Rf Glow Discharge Plasma Research Articles

Development of universal fabric dyeing and adhesion through RF glow discharge plasma treatment

Various dyeing techniques are utilised at dyeing different types of fabrics and current study discuss the possibility of using a single dye bath for the given purpose. The current study utilised a radio frequency glow discharge plasma source maintained at near atmospheric conditions (around 200 mbar) in nitrogen and air environments to treat cotton, nylon, and polyester fabrics. Similar surface modifications produced in all three types of fabrics by OH and O radicals tailoring them more sensitive to certain dyes and glues. SEM images verified that bulk material is well protected by plasma treatment and the presence of additional surface functionalities (hydroxyl, carboxylic, and carbon-nitrogen groups) on the treated fabric surfaces were determined by FTIR and XPS analysis. The plasma-treated samples were dyed in a single dye bath using a reactive dye under atmospheric neutral conditions and a significant enhancement in fabric dyeability (cotton- 124%, nylon- 61%, polyester- 38%) was observed. PVA glue was used for fastening the fabric samples and the adhesion was analysed through tensile measurement. Well improved adhesion capabilities (148%, 95%, and 57.3% respectively for cotton, nylon, and polyester) also confirm the advantages of RF glow discharge plasma treatment for unified fabric processing.

Rectification experiments and 3D simulations in a dusty plasma ratchet

Realizing the control of charged dust particles in a plasma environment has important scientific significance and application prospects. This paper realizes the rectification of dust particles in RF glow discharge plasma by designing a dusty plasma ratchet experiment. The direction of the particle flow can be controlled by adjusting the discharge power and gas pressure. To reveal the rectification mechanism of dust particles, this paper reconstructs a three-dimensional distribution of plasma parameters in the ratchet channel, analyzes the dust particle dynamics, and performs Langevin simulation. Numerical simulations can quantitatively reproduce the rectification phenomena of particles. Results show that the non-equilibrium ion drag force along the ratchet channel drives the charged particles to form a directional motion. Experimental and simulation results provide an experimental support and model basis for the profound study of the control of charged dust particles and energy conversion in plasma.

Plasma intensification in 2 MHz RF glow discharge in carbon film plasma sputtering deposition by means of a hollow cathode

A hollow cathode has been one of the methods to intensify the plasma in the etching or ashing process. This work examined a number of technologies in the intensification of a 2 MHz RF glow discharge plasma to deposit carbon film by means of the hollow cathode. Three types of the cathode configurations, which were cylindrical, rectangular and a cylindrical-rectangular combination, were tested to get an optimum condition for the carbon deposition. Both carbon target and substrate were fixed inside the hollow cathode. The plasma was characterized by means of optical emission spectroscopy (OES) at the range of 200 nm – 1000 nm. The results showed that the combination where the rectangular hollow was placed inside the cylindrical one, produced the most intense glow. Ion density and electron temperature in the plasma were determined by a calculation based on the atomic data related to the specific electronic transitions of the ions. The density of ions was very high in the centre area of the rectangular hollow producing complex reactions. On the other hand, the high density of the ions decreases the electron temperature. The energy of the ions was difficult to be predicted since the spectrum showed the existence of a large number of ion states. Observations on the resulted deposit on the surface of quartz substrate suggest that the intensification needs to be further investigated related to the effectiveness of sputtering and deposition process.

Highly-reactive haloester surface initiators for ARGET ATRP readily prepared by radio frequency glow discharge plasma.

New surface initiators for ARGET ATRP (activators regenerated by electron transfer atomic transfer radical polymerization) have been prepared by the plasma deposition of haloester monomers. Specifically, methyl 3-bromopropionate (M3BP), methyl 2-chloropropionate, and ethyl 2-fluoropropionate (E2FP) were plasma deposited onto glass discs using RF glow discharge plasma. This technique creates surface coatings that are resistant to delamination and rich in halogen species making them good candidates for surface initiators for ARGET ATRP. Of all the plasma polymerized surface coatings, M3BP showed the highest halogen content and was able to grow 2-hydroxyethyl methacrylate (HEMA) polymer brushes on its surface via ARGET ATRP in as little as 15 min as confirmed by XPS. Surprisingly, E2FP, a fluoroester, was also able to grow HEMA polymer brushes despite fluorine being a poor leaving group for ARGET ATRP. The versatility of RF glow discharge plasma offers a clear advantage over other techniques previously used to immobilize ARGET ATRP surface initiators.

Methods for the characterization of imposed, ordered structures in MDPX

Dusty plasmas have been studied in argon, radio frequency (rf) glow discharge plasmas with magnetic fields up to 1.5 T. Plasmas were formed between a powered bottom electrode and a grounded top electrode in which an aluminum wire mesh is fixed in the center. This work will examine the experimental conditions at which imposed, ordered structures form within the dusty plasma. These imposed, ordered structures, as reported in earlier works, are characterized by the alignment of dust particles to the spatial structure of the wire mesh in the top electrode and occur at high magnetic fields (B ≥ 1 T) and low neutral pressure (P ≤ 100 mTorr). A pair of parameters will be established to characterize the degree to which the dust particles are affected by these imposed ordered structures on both long and short time scales. Using these parameters, it will be shown that a correlation exists between the onset of imposed, ordered structures and the magnetization of ions within the plasma.

Quasi-discrete particle motion in an externally imposed, ordered structure in a dusty plasma at high magnetic field

Dusty plasmas have been studied in argon, radio frequency (rf) glow discharge plasmas at magnetic fields up to 2.5 T where the electrons and ions are strongly magnetized. Plasmas are generated between two parallel plate electrodes where the lower, powered electrode is solid and the upper electrode supports a dual mesh consisting of #24 brass and #30 aluminum wire cloth. In this experiment, we study the formation of imposed ordered structures and particle dynamics as a function of magnetic field. Through observations of trapped particles and the quasi-discrete (i.e., “hopping”) motion of particles between the trapping locations, it is possible to make a preliminary estimate of the potential structure that confines the particles to a grid structure in the plasma. This information is used to gain insight into the formation of the imposed grid pattern of the dust particles in the plasma.

Variation of antioxidative activity and growth enhancement of Brassicaceae induced by low-pressure oxygen plasma

The mechanism of growth enhancement induced by active oxygen species generated in an oxygen plasma is investigated. The plant growth enhancement induced by the active oxygen species would relate to an antioxidative activity, which is one of the biological responses. The amount of generated active oxygen species is varied by the oxygen gas pressure in a low-pressure RF glow discharge plasma. The antioxidative activity of sprouts of Brassicaceae induced by the oxygen plasma is maximized at pressures between 30 and 40 Pa, whereas the antioxidative activity becomes small at around 60 and 80 Pa. The pressure dependence of the antioxidative activity of sprout stems is opposite to that of the stem length of the sprouts. The growth enhancement would be induced by the increase in the concentration of active oxygen species in plants owing to the decrease in the amount of antioxidative substances.

Observations of imposed ordered structures in a dusty plasma at high magnetic field

Dusty plasmas have been studied in argon, rf glow discharge plasmas at magnetic fields up to 2 T, where the electrons and ions are strongly magnetized. In this experiment, plasmas are generated between two parallel plate electrodes where the lower, powered electrode is solid and the upper, electrically floating electrode supports a semi-transparent, titanium mesh. We report on the formation of an ordered dusty plasma, where the dust particles form a spatial structure that is aligned to the mesh. We discuss possible mechanisms that may lead to the formation of the “dust grid” and point out potential implications and applications of these observations.

Thermal Stability of Plasma Generated Oxygenated Functionalities on Carbon Nanotubes

Colloidal suspensions of functionalized carbon nanotubes (CNT nanofluids) have the potential to be used in a variety of applications, many of which require operation at elevated temperatures. In this study, we examine what effect exposure to an argon/oxygen/ethane RF glow discharge plasma has on the surface chemistry and structure of CNTs and what happens to the plasma‐generated functionalities at high temperatures. An analysis performed using X‐ray photoelectron spectroscopy and Raman spectroscopy indicates that longer and higher power plasma treatments decrease the sp2 graphitic nature of the CNTs without increasing the degree of oxygen functional groups. Heating of the functionalized‐CNTs up to 350 °C in air and 600 °C in argon, both lead to a substantial decrease in the surface oxygen concentration, which can be attributed to the decomposition of carboxylic functionalities at low temperatures (< 350 °C).

Comparative study of structural and optical properties of pulsed and RF plasma polymerized aniline films

Abstract Plasma polymerization of aniline is carried out by means of continuous RF and pulsed DC glow discharge plasma in a common reactor at different applied powers. The discharge control variables are optimized for good quality film growth and the role of fragmentation of the molecular structure on the structural, optical, morphological and optophysical properties of the deposited plasma polymerized aniline (PPAni) layers is investigated. Retention of the conjugated structure is found to be prominent at optimum applied power to the plasma in both the continuous RF and pulsed DC polymerization techniques. Improvement in conjugated structure and chain length have been observed in both the continuous RF and pulse DC PPAni thin films with the increase in applied power to the plasma up to a certain limit of applied power when working pressure is fixed at 0.15 mbar. A decrease in optical bandgap with the increase in applied power to the plasma is observed in both the pulsed DC and RF PPAni thin films, but it is more significant in case of RF PPAni films. The plasma polymerized aniline thin films are found to emit photoluminescence due to band to band transition and defects generated in the structure.

Correlation between phosphorus concentration and opto-electrical properties of doped a-Si:H films

Phosphorus doped hydrogenated amorphous silicon (a-Si:H) films were prepared by decomposition of silane using RF plasma glow discharge. Both DC dark conductivity measurements, and spectrophotometric optical measurements through the range 200–3000nm were recorded for the prepared films. The DC conductivity activation energy Ea decreased from 0.8eV for the undoped sample to 0.34eV for the highest used doping value. The optical energy gap Eg decreased ranging from 1.66eV to 1.60eV. The refractive index n, the density of charge carriers N/m* and the plasma frequency ωp showed an opposite behavior, i.e. an increase in value with doping. Fitting the dispersion values to Sellmeier equation led to the determination of the material natural frequency of oscillating particles. A correlation between the changes in these parameters with the doping has been attempted.

Atmospheric rf plasma deposition of superhydrophobic coatings using tetramethylsilane precursor

Non-fluorine-based organic–inorganic-hybrid coatings exhibiting superhydrophobic properties were prepared using a single-step process of atmospheric rf glow discharge plasma deposition with a tetramethylsilane (TMS) precursor. The plasma was generated with He in air and the TMS precursor concentration was 0.01–0.04 vol.% of the He carrier gas. The dissociation of TMS in the atmospheric plasma accompanied the formation of particulates through gas-phase condensation reactions, which lead to organic–inorganic-hybrid coatings with a root-mean-squared roughness in the ~30–80nm range and a water contact angle of ~150°–165° on a variety of substrates including flat wafers, papers, and cotton fabric without any sample pre-treatments. Due to the excitation and dissociation of ambient molecules (oxygen, nitrogen, and water) in the atmospheric plasma, the produced coatings contained oxygen and nitrogen, in addition to silicon and hydrocarbon groups. The oxygen species in the film appears to be a part of Si–O–Si networks similar to silicone compounds. The films produced with TMS exhibited an improved environmental durability compared to purely hydrocarbon-based films deposited with the same atmospheric plasma process.

Synthesis of nano ZnO thin film on Al foil by rf glow discharge plasma and its effect on E. coli and P. aeruginosa

Nano ZnO thin films were deposited on thin Al foils by a rf glow discharge plasma method in which sublimed zinc acetate vapor (precursor) reacted with oxygen plasma inside a low-pressure reactor. The films were microstructurally characterized using XRD, TEM, FESEM, optical reflectance and micro-Raman spectroscopy methods. In view of the good scope of ZnO coating in food packaging, the antibacterial activity in the ZnO thin films was studied by exposing the films to E. coli and P. aeruginosa for up to 8 h. Bacterial cell inhibition of up to 98–99 % was observed in the thin films.

Prevention of bacterial biofilms by covalent immobilization of peptides onto plasma polymer functionalized substrates

In this study, robust antibacterial coatings were created on stainless steel through the covalent grafting of antibacterial peptides onto an organic–polymeric interlayer deposited by RF-glow discharge plasma. X-Ray photoelectron spectroscopy was used to characterize and optimize the two steps of the coating process. The biocidal activity of these surfaces was demonstrated against both Gram+ and Gram− bacteria using ISO tests. 3 to 6 log10 reductions of both Gram+ and Gram− bacterial strains were obtained compared to uncoated stainless steel and depending on the particular antibacterial peptide immobilized. Importantly the antibacterial surfaces were resistant to several cleaning conditions. The latter is significant as the stability of such antibacterial surfaces in close to real life conditions is a major concern and leaching, de-lamination, rearrangement and ageing of the coating can lead to insufficient long term biofilm resistance of the surface.

Effect of illumination on hydrogenated amorphous silicon thin films doped with chalcogens

Hydrogenated amorphous silicon thin films doped with chalcogens (Se or S) were prepared by the decomposition of silane (SiH 4 ) and H 2 Se/H 2 S gas mixtures in an RF plasma glow discharge on 7059 corning glass at a substrate temperature 230 °C. The illumination measurements were performed on these samples as a function of doping concentration, temperature and optical density. The activation energy varied with doping concentration and is higher in Se-doped than S-doped a-Si:H thin films due to a low defect density. From intensity versus photoconductivity data, it is observed that the addition of Se and S changes the recombination mechanism from monomolecular at low doping concentration films to bimolecular at higher doping levels. The photosensitivity ( σ ph / σ d ) of a-Si, Se:H thin films decreases as the gas ratio H 2 Se/SiH 4 increased from 10 −4 to 10 −1 , while the photosensitivity of a-Si, S:H thin films increases as the gas ratio H 2 S/SiH 4 increased from 6.8 × 10 −7 to 1.0×10 −4 .

Spatial distributions of gas composition in rf glow discharge plasmas measured using a quartz sensor

A quartz sensor can detect changes in gas composition caused by plasma because the quartz sensor output depends on the total pressure, viscosity, and molecular weight of the gas. This simple mode of quartz sensor measurement was used to obtain spatial distributions of the gas composition changes in the plasmas between a chamber inner wall and a plasma electrode. These spatial distributions reflect gas phase reactions in the plasmas. For that reason, they are helpful to elucidate the reaction mechanisms occurring in the plasmas. Applying such quartz sensor measurements for hydrogen and argon–hydrogen plasmas, we found that the spatial distributions of the gas composition change, as measured using a quartz sensor, depend on source gases. The positions at which the quartz sensor output show the maximum gas composition change for hydrogen and argon–hydrogen plasmas were at the chamber inner wall and near the edge of the plasma electrodes that are the closest positions to the plasma glow. These results show that the gas composition change detected using the quartz sensor resulted from degassing from the chamber inner wall and the plasma electrodes.

Emitting a-SiOx(Er) films and a-SiOx(Er)/a-Si:H microcavities doped with Er by remote magnetron sputtering technique

We have developed the technique of growing amorphousa-SiOx(Er) filmsand a-SiOx(Er)/a-Si:H multilayer structures based on spatially separating the processes of the decompositionof an oxygen–silane gas mixture in an rf glow discharge plasma and remote magnetronsputtering of an Er target. This approach allows us to control independently the filmdeposition rate, the Er-ion concentration and its depth distribution in the film. Time-resolvedphotoluminescence measurements have shown that films and planar microcavities with anEr-doped active layer exhibit internal quantum efficiency for Er ion emission of∼75%. The method that we suggest is a way of producing effectively emitting microcavitystructures, in which the distribution profile of emission centers coincides with that of theelectromagnetic field in individual layers of the structure.

Mass spectroscopic measuring of SiCln (n = 0–2) radicals in SiCl4 RF glow discharge plasma

The relative densities of SiCln (n = 0–2) in SiCl4 radio frequency (rf) glow discharge plasma are measured by mass spectrometry. The effects of discharge parameters, i.e., rf power, discharge pressure, substrate temperature, and SiCl4 flow rate on the relative densities of SiCln (n = 0–2) are investigated in detail. An optimum configuration of discharge parameters (low rf power, high discharge pressure, low substrate temperature, and low flow rate), which enhanced the formation of SiCln (n = 0–2) radicals, is searched by a great deal of measurements and discussions. In the optimum configuration of discharge parameters, we measure the spatial distribution of SiCln (n = 0–2) radicals in the most optimized plasma parameters. The experimental results reveal that Si and SiCl may be the dominant precursors in forming the thin film.

Substitutional nitrogen incorporation through rf glow discharge treatment and subsequent oxygen uptake on vertically aligned carbon nanotubes

By employing polarization- and temperature- dependent near- edge x- ray- absorption fine structure (NEXAFS) studies, we show that vertically aligned carbon nanotubes when subjected to low- pressure radio- frequency (rf) glow discharge can easily be doped with nitrogen atoms at predominantly graphitelike substitutional sites and at the same time preserve their vertical alignment in contrast to commonly used wet chemical functionalization methods. The O K edge NEXAFS spectra and angle- dependent x- ray phoelectron spectroscopy measurements established the presence of a significant amount of oxygen containing functional groups localized at the outer part of the walls. The amount of oxygen adsorbed on the carbon nanotubes is dependent on the introduction of nitrogen sites and exposed edge plane defects generated by plasma N treatment. Thermal gravimetric analysis measurements revealed a lower decomposition temperature for the plasma treated carbon nanotubes, which has its origin in the presence of a large fraction of active sites induced by rf glow discharge plasma treatment that accelerates the oxidation rate of N- doped carbon nanotubes. Our results indicate that rf low- pressure glowdischargemediated doping of nanotubes is a promising route to control the electronic structure of nanotubes and their reactivity due to introduction of active site defects.

Effects of deposition parameters on SiCl n ( n=0–2) densities in SiCl 4 glow discharge plasma

The relative densities of SiCl n ( n=0–2) in SiCl 4 radio frequency (rf) glow discharge plasma are measured by mass spectrometry. The effects of discharge parameters, including rf power, discharge pressure, substrate temperature and SiCl 4 flow rate on the relative densities of SiCl n ( n=0–2) are investigated in detail. The experimental results demonstrate that the relative densities of SiCl n ( n=0–2) in SiCl 4 plasma are dependent strongly on these discharge parameters. An optimum configuration of discharge parameters (low rf power, high discharge pressure, low substrate temperature and low flow rate), which enhanced the formation of SiCl n ( n=0–2) radicals, was searched. Further, researching of SiCl n ( n=0–2) spatial distribution for seeking a suitable deposition condition is beneficial for understanding the deposition mechanism of thin films.