ION HEATING PROCESS DURING PLASMA IMMERSION ION IMPLANTATION

The research on plasma immersion ion implantation has been conducted for a little over ten years. Much is needed to investigate including processing technlogy, plasma sheath dynamics, interaction of plasma and surface, etc. Of the processing methods elavated temperature technique is usually used in PIII to produce a thick modified layer by means of the thermal diffusion. Meanwhile plasma ion heating is more recently developed by Ronghua Wei et al[1]. Therefore the temeperature is a critical parameter in plasma ion processing. In this paper we present the theoretical model and analysize the effect of imlantation voltage, plasma density, ion mass,etc on the temperature rise.

TWO-DIMENSIONAL NUMERICAL ANALYSIS OF PLASMA IMMERSION ION IMPLANTATION OF CYLINDRICAL BORES

Plasma immersion ion implantation (PIII), unrestricted by sight-light process, is considered a proper method for inner surface strengthening. Two-dimensional simulation oj inner surface PIII process of cylindrical bores were carried out in this paper using cold plasma fluid model, and influence of the bore's dimension on impact energy, retained dose and uniformity of inner surface were investigated.

Structure and Tribological Property of TiBN Nanocomposite Multilayer Synthesized by Ti-BN Composite Cathode Plasma Immersion Ion Implantation and Deposition

A Ti-BN complex cathode is made from Ti and h-BN powders by the powder metallurgy technology, and TiBN coating is obtained by plasma immersion ion implantation and deposition with this Ti-BN composite cathode. The TiBN coating shows a self-forming multilayered nanocomposite structure while with relative uniform elemental distributions. High resolution transmission electron microscopy images reveal that the multilayered structure is derived from different grain sizes in the nanocomposite. Due to the existence of h-BN phase, the friction coefficient of the coating is about 0.25.

Realization of conformal doping on multicrystalline silicon solar cells and black silicon solar cells by plasma immersion ion implantation

Emitted multi-crystalline silicon and black silicon solar cells are conformal doped by ion implantation using the plasma immersion ion implantation （PⅢ） technique. The non-uniformity of emitter doping is lower than 5 %. The secondary ion mass spectrometer profile indicates that the PⅢ technique obtained 100-rim shallow emitter and the emitter depth could be impelled by furnace annealing to 220 nm and 330 nm at 850 ℃ with one and two hours, respectively. Furnace annealing at 850 ℃ could effectively electrically activate the dopants in the silicon. The efficiency of the black silicon solar cell is 14.84% higher than that of the mc-silicon solar cell due to more incident light being absorbed.

Effect of Yttrium Pre-Implantation on Implantation Behavior of Ti-6Al-4V Alloy in Nitrogen Plasma Immersion Ion Implantation

In order to increase the peak depth of nitrogen atoms during the nitrogen plasma immersion ion implantation of Ti-6Al-4V alloy, the rare earth metal yttrium was applied. In the experiment, yttrium and nitrogen ions were implanted under the voltage of 20 and 30 kV, respectively. In the samples with yttrium pre-implantation for 30 min, the Anger electron spectroscopy (AES) analysis shows that the peak depth of the nitrogen atoms increases from 50 up to 100 nm. It can also be seen from the tribological tests that the wear resistance of these samples is increased remarkably.

Work Function Enhancement of Indium Tin Oxide via Oxygen Plasma Immersion Ion Implantation

Indium tin oxide （ITO） transparent conducting film was treated with oxygen plasma immersion ion implantation （PIII）. X-ray photoelectron spectroscopy （XPS） was employed to characterize the effect. The results suggested that the oxygen content in the surface was increased and maintained for more than 50 h compared with traditional plasma-treated samples. Meanwhile, the work function of ITO estimated by comparing the peak shift in the XPS diagram suggested a corresponding increase by more than 1 eV.

Development and experimental study of large size composite plasma immersion ion implantation device

Plasma immersion ion implantation （PI） overcomes the direct exposure limit of traditional beam- line ion implantation, and is suitable for the treatment of complex work-piece with large size. Pm technology is often used for surface modification of metal, plastics and ceramics. Based on the requirement of surface modification of large size insulating material, a composite full-directional PHI device based on RF plasma source and metal plasma source is developed in this paper. This device can not only realize gas ion implantation, but also can realize metal ion implantation, and can also realize gas ion mixing with metal ions injection. This device has two metal plasma sources and each metal source contains three cathodes. Under the condition of keeping the vacuum unchanged, the cathode can be switched freely. The volume of the vacuum chamber is about 0.94 m3, and maximum vacuum degree is about 5 x10-4 Pa. The density of RF plasma in homogeneous region is about 109 cm-3, and plasma density in the ion implantation region is about 101x cm-3. This device can be used for large-size sample material PHI treatment, the maximum size of the sample diameter up to 400 mm. The experimental results show that the plasma discharge in the device is stable and can run for a long time. It is suitable for surface treatment of insulating materials.

Fluid simulation of the pulsed bias effect on inductively coupled nitrogen discharges for low-voltage plasma immersion ion implantation

Planar radio frequency inductively coupled plasmas（ICP） are employed for low-voltage ion implantation processes,with capacitive pulse biasing of the substrate for modulation of the ion energy. In this work, a two-dimensional（2D） selfconsistent fluid model has been employed to investigate the influence of the pulsed bias power on the nitrogen plasmas for various bias voltages and pulse frequencies. The results indicate that the plasma density as well as the inductive power density increase significantly when the bias voltage varies from 0 V to-4000 V, due to the heating of the capacitive field caused by the bias power. The N＋fraction increases rapidly to a maximum at the beginning of the power-on time, and then it decreases and reaches the steady state at the end of the glow period. Moreover, it increases with the bias voltage during the power-on time, whereas the N2-＋ fraction exhibits a reverse behavior. When the pulse frequency increases to 25 kHz and40 kHz, the plasma steady state cannot be obtained, and a rapid decrease of the ion density at the substrate surface at the beginning of the glow period is observed.

Nanomodificated Surface CoCr Alloy for Corrosion Protection of MoM Prosthesis

Problems in metal-on-metal (MoM) hip replacement systems still persist due to high wear rates, low corrosion resistance and release of toxic ions and nanoparticles. As a consequence of these effects, failure, infections, loosening or bone resorption is the typical problems in the hip prosthesis. In order to reduce failure due to corrosion and/or releasing ions and particles, this study presents some works in a novel nanoscale surface modification of cobalt-chromium alloy (CoCr) for obtaining improved surface conditions in these alloys for these applications. Improving corrosion resistant of these alloys and achieving a low wear rate are possible to reduce the total released ions and particles released from the surface of this material. According to it, three different treatments using oxygen at temperatures of 300&degC, 350&degC and 400&degC were carried out by plasma immersion ion implantation technique (PI3). X-ray diffraction (XRD) analysis shows an increase in the formation of chromium oxides in the outer surface of the CoCr alloy. It allows improving in corrosion resistant in CoCr alloys. Moreover, total quantity of released Co, Cr and Mo ions have been reduced. Wear rate studies showed a very similar behaviour after the treatments in relation to untreated CoCr alloy and release rate from the treated surface of CoCr alloys was reduced in comparison with untreated CoCr alloy.

A combination strategy of functionalized polymer coating with Ta ion implantation for multifunctional and biodegradable vascular stents

Biodegradable stents made of magnesium(Mg)and its alloys have been developed to minimize persistent inflammation or in-stent restenosis,which are the main problems for permanent stents.However,their rapid corrosion behavior under physiological conditions leads to poor vascular compatibility and premature structural failure,which remains an important unsolved clinical problem.Herein,we demonstrate a new strategy for solving this problem by combining poly(ether imide)(PEI)coating and subsequent tantalum(Ta)ion implantation.The PEI coating covers the whole surface of the Mg stent uniformly via a spray coating technique and provides Mg with superior corrosion resistance and stable sirolimus-carrying ability.Ta ion implantation is conducted by a sputtering-based plasma immersion ion implantation technique only onto the luminal surface of the PEI-coated Mg stent.Its extremely short processing time(<30 s)permits preservation of the PEI coating’s corrosion protection ability and sirolimus loading characteristics.In addition,a Ta-implanted skin layer that forms on the topmost surface of the PEI coating plays an effective role in not only preventing a rapid release of sirolimus from the surface but also improving the PEI coating’s surface hydrophilicity.Based on in vitro cellular response and blood compatibility tests,Ta ion implantation leads to the improvement of endothelial cell adhesion/proliferation and suppression of platelet adhesion/activation regardless of sirolimus loading.These results indicate that the combination of PEI coating and Ta ion implantation has significant innovative potential to provide excellent vascular compatibility and prevent in-stent restenosis and thrombosis.

Electrochemical Corrosion Behavior of the DLC Coated and Uncoated NiTi Alloys

A dense and well-adhered diamond-like carbon （DLC） coating was prepared on the nickel-titanium （NiTi） alloys by plasma immersion ion implantation and deposition （PIIID）. Potentiodynamic polarization tests indicated the corrosion resistance of the NiTi alloys was markedly improved by the DLC coating. The Ni ions release of the NiTi alloys was effectively blocked by the DLC coating.

Co-implantation of magnesium and zinc ions into titanium regulates the behaviors of human gingival fibroblasts

Soft tissue sealing around implants acts as a barrier between the alveolar bone and oral environment,protecting implants from the invasion of bacteria or external stimuli.In this work,magnesium(Mg)and zinc(Zn)are introduced into titanium by plasma immersed ion implantation technology,and their effects on the behaviors of human gingival fibroblasts(HGFs)as well as the underlying mechanisms are investigated.Surface characterization confirms Mg and Zn exist on the surface in metallic and oxidized states.Contact angle test suggests that surface wettability of titanium changes after ion implantation and thus influences protein adsorption of surfaces.In vitro studies disclose that HGFs on Mg ion-implanted samples exhibit better adhesion and migration while cells on Zn ion-implanted samples have higher proliferation rate and amounts.The results of immunofluorescence staining and real-time reverse-transcriptase polymerase chain reaction(RT-PCR)suggest that Mg mainly regulates the motility and adhesion of HGFs through activating the MAPK signal pathway whereas Zn influences HGFs proliferation by triggering the TGF-βsignal pathway.The synergistic effect of Mg and Zn ions ensure that HGFs cultured on co-implanted samples possessed both high proliferation rate and motility,which are critical to soft tissue sealing of implants.

In vitro and in vivo antibacterial performance of Zr&O PIII magnesium alloys with high concentration of oxygen vacancies

The effects of dual Zr and O plasma immersion ion implantation(Zr&O PIII)on antibacterial properties of ZK60 Mg alloys are systematically investigated.The results show that a hydrophobic,smooth,and ZrO_(2)-containing graded film is formed.Electrochemical assessment shows that the corrosion rate of the plasma-treated Mg alloy decreases and the decreased degradation rate is attributed to the protection rendered by the surface oxide.In vitro and in vivo antibacterial tests reveal Zr&O PIII ZK60 presents higher antibacterial rate compared to Zr PIII ZK60 and untreated control.The hydrophobic and smooth surface suppresses bacterial adhesion.High concentration of oxygen vacancies in the surface films are determined by X-ray photoelectron spectroscopy(XPS),UV-vis diffuse reflectance spectra(UV-vis DRS)and electron paramagnetic resonance(EPR)and involved in the production of reactive oxygen species(ROS).The higher level of ROS expression inhibits biofilm formation by down-regulating the expression of icaADBC genes but up-regulating the expression of icaR gene.In addition,Zr&O PIII improves cell viability and initial cell adhesion confirming good cytocompatibility.Dual Zr&O PIII is a simple and practical means to expedite clinical acceptance of biodegradable magnesium alloys.

Zinc ion implantation-deposition modification of titanium for enhanced adhesion of focal plaques of osteoblast-like cells

Background Surface modification by ion implantation-deposition is well established in materials science and can be an effective way to improve biocompatibility. The aim of this study is to evaluate the chemical composition of a modified titanium （Ti） surface after zinc （Zn） ion implantation and deposition and examine the effect of the modification on the formation of cellular focal adhesion plaques in vitro. Methods cp-Ti discs were modified with Zn ion implantation and deposition via PIIID. The chemical composition of the surface modification was characterized by X-ray photoelectron spectroscopy （XPS）. The formation of focal adhesion plaques on the modified Ti was investigated with human osteoblast-like MG-63 cells that were seeded onto the Ti surfaces and quantified by morphometric analysis under a confocal microscope. Results XPS data revealed that the modified Zn-Ti surface consisted of Ti, oxygen, Zn, and carbon. In addition, Gaussian fitting of the spectra indicated that the modified surface contained titanium dioxide and zinc oxide. After 6 hours of MG-63 cell culture, there were significantly more focal adhesion plaques on the modified surfaces than observed on the nonmodified Ti （P 〈0.05）. Conclusion Zn ion implantation and deposition greatly improved the biocompatibility of Ti for the growth of MG-63 cells.

Development of tropoelastin-functionalized anisotropic PCL scaffolds for musculoskeletal tissue engineering

The highly organized extracellular matrix(ECM)of musculoskeletal tissues,encompassing tendons,ligaments and muscles,is structurally anisotropic,hierarchical and multi-compartmental.These features collectively contribute to their unique function.Previous studies have investigated the effect of tissue-engineered scaffold anisotropy on cell morphology and organization for musculoskeletal tissue repair and regeneration,but the hierarchical arrangement of ECM and compartmentalization are not typically replicated.Here,we present a method for multi-compartmental scaffold design that allows for physical mimicry of the spatial architecture of musculoskeletal tissue in regenerative medicine.This design is based on an ECM-inspired macromolecule scaffold.Polycaprolactone(PCL)scaffolds were fabricated with aligned fibers by electrospinning and mechanical stretching,and then surface-functionalized with the cell-supporting ECM protein molecule,tropoelastin(TE).TE was attached using two alternative methods that allowed for either physisorption or covalent attachment,where the latter was achieved by plasma ion immersion implantation(PIII).Aligned fibers stimulated cell elongation and improved cell alignment,in contrast to randomly oriented fibers.TE coatings bound by physisorption or covalently following 200 s PIII treatment promoted fibroblast proliferation.This represents the first cytocompatibility assessment of novel PIII-treated TE-coated PCL scaffolds.To demonstrate their versatility,these 2D anisotropic PCL scaffolds were assembled into 3D hierarchical constructs with an internally compartmentalized structure to mimic the structure of musculoskeletal tissue.

Enhancing cell adhesive and antibacterial activities of glass-fibre-reinforced polyetherketoneketone through Mg and Ag PIII

Glass-fibre-reinforced polyetherketoneketone(PEKK-GF)shows great potential for application as a dental implant restoration material;however,its surface bioinertness and poor antibacterial properties limit its integration with peri-implant soft tissue,which is critical in the long-term success of implant restoration.Herein,functional magnesium(Mg)and silver(Ag)ions were introduced into PEKK-GF by plasma immersion ion implantation(PIII).Surface characterization confirmed that the surface morphology of PEKK-GF was not visibly affected by PIII treatment.Further tests revealed that PIII changed the wettability and electrochemical environment of the PEKK-GF surface and enabled the release of Mg^(2+)and Ag^(+)modulated by Giavanni effect.In vitro experiments showed that Mg/Ag PIII-treated PEKK-GF promoted the proliferation and adhesion of human gingival fibroblasts and upregulated the expression of adhesion-related genes and proteins.In addition,the treated samples inhibited the metabolic viability and adhesion of Streptococcus mutans and Porphyromonas gingivalis on their surfaces,distorting bacterial morphology.Mg/Ag PIII surface treatment improved the soft tissue integration and antibacterial activities of PEKK-GF,which will further support and broaden its adoption in dentistry.