Improve retained dose and impact energy of inner surface plasma immersion ion implantation using long pulse duration with deflecting electric field

Not restricted by the line-of-sight process, plasma immersion ion implantation (PIII) has shown great potential for inner surface modification, but the impact energy and retained dose turned to be very low. The process was investigated numerically and experimentally in this paper. The results show that a high percentage of low impact energy ions was the key factor that resulted in low impact energy on the inner surface. This was caused by sheath overlapping and appearance of the dead zone during inner surface PIII. Long pulse duration could alleviate this problem and increase ion impact energy on the inner surface, hence the implant depth, which was key factor for the modifying effect of PIII. Also, long pulse duration was helpful in improving the retained dose on the inner surface.     

COMPUTATIONAL SCHEME FOR SIMULATING PLASMA DYNAM-ICS DURING PLASMA-IMMERSION ION IMPLANTATION

Plasma--immersionionimplantation(Pill)isapowerfultechniqueforsurfacemodificationofmaterials[1'2].InthePillprocess)theobjectbeingimplantedisimmersedinaplasmaandrepeatedlypulsedtoahigh,negativevoltage(scallto--100kV).AtypicaltargetgeometryisshowninFig.la.Theapplicationofthisbiascreatesasheaththatexpandsintothesurroundingplasma,uncoveringpositiveionsandacceleratingthemtothetargetsurfaCe,wheretheymaybeimplanted.Theseimplantedionsmodifythesurfacewhiletightdimensionaltolerancesaremaintained.Aprin…     

Effect of pulse rise time on charging effects in plasma immersion ion implantation with dielectric substrates with planar and cylindrical geometries

Using a one-dimensional self-consistent fluid model, the effect of pulse rise time on charging effects at dielectric surfaces is investigated during plasma immersion ion implantation (PIII) with planar and cylindrical geometries. The numerical results demonstrate that the pulse rise time plays an important role in PIII process with dielectric substrates. It is found that the charge dose accumulated on the dielectric surface is significant as decreasing pulse rise time, and the surface potential decreases at the later stage of the pulse, which results in the lower ion impact energy. On the other hand, the longer pulse rise time would lead to the lower charge dose accumulated on the dielectric surface and higher ion impact energy at the later stage of the pulse, which would elevate the effective implanted dose and introduce the ions to the depth deep enough for surface modification.     

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

1.IntroductionPlasmaimmersionionimplantation(Pill)[']unrestrictedbysight--lightprocess,isconsideredapropermethodforinnersurfacestrengthening.Inrecentyears,researchershavepaidalotofattentiononapplyingPillininnersurfacemodification.T.E.Sh.,idan[2,3]hassimulatedtheinnersurfacePillprocessofaboreusingone--dimensionalfluidmodel,andpresentedthelowimpactenergyproblemforthefirsttime.Zengetall4'5]presentedanideatoimprovetheimpactenergyusinganauxiliaryelectrode,basedonsimilaranalysis.Wepresentedametho…     

Plasma immersion ion implantation into cylindrical bore using internal inductively-coupled radio-frequency discharge

Plasma immersion ion implantation (PIII) is a potentially excellent interior surface treatment technique due to no line-of-sight restriction. However, some problems have been encountered due to the low ion energy and ion fluence non-uniformity especially for treatment of the interior wall of a thin tube. In this paper, a new method for inner surface PIII using internal inductively-coupled radio-frequency (RF) discharge is described. A cylindrical inductive coil inserted inside the tube serves as both the plasma source and grounded electrode to avoid overlapping of the plasma sheath fronts propagating from opposite sides. The effects of the gas species, gas pressure, RF power, and number of coil turns are investigated. Our results demonstrate the feasibility of this novel inner surface treatment method and the number of turns in the coil has a critical influence on the discharge behavior. If the number of turns is little, the plasma density is low and non-uniform inside the tube due to the relatively intense capacitively-coupled RF discharge at the two ends. In contrast, the plasma density and uniformity are evidently improved by using more turns in the coil.     

银基体上铜等离子体基离子注入层的成分分布

研究了银基体上铜等离子体基离子注入 (CuPBII)层成分深度分布与试验工艺参数的关系。选择影响注入离子能量的脉冲偏压和注入剂量的不平衡磁控靶放电电流和靶基距作为试验参数 ,用X射线光电子谱 (XPS)进行注入层成分深度分析。结果表明 ,对较高的脉冲偏压 (80kV)、中等的磁控靶电流 (75mA)和近的靶基距 (2 0 0mm) ,容易形成厚的银铜过渡层 (7.6μm) ,且铜离子注入、铜原子的反冲注入与铜的沉积很好地匹配。与气体等离子体基离子注入不同 ,铜的沉积速率成为影响银铜过渡层的又一决定因素。     

Reactive plasma immersion ion implantation for surface passivation

Plasma immersion ion implantation (PIII) using halogen or oxygen plasmas has been employed for the surface passivation of advanced alloys with a view to their applications for high-temperature oxidation protection and in medicine. Special devices have been designed to ensure efficient plasma generation and reduce sample contamination arising from the interaction of the aggressive plasmas with the chamber components under bias. The paper addresses two main applications of PIII, namely oxidation protection of gamma-titanium aluminides (γ-TiAl), and modification of the surface properties of shape-memory superelastic nickel-titanium (NiTi) alloys. TiAl intermetallics are of great interest for advanced automobile, aerospace and power generation applications due to their low specific weight and high strength. However, excessive oxidation occurring in these materials at temperatures above 700 °C has hindered their widespread use. Samples of technical γ-TiAl alloys have been treated by both beamline implantation of Cl or F, and PIII of Cl using an Ar/Cl gaseous blend or alternative precursor gases. High-temperature oxidation behavior has been examined under conditions of either isothermal or thermocyclic oxidation at 900 °C. Optimized implantation processing produces marked improvement in the oxidation behavior of the γ-TiAl samples. On the basis of these results, a commercially viable process for enhancing the high-temperature oxidation resistance of γ-TiAl alloys using PIII of halogens is being developed. NiTi alloys are promising materials for use in biomedicine, provided that the release of Ni ions into the body environment can be sufficiently reduced. Oxygen PIII at substrate temperatures below 250 °C results in the formation of a transparent rutile TiO₂ surface layer with a Ni content down to below 1 at.%. This layer in turn serves as a barrier to the corrosion and out-diffusion of Ni ions. Biocompatibility tests show superior in vitro blood compatibility in comparison with untreated NiTi samples.     

窄脉冲保形全方位离子注入技术

叙述了全方位离子注入过程中,由于被处理零件与其周围离子鞘层之间厚度的增加,引起零件与鞘层之间保形性变差,导致零件表面注入剂量不均匀性;文中系统分析了注入电压、等离子体密度、脉冲宽度和脉冲频率等处理工艺参数对注入剂量不均匀性的影响,用鞘层动力学计算机数值模拟方法从理论上研究了轴承内外圈处理中工艺参数对注入剂量不均匀性的影响,并用实验方法进行了测量验证,理论研究和试验测量结果的一致性,说明所提出的窄脉冲保形全方位离子注入技术完全适用于复杂形状零件表面均匀强化处理。     

Nitrogen diffusion in medical CoCrNiW alloys after plasma immersion ion implantation

CoCr alloys are widely used for medical applications, e.g. total hip replacements or coronary stents. Nevertheless, an increase in the surface hardness and a reduction of the wear rate is still desirable to improve the biocompatibility. Plasma immersion ion implantation (PIII) at different temperatures, acceleration voltages and working pressures is used to determine the nitrogen diffusivity in the CoCr alloys SY21med, L605 and HS188. Depending on the temperature, two different treatment regimes can be distinguished, independent of the ion energy. At low temperatures, a diffusion process with an activation energy of 1.0-1.1 eV is present, indicative of interstitial nitrogen diffusion. Beyond 350 °C, a reduced activation energy of 0.5-0.7 eV is observed. Additionally, a strong dependency of the layer thickness on the working pressure in the range 0.3-0.8 Pa was observed for the temperature dependent diffusion regime, which suggests a synergistic interplay of adsorption and implantation during PIII. Below 500 °C, an increase of the diffusion coefficient by three orders of magnitude was observed for PIII, compared with pure plasma nitriding.     

Hybrid elevated-temperature,low/high-voltage plasma immersion ion implantation of AISI304 stainless steel

Elevated-temperature plasma immersion ion implantation (PIII) is an effective non-line-of-sight technique to harden austenitic stainless steel by producing expanded austenitic phases in the near surface region. We report here a hybrid elevated-temperature, low/high voltage approach, which improves the efficiency while retaining the non-line-of-sight advantages of PIII. A low-voltage (4 kV), elevated-temperature (355°C) PIII process is first used to produce the modified layer, but the nitrogen concentration in this layer is typically relatively low and the thickness may not be adequate. This is followed by high-voltage (25 kV) PIII at a lower temperature to increase the nitrogen concentration and to achieve the desirable surface enhancement effects. To assess the efficacy of the technique, the samples are characterized using X-ray diffraction (XRD), nanohardness measurements, and secondary ion mass spectrometry (SIMS) depth profiling. The experimental results show that the nitrogen concentration increases by nearly 75% and the nitrogen penetration depth nearly doubles that of the low-voltage sample. The surface microhardness also improves by 150% and our data suggest that it is due to the formation of expanded austenites.     

TC4合金表面全方位离子注入Ag的耐摩擦磨损和抗腐蚀性能

为改善TC4合金表面的耐磨性能和抗腐蚀性能,用等离子体浸没离子注入(PIII)技术在合金表面注入不同剂量的金属银.采用XRD、XPS、AES等方法分析改性层的元素浓度分布和化学组成,研究Ag离子注入后试样表面的耐摩擦磨损性能、抗腐蚀性能、纳米硬度和弹性模量.结果表明,表面改性层中主要存在Ag相,同时含有少量的TiAg;处理后注入剂量为1×10~(17) ions/cm~2试样的纳米硬度和弹性模量分别提高62.5%和54.5%;磨损面积减小57.6%;摩擦系数由基体合金的0.78下降到0.2.在3.5%NaCl溶液中的腐蚀电位升高,腐蚀电流密度明显减小,耐蚀性得到了显著改善.     

Batch treatment of industrial components using plasma immersion ion implantation and deposition

Surface modifications of industrial components, such as the balls, inner and outer rings of bearings, are very difficult to perform for their sophisticated shapes. Plasma immersion ion implantation and deposition (PIIID) offers an effective way for surface treatment of such components. However, implantation doses of these components are not uniform in a conventional PIIID process. To obtain uniform surface modifications, we designed a rotating target holder. Using the target holder and proper process parameters, the PIIID batch treatment of sophisticated-shape components has become easy work. In the PIIID batch treatments of balls, outer and inner surfaces of cylinder-like components, the dose uniformity can be evidently improved by using sample rotation, short width high frequency implantation pulse, and middle-frequency and -voltage glow discharge, respectively. The practical test results reveal that the life of these components can be improved significantly by this novel PIIID batch treatment.     

Incident ion fluence gradients on the front and backside of flat samples

Plasma immersion ion implantation (PIII) is ideal for fast and efficient treatment into three-dimensional objects, as shown by experiments and simulations. In this presentation, a direct comparison of implantations into the front and backside of flat sample (disc, square and rectangle) at 5-15 kV pulse voltage with argon ions is performed with the spatial distribution of the incident ion fluence measured by spectroscopic ellipsometry on SiO₂/Si coupons. A strong influence of the supporting rod for the fluence distribution on the backside of the low symmetry samples, i.e. square and rectangle was observed, in contrast to no influence for the disc sample.     

AlN nanoclusters formation by plasma ion immersion implantation

We report on simultaneous (Al + N) implantation of Al and N into layers of amorphous thermal silica (SiO₂) in an attempt to bond Al with N and form the binary compound AlN. As an implantation technique, plasma ion immersion implantation (PIII) is used. The energy and ion fluence were varied in order to obtain nanocluster containing films in the thickness range 10-50 nm. The elemental distribution profiles in the substrate were evaluated by means of elastic recoil detection analysis technique (ERDA). The nature of the chemical bonds was determined by X-ray photoelectron spectroscopy (XPS). The simultaneous implantation using rf plasma source for N ions and a cathodic arc to produce the Al ions provides good overlap of the elemental profiles and high retained doses of Al and N are achieved. The binding energies of the Al 2p and N 1s core electrons indicate that formation of near-stoichiometric aluminium nitride is achieved.     

High frequency and low voltage plasma immersion ion implantation of nitrogen on industrial pure iron at different Rf power

Traditional plasma ion immersion implantation (PIII) can effectively improve material mechanical property and corrosion resistance. But the modified layer by PIII is too thin for many industrial applications. High frequency and low voltage plasma immersion ion implantation (HLPIII) has advantages of PIII and nitriding. Comparing with traditional ion nitriding, HLPIII can obtain higher implantation energy and create a thick modified surface layer. In the present paper nitriding layers were synthesized on industrial pure iron using high frequency and low voltage plasma immersion ion implantation with different RF power (400 W, 600 W, and 800 W). The microstructure of the nitriding layers was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical properties such as microhardness and wear resistance were analyzed using HXD1000 microhardness and CSEM pin-on-disk wear testing machine. The anodic polarization characteristics were measured in a 0.9% NaCl solution at room temperature to examine the corrosion resistance of the nitriding layer. The results reveal that Fe₂N, Fe₃N and Fe₄N coexist in the nitriding layer. The nitriding layer is a corrosion protective coating on industrial pure iron in 0.9% NaCl solution. The hardness, wear resistance and corrosion resistance of the nitrided layers on industrial pure iron increase with RF power.     

等离子体浸没离子注入(PⅢ)在材料表面改性中的应用及发展

等离子体浸没离子注入(PⅢ)是一种用于材料表面改性的新的离子注入技术.系统地分析和讨论了等离子体浸没离子注入技术的原理和特点:该技术直接将待处理材料浸没在等离子体中进行注入,保留了常规束线离子注入(CBⅡ)技术的主要特点,消除了常规束线离子注入所固有的视线限制,克服了保持剂量问题,使注入装置变得简单和价廉.综述了等离子体浸没离子注入技术在金属材料、半导体材料和高分子材料改性方面的应用.展示了等离子体浸没离子注入技术应用的发展前景.     

Sheath structure and ion current onto a patterned surface immersed in a plasma at floating potential

Using a two-dimensional hybrid simulation scheme, we have studied the processes occurring above a patterned surface immersed in a plasma at floating potential, focussing on the structure of the two-dimensional plasma wall sheath and the uniformity of the ion current onto the wall in steady state. The surface consists of a periodic alternation of a trench and a ridge. We discuss the sheath structure by comparing it to that in front of a planar target. It is found that the sheath is not conformal since the trench widths studied are not large compared to the sheath width. Thus, the electrical potential and the ion and electron densities in the trench show characteristic differences to those of the planar sheath. We show that, in all cases, the ion dose is strongly non-uniform on the target surface. This non-uniformity is traced back to the enhanced electrical fields at the convex corners of the ridge and to the aspect ratio of the surface structure.     

Plasma-based ion process in the dual-plasma configuration

A novel plasma-based ion process characterized by the dual plasma configuration, which we call the dual-plasma immersion ion process and which has been developed for the surface treatment of electrically insulating materials, is reported. In this process, the plasma is divided into two parts by a negatively biased grid: the target plasma and the driver plasma. The workpiece to be treated is set in the target plasma. If a dc or pulsed positive bias is applied to the driver plasma against the target plasma at ground potential, an ion sheath develops on the grid and a potential difference happens across the ion sheath. When we see the dual-plasma process from the workpiece, it gets the impact of ions from the driver plasma while being immersed in the target plasma at ground potential. Thus, this new process enables treatment of insulating materials because the surface charge induced by the ion impact is completely reduced by the inflow of electrons from the target plasma.In the present paper, the basic idea of the dual-plasma immersion ion process and results of the proof-of-principle experiment are presented.     

ION HEATING PROCESS DURING PLASMA IMMERSION ION IMPLANTATION

1.IntroductionIonbombardmelltusingplasmaimmersionmethodhasprovenaneffectivesurfacemodificationtechnique[2,3].Plasmaimmersionionimplantation(Pill)cansignificantlyimprovethesurfacepropertiesofthecomponents,suchashardness,friction,wear--resistanceandcorrosion--resistanceofthematerials.Meanwhileitsbiggestadvantageistheabilitytotreatirregularlyshapedobjectswithoutthenecessityoftargetmanipulation.Pillprocesscanbeconductedbyeitheratalowtemperature(<100'C)orelevatedtemperatureconditions(usually300'C…