SiOxCyHz Films Research Articles

Transparent SiOxCyHz Barrier Film Prepared by PECVD with Upper and Lower Pair Electrode Rolls Structure

Flexible and transparent barrier film is demanded in the fields of organic solar thin-film cells, flexible organic light-emitting diodes, electronic paper and vacuum insulation boards. To prepare films with high water resistance, flexible SiOxCyHz films were prepared on PET using HMDSO as monomer and Oxygen (O2) as reaction gas. SiOxCyHz films were prepared by plasma enhanced chemical vapor deposition (PECVD) with upper and lower pair electrode rolls structure, with the width of electrode rolls up to 600 mm. The influences of oxygen content, film thickness, oxygen/monomer ratio, reaction vacuum degree on water vapor transmission rate (WVTR) were studied. This coating method of oxide high barrier film has great application potential in the development of barrier film industry.

Effect of Plasma Oxidation Treatment on Production of a SiOx/SiOxCyHz Bilayer to Protect Carbon Steel Against Corrosion

Because of its excellent properties, carbon steel is a material widely used in several sectors. However, it is easily corroded when exposed to the environment. Seeking to remedy this problem, the possibility of coating carbon steel with SiOx/SiOxCyHz films generated by deposition and oxidation in low-pressure plasmas was investigated. Specifically, the effects of excitation power of the oxidation plasma on layer thickness, chemical structure, elemental composition, and barrier properties of the obtained coatings were investigated. The coating of the steel with the SiOxCyHz film, generated by plasma in an atmosphere of hexamethyldisiloxane (HMDSO), increased the total resistance to the passage of electric current, measured by electrochemical impedance spectroscopy. However, under the condition of moderate power oxidation (50 W), the results point to the creation of a bilayer system with high resistance to electrochemical attack compared to the SiOxCyHz film, even though its thickness is less than this.

Deposition of polysiloxane coatings by runaway electrons preionized diffuse discharge in nitrogen flow

A deposition of polysiloxane coating on titanium substrate by means of atmospheric pressure plasma enhanced chemical vapor deposition (PECVD) in a runaway electron preionized diffuse discharge (REP DD) has been investigated. The coating was produced from vapor of hexomethyldisiloxane (HMDSO) diluted in nitrogen at a flow rate of 1 nl/min. After deposition, the mechanical properties of the coatings have been measured by means of a nanoidentation. The maximum nanohardness of the coating with 3 μm thickness was 4.7 GPa. Energy dispersive analysis has shown that the coatings contain a significant content of carbon and titanium (about 52 at. %, 32 at. %, respectively) and a low content of silicon (about 16 at. %). In the FTIR spectrum, high intensity bands corresponding to stretching vibrations of the Si-O-Si, the Si(CH3)x and CH3 groups are observed, that indicates the organic and inorganic coating structure. Carbon free coating can be produced by REP DD plasma treatment of the deposited SiOxCyHz film, when REP DD operated only in nitrogen.

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

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 75W, the deposition time and total gas pressure were kept constant at 1800s and 8.0Pa, 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 SiO backbones surrounded by methyl groups, very similar to conventional polydimethylsiloxane. Increases in the proportions of SiO 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.

100 nm Thin‐Film Solid‐Composite Electrolyte for Lithium‐Ion Batteries

A thin‐film composite electrolyte (CE) with thickness of only 100 nm is fabricated for the first time. The conductivity of the solid electrolyte is 2 × 10−7 S cm−1 which corresponds to a cell resistance of only 50 Ω cm2 at this thickness. The electrolyte is composed of a nanoporous thin film, a lithium salt, and a polymer, and is fabricated by a two‐step approach. First, a porous SiOxCyHz film is deposited on the electrode substrate, then the porous structure is filled with a polyethylene glycol (PEG)‐LiX mixture by spin‐coating. The filling ratio of the mesoporous SiOxCyHz is as high as 90% with less than 1% remaining porosity, as determined from ellipsometric porosimetry. The effect of the anion, X−, of the LiX salt as well as the molecular weight of the PEG on the Li+ ion conductivity of the CE is investigated. The CE with smaller anion and with lower molecular weight PEG yields the highest conductivity. A functional Li/CE/TiO2 battery is built for demonstration purposes.

Wettability and surface microstructure of polyamide 6 coated with SiOXCYHZ films

Polyamide, PA, is a thermoplastic very used in practical applications once it associates a series of convenient properties. However, its affinity towards water promotes swelling and thus dimensional changes, a drawback for most of the applications. There exist alternative polymers but the fully bulk replacement is hindered by costs. In this sense, the modification of polymer surfaces using a versatile, simple and low cost methodology emerges as an important tool. In this work, low pressure plasmas were employed to adjust the surface properties of the commercial polyamide 6 aiming to decrease its affinity to water. Organosilicon films were deposited from hexamethyldisiloxane, HMDSO, oxygen and argon plasma mixtures. The plasma reactor was pumped down to 3.0Pa and HMDSO, oxygen and argon were admitted to the reactor establishing the pressure of 24Pa. In each one of the four deposition cycles, the HMDSO proportion was fixed at 70% while those of oxygen (0 to 30%) and argon (30 to 0%) were varied in opposite ways. The plasma was ignited by the application of radiofrequency power (13.56MHz, 150W) to the lowermost sample holder, earthening the top electrode. Deposition was conducted for 1800s. It was specifically investigated if the receptivity of the organosilicon film to water can be further reduced by adjusting its topography. Infrared spectroscopy was used to determine the molecular structure of the samples while water wettability was measured by the contact angle approach. Surface microstructure was inspected by scanning electron microscopy and atomic force microscopy. Elemental composition was derived from energy dispersive spectroscopy. Films are in general organosilicon with methyl functionals connected to the SiOSi backbone as lateral groups and/or chain termination in a more crosslinked way than the conventional silicone. A granular structure composed by agglomerates of different diameters was generated. Roughness is affected by the proportion of the dilution gases since it influences the deposition kinetics and then the rate of polymerization in the plasma phase. Independently of the oxygen and argon proportions used in the plasma polymerization process, the bare hydrophilic PA was converted into hydrophobic upon film deposition.

The effect of surface reactions of O, O3 and N on film properties during the growth of silica-like films

The effect of surface reactions of O, O3 and N radicals during the growth of silica-like (SiOxCyHz) films on film properties is investigated. A SiOxCyHz film is deposited from a He/Hexamethyldisiloxan (HMDSO) cold atmospheric plasma on a rotating substrate. The surface of this film is, during the growth, treated on the opposite site of the substrate by a second cold atmospheric plasma with helium and an addition of O2 or N2. A reactor with four separated cells and gas curtains between them is used to avoid cross-contamination of the ambient atmosphere in each cell. The changes in film composition after the deposition with and without a treatment by O, O3 and N are investigated by Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy. Additionally, the effect of each species on the deposition rate is also presented and discussed.

Assessment of non-uniform thin films using spectroscopic ellipsometry and imaging spectroscopic reflectometry

Standard variable-angle spectroscopic ellipsometry, mapping spectroscopic ellipsometry with microspot and imaging spectroscopic reflectometry are applied to optical characterisation of a thin SiOxCyHz film considerably non-uniform in thickness and which is also suspected of non-uniformity also in the optical constants. It is shown that using the combination of these three optical methods, enables us to determine the spectral dependencies of the optical constants of the film together with parameters characterising the shape of thickness non-uniformity and fine map of local thickness. The mapping spectroscopic ellipsometry with microspot enables deciding whether the film is non-uniform in optical constants. For the thin film studied it is found that the non-uniformity in optical constants is under experimental accuracy. The consistency of results obtained using individual techniques is checked and the advantages and disadvantages of the techniques are discussed.

Plasma-Deposited SiOxCyHz Barrier Coatings for Organic Device Encapsulation

A plasma-deposited SiOxCyHz barrier coating was investigated for the encapsulation of an organic photovoltaic (OPV). A closed drift linear plasma source, which is a modified extended layer linear ion source, was used to deposit SiOxCyHz films without any plasma damage due to plasma heating and ion bombardment on the organic devices. The deposition precursor was a gas mixture of hexamethyldisiloxane (HMDSO) and oxygen. The effect of the HMDSO/(HMDSO+O2) ratio over the range from 3.7 to 14.2% on the silicon content in Si(–O)x bonding was studied. HMDSO reacted effectively with oxygen radicals to form pure SiO2 bonds at the ratio of 3.7%. However, additional HMDSO injection led to insufficient HMDSO oxidation resulting in SiOxCyHz film deposition. In this work, a SiO2 single layer deposited at the ratio of 3.7% was adapted for the encapsulation of OPV. The encapsulated OPV showed an original power conversion efficiency (PCE) of ∼2% without any degradation.

Morphological Description of Ultra‐Smooth Organo‐Silicone Layers Synthesized Using Atmospheric Pressure Dielectric Barrier Discharge Assisted PECVD

AbstractThe SiOxCyHz layers synthesized by means of the atmospheric pressure glow‐like DBD assisted PECVD technology show remarkable planarizing film properties, observed for the first time. The films were deposited in a roll‐to‐roll mode on large area polymeric webs using HMDSO and air as the precursor and oxidiser. FTIR analysis show the carbon content in the SiOx films is strongly correlated with the precursor flow rate resulting in SiO2‐like layers with negligible carbon content at lower flow values (0.4 g/h), while at higher flow rates carbon rich SiOxCyHz films were obtained. Detailed AFM surface profile analysis show that the SiOxCyHz films smoothen out the global and local surface structures of the polymer comprising a reduction in rms surface roughness (0.99 ± 0.11 nm) and increase of roughness exponent (α = 0.97 ± 0.02) compared to that of PEN polymer. These ultra‐smooth organic layers together with the smooth inorganic SiOx layers (1.75 ± 0.12 nm), exhibiting roughness comparable to the polymer (1.50 ± 0.07 nm) at lower precursor input, provide an efficient route to fabricate multilayer hybrid structures in a single chamber synthesis. magnified image

Complex analysis of SiOxCyHz films deposited by an atmospheric pressure dielectric barrier discharge

SiOx films are deposited with an atmospheric pressure dielectric barrier discharge (apDBD) using Ar, O2 and different precursor gases (HMDSO and Silane). An experimental study on the influence of the discharge operation parameters on the chemical composition of the deposited films and the vertical structure over the film thickness is carried out by means of SEM, EDX, and ATR–FTIR. Particularly the IR absorption of hydroxyl groups (OH) incorporated in the films is considered in dependence of the deposition conditions. OH can be regarded as an indicator for the barrier properties of the coating or its capability to transport metal ions through the film. The latter process leads to applications in antimicrobial coatings that gradually, over time release e.g. copper or silver ions under wet conditions. The potential of organosilicon films produced in such an atmospheric pressure PECVD with regard to this application is demonstrated for the first time.

Deposition of carbon-free silicon dioxide from pure hexamethyldisiloxane using an atmospheric microplasma jet

Carbon-free silicon dioxide has been deposited at room temperature by injection of pure hexamethyldisiloxane (HMDSO) into an atmospheric pressure microplasma jet from argon. At low HMDSO flow rates [<0.1SCCM (SCCM denotes cubic centimeter per minute at STP)], the SiOxHz films contain no carbon and exhibit an oxygen to silicon ratio close to 2 according to x-ray photoelectron spectroscopy. At high HMDSO flow rates (>0.1SCCM), SiOxCyHz films with a carbon content of up to 21% are obtained. The transition between organic to inorganic film is confirmed by Fourier transformed infrared spectroscopy. The deposition of inorganic films without oxygen admixture is explained by an ion-induced polymerization scheme of HMDSO.

Investigation of Gas Phase Species and Deposition of SiO2 Films from HMDSO/O2 Plasmas

AbstractSummary: SiOxCyHz films are deposited by radio frequency plasma enhanced chemical vapor deposition (PECVD) using a mixture of HMDSO and oxygen as source gases. The gas phase species produced in HMDSO and HMDSO/O2 plasmas are investigated by optical emission spectroscopy (OES) and mass spectrometry (MS). These data reveal that oxygen dilution causes strong dissociation of the HMDSO monomer. The film composition was investigated with X‐ray photoelectron spectroscopy (XPS) and Fourier‐transform infrared (FT‐IR) spectroscopy. Low O2 dilution (≤50%) results in the deposition of polymer‐like SiOxCyHz films while higher O2 dilution (≥80%) results in the deposition of inorganic SiO2‐like films. Surface energy measurements show that the SiO2 films have higher surface energy than the polymer‐like SiOxCyHz films. Deposition rates are measured with variable angle spectroscopic ellipsometry and are strongly dependent on the percentage of O2 dilution in the feed mixture.Si 2p high‐resolution XPS spectra of films deposited in 50 W HMDSO/O2 plasmas with different gas ratios in the feed.magnified imageSi 2p high‐resolution XPS spectra of films deposited in 50 W HMDSO/O2 plasmas with different gas ratios in the feed.

PECVD of biocompatible coatings on 316L stainless steel

This study details the variation of the SiOxCyHz film properties deposited on 316L stainless steel in a 13.56 MHz RF Plasma Enhanced Chemical Vapor Deposition (PECVD) reactor. The films were characterized for their hardness, hydrocarbon content and wettability. The film properties are found to be dependent on the oxygen/HMDSO flow ratio and RF power. The hardness increases with increased O2/HMDSO flow and with RF power. Films deposited on a powered electrode show a linear dependency of hardness with RF power. The hardness correlates with the hydrocarbon and silica content of the films as measured by FTIR spectroscopy. The water contact angle was found to decrease with an increase in O2/HMDSO ratio and RF power. The high hydrophilicity observed immediately after deposition for high O2/HMDSO ratio was temporary and the contact angle increased with time and saturated. Preliminary biocompatibility studies were carried out using Rat Aortic Smooth Muscle (RASM) cells. The results of cell proliferation, viability and toxicity are presented.

Structural changes of plasma deposited SiOxCyHz thin films attained by thermal annealing

The objective of the present work was to investigate the influence of thermal annealing on the optical and mechanical properties as well as on the chemical structure of plasma deposited SiOxCyHz films. The films were prepared by PECVD from HMDSO/oxygen mixtures under a wide range of deposition conditions. Their optical and mechanical properties were studied by spectroscopic ellipsometry and depth sensing indentation technique, respectively. The atomic composition was determined by RBS and ERDA measurements. FTIR analysis was used to find the densities of particular chemical bonds in the films. The annealed films exhibited changes of the refractive index and extinction coefficient. The refractive index always decreased with increasing annealing temperature. The observed increase in hardness and elastic modulus after annealing was probably correlated with dehydration of the films and an increase of Si-O-Si bonds with increasing annealing temperature.

Silicon dioxide deposition in a microwave plasma reactor

SiOxCyHz films were deposited using hexamethyldisiloxane (HMDSO) in a 2.45 GHz microwave plasma reactor. The plasma was characterised by optical emission spectroscopy as a function of the HMDSO-to-oxygen ratio. The emission of species resulting from the dissociation and recombination of the monomer was identified. The film structure was investigated by means of FTIR spectroscopy and ellipsometry was used to determine the thickness and refractive index of the layer. The infrared spectrum and the deposition rate are strongly dependent on the HMDSO-to-O2 ratio, whereas the refractive index is quite constant and lower than expected.