNFA for the first time but also provides fresh insights for the exquisite preparation strategy of CNFAs.

Wear and Corrosion Resistance of a-C:H:SiOx Coating on Medical 316L Stainless Steel

Wear and Corrosion Resistance of a-C:H:SiOx Coating on Medical 316L Stainless Steel

The study of platelet reaction on a-C:H:SiOx coatings obtained via plasma enhanced chemical vapor deposition with bipolar bias voltage

Aim. To study platelet adhesion to a-C:H:SiO x film on titanium in an in vitro experiment to evaluate its antithrombogenic potential. Materials and methods. Thin (less than 1 μm) a-C:H:SiO x films were deposited on VT-6 titanium plates with a size of 10 × 10 mm 2 and a thickness of 0.2 mm using a vacuum ion-plasma unit using pulsed bipolar bias. The surface roughness was evaluated according to GOST 2789-73 using an atomic force microscope. The test samples were cultured at 37 °C for 30 min in platelet-rich human blood plasma, prepared for scanning electron microscopy, after which the distribution density of blood plates adhering to the test coating was calculated. Results. With the same roughness index of the studied a-C:H:SiO x samples, the film decreased 116 times (in comparison with untreated titanium) the platelet count per 1 mm 2 of the surface. Conclusion . The deposition of a-C:H:SiO x thin film on the surface of VT-6 titanium alloy by PACVD method using pulsed bipolar bias significantly reduces the distribution density of platelets in comparison with an untreated metal surface. In vitro data suggest a significant antithrombogenic potential of this type of coating on the surface of devices in contact with blood.