Gold particles containing plasma-polymerized styrene as an X-ray absorber

Gold particles containing plasma-polymerized styrene film were formed simultaneously by plasma polymerization and evaporation using an inductively coupled argon gas flow type reactor. Gold was used as the evaporated metal and styrene as the monomer. The plasma etching characteristics of the film were evaluated by O₂ and CO₂ plasmas using a reactor with parallel-plate electrodes. A structure of lines and spaces of 4m width was successfully fabricated in the film on Si wafer by CO₂ plasma etching through a mask pattern of plasma-polymerized resist. A self-developed pattern was obtained through the X-ray mask with polyimide substrate by synchrotron radiation. The molecular structure and atomic composition of the film were investigated by ESCA and TEM.     

Vacuum lithography—A completely dry lithography using plasma processing

The purpose of this paper is to describe a thoroughly dry lithography using plasma polymerization and plasma etching. The new lithography is named vacuum lithography because all processes are performed at reduced pressures. Resist films were formed in bell-jar-type and argon-flow-type reactors. The controllability of plasma polymerization is discussed with respect to the type of reactor and gas mixture. A pattern was delineated in the resist using an electron beam, and it was developed by plasma etching with a mixture of argon and oxygen. It was found that the quality of the plasma-polymerized resist depends strongly on the polymer structure and on the plasma etching conditions. In this experiment, the recorded values of sensitivity and value of plasma-polymerized methyl methacrylate were 700 µC/cm² and 1, respectively.     

Deposition of Ethylene-Hexafluoropropene Gradient Plasma-Copolymer Using Dielectric Barrier Discharge Reactor at Atmospheric Pressure: Application to Release Coatings on Pressure-Sensitive Tape

Plasma-polymerized hexafluoropropene (PPHFP) film deposited using a dielectric barrier discharge reactor at atmospheric pressure had low enough adhesive strength, 22.2 Nm^–1, for use as a release coating of pressure-sensitive adhesive tapes, but the bond strength between PPHFP film and a poly (ethylene terephthalate) (PET) substrate film was slightly weak: some part of the PPHFP deposits could be peeled from the PET substrate. Since the XPS results indicated that the bond strength between plasma-polymerized ethylene (PPE) film and PET substrate was strong enough, we tried to deposit PPE and plasma-polymerized ethylene - hexafluoropropene gradient plasma-copolymer between the PET substrate and the PPHFP film. This multi-layer film (MLF) had low enough adhesive strength, 36.6 Nm^–1, for use as the release coating; this value was near that of a control sample, Teflon sheet, 21.6 Nm^–1. Moreover, the bond strength between MLF and PET substrate became stronger than that between PPHFP and PET films.     

Surface characterization of plasma‐modified poly(ethylene terephthalate) film surfaces

Poly(ethylene terephthalate) (PET) film surfaces were modified by argon (Ar), oxygen (O₂), hydrogen (H₂), nitrogen (N₂), and ammonia (NH₃) plasmas, and the plasma‐modified PET surfaces were investigated with scanning probe microscopy, contact‐angle measurements, and X‐ray photoelectron spectroscopy to characterize the surfaces. The exposure of the PET film surfaces to the plasmas led to the etching process on the surfaces and to changes in the topography of the surfaces. The etching rate and surface roughness were closely related to what kind of plasma was used and how high the radio frequency (RF) power was that was input into the plasmas. The etching rate was in the order of O₂ plasma > H₂ plasma > N₂ plasma > Ar plasma > NH₃ plasma, and the surface roughness was in the order of NH₃ plasma > N₂ plasma > H₂ plasma > Ar plasma > O₂ plasma. Heavy etching reactions did not always lead to large increases in the surface roughness. The plasmas also led to changes in the surface properties of the PET surfaces from hydrophobic to hydrophilic; and the contact angle of water on the surfaces decreased. Modification reactions occurring on the PET surfaces depended on what plasma had been used for the modification. The O₂, Ar, H₂, and N₂ plasmas modified mainly CH₂ or phenyl rings rather than ester groups in the PET polymer chains to form C? O groups. On the other hand, the NH₃ plasma modified ester groups to form C? O groups. Aging effects of the plasma‐modified PET film surfaces continued as long as 15 days after the modification was finished. The aging effects were related to the movement of C?O groups in ester residues toward the topmost layer and to the movement of C? O groups away from the topmost layer. Such movement of the C?O groups could occur within at least 3 nm from the surface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3727–3740, 2004     

Modeling of H2 and H2/CH4 Moderate-Pressure Microwave Plasma Used for Diamond Deposition

One-dimensional transport models of moderate-pressure H ₂ and H ₂ /CH ₄ plasmas obtained in a diamond deposition microwave reactor are presented. These models describe the plasma as a thermochemically nonequilibrium flow with three different energy modes. The solution of the one-dimensional plasma transport equations enabled the estimation of plasma species concentrations and temperatures on the axis of the reactor. As far as pure H ₂ plasmas are concerned, results showed that the model predictions of gas and vibration temperatures are in good agreement with experimental measurements. The model also yields a relatively good qualitative prediction of the variations of H-atom mole fraction with the power density absorbed by the plasma. The results obtained for H ₂ /CH ₄ discharges showed that the model prediction on the variations of H-atom mole fraction with methane percentage in the discharge is in good qualitative agreement with experimental results. They also showed that methane is rapidly converted to acetylene before reaching the discharge zone. The concentrations of neutral hydrocarbon species in the reactor are mainly governed by thermal chemistry. The addition of methane strongly affects the ionization kinetics of the plasma. Three major ions are generally obtained in H ₂ /CH ₄ plasmas: C ₂ H ₂ ⁺ , C ₂ H ₃ ⁺ , and C ₂ H ₅ ⁺ . The relative predominance of these ions depends on the considered plasma region and on the discharge conditions. The ionic species concentrations are also mainly governed by chemistry, except very near the substrate surface. Finally the use of this transport model along with the surface chemistry model of Goodwin ⁽¹⁾ enabled us to estimate the diamond growth rate for several discharge conditions.     

Hydrogen Plasmas Processing of Graphene Surfaces

To assist the development of plasma processes to pattern graphene in a controlled way, interactions between hydrogen plasma species (H, H⁺, H₂ ⁺) and various types of graphene surfaces (monolayer, nanoribbons, multilayer) are investigated using atomic-scale simulations. It is shown that only “hot” H particles (i.e., with a kinetic energy greater than ~0.4 eV at 300 K) can adsorb on the basal plane of surface-clean graphene while adsorption is barrierless on free edges or vacancies. Surface reaction probabilities (reflection, adsorption, penetration) are found to strongly vary with the incident species energy, which allows to determine specific energy ranges (or process windows) for different types of H₂ plasma treatment: lateral etching of graphene nanoribbons (GNRs), cleaning of graphene surfaces or vertical etching of multilayer graphene (MLG) stacks. Molecular dynamics simulations of GNRs trimming in downstream H₂ plasmas allow to understand the mechanism which governs the anisotropic etching of ribbons and explains the absence of line-edge roughness on their edges. Interactions between low-energy (5–25 eV) H _x ⁺ (x = 1, 2) ions with MLG are also investigated. Ion-induced damage (hydrogenation of successive graphene sheets, creation of vacancies) and etching of the MLG stack are found to vary with the ion energy, the ion fluence and the ion composition.     

基于 H2/O2 等离子体和钛硅沸石的丙烯气相环氧化方法

 将 H₂/O₂ 非平衡等离子体现场产生的气态 H₂O₂和丙烯与耦合反应器中钛硅沸石 TS-1 直接接触, 实现了丙烯气相环氧化反应. 结果表明, 非平衡等离子体生成气态 H₂O₂ 的速率由介质阻挡放电的输入功率决定, 环氧丙烷的生成速率和选择性取决于钛硅沸石催化剂和反应条件. 在 H₂ 和 O₂ 进料流量分别为 170 和 8 ml/min, 介质阻挡放电输入功率为 3.5 W, 环氧化反应温度为 110 ^oC, 丙烯进料量为 18 ml/min, 催化剂用量为 0.8 g 的条件下, 生成环氧丙烷产率达 246.9 g/(kg•h)、环氧丙烷选择性和 H₂O₂ 有效利用率分别为 95.4% 和 36.1%, 反应 36 h 内未见催化剂失活.     

Ion and radical reactions in the silane glow discharge deposition of a-Si:H films

A mass spectrometric analysis of the positive ions and neutral products in a silane glow discharge has been performed. The active species, created by dissociation, disproportionation, and ion-molecule reactions are mainly SiH₂, SiH₃, and H. A calculation of the distribution of the SiH _n ⁺ ions shows that the silane concentration monitors the abundance of SiH ₃ ⁺ . The diffusional transport of radicals toward the discharge-tube walls can explain the observed deposition rates. The study of SiH₄-SiD₄ and SiH₄-D₂ plasmas emphasizes several reactions which modify the free-radical populations depending on the discharge conditions: disproportionation, termination, recombination, and abstraction. Heterogeneous reactions have also been observed: etching of the film by H atoms and direct incorporation of hydrogen in the growing film. A general scheme for the plasma deposition mechanism is proposed.     

Plasma reactions of self-assembled monolayers to model oxygen atom effects on polymers

The plasma treatment of self-assembled monolayers of octadecyl mercaptan on gold substrates has been investigated as a model for oxygen atom effects on polymers. Both O₂ and H₂O low pressure gas plasmas have been used. X-ray photoelectron spectroscopy has revealed that the two plasma treatments differ from each other in the extent of oxidation and etch rate with O₂ being the more aggressive plasma. The results have confirmed that the plasma modification of organic surfaces involves a balance between surface oxidation and surface etching. The well-defined structure of the monolayer enables quantitation of these atom-substrate reactions. © 1998 John Wiley & Sons, Ltd.     

Chemical characterization of plasma-polymerized films from acetylene and nitrogen-containing mixtures and their ethanol vapor sensitivity

In this study, plasma-polymerized thin films were prepared from plasma enhanced chemical vapor deposition (PECVD) of acetylene (C₂H₂), acetylene/nitrogen (C₂H₂/N₂), or acetylene/ammonia (C₂H₂/NH₃). When N₂ or NH₃ was mixed with C₂H₂ in the feed, the films were identified to contain all elements of the mixture and the properties of the films were implied by the C–H bonds and nitrogen functionalities. As shown by X-ray photoelectron spectroscopy (XPS) the [N]/[C] atomic ratio varies by changing the mixture composition and reaches a maximum of 0.12 for mixing C₂H₂ with NH₃. It is found that the resistance of the thin film sensors prepared from C₂H₂, C₂H₂/N₂, and C₂H₂/NH₃ is distinctly decreased by over 2 orders of magnitude by the adsorption of ethanol vapor.     

Deposition of Diamondlike Carbon Film and Mass Spectrometry Measurement in CH4/N2 RF Plasma

The deposition of diamondlike carbon (DLC) film and the measurements of ionic species by means of mass spectrometry were carried out in a CH₄/N₂ RF (13.56 MHz) plasma at 0.1 Torr. The film deposition rate greatly depended on both CH₄/N₂ composition ratio and RF power input. It was decreased monotonically as CH₄ content decreased in the plasma and then rapidly diminished to negligible amounts at a critical CH₄ content, which became large for higher RF power. The rate increased with increasing RF power, reaching a maximum value in 40% CH₄ plasma. The predominant ionic products in CH₄/N₂ plasma were NH⁺ ₄ and CH₄N⁺ ions, which were produced by reactions of hydrocarbon ions, such as CH⁺ ₃, CH⁺ ₂, CH⁺ ₅, and C₂H⁺ ₅ with NH₃ molecules in the plasma. It was speculated that the production of NH⁺ ₄ ion induced the decrease of C₂H⁺ ₅ ion density in the plasma, which caused a reduction in higher hydrocarbon ions densities and, accordingly, in film deposition rate. The N⁺ ₂ ion sputtering also plays a major role in a reduction of film deposition rate for relatively large RF powers. The incorporation of nitrogen atoms into the bonding network of the DLC film deposited was greatly suppressed at present gas pressure conditions.     

Effects of process parameters on ultrafine SiC synthesis using induction plasmas

A study is reported of the formation of ultrafine SiC powder through the reaction of elemental silicon and CH₄ in an induction plasma. The reaction route used involved in the first place the vaporization of a fine elemental silicon powder axially injected into the center of the discharge followed by the carburization reaction through the coinjection of CH₄. The powder obtained was composed of a mixture of α- and β-SiC with varying amounts of free carbon and free silicon. The particle size distribution was typically in the range of 40–60 nm with a corresponding specific surface area of 30–50 m²/g. A parametric study showed that the quality of the powder obtained varied with the plasma plate power and the position of the injection probe. The plasma gas composition employed was found to influence the proportions of α- and β-SiC in the synthesized SiC powder. With an Ar/N₂ mixture as the plasma gas, the ratio of the α to β phases was less than 1.0, whereas the ratio was greater than 1.5 when using a mixture of Ar/H₂ as plasma gas. The Si powder feed rate and the input C/Si molar ratio in the injected reactants significantly affected both the formation of the SiC and the free Si and free C content in the synthesized powder. Lining the cylindrical reactor wall with graphite resulted in improved conversion of Si to SiC. The weight fraction of the powder collected at different sections of the reactor system varied with the reactor operating conditions. The experimental results support the view that the formation mechanism for ultrafine SiC is dominated by the reaction of Si vapor with the thermal decomposition products of CH₄.     

Surface Modification of Poly(tetrafluoroethylene) Films by Plasma Pre-Activation and Plasma Polymerization of Glycidyl Methacrylate

Surface modification of poly(tetrafuoroethylene) (PTFE) film by plasma polymerzation and deposition of glycidyl methacrylate (GMA), in the presence and absence of Ar or O₂ plasma pre-activation, was carried out to enhance the adhesion with polyimides (PI) film in the presence of an epoxy adhesive. For deposition carried out at low RF power, a high epoxide concentration was preserved in the plasma-polymerized GMA (pp-GMA) layer on PTFE (pp-GMA-PTFE). However, high adhesion strength of the PI/pp-GMA-PTFE laminate was obtained only in the presence of O₂ plasma pre-activation of the PTFE substrates prior to plasma polymerization and deposition of GMA. In the absence of any plasma pre-activation or in the presence of Ar plasma pre-activation, the deposited pp-GMA layer on the PTFE surface could be readily removed by solvent extraction. The adhesion enhancement of the PI/pp-GMA-PTFE laminates in the presence of O₂ plasma pre-activation was attributed to the preservation of the epoxide functional groups in the pp-GMA layer, the curing of the GMA chains into the matrix of the epoxy adhesive, and the covalent bonding of the pp-GMA layer on the PTFE surface.     

A novel photoelectrochemical hydrogen peroxide sensor based on nickel(II)-potassium hexacyanoferrate-graphene hybrid materials modified n-silicon electrode

A platinum (Pt) film coated n-silicon (Pt/n-n⁺-Si) was modified with nickel(II)-potassium hexacyanoferrate (NiHCF)-graphene sheets (GS) hybrid and used as a photo-electrochemical (PEC) sensor for non-enzyme hydrogen peroxide (H₂O₂) detection. A NiHCF film was deposited on the surface of GS/Pt/n-n⁺-Si electrode by chemical method. The structure and composition of the NiHCF film was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). PEC behavior of the NiHCF-GS/Pt/n-n⁺-Si electrode was investigated using cyclic voltammetry (CV) under illumination. The modified electrode has been used as PEC sensor for H₂O₂ detection with a linear range of 2.0 × 10^?6–2.9 × 10^?3 M and a detection limit of 1.0 × 10^?6 M at a signal-to-noise ratio of 3 in a two-electrode cell with a Pt plate as counter electrode. The characteristics of GS layer have been discussed in both the improvement of sensibility and selectivity.     

Compact plasma source for removal of hydrocarbons for surface analysis

A low–energy, constricted‐anode Anders‐type plasma source was built and tested for the chemical removal of adventitious carbon on surfaces. Oxygen plasma, generated in the source, extends to the sample surface through an aperture in the anode. This plasma reacts with surface hydrocarbons and removes them in less than a minute without influencing the intrinsic surface stoichiometry of nonoxidizing samples such as minerals, glasses, and metal oxides. Adventitious carbon removal is critical for accurate binding energy determination and quantitative measurements in XPS and AES, particularly in multicomponent materials. We measure the plasma to be composed primarily of O⁺ and O₂⁺, with minor H⁺, H₂⁺, and O⁺⁺ components. Ion energy distributions were measured for O⁺ and O⁺⁺ and show all emitted ions have energies less than 50 eV, confirming chemical desorption as the primary removal mechanism. The plasma source, easily built ‘in house’, is compact and can be mounted on a 2.75‐in flange for in situ specimen cleaning prior to surface analysis. Copyright © 2009 John Wiley & Sons, Ltd.     

The influence of Ti plasma etching pre-treatment on mechanical properties of DLC film on cemented carbide

The pre-treatment of substrate surface had been a key part of DLC film preparation to improve mechanical and tribological properties. Ti plasma etching pre-treatment was investigated in this paper as a new effective surface pre-treatment method to substitute transition layer. This pre-treatment used high-energy Ti plasma to impact substrate surface. Ti plasma etched the substrate to a depth of 407 nm and increased the roughness from 1.36 to 40.39 nm. A trace layer of substrate, together with cobalt, oxides, and other impurities, was removed. Ti plasma broke some top WC crystals and combined with the free carbon ions separating from the substrate. A DLC film was deposited on the etched surface. Compared with DLC films deposited on the untreated substrate and Ti transition layer, the DLC film on the Ti plasma etched substrate had best adhesion strength of 34.14 N. The three DLC films had the same sp³ bonding carbon content, but Ti plasma etching treatment could promote the formation of sp³ bonds on the interface of substrate and DLC film. This DLC film had low friction coefficient of 0.12 and low wear rate of 5.11 × 10⁻⁷ mm³/m·N. In summary, Ti plasma etching pre-treatment could significantly improve the adhesion of DLC film and keep its excellent tribological properties.     

A zirconium modified Co/SiO2 Fischer-Tropsch catalyst prepared by dielectric-barrier discharge plasma

Co/SiO₂ and zirconium promoted Co/Zr/SiO₂ catalysts were prepared using dielectric-barrier discharge (DBD) plasma instead of the conventional thermal calcination method. Fischer-Tropsch Synthesis (FTS) performances of the catalyst were evaluated in a fixed bed reactor. The results indicated that the catalyst treated by DBD plasma shows the higher FTS activity and yield of heavy hydrocarbons as compared with that treated by the conventional thermal calcination method. Increase in CO conversion was unnoticeable on the Co/SiO₂ catalyst, but significant on the Co/Zr/SiO₂ catalyst, both prepared by DBD plasma. On the other hand, heavy hydrocarbon selectivity and chain growth probability (α value) were enhanced on all the catalysts prepared by the DBD plasma. In order to study the effect of the DBD plasma treatment on the FTS performance, the catalysts were characterized by N₂-physisorption, H₂-temperature programed reduction (H₂-TPR), H₂-temperature-programmed desorption (H₂-TPD) and oxygen titration, transmission electron microscope (TEM) and X-ray diffraction (XRD). It was proved that, compared with the traditional calcination method, DBD plasma not only could shorten the precursor decomposition time, but also could achieve better cobalt dispersion, smaller Co₃O₄ cluster size and more uniform cobalt distribution. However, cobalt reducibility was hindered to some extent in the Co/SiO₂ catalyst prepared by DBD plasma, while the zirconium additive prevented significantly the decrease in cobalt reducibility and increased cobalt dispersion as well as the FTS performance.     

H2S and NH3 Removal by Silent Discharge Plasma and Ozone Combo-System

Treatment of H₂S and NH₃ using the non-thermal plasma (NTP) methods was investigated. Two NTP systems were used in this study, one consisting of a multi-cell plate-to-wire reactor (PTW), and the other consisting of an ozonization chamber and the multi-cell PTW reactor. Each cell of the PTW reactor had a sheet of copper foil embedded in dielectric layers as its high voltage electrode and a wired rack as its gounded electrode. Use of the wired rack type electrode allowed large flow throughput, and promoted intense local electric fields. The experiments showed that under constant energy input, the decomposition efficiency of H₂S or NH₃ decreased with increasing initial concentration of the gas, and increased with increasing injected ozone and relative humidity. Injection of NH₃ into H₂S stream did not improve the H2S decomposition efficiency but was necessary for removal of sulfite-containing compounds in the discharge air.     

A Novel Dielectric-Barrier-Discharge Loop Reactor for Cyanide Water Treatment

A novel dielectric-barrier-discharge (DBD) loop reactor was designed for the efficient degradation of cyanide anion (CN^?) in water. The circulation of cyanide water as a falling film through plasma gas discharge zone enhanced gas–liquid mass and energy transfer and induced formation of H₂O₂ which was associated with the efficient destruction of CN^?. It was observed that among different discharge gases, the CN^? degradation rate decreased in the order of Ar > air > H₂/air mixture. Depending on discharge voltage, the treatment time for complete removal of 100 ppm CN^? in this DBD loop reactor is in the range 120–300 min. The dose of Cu²⁺ catalyst in combination with in situ production of H₂O₂ enhanced the destruction of CN^? apparently in this DBD loop reactor. The treatment time for complete degradation of 100 ppm CN^? decreased from 180 min with Ar DBD discharge alone to 40 min with 40 mg/L dose of Cu²⁺ ion in water, making it an efficient means to degrade cyanide water.     

Mixing study of the induction plasma reactor: Part I. Axial injection mode

A systematic study of the gas-mixing pattern in an induction plasma reactor under atmospheric and low pressure conditions is reported. Different reactor configurations were investigated in which nitrogen is injected as an auxiliary gas either axially into an Ar/H₂, discharge in the center of the induction coil region, or radially through multiple orifices, into the plasma jet at tire exit nozzle of the torch. Concentration mapping in the mixing zone was carried out, using a VG-Microniass-PC 300 D mass spectrometer at plasma power levels and reactor pressures, in the range of 13–24 k 6V and 35–93 kPa, respectively. Comparison of these results with cold-flow measurements underlined the substantial difference in the mixing pattern in each of these two cases. A considerably faster mixing of the gases is noted under cold flow conditions compared to that in the presence of the discharge. The results are discussed from the viewpoint of their use for optimum reactor design applied to tire vapor-phase synthesis of ultrafine ceramic powders, using induction plasma technology.