Plasma Source Ion Implantation Research Articles

Double Temperature and Density Phenomenon in Grid Enhanced Plasma Source Ion Implantation for Inner Surface Modification of Tubes

Inner surface coating for tubular samples was realized by the grid enhanced plasma source ion implantation (GEPSII) method. In the GEPSII system, two electrodes, a central rod electrode and a coaxial grid electrode were coaxially assembled inside the tube. Plasma was generated between the electrodes by a radio-frequency (RF) oscillating power source. Plasma then diffused through the grid and realized inner surface ion implantation by a negative high voltage applied to the tube. The plasma was then divided, by the grid, into two regions, namely the source plasma region and the diffused plasma region. The plasma's self-bias between two RF power source electrodes was measured. At the same time, the electron temperature and plasma density in the GEPSII system were measured by a scattering spectrometer. Results showed that the plasma properties of the two regions were entirely different; the plasma self-bias, which might greatly affect the sputtering rate of the central titanium electrode, depended on the electrode structure, gas pressure and RF power.

Tribological behavior of a 20CrMo alloy implanted with nitrogen ions by plasma source ion implantation

A 20CrMo alloy was implanted with nitrogen ions using plasma source ion implantation (PSII), at a dose range of 1.0×1017 to 6.0×1017ionscm−2. Electron Probe Micro-Analysis (EPMA) was used to investigate the depth profile of the implanted layer. Friction and wear tests were carried out on a multi-purpose wear tester. Scanning electron microscopy (SEM) was used to observe the micro-morphology of the worn surface. The results revealed that after being implanted with nitrogen ions, the friction coefficient of the surface layer decreased, and the wear resistance increased with the nitrogen dose. The tribological mechanism was mainly adhesive, and the adhesive wear tended to become weaker oxidative wear with the increase of the nitrogen dose. The effects were mainly attributed to the formation of a hard nitride precipitate and a supersaturated solid solution of nitrogen in the surface layer.

Development of 60 kV, 300 A, 3 kHz Pulsed Power Modulator for Wide Applications

In this paper, a novel pulsed power generator based on IGBT stacks is proposed for wide pulsed power applications. Because it can generate high voltage pulsed output without any step-up transformer or pulse forming network, it has advantages of fast rising time, easiness of pulse width variation, high repetition rate and rectangular pulse shapes. Proposed scheme consists of multiple power stages which were charged parallel from series resonant power inverter. Depending on the number of power stages it can increase maximum voltage up to 60 kV or higher with no limits of power stages. To reduce component for gate power supply, a simple and robust gate drive circuit which delivers gate power and gate signal simultaneously by way of one high voltage cable is proposed. For gating signal and power a full bridge inverter and pulse transformer generates on-ofi signals of IGBT gating with gate power simultaneously and it has very good characteristics of protection of IGBT switches over arcing condition. It can be used for various kinds of pulse power application such as plasma source ion implantation, sterilization, water and gas treatment which requires few kHz pulse repetition rate with few to ten of microseconds pulse width.

Surface modification of ethylene‐vinyl alcohol copolymer treated with plasma source ion implantation

AbstractThe plasma source ion implantation technique was applied to modify the surface of ethylene‐vinyl alcohol (EVOH) film using various working gases. The effects of the treated films were observed on the adhesion efficiency and physical properties. The hydrophobic properties of EVOH films were greatly enhanced after tetrafluoromethane‐plasma source ion implantation (PSII) treatment. On the other hand, the higher hydrophilic properties of EVOH films increased after oxygen‐PSII treatment. The results of X‐ray photoelectron spectroscopy showed that the improved hydrophobic or hydrophilic properties of the film were closely related to the formation of fluorine‐containing functional groups (i.e., CF, CF2, and CF3) or oxygen‐containing functional groups (i.e., CO, CO) on the modified surface. According to the result observed by atomic force microscopy, the surface roughness was not influenced on the change of contact angle. Both the peel strength and oxygen barrier property were improved in the case of CF4+O2‐PSII‐treated EVOH films. As a function of aging time, the properties of modified EVOH surfaces were maintained after PSII treatment using CF4 and O2 at the energy level of −5 kV for 1 min. When using PSII treatment, the properties of the EVOH surface were controlled by working gas and treatment conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Possibility of SOI Fabrication Using Plasma Source Ion Implantation with High-Power Pulsed RF Plasma

Silicon-on-insulator (SOI) structure fabricated by plasma source ion implantation (PSII) with high-power pulsed RF plasma has been studied. Oxygen ions were implanted into p-type silicon wafer and high temperature annealing was subsequently used to form SOI structure. The top silicon and the buried oxide (BOX) layer were formed with 500 Å and 400 Å, respectively, in the sample implanted with the dose of 2.5 × 1017 #/cm2 at the ion energy of -75 kV and annealed at 1350 °C for 30 min in Ar+O2 (0.5 %) ambient. This study showed the possibility of SOI fabrication using the PSII with pulsed ICP source.

Mechanical and electrical properties of diamond-like carbon films deposited by plasma source ion implantation

Diamond-like carbon (DLC) films were prepared by a plasma source ion implantation method with superposed negative pulse and negative DC voltage. Acetylene gas was used as working gas for plasma formation. A negative DC voltage and a negative pulse voltage were superposed and applied to the substrate holder. The DC voltage was changed in the range from 0 to −4.8kV and the pulse voltage was changed from −18 to −13.2kV. The films were annealed in the range of 200–450°C for 1h. The surface morphology of the films and the film thickness were observed by atomic force microscopy and scanning electron microscopy. The film structure was characterized by Raman spectroscopy. The hardness of DLC films was evaluated by an indentation method. Measurement of the electrical resistivity was performed using a four-point probe station. Furthermore, a ball-on-disc test with 2N load was employed to obtain information about the friction properties and sliding wear resistance of the films.The surface of the DLC films was very smooth and featureless. The deposition rate was changed with the DC voltage and pulse conditions. Integrated intensity ratios ID/IG of Raman spectroscopy and electrical resistivity of the DLC films changed with DC voltage. The electrical resistivity decreased with increasing ID/IG ratio. The ID/IG ratio was increased and the electrical resistivity was decreased with annealing temperature owing to graphitization. Very low friction coefficients around 0.05 were obtained for as-deposited films.

Antibacterial metal implant with a TiO2‐conferred photocatalytic bactericidal effect against Staphylococcus aureus

AbstractPhotocatalysis with anatase Titanium dioxide (TiO2) under ultraviolet A (UVA) has a well recognized bactericidal effect. There have been a few reports, however, on the effects of photocatalysis on bio‐implant‐related infections. The purpose of present study was to evaluate the photocatalytic bactericidal effects of anatase TiO2 on Staphylococcus aureus (S. aureus) associated with surgical site infections.TiO2 films were synthesized on commercially pure titanium substrates and SUS316 stainless steel using a plasma source ion implantation method followed by annealing. The chemical composition of the surface layers was determined using GXRD and XPS. The disks were seeded with cultured S. aureus and exposed to UVA illumination from black light. The bactericidal effect of the TiO2 films was evaluated by counting the survived colonies statistically.A structural gradient anatase type TiO2 layer formed on all substrates. The viability of the bacteria on the photocatalytic TiO2 film coated on titanium was suppressed to 7.0% at 30 minutes and 5.5% at 45 minutes, whereas that on a similarly coated stainless steel was suppressed to 45.8% at 30 minute and 28.6% at 45 minutes (ANOVA: p < 0.05). Complete bacterial inactivation was achieved after 90 minutes on titanium and after 60 minutes on stainless steel. The photocatalytic bactericidal effect of TiO2 is useful for sterilizing the contaminated surfaces of bioimplants. Copyright © 2008 John Wiley & Sons, Ltd.

Carbon‐ion implantation improves the tribological properties of CoCrMo alloy against ultra‐high molecular weight polyethylene

AbstractAmorphous diamond‐like carbon (DLC) has drawn a great deal of attention for its superior wear properties against ultra‐high molecular weight polyethylene (UHMWPE). Its rate of wear, however, is not necessarily maintained within a specific range. The aim of this study was to evaluate the mechanical features and tribological properties of three types of surfaces: (i) uncoated, (ii) carbon‐ion implantation (CII)‐treated, and (iii) DLC‐film‐coated substrate. The surface alterations were carried out on cobalt–chrome (CoCrMo) alloy by the plasma‐source ion implantation (PSII) method. The wear properties and friction coefficient were estimated by a pin‐on‐plate wear‐tester. We found, as a result, that the implanted carbon penetrated the substrates in which good adhesion was expected. Though the surface modifications by CII and DLC hardened the surfaces, the surface with DLC was also roughened (Ra = 39 nm). In contrast, the surface modified by CII had a very smooth surface (Ra = 15 nm) and low friction coefficient (ranging from 0.15 to 0.20), resulting in a low rate of wear. Our findings suggest that CII on the CoCrMo alloy/UHMWPE pair offers potential benefits as a hard coating for artificial total‐joint arthroplasty. Copyright © 2008 John Wiley & Sons, Ltd.

Modification of wetting properties of CR39 by plasma source ion implantation

Plasma source ion implantation (PSII), a hybrid implantation technique between ion beams and immersion plasmas has been used to modify CR39 surfaces for improved wettability providing both advancing ( θ a ) and receding ( θ r ) contact angles below 5 ° . The modifications brought to the polymer surface structure have been characterized by X-ray photoelectron spectroscopy (XPS) and its combination with chemical derivatization (CD-XPS). Oxygen desorption has been observed in spite of the very hydrophilic surfaces. C 1s XPS peak has been displaced toward greater energies, while the opposite has been found for O 1s, both involving new components and strong modifications after ion implantation treatment. Strong evidences about the formation of new chemical functions, like OOH, COOH and C C, have been found and have provided an explanation for the increased wettability.

Surface-engineered metal-on-metal bearings improve the friction and wear properties of local area contact in total joint arthroplasty

Metal-on-metal articulating total joint arthroplasty has the potential to eliminate polyethylene-wear-induced osteolysis and aseptic loosening around the prosthesis. Metal surface coatings, however, are subject to delamination in areas of local contact. Various studies have been conducted to reduce metal wear debris and corrosion by introducing surface treatments. In this study we applied carbon ion implantation (CII) and diamond-like carbon (DLC) films to a cobalt-chrome alloy substrate by plasma source ion implantation. Once the films were prepared, we put them through simple geometry wear tests under high contact pressure (an average load of 1030 MPa) to establish the tribological properties during the phase of local contact that leads to severely increased wear in total joint arthroplasty. The CII-coated bearings showed less wear, lower friction coefficients, and higher resistance to catastrophic damage compared to uncoated Co–Cr alloy and DLC couples, even under high contact pressure. The CII-coated surface offers potential advantages as a hard coating for articulating joints.

Photo‐induced hydrophilicity enhances initial cell behavior and early bone apposition

The anatase form of titanium dioxide (TiO(2)) exhibits photo-induced hydrophilicity when it is irradiated with ultraviolet (UV) light. In the present study, the effect of photo-induced hydrophilicity on initial cell behavior and bone formation was evaluated. Plasma source ion implantation method and post-annealing were employed for coating the anatase form of TiO(2) to the surface of the titanium disk and implant. Half of the disks and implants were illuminated with UV for 24 h beforehand, whereas the other halves were blinded and used as controls. Photo-induced hydrophilicity was confirmed by a static wettability assay. The effects of this hydrophilicity on cell behavior were evaluated by means of cell attachment, proliferation and morphology using pluripotent mesenchymal precursor C2C12 cells. Thereafter, bone formation around the hydrophilic implant inserted in the rabbit tibia was confirmed histomorphometrically. The water contact angle of the photo-induced hydrophilic disk decreased markedly from 43.5 degrees to 0.5 degree. Cell attachment and proliferation on this hydrophilic disk showed significant improvement. The cell morphology on this hydrophilic disk was extremely flattened, with an elongation of the lamellipodia, whereas a round/spherical morphology was observed on the control disk. The photo-induced hydrophilic implant enhanced the bone formation with the bone-to-metal contact of 28.2% after 2 weeks of healing (control: 17.97%). The photo-induced hydrophilic surface used in the current study improves the initial cell reactions and enhances early bone apposition to the implant.

Self-consistent circuit model for plasma source ion implantation

A self-consistent circuit model which can describe the dynamic behavior of the entire pulsed system for plasma source ion implantation has been developed and verified with experiments. In the circuit model, one-dimensional fluid equations of plasma sheath have been numerically solved with self-consistent boundary conditions from the external circuit model including the pulsed power system. Experiments have been conducted by applying negative, high-voltage pulses up to -10 kV with a capacitor-based pulse modulator to the planar target in contact with low-pressure argon plasma produced by radio-frequency power at 13.56 MHz. The measured pulse voltage and current waveforms as well as the sheath motion have shown good agreements with the simulation results.

Two-dimensional particle-in-cell simulation of the ion sheath dynamics in plasma source ion implantation of a hemispherical bowl-shaped target

Plasma source ion implantation into a hemispherical bowl-shaped target is simulated by the two-dimensional particle-in-cell method. The numerical procedure is based on solving the Poisson's equation on a grid and tracing the movement of the ions through the grid. The potential and the ion density distributions in the sheath are studied in detail and the trajectories and dynamic states of ions are considered. The implantation dose and impact angle of the ions at different parts of the target surface are obtained. The ion focusing effect due to the nonuniformity of the sheath potential near the brim of the vessel is observed. The results presented here show that the ion focusing causes the nonuniformity of dose on the target surface.

Effect of R.F. Power on Structures and Properties of Amorphous Fluorinated Carbon Films Prepared by PSII

Fluorinated amorphous carbon films (a-C:H:F) were deposited by plasma source ion implantation (PSII) with precursor gas of CH2FCF3 + C2H2 + H2 with various radio frequency (r.f.) power. Structures and properties evolution varied with r.f. power was discussed in detail. X-ray photoelectron spectroscopy (XPS), Raman spectrum, X-Ray reflection(XRR), atomic force microscopy (AFM) were used to analyze composition, chemical state, sp2 cluster structure, density and surface morphology of prepared films. Nano-indentation test was used to get hardness and modulus. The results show that with the increase of r.f. power, the size and amount of sp2 cluster increase, so does the surface roughness; however, the density and the hardness of films decrease.

High Voltage Pulsed Power Supply Using IGBT Stacks

High voltage pulsed power supply using IGBT (insulated gate bipolar transistor) stacks and pulse transformer for plasma source ion implantation is proposed. To increase voltage rating, twelve IGBTs are used in series at each IGBT stack and a step-up pulse transformer is utilized. To increase the current rating, the proposed system makes use of synchronized three pulse generator modules composed of diodes, capacitors and IGBT stacks. The proposed pulsed power supply uses semiconductor switches as main switches. Hence, the system is compact, and has semi-infinite lifetime. In addition, it has high flexibility in parameters such as voltage magnitude (10-60 kV), pulse repetition rate (PRR) (10-2000 pps), and pulse width (2-5 muS).

Preparation and properties of W-containing diamond-like carbon films by magnetron plasma source ion implantation

W-containing diamond-like carbon (DLC) films were prepared on silicon wafers by a process combining reactive magnetron sputtering with plasma source ion implantation (PSII). A tungsten disc was used as a target for the sputter source. Ar/C 2H 2 mixed gas was introduced into the discharge chamber. Superposed negative high voltage pulses (− 10 kV, 100 Hz, 100 μs and DC − 0.5 kV) were applied to the substrate holder. The chemical composition of the films was determined using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Surface morphology was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The film structure was characterized by Raman spectroscopy, X-ray diffractometry and high resolution transmission electron microscopy (HREM). Sheet resistivity of the films was measured by a four-point probe method. Furthermore, a ball-on-disc test was employed to obtain information about the frictional properties and sliding wear resistance of the films. The structure of the films changed from metal-containing DLC to a composite of metal-containing DLC and metal carbides with increasing metal content in the films. WC 1− X carbides were observed for films composed of higher amounts of W than 20 at.%. Around 10 nm diameter nanocrystallites of WC 1− X were observed by HREM. The sheet resistivity of the films decreased drastically with increasing metal content in the films. The tribological properties of the films were improved by metal element doping. A low friction coefficient 0.09 was derived for 0.5 at.% W-containing DLC film.

REMOVED: Ion kinetics in low-pressure magnetic collisional plasma source ion implantation

REMOVED: Ion kinetics in low-pressure magnetic collisional plasma source ion implantation

Numerical analysis of ion-implantation in target with a rectangular groove

Ion dynamics of pulsed plasma sheath during the plasma source ion-implantation (PSII) affects the resultant surface properties and structures. In this work, a two-dimensional fluid model is applied to the problem of computing ion dynamics in the sheath of a target with a rectangular groove. The evolution of sheath edge, x and y components of ion velocity on the target surface are simulated to describe the physics of sheath in PSII.

Influences of acetylene gas flow rate on mechanical properties and chemical structure of nanocomposite TiC diamond-like carbon films

Nanocomposite TiC diamond-like carbon (DLC) films were prepared on silicon (100) wafer and Ti alloy samples by reactive magnetron sputtering combining with plasma source ion implantation. The hardness of the films was evaluated using nanoindentation. Micro-nick was employed to investigate the critical loading of the films. X-ray photoelectron spectroscopy and X-ray diffraction were used to analyze the chemical structure of the DLC films containing Ti. The results showed that changing acetylene gas flow rate could control Ti concentration in the films. Many nanometer TiC crystalline grains and nanocomposite TiC/DLC structure were formed by choosing proper C and Ti ratio, and the mechanical properties of the films were distinctly improved. In addition, ion implantation formed the transition layer which enhanced the adherence of the films.

Axial property of the inner surface of a metal tube processed by GEPSII

As a novel inner surface processing method, grid enhanced plasma source ion implantation (GEPSII) method can realize uniform inner surface ion implantation of a metal tube and metal binary compound can be produced. In the experiment, three 0.45% carbon steel (45-steel) work pieces were axially put on the inner surface of the tube, and golden titanium nitride (TiN) films were produced on the work pieces by GPSII. Structure analysis shows that the TiN films have the preferred crystal faces (111) and (200), and the depth of the films is about 20 nm with partial embedding in the substrate. Analysis on the electrochemistry corrosion, hardness and friction of the work pieces indicates that the surface property of the 45-steel has been greatly improved by the protective TiN film, and very good axial uniformity has been obtained.