Glow Discharge Conditions Research Articles

Preparation of plasma poly(1-isoquinolinecarbonitrile) thin film and its ultrafast nonlinear optical property

How to get a uniform, defect-free, and reproducible conjugated polymer thin films is now becoming the main fabrication problem for the practical application of these materials as the fast switches and modulators in opto-electronic devices. In this research, a novel plasma-polymerized 1-isoquinolinecarbonitrile (PPIQCN) thin film was prepared by plasma polymerization under different glow discharge conditions. The effect of the discharge power on the chemical structure and surface compositions of the deposited PPIQCN films was investigated by Fourier transform infrared (FTIR), UV-Visible absorption spectra and X-ray photoelectron spectroscopy (XPS). The results show that a high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained when a low discharge power of 10 W was used during film formation. In the case of higher discharge power of 30 W, more severe monomer molecular fragmentation can be observed, which results in a decrease in the effective conjugation length of PPIQCN film. The morphology characterized by atomic force microscopy (AFM) indicates that a fine, homogenous PPIQCN film could be obtained under a relatively low discharge power. A femtosecond time-resolved optical Kerr effect technique at a wavelength of 820 nm has been applied to investigate the third-order nonlinearity of the plasma PPIQCN film. For the first time, a non-resonant optical Kerr effect and ultrafast response of the PPIQCN film was observed.

AFM of titanium nitride layers prepared under glow discharge conditions

Optimization of titanium-based materials for medical application is a complex task linking specialists in various disciplines. This is a consequence of a system of self-dependent critical conditions required for their application. It is well known that majority of processes proceeding in the human body occur at surfaces and interfaces. Hence the knowledge concerning surfaces of the applied materials is essential for understanding the occurred processes and for optimization of the applied material. In this paper the atomic force microscopy was applied for investigation of the surface topography of nitrided layers of titanium alloys in a nano and mezoscopic scale. Topography of layers nitrided at temperatures: 730, 850 and 1000 °C were compared. Results indicate that the size and distribution of the grains structure formed during nitriding processes strongly depends on the preparation temperature. This observation is related with the differences in chemical composition. The most appropriate temperature from the point of view of surface homogeneity is 850 °C. This conclusion correspond with the results of biological investigations which showed that layer of titanium nitride prepared at this temperature is characterized by the maximal biocompatibility [E. Czarnowska, T. Wierzchoń, A. Maranda-Niedbała, E. Kaczmarewicz, J. Mater. Sci.: Mater. Med. 11 (2000) 1].

Three-chamber low-output-pressure glow-discharge-based plasma generator as a negatively charged ion source

A stationary glow discharge initiated in a two-chamber inverted gas magnetron is studied. In the third (emission) chamber, such a discharge system generates a plasma that can be subdivided into two, circumferential and near-axis, regions with considerably differing parameters and also provides a pressure difference in desired areas. It is concluded that the device suggested could be used as an efficient continuous-mode plasma generator making it possible to produce negatively charged gas ions. The results obtained may serve as a basis for negative ion source design optimization.

Response of Human Osteoblast-Like Cells and Fibroblasts to Titanium Alloy Nitrided under Glow Discharge Conditions

Cell adhesion to biomaterials and cell proliferation are affected, among others, by the chemical composition and surface microtopography of the biomaterial. These are, in turn, influenced by sterilisation processes. The aim of this study was to evaluate the sensitivity of osteoblasts and fibroblasts to TiN surfaces deprived of an oxide film or with an enhanced oxide film due to sterilisation in plasma or in an autoclave, respectively. Type TiN+T2N+aTi(N) nitrided surface layers were produced under glow discharge conditions and sterilized in plasma Sterrad 100 and in a steam autoclave. The results provide evidence that nitrided surface layers improved wearand corrosion resistance of the titanium alloy and that these features were not influenced by sterilisation procedures that resulted in various oxide films. In vitro study of human fibroblast and osteoblast-like cells cultured on TiN surfaces modified by sterilisation processes showed that cells respond to the presence of an enhanced oxide film by aggregating, exhibiting lower viability and increased apoptosis, while to a surface deprived of oxides, by regular spreading and high viability. It can be concluded that differences in surface composition and topography of the nitrided surface layers due to various types of sterilisation elicit specific cell responses, and plasma sterilisation seems to be optimal for bone implants with this surface layer.

Development of NSTX particle control techniques

Density control in NSTX, involves primarily controlling impurity influxes and recycling. We have compared boronization on hot and cold surfaces, varying helium glow discharge conditioning (HeGDC) durations, helium discharge cleaning, brief daily boronization, and between discharge boronization to reduce and control spontaneous density rises. Access to Ohmic H-modes was enabled by boronization on hot surfaces, however, the duration of the effectiveness of hot and cold boronization was comparable. A 15min HeGDC between discharges was needed for reproducible L–H transitions. He discharge conditioning yielded slower density rises than 15min of HeGDC. Brief daily boronization followed by a comparable duration of applied HeGDC restored and enhanced good conditions. Additional brief boronizations between discharges did not improve plasma performance, if conditions were already good. Between discharge boronization required increases in the NSTX duty cycle due to the need for additional HeGDC to remove codeposited D.

Preparation, characterization and electronic and optical properties of plasma-polymerized nitriles

Conjugated polymers are among the most promising organic materials for optoelectronic devices. In such applications, the main fabrication challenge is to get uniform, defect-free and reproducible thin films of these materials. In this research, a series of novel plasma-polymerized 4-cyanopyridine (PPCPD) thin films of desired thickness were prepared through plasma polymerization under different glow discharge conditions. They were transparent, pinhole-free and uniform. The effect of the discharge power on the chemical structure and surface compositions of the plasma-polymerized 4-cyanopyridine (PPCPD) films was investigated by Fourier transform infrared (FTIR), UV-visible absorption spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS) and the deposition rate measurements. A high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained when a low discharge power of 3 to 10 W was used during film formation. A red shift in the maximum absorption wavelength ( λ max) for all the plasma-deposited films was observed as compared with the monomer absorption spectrum. The atomic force microscopy (AFM) measurement shows that the PPCPD film with quite smooth surface could be grown under a relatively low discharge power.

Ultrafast third-order optical nonlinearity of polycyanopyridine

A novel plasma-polymerized 4-cyanopyridine (PP4CPD) thin film of desired thickness was prepared by plasma polymerization under different glow discharge conditions. The effect of the discharge power on the chemical structure and surface compositions of the PP4CPD films was investigated by FT-IR, UV–Vis and X-ray photoelectron spectroscopy (XPS). A high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained at a low discharge power. A red shift in the maximum absorption wavelength ( λ max) for PP4CPD films was observed as compared with the monomer absorption spectrum. The atomic force microscopy (AFM) measurement shows that the PP4CPD film with quite a smooth surface could be grown under a relatively low discharge power. A femtosecond time-resolved optical Kerr effect (OKE) technique has been applied to investigate the third-order nonlinearity of the plasma PP4CPD film. For the first time, a non-resonant optical Kerr effect and ultrafast response of polycyanopyridine was observed.

Material probe analysis for plasma facing surface in the Large Helical Device

Material probes have been installed at the inner walls along the poloidal direction in large helical device (LHD) from the first experimental campaign. After each campaign, the impurity deposition and the gas retention have been examined to study the plasma surface interaction and the degree of wall cleaning. In the 2nd campaign, the entire wall was thoroughly cleaned by glow discharge conditioning and the number of main discharge shots increased. For the 3rd and 4th campaigns, graphite tiles were installed over the entire divertor strike region, and then the wall condition was significantly changed compared with the case of a stainless steel (SS) wall. It was seen that graphite tiles in the divertor were eroded mainly during main discharges, and the SS first wall mainly during glow discharges. During main discharges the eroded carbon was deposited on the entire wall. A reduction of metal impurities in the plasma was observed, which corresponds to the carbonized wall. The deposition thickness was great at the wall far from the plasma. Since the entire wall was carbonized, the amount of discharge gases retained such as H and He became large. In particular, helium retention was large at a position close to the anodes used for helium glow discharge cleanings. One characteristic of the LHD wall is a large retention of helium since the wall temperature is limited to below 368 K. In order to reduce the recycling of the discharge gas, wall heating is necessary.

Simulation and Characteristic Measurement with Sputtering Conditions of Triode Magnetron Sputter

An rf triode magnetron sputtering system is designed and installed its construction in vacuum chamber. In order to calibrate the rf triode magnetron sputtering for thin films deposition processes, the effects of different glow discharge conditions were investigated in terms of the deposition rate measurements. The basic parameters for calibrating experiment in this sputtering system are rf power input, gas pressure, plasma current, and target-to-substrate distance. Because a knowledge of the deposition rate is necessary to control film thickness and to evaluate optimal conditions which are an important consideration in preparing better thin films, the deposition rates of copper as a testing material under the various sputtering conditions are investigated. Furthermore, a triode sputtering system designed in our team is simulated by the SIMION program. As a result, it is sure that the simulation of electron trajectories in the sputtering system is confined directly above the target surface by the force of E<TEX>${\times}$</TEX>B field. Finally, some teats with the above 4 different sputtering conditions demonstrate that the deposition rate of rf triode magnetron sputtering is relatively higher than that of the conventional sputtering system. This means that the higher deposition rate is probably caused by a high ion density in the triode and magnetron system. The erosion area of target surface bombarded by Ar ion is sputtered widely on the whole target except on both magnet sides. Therefore, the designed rf triode magnetron sputtering is a powerful deposition system.

The effects of HEMA-monomer and air atmosphere treatment of glass fibre on the transverse strength of a provisional fixed partial denture resin.

This study focused on some mechanical properties such as the transverse strength, the maximal deflection, and the modulus of elasticity of resin reinforced with two different types of agents-treated and with untreated glass fibre, and without fibre. A Teflon mould was used to prepare six groups of specimens. Two different types of chemical modification agents, hydroxyethyl-methacrylate (HEMA)-monomer and air atmosphere were applied to create hydrophilic surfaces on the glass fibres. The flow rate was kept at two different levels, 25 and 60 mL min-1. The discharge powers of the surface treatment process were 15 or 20 W. The fibres were exposed to glow discharge conditions for the periods of 10 or 15 min. Without fibre specimens were the control group. The provisional resin was same in all groups. All the specimens were subjected to transverse testing with a cross-head speed of 5 mm min-1. The three-point load test was used to record the load of the fracture for each specimens. The Kruskal-Wallis analysis of variance was used to compare the transverse strength, the maximal deflection and the modulus of elasticity. The differences in the transverse strength and the maximal deflection between the six groups were found statistically significant but the modulus of elasticity was not statistically significant. The transverse strength of HEMA-monomer (group A) was shown the highest value (66.3 MPa). For without-fibre group, the value was 52.9 MPa. This difference was statistically significant when the Mann-Whitney U-test was used for comparing. Repairing or remaking provisional restorations can be a time-consuming endeavour. The added strength of the polymethyl methacrylate with the fibre can reduce clinical failures of provisional fixed partial dentures. The surface treatment process was increased the transverse strength and the maximal deflection. The clinical implication of chemical modification agents-coated fibres is reduced incidence of fixed provisional restoration failure.

Atom-bombardment-induced electron emission from a cathode in a glow discharge: Example of an open discharge

An analysis of the glow discharge conditions shows that processes involved in this phenomenon should be described in terms of the electron emission coefficients γ determined in a technical (γt) rather than in an ultrahigh vacuum. The results of calculations of the electron beam formation efficiency η in a glow discharge, performed using the γt values, agree well with the experimentally measured efficiencies. Further refinement of these calculations is inexpedient because of unavoidable uncertainty of the γ values under real discharge conditions.

Electroless Plating of Copper on Fluorinated Polyimide Films Modified by Plasma Graft Copolymerization and UV‐induced Graft Copolymerization with 4‐Vinylpyridine

AbstractSurface modification of two types of fluorinated polyimide (FPI) films, either by plasma polymerization and deposition of 4‐vinylpyridine (4VP) or by UV‐induced graft copolymerization with 4VP under atmospheric conditions, was carried out for adhesion enhancement with the electrolessly deposited copper. X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) results revealed that the pyridine groups in the plasma polymerized 4VP (pp‐4VP) layer could be preserved to a large extent under proper glow discharge conditions. The grafted 4VP layer with well‐preserved pyridine groups was used not only as the chemisorption sites for the palladium complexes (without the need for prior sensitization by SnCl2) during the electroless plating of copper, but also as an adhesion promotion layer for the electrolessly deposited copper. The T‐peel adhesion strength of the electrolessly deposited copper with both the 4VP plasma‐polymerized FPI (pp‐4VP‐FPI) film and the 4VP graft‐copolymerized FPI (4VP‐g‐FPI) film was much higher than that of the electrolessly deposited copper with the pristine or the Ar plasma‐treated FPI films. The high adhesion strength between the electrolessly deposited copper and the surface‐modified FPI film was attributed to the fact that the plasma‐polymerized and the UV graft‐copolymerized 4VP chains were covalently tethered on the FPI surfaces, as well as the fact that these grafted 4VP polymer chains were spatially and reactively distributed into the copper matrix. magnified image

Plasma polymerization and deposition of linear, cyclic and aromatic fluorocarbons on (100)-oriented single crystal silicon substrates

Fluoropolymer films were deposited on the Ar plasma-pretreated Si(100) surfaces by plasma polymerization of perfluorohexane (PFH, a linear fluorocarbon), perfluoro(methylcyclohexane) (MCH, a cyclic fluorocarbon), and hexafluorobenzene (HFB, an aromatic fluorocarbon) under different glow discharge conditions. The effects of the radio-frequency plasma power on the chemical composition and structure of the plasma-polymerized fluoropolymer films were studied by x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, time-of-flight secondary ion mass spectrometry, and water contact angle measurements. The changes in structure and composition of the three types of the plasma-deposited films from those of the respective fluorocarbons were compared. Under similar glow discharge conditions: (i) the extent of defluorination was highest for the PFH polymer, (ii) the deposition rate was highest for the HFB polymer, (iii) the cyclic structure of MCH was less well preserved than the aromatic structure of HFB, (iv) aliphatic structures appeared in the plasma-deposited MCH polymer, and (v) the plasma-polymerized HFB has the highest thermal stability due to the preservation of the aromatic rings. The adhesive tape peel test results revealed that the plasma-polymerized and deposited fluoropolymer layers were strongly bonded to the Ar plasma-pretreated Si(100) surfaces.

Electroless Plating of Copper on (100)-Oriented Single Crystal Silicon Substrates Modified by Plasma Graft Polymerization of 4-Vinylpyridine

Plasma graft polymerization of 4-vinylpyridine (4VP) on Ar plasma-pretreated Si(100) surfaces was carried out. The plasma graft-polymerized 4VP films (pp-4VP films) were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). XPS and FTIR results revealed that the pyridine functional groups of the grafted pp-4VP films could be retained, to a certain extent, under proper glow discharge conditions, such as a low input radio frequency power. AFM images revealed that the pp-4VP-grafted Si(100) (pp-4VP-Si) surfaces remained relatively smooth. The grafted pp-4VP film on the Si(100) surface was used not only as the chemisorption sites for the palladium complexes (without the need for prior sensitization by during the electroless plating of copper, but also as an adhesion promotion layer for the electrolessly deposited copper. The electrolessly deposited copper on the pp-4VP-Si surface exhibited a 180°-peel adhesion strength above 5 N/cm. The adhesion strength was attributed to the strong interaction of the pyridine functional groups of the pp-4VP layer with palladium and copper, the spatial distribution of the pp-4VP chains on the Si(100) surface and into the metal matrix, and the fact that the pp-4VP chains were covalently tethered on the Si(100) surface. © 2002 The Electrochemical Society. All rights reserved.

Electroless plating of copper on polyimide films modified by plasma graft copolymerization with 4-vinylpyridine

Surface modification of argon plasma-pretreated polyimide (PI, Kapton® HN) films by plasma graft copolymerization with 4-vinylpyridine (4VP) was carried out. The effects of glow discharge conditions on the chemical composition and structure of the plasma-polymerized 4VP (pp-4VP) films were analyzed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy, respectively. The XPS and FTIR results revealed that the pyridine groups in the pp-4VP layer could be preserved to a large extent under proper glow discharge condition. The topography of the modified PI surface was investigated by atomic force microscopy (AFM). The pp-4VP film with well-preserved pyridine groups was used not only as the chemisorption sites for the palladium complexes (without the need for prior sensitization by SnCl2) during the electroless plating of copper, but also as an adhesion promotion layer to enhance the adhesion of the electrolessly deposited copper with the PI film. The T-peel adhesion strength of the electrolessly deposited copper to the pp-4VP grafted PI (pp-4VP-PI) film could reach about 7 N/cm. This adhesion strength was much higher than that of the electrolessly deposited copper to the pristine or the Ar plasma-treated PI film.

Plasma immersion ion implantation based on glow discharge with electrostatic confinement of electrons

A new approach to plasma immersion ion implantation (PIII) is presented featuring glow discharge with electrostatic confinement of electrons being used for plasma generation. Its obvious advantage is a comparatively low cost price of related equipment capable to establish at gas pressures of 10 −5–10 −2 mbar in the working chamber volume of several liters up to dozens cubic meters dense and homogeneous plasma. Any vacuum chamber made of conductive material may be used as an electrostatic trap for plasma electrons and a DC power supply is well enough to maintain the discharge. Theoretical and experimental results reveal dependence of stationary glow discharge on electron losses and reduction of anode-to-chamber voltage under the influence of energetic electrons emitted from the surface of negatively biased substrate. Plasma density growth rate depends on amplitudes of high voltage pulses applied to the substrate and to the plasma. Two variants of PIII-systems are described. In the first system plasma ‘on duty’ is established with stationary discharge and negative high voltage pulses applied to the substrate, give rise to high current pulses in its circuit. In the second system two high voltage pulses of equal amplitude are being simultaneously applied to the substrate (negative pulse) and to the plasma (positive pulse). Energy of electrons bombarding the chamber walls and the anode of the second system is two times lower than the energy of singly charged ions bombarding the substrate. Practically, the second system ensures 1 order of magnitude reduction of X-ray yield, thus improving the safety.

Plasma polymerization of allylpentafluorobenzene on copper surfaces

Fluoropolymer films were deposited on pristine and N2 plasma-pretreated copper foil surfaces by plasma polymerization of allylpentafluorobenzene (APFB) under different glow discharge conditions and using argon as the carrier gas. The effect of the radio-frequency (RF) plasma power on the surface composition and chemical structure of the plasma-polymerized APFB (pp-APFB) films was studied by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and water contact angle measurements. The XPS, ToF-SIMS and FTIR results suggested that the fluorinated aromatic structure in the deposited polymer films had been preserved to various extents, depending on the input RF power used for the plasma polymerization. The roughness of the APFB plasma-polymerized copper (pp-APFB-Cu) surface increased substantially with the RF power, as revealed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Ultra-hydrophobic pp-APFB-Cu surfaces with water contact angles greater than 140° were obtained at RF powers above 50 W. The solvent extraction and the Scotch® tape peel test results revealed that the pp-APFB layers were strongly bonded to the N2 plasma-pretreated copper surfaces.

Electroless Deposition of Copper on Poly(tetrafluoroethylene) Films Modified by Plasma-Induced Surface Grafting of Poly(4-vinylpyridine)

Argon plasma-pretreated poly(tetrafluoroethylene) (PTFE) films were solution coated with a thin layer of poly(4-vinyl pyridine) (P4VP). Subsequent exposure of the films to argon plasma resulted in the grafting of P4VP on the PTFE films. Electroless plating of copper could be carried out effectively on the P4VP-grafted PTFE (P4VP-g-PTFE) surface after PdCl2 activation and in the absence of SnCl2 sensitization (the Sn-free process). The catalytic processes of the electroless plating of copper in the presence and absence of sensitization by SnCl2 were also compared. The effect of glow discharge conditions on the P4VP concentration and the adhesion strength of the electrolessly deposited copper was investigated. The T-peel adhesion strength of the electrolessly deposited copper with the graft-modified PTFE film was improved in the absence of SnCl2 sensitization and could reach about 3 N/cm. PdCl2 activation and electroless deposition of copper could not be carried out on the pristine or the Ar plasma-treated PTFE surface in the absence of prior sensitization by SnCl2. X-ray photoelectron spectroscopic (XPS) analysis revealed that the electrolessly deposited copper delaminated from the P4VP-g-PTFE film by cohesive failure inside the PTFE film.

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

AbstractThin 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 &amp; Sons, Ltd.

Characterization and conditioning of SSPX plasma facing surfaces

The Sustained Spheromak Physics Experiment (SSPX) will examine the confinement properties of spheromak plasmas sustained by DC helicity injection. Understanding the plasma-surface interactions is an important component of the experimental program since the spheromak plasma is in close contact with a stabilizing wall (flux conserver) and is maintained by a high current discharge in the coaxial injector region. Peak electron temperatures in the range of 400 eV are expected, so the copper plasma facing surfaces in SSPX have been coated with tungsten to minimize sputtering and plasma contamination. Here, we report on the characterization and conditioning of these surfaces used for the initial studies of spheromak formation in SSPX. The high pressure plasma-sprayed tungsten facing the SSPX plasma was characterized in situ using β-backscattering and ex situ using laboratory measurements on similarly prepared samples. Measurements showed that water can be desorbed effectively through baking while the removal rates of volatile impurity gases during glow discharge and shot conditioning indicated a large source of carbon and oxygen in the porous coating.