Deposition of Polyacrylic Acid Films by Means of an Atmospheric Pressure Dielectric Barrier Discharge

The present work describes the plasma polymerisation of acrylic acid at atmospheric pressure. The influence of two operating parameters (monomer concentration and discharge power) on the properties of the deposited films is investigated. Results show that at a monomer concentration of 2.5 ppm and a discharge power of 9.5 W, the monomer is only slightly fragmented leading to a high amount of carboxylic acid groups on the deposited films. In contrast, when monomer concentration is decreased or discharge power increased, the incidence of monomer fragmentation processes is higher, leading to a lower amount of carboxylic acid groups on the films. This behaviour can be explained by a higher energy amount available per monomer molecule at low monomer concentrations and high discharge powers and a higher flux of positive ions attacking the surface at high discharge powers. Taking into account these results, it can be concluded that the deposition parameters should be carefully selected in order to preserve the stability of the monomer and thus obtain coatings with high carboxylic acid densities.     

Tuning the Surface Properties of Oxygen-Rich and Nitrogen-Rich Plasma Polymers: Functional Groups and Surface Charge

Controlling the concentration and nature of functional groups in plasma polymer films by adjusting the flow ratio of constituent precursor gases can be exploited to tune the surface charge of the resulting coating. Plasma polymer films containing various concentrations of nitrogen and oxygen functional groups were deposited in a low-pressure capacitively-coupled glow discharge reactor by plasma polymerization of binary gas mixtures of a hydrocarbon (ethylene or butadiene) and a heteroatom source gas (ammonia and/or carbon dioxide). Increasing the flow ratio of heteroatom to hydrocarbon gases increased the concentration of bonded nitrogen or oxygen, including that of primary amine or carboxylic groups as determined by X-ray photoelectron spectroscopy and chemical derivatization procedures. The zeta potential of samples was measured using an electro-kinetic analyser in a diluted sodium chloride solution. The deposition parameters controlled the composition of the coatings, allowing to tune the surface charge to either positive (ammonia based films)—or negatively (carbon dioxide base films) values at physiological pH.     

Polyethylene Glycol Grafting on Polypropylene Membranes for Anti-fouling Properties

Polyethylene glycol (PEG) chains with different lengths were covalently bonded to polypropylene membranes by means of RF plasma polymerisation of acrylic acid (pp-Aac) followed by mono-amino PEG attachment in liquid phase. Two reactor configurations were tested for the plasma deposition of ppAAc in order to obtain high retention of carboxylic groups in the deposited thin films. A best configuration was assessed evaluating the membrane surface modifications by means of water droplet adsorption time and contact angles measurements, attenuated total reflection (ATR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis. PEG chains were covalently bonded to the best plasma modified membranes and the resulting anti-fouling properties were evaluated.     

Polytetrafluoroethylene Sputtered PES Membranes for Membrane Distillation: Influence of RF Magnetron Sputtering Conditions

Thin films of fluorocarbon were deposited on polyethersulfone membranes via argon plasma sputtering of a poly(tetrafluoroethylene) (PTFE) target in an RF magnetron plasma reactor. The obtained deposited ultrathin coatings had nanoscale roughnesses and high degrees of fluorination. The intensity of fluorine atom in plasma environment during fluorocarbon deposition was investigated. Depending on the deposition conditions comprising working gas pressure, applied RF power, and distance between the target and the substrate, polymeric films with different chemical compositions and/or morphologies were obtained. The morphologies of the films were analyzed by means of SEM, XPS, and AFM. The results suggested that the sputtered film deposited at a higher pressure and longer target–substrate distance and moderate RF power had a surface composition and chemical structure closer to those of the PTFE film. The treated hydrophobic PES membranes with water contact angles as high as 115° were applied for the first time in an air gap membrane distillation setup for removal of benzene as a volatile organic compound from water. The results showed that the plasma-treated membranes have a comparable or superior performance to that of commercial PTFE used in membrane distillation with similar permeate flux and separation factor after 20 h long term performance.     

PE-CVD of Organic Thin Films with Controlled Surface Concentration of Carboxylic Groups

Organic thin films have been deposited onto various substrates by means of radiofrequency glow discharges fed with acrylic acid vapors. The effect of the experimental parameters on film composition has been investigated with X-ray Photoelectron and FT-IR spectroscopies; Optical Emission Spectroscopy has been carried out for plasma phase characterization. It is shown that the concentration of oxygen and carboxylic groups in the coating decreases with increasing power, while the concentration trend of CO species in the plasma increases. It is demonstrated that films deposited from acrylic acid, which can be used as functional layers for biomolecule immobilization, can be deposited with a controlled surface concentration of -COOH groups through a simple in situ monitoring of the deposition process.     

Preparation of Silicon Thin Films of Different Phase Composition from Monochlorosilane as a Precursor by RF Capacitive Plasma Discharge

Monochlorosilane/argon/hydrogen (SiH₃Cl-Ar-H₂) mixture of different ratios was investigated from the point of PECVD application. RF capacitive plasma discharge of 40.68 MHz frequency was used. The process of deposition was studied by optical emission spectroscopy. The silicon thin films of different phase composition were obtained. The thin films were characterized by Raman-spectroscopy, atomic force microscopy, and secondary ion mass spectrometry. The exhaust gas mixture was analyzed by IR-spectroscopy in outlet of the reactor during PECVD process. The chemical mechanism for the deposition process was also proposed.     

Deposition of polyacrylic acid films on PDMS substrate in dielectric barrier corona discharge at atmospheric pressure

This paper reports on deposition of acrylic acid films polymerized by an efficient and cost‐effective technique of dielectric barrier corona discharge at atmospheric pressure. The liquid acrylic acid was vaporized and carried by argon gas into plasma to deposit polyacrylic acid films on polydimethylsiloxane substrate. A nonthermal corona discharge was generated in a pyrex flask using a steel tube‐to‐plate asymmetric electrode configuration. The plasma was excited using an in‐house developed power supply operating with continuous wave signals of 10‐kHz frequency. The emission spectra of plasma species were recorded to know their contribution during deposition process. The deposited surfaces were characterized using contact angle measurements, atomic force microscopy, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy and film thickness measurements. A maximum film growth rate of 363 nm/min was achieved under optimal condition of discharge. The results suggest that this plasma technique is capable of depositing organic coatings with a high concentration of carboxylic functional groups that could be potentially used for biomedical and microfluidic applications.     

Effect of Fatty Acid Polyunsaturation on Synthesis and Properties of Emulsion Polymers Based on Plant Oil-Based Acrylic Monomers

This study demonstrated that polymerization behavior of plant oil-based acrylic monomers (POBMs) synthesized in one-step transesterification reaction from naturally rich in oleic acid olive, canola, and high-oleic soybean oils is associated with a varying mass fraction of polyunsaturated fatty acid fragments (linoleic (C18:2) and linolenic (C18:3) acid esters) in plant oil. Using miniemulsion polymerization, a range of stable copolymer latexes was synthesized from 60 wt.% of each POBM and styrene to determine the impact of POBM chemical composition (polyunsaturation) on thermal and mechanical properties of the resulted polymeric materials. The unique composition of each plant oil serves as an experimental tool to determine the effect of polyunsaturated fatty acid fragments on POBM polymerization behavior and thermomechanical properties of crosslinked films made from POBM-based latexes. The obtained results show that increasing polyunsaturation in the copolymers results in an enhanced crosslink density of the latex polymer network which essentially impacts the mechanical properties of the films (both Young’s modulus and toughness). Maximum toughness was observed for crosslinked latex films made from 50 wt.% of each POBM in the monomer feed.     

Deposition of SiO2-Like Films by HMDSN/O2 Plasmas at Low Pressure in a MMP-DECR Reactor

The effects of process parameters such as O₂/HMDSN (hexamethyldisilazane) ratio, microwave discharge power and deposition pressure on the growth rate, chemical bonding nature, and refractive index of thin films deposited by microwave plasma from HMDSN with oxygen, have been investigated. The plasma was created in a Microwave Multipolar reactor excited by Distributed Electron Cyclotron Resonance. The films were deposited at room temperature and characterized by Fourier Transform Infrared spectroscopy and ellipsometry. Growth rate increased with the discharge power P or the deposition pressure but decreased significantly with increasing O₂/HMDSN ratio. A large change in the film composition was observed when the O₂/HMDSN ratio was varied: films deposited with only HMDSN precursor are polymer-like but as the O₂/HMDSN ratio increased, organic groups decreased. For relative pressure values over 70%, deposited films are SiO₂-like with refractive index values close to those found for thermal silicon dioxide.     

Interaction of anhydride and carboxylic acid compounds with aluminum oxide surfaces studied using infrared reflection absorption spectroscopy

The chemical bonding of three different anhydride and carboxylic acid based compounds with a set of differently prepared aluminum substrates has been investigated using infrared reflection absorption spectroscopy. The compounds were selected to model typically used adhesives, coatings, and self-assembling monolayers. The purpose of the investigation was to study the interaction of these functional groups with the aluminum oxide surface and to determine whether this interaction is influenced by the changes in chemistry and composition of the oxide layer. The extent to which the compounds resisted disbondment in water was also investigated. The oxide layers on the differently prepared substrates were all found to be capable of hydrolysis of the anhydride group, resulting in the formation of two carboxylic acid groups. Subsequently, both of the carboxylic acid groups became deprotonated, to form a coordinatively bonded carboxylate species. The same behavior was also observed for monofunctional carboxylic acids. For all different oxides layers, the carboxylate was found to be coordinated in a bridging bidentate way to two aluminum cations in the oxide layer. The oxide layers showed however clear differences in the amount of molecules being chemisorbed. A relation was established with the amount of hydroxyls present on their surfaces, as determined from X-ray photoelectron spectroscopy measurements. The coordinative bonding of a monofunctional carboxylic acid group to the oxide surface was found to be not stable in the presence of water, while a bifunctional carboxylic acid group could resist displacement by water for a prolonged period of time.     

Oxynitride perovskite LaTiOxNy thin films deposited by reactive sputtering

This paper reports on the first study of structural and optical properties of reactively RF-sputtered lanthanum titanium oxynitride thin films using an original oxynitride LaTiO₂N target and an argon–nitrogen mixture as reactive plasma. The depositions were carried out by varying the process parameters such as RF power, total pressure, argon and nitrogen rates and substrate temperature. Wavelength dispersive spectrometry (WDS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–visible spectroscopy show that titanate lanthanum oxynitride compounds can exist as a domain composition, LaTiO_xN_y. Films prepared in pure argon are oxide films, transparent, amorphous and insulating. Polycrystalline and [001]-textured oxynitride thin films, with different nitrogen contents, can be deposited on SrTiO₃ substrates, depending on the sputtering conditions. As expected, the introduction of nitrogen in the coatings leads to a band gap narrowing. Oxynitrides' thin films are thus coloured and semiconductive.     

Study of Thin Polymeric Film Deposited by the PECVD Process for use at 193 nm

A plasma enhanced chemical vapor deposition (PECVD) reactor was used to deposit thin polymeric films with high absorption at 193 nm. The reactor is suitable to deposit uniform and pinhole free thin polymeric films with conformality over 95%. Conformal films with thickness as low as 200 Å have been deposited on silicon, glass, and quartz substrates, as well as silicon oxide, silicon nitrate, and aluminum films. Deposited films had variations in thickness of 3 to 5% over an area of 8 inches in diameter. Thin films deposited on silicon substrates under varying levels of RF power were scanned using the AFM technique. The measurements show increasing surface roughness of the scanned samples as the RF power increases.     

预辐射接枝四氟乙烯-乙烯共聚物湿敏膜的制备及特性研究

利用2 MeV电子加速器, 在常温下采用预辐照引发接枝的方法, 在四氟乙烯-乙烯共聚物(ETFE)上接枝丙烯酸(AA)和对苯乙烯磺酸钠(SSS), 制备了一种含羧酸基团和磺酸基团的接枝膜. 傅里叶变换红外光谱(FTIR)分析结果证明了磺酸基团和羧酸基团的成功引入, 并对接枝膜的热力学和化学特性进行了研究. 结果表明, 随着接枝率的增加, 接枝膜的结晶度逐渐降低, 接触角逐渐减小, 接枝膜的亲水性逐渐增强. 利用制备的接枝膜构建了电阻型湿度传感器, 并测定了传感器的电学特性. 在相对湿度(RH)从5%变化到98%时, 传感器电阻线性变化范围接近4个数量级, 具有响应速度快(吸附<1 min, 解吸<2 min), 湿滞小(<2%RH)的特点.     

Structure,Composition, Mechanical,and Tribological Properties of BCN Films Deposited by Plasma Enhanced Chemical Vapor Deposition

In this work thin BCN films were deposited by plasma enhanced chemical vapor deposition (PECVD) using chloridic precursors. Through adjusting the BCl₃ content in the inlet gas mixture the chemical composition of the deposited films was changed from carbon rich to boron rich. Based on optical emission spectroscopy (OES) measurements, a correlation between film composition and precursor species concentration in the plasma was established. The films were amorphous as detected by grazing incidence X-ray diffraction (GIXRD). The hardness and the elastic modulus have maximal values of 25.5±1.2 and 191±6 GPa, respectively, for the films with a boron concentration of 45.2 at.%. GIXRD data suggest that a depletion in boron content may initiate the formation of graphitic domains in the amorphous matrix. The observed degradation of the mechanical properties is associated with the graphitization. The tribological behavior was studied with a tribometer operated in pin-on-plate configuration at the temperatures 25 and 400°C. The wear mechanisms were discussed with respect to the formation of a boric acid surface layer which was detected by reflection electron energy loss spectroscopy (REELS) analysis.     

Deposition of Super-Hydrophobic and Oleophobic Fluorocarbon Films in Radio Frequency Glow Discharges

Fluorocarbon films using a monomer, 1H, 1H, 2H-perfluoro–1-dodecene were deposited in a continuous radio frequency (RF) glow discharge, the process was carried out in a parallel-plate RF discharge onto stainless steel reactor in order to produce coating with a water-and oil–repellent surface. Fourier-Transform Infrared spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS) revealed that the films obtained contain mainly perfluoromethylene (CF₂) species. Film wettability was tested using water and hydrocarbon liquids for contact angle measurements, furthermore surface energy was also calculated. Oil-repellency was found to increase as the amount of CF₂ species increases in the film structure. Film morphology was studied by Atomic Force Microscopy (AFM), films showing an usual morphology from that typical of Plasma Polymerised Fluorocarbon (PPFC) films. The combination of the low surface energy coating and the surface morphology produces materials which are both water and oil repellency.     

溅射功率对氧化锡薄膜结构和电化学性能的影响

应用射频磁控溅射技术在硅基底上制备氧化锡薄膜,着重研究溅射功率对薄膜结构和电化学性能的影响.XRD,SEM分析及恒电流充放电测试表明,随着溅射功率的增大,薄膜的结晶程度提高;生长速率和晶粒尺寸增大;电池的贮锂容量减少,且首圈不可逆容量损失增大.溅射功率对薄膜的电化学性能有较大的影响.     

Structural,optical and secondary electron emission properties of diamond like carbon thin films deposited by pulsed-DC plasma CVD technique

Plasma enhanced chemical vapor deposition (PECVD) technique using pulsed-DC power supply was used to fabricate diamond like carbon (DLC) films at deposition rates as high as 110 nm/min. The DLC films deposited by pulsed-DC and DC based power supplies under different gas flow ratios were studied for their suitability as dielectric layer coatings in plasma display panels (PDPs). The effect of deposition parameters on the properties of the DLC films were studied using Fourier transform infra-red spectroscopy (FTIR) and spectroscopic ellipsometry (SE). FTIR reveals that higher hydrogen dilution in gas mixture leads to higher sp³ content. SE studies in wide spectral range were analyzed using Tauc-Lorentz model dielectric function. A rise in the extracted refractive index was seen on increasing the H₂ content in the feed gas, thus resulting in optically denser films. Secondary electron emission coefficient (γ) was measured in the films deposited by the DC and pulsed-DC based PECVD. Firing voltage in the DLC samples was found to have very low variation in the operating pressure range used in commercial PDPs, suggesting possibility of enhanced long term reliability of DLC coatings in future PDP applications.     

Plasma-Deposition of Ag-Containing Polyethyleneoxide-Like Coatings

Ag-containing polyethyleneoxide (PEO)-like thin films have been deposited in Radio Frequency Glow Discharges fed with vapors of diethyleneglycol-dimethylether and argon. Proper experimental conditions have been utilized in order to fragment the monomer in the glow and, at the same time, sputter Ag from the silver RF cathode of the reactor, in a way that polyethyleneoxide(PEO)-like coatings with embedded Ag clusters have been deposited at the ground electrode. The compostion of the coatings has been investigated by means of different techniques; the plasma process has been investigated by means of Actinometric Optical Emission Spectroscopy. A correlation has been found between the amount of silver embedded in the coatings and that sputtered in the discharge, monitored by actinometry, that could eventually be utilized to control in situ the deposition process.     

Parametric study of atmospheric-pressure diamond synthesis with an inductively coupled plasma torch

Polycrystalline diamond coatings have been deposited run molybdenum and silicon substrates using an inductively coupled, atmospheric-pressure plasma torch. Growth rates are on the order of 10 hr. The inductively coupled plasma reactor is found to produce a uniform, well-characterized growth environment for experimental and computational .study of the atmospheric-pressure diamond growth regime. Growth morphology is found to be sensitive to reactor conditions such as substrate surface temperature and methane-to-hydrogen feed ratio. An experimental parametric study of these variables is performed and the resultant growth analyzed by scanning electron microscopy, Raman spectroscopy, and X-ray diffraction Spectroscopic analysis of the gas phase is also performed. Results indicate that the, substrate temperature range over which diamond growth occurs shifts toward higher temperatures as the methane-to-hydrogen feed ratio is increased. The growth rate is observed to reach a maximum with varying methane-to-hydrogen feed ratio at constant substrate temperature. Raman analysis of the deposits indicates that higher-quality diamond is achieved at the highest limits of substrate temperature for a given methane-to-hydrogen ratio. Higher-quality diamond is also observed to be, formed at lower methane-to-hydrogen feed ratios.     

Plasma polymerization and deposition of glycidyl methacrylate on Si(100) surface for adhesion improvement with polyimide

Thin polymer films were deposited on Si(100) surfaces by plasma polymerization of glycidyl methacrylate (GMA) under different glow discharge conditions. The FT‐IR, X‐ray photoelectron spectroscopy (XPS), and amine treatment results suggested that the epoxide functional groups of the deposited films had been preserved to various extents, depending on the plasma deposition conditions. The use of a low radio frequency power (～ 5 W) and a relatively high system pressure (100–400 Pa) readily resulted in the deposition of thin films having nearly the same composition of the epoxide functional groups as that of the GMA homopolymer. The plasma‐polymerized GMA (PP‐GMA) thin films deposited on the Ar plasma‐pretreated Si(100) surfaces were retained to a large extent after acetone extraction, suggesting the presence of covalent bonding between the PP‐GMA layer and the Si surface. Thermal imidization of the poly(amic acid) precursor of polyimide on the GMA plasma‐polymerized Si(100) surface resulted in a strongly adhered polyimide film. The adhesion results further suggested that the GMA polymer had been grafted on the Si(100) surface and the epoxide functional groups had undergone reactive interaction (curing) with the carboxylic and amine groups of the poly(amic acid) during thermal imidization. Copyright © 2001 John Wiley & Sons, Ltd.