High-frequency short-pulsed metal plasma-immersion ion implantation or deposition using filtered DC vacuum-arc plasma

A new approach to the development of advanced coating deposition and ion implantation method including an application of filtered dc metal plasma and high-frequency short-pulsed negative bias voltage with a duty factor in the range of 10-99% are considered. The ion energy spectrum for different negative bias potential pulse durations (120-1100 ns) was measured. The chart of various methods of ion beam and plasma material treatment using high-frequency short pulse metal plasma immersion ion implantation or deposition depending on bias pulse duty factor and amplitude for Cu plasma is presented. The ion assisted coating deposition has been examined depending on samples conductivity and thickness, plasma concentration, pulse repetition rate, amplitude, and duty factor.     

钢的等离子体基低能离子注入的传质机制

等离子体基低能离子注入是一种钢的低温,低压表面改性方法,它包括等离子体源离子渗氮和等离子体源离子渗碳两种工艺。等离子体基低能离子注入的主要传质机制是低能离子注入－同步热扩散,即在脉冲负偏压作用下的离子首先完成不依赖于工艺温度的低能离子注入,然后已注入的原子在较低的工艺温度上发生足够的热扩散,等离子体热扩散吸收具有补充的传质作用,但由于工艺温度较低,这种作用很小,连续的热扩散过程有利于改善注入吸收条     

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 extraction from magnetically driven shunting arc and estimation of ion density at sheath boundary

Ion density of a magnetically driven shunting arc discharge is estimated from the target voltage characteristics of the pulse modulator circuit in plasma-based ion implantation (PBII). The voltage recovery time constant directly reflects the ion sheath characteristics, and the sheath resistance is related to the ion density inside the transient sheath. The measured characteristics are analyzed using an equivalent circuit of the pulse modulator in PBII. The estimated ion density decreases from 3 × 10⁸ to 4 × 10⁷ cm^− 3 with time after the arc ignition from 100 to 400 μs. This characteristic almost agrees with that of an ion current extracted from the arc plasma by applying a negative pulse voltage to the target.     

Influence of auxiliary plasma source and ion bombardment on growth of TiO2 thin films

By inserting an auxiliary rf plasma source in an experimental setup for depositing TiO₂ thin films with a cathodic vacuum arc and high voltage pulses, i.e. metal plasma immersion ion implantation & deposition (MePIIID), it is shown that this auxiliary plasma source can increase the growth rate at low gas flow ratios only but not increase the oxygen/titanium ratio. It can be surmised that the plasma source creates activated oxygen species which are otherwise supplied from collisions of the titanium plasma stream with the background gas at higher pressures.     

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…     

Nitrogen plasma source ion implantation of AISI S1 tool steel

Significant economic savings can be achieved by improving the wear lifetime of precision manufacturing tools through nitrogen-ion implantation. This near-ambient temperature, surface modification process preserves dimensional integrity and surface finish while eliminating delamination problems that are often associated with overlay coatings. Conventional ion implantation is a line-of-sight process which requires elaborate manipulation and masking to uniformly implant components of complex shapes. A recently developed process, plasma source ion implantation (PSII), circumvents this line-of-sight restriction and makes ion implantation more attractive economically. In this article, the effects of PSII of nitrogen at a target bias of 50 kV, to a dose of 0.3 × 10¹⁸ atoms/cm² on the surface microstructure and mechanicalproperties of AISI S1 tool steel are presented.     

Structure and properties of silver-containing a-C(H) films deposited by plasma immersion ion implantation

In this study, we have grown silver-containing hydrogenated (a-C:H) and non-hydrogenated (a-C) amorphous carbon coatings by two plasma immersion ion implantation methods: I) chemical vapor deposition of methane combined with pulsed filtered cathodic arc deposition of silver, and II) by alternating arc pulses from graphite and silver in a dual cathodic arc plasma source. This unique “bias selective” feature of the deposition system allowed the deposition of silver with the substrates at ground and avoided the sputtering of the grown a-C film. Chemical composition of the samples was analyzed by acquiring their compositional depth-profiles using radio-frequency Glow Discharge Optical Emission Spectroscopy (rf-GDOES), while the microstructural properties were analyzed by X-ray absorption near edge spectroscopy (XANES) and Raman spectroscopy. In this contribution, we compare mechanical and biomedical properties by means of nanoindentation and cell viability tests, respectively, of a-C(H) films obtained by two different plasma immersion ion implantation techniques.     

Pulsed ion extraction from a hybrid plasma using a shunting arc discharge

A hybrid plasma is generated by combining a burst methane rf (195 kHz) plasma with a carbon shunting arc discharge. The shunting arc discharge triggers the rf methane plasma. As a result, the rf plasma is initiated over a wide range of ambient gas pressure from 0.045 Pa as a base pressure to a methane pressure of 1.26 Pa, at which the rf plasma is not self-ignited. When a target is immersed in the rf- and shunting arc-hybrid plasma, and a negative pulse voltage is applied to the target, carbon ions are extracted from the hybrid plasma. When the carbon shunting arc ionizes the methane gas, an rf plasma is initiated and the ionization of methane is significantly enhanced in the rf plasma. The plasma density in the hybrid plasma increases by a factor of approximately 5-9 compared to that of the shunting arc discharge.     

低温等离子复合技术制备氧化铝阻氚涂层的研究

采用低温等离子体复合技术在不锈钢基体上制备了氧化铝阻氚涂层,先后经过磁控溅射镀铝,热处理及氧离子注入。利用XRD、SEM、EDS、AES对涂层进行了相结构、表面形貌、成分、元素分布等分析,并进行了划痕实验、抗热震性能及阻氚性能测试,结果表明：磁控溅射获得了高质量的铝涂层,热处理后形成了FeAl合金过渡层。在离子注入中,当注入剂量不变电压增加时,离子注入深度增加而氧元素分布梯度减少;当注入剂量达到8×10₁₇ ions/cm₂以上时,氧元素分布变得均匀。所获得的氧化铝涂层具有较好膜基结合力、抗热震性能及阻氚性能。经过叠加电压注入且剂量达到8×10₁₇ ions/cm₂的膜层具有最好的阻氚性能,在600_oC能使不锈钢的氚渗透率降低3个数量级。     

Behavior of endothelial cells on micro-patterned titanium oxide fabricated by plasma immersion ion implantation and deposition and plasma etching

Titanium oxide films synthesized by plasma immersion ion implantation and deposition (PIII&D) were micro-patterned using argon plasma etching. Wells containing organized arrays of square holes of different depths separated by gaps of 25 μm were produced on the surface of the titanium oxide by etching for 30, 60, 90, and 120 min. The surface wettability and tension of the samples were evaluated. Human umbilical vein endothelial (HUVE) cells were cultured on both smooth and patterned surfaces. The effects of surface micro-patterning on the behavior of the HUVE cells were investigated. Our results show that the titanium oxide prepared by PIII&D has good cyto-compatibility and the micro-patterns influence both the surface energy and cell behavior. Our results demonstrate the feasibility of using micro-patterned surfaces to modulate HUVE cell behavior.     

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.     

Shunting arc-produced hybrid plasma and its magnetic drive for PBII&D

Hybrid plasmas produced by shunting arc discharge are described in this article. The shunting arc was generated in various ambient atmospheres. When a carbon-shunting arc was generated in a nitrogen atmosphere, the carbon ion species were produced at the arc stage, the electrons of which accelerated toward the wall, colliding with the gas species in the chamber to produce nitrogen ions. When the arc was generated in a methane atmosphere, the hydrogen content in the deposited carbon film changed with the gas pressure. When the arc was generated in gaseous RF plasma, an enhancement in the plasma density was confirmed with ion current measurement. Another method of the shunting arc application is the usage of the Lorentz force, which accelerates the entire plasma body toward the target. This results in a fast deposition of the plasma species such as carbon.     

Austenite modification of AISI 316L SS by pulsed nitrogen ion beams generated in dense plasma focus discharges

We present the results of a surface modification of AISI 316L stainless steel by surface irradiation with high energy, pulsed nitrogen ion beams generated with 0.8 kJ dense plasma focus. The surface characterization was done using GAXRD, Auger electrons spectroscopy, TEM and optical microscopy. After the irradiation, we found a modification of a 1 μm thick surface layer, on which a gradual lattice expansion of the austenite with the number of irradiation pulses, i.e. with the total nitrogen ion fluence, was observed.In addition, ~ 40 nm close to the surface layer, a disordered lattice structure had been observed through TEM analysis. Those results can be explained in terms of the extreme thermal effect induced on the surface through the fast high energy release during the pulsed ion interaction with the steel surface, followed by an also rapid cooling down process which limits the nitrogen diffusion to the bulk.     

Thermal effect of ion implantation with ultra-short ion beams

Ion implantation with plasma guns operated in the detonation mode presents several differences from normally used low current ion implanter systems.

The most important differences are the high power of the beams generated with the plasma guns owing to their pulsed nature on one hand, and the plasma environment in which the target is immersed during the process of implantation on the other hand. Both effects were studied in this work.

The temperature profiles and their evolutions during and after nitrogen implantation in pure titanium, stainless steel and copper were investigated by using the finite differences method. The calculation for nitrogen ion implantation (fluence of 10¹³ cm⁻² and pulse time of 400 ns) in pure titanium, shows melting layers of 20 ns after the first 200 ns of implantation, with a fast cooling after the end of implantation. Thermal gradients of 1000 K μm⁻¹ and a heating rate of 5 K ns⁻¹ were also observed.

Optical spectroscopy observations (real time spectroscopy) of the implantation region show a highly activated nitrogen plasma.

Both effects can be of extreme importance in several applications such as, for example, titanium nitriding because of an extra temperature assisted absorption by the getter effect.     

Secondary electron suppression in nitrogen plasma ion implantation using a low DC magnetic field

Experiments aiming at the reduction or even total suppression of secondary electrons during the plasma immersion ion implantation were carried out using a plasma device with low DC magnetic field. Comparison of ion implantations in B = 0 and another case with B = 43 G, indicated that the magnetic field was effective to suppress SE flow in the direction transversal to B but only partial suppression was attained in the longitudinal direction. However, these results are already significant since the efficiency of implantation was increased and the flow of SE to the walls became localized to the regions with B crossing the walls.     

Applications of combined ion implantation for improved tribological performance

Ion implantation set-up on the base of ion gun with target sputtering by Penning discharge plasma was created. The set-up allows to conduct implantation of ions of various materials with an implantation current of 100 μA/cm² at acceleration voltage of up to 30 kV. Combined implantation of TiB₂ compound and Argon or Nitrogen were applied for surface properties modification of WC-Co hard alloy and SKD11 steel. The effect of implantation on mechanical and tribological properties has been studied and discussed with respect to implantation fluence. It was shown that the main effect of implantation is the modification of thin surface layer with formation of Ti, B, N₂ — base compounds, which leads to modification of surface adhesion interaction and wear resistance improvement. Examples of application to real products are presented.     

Uniformity enhancement of incident dose on concave surface in plasma immersion ion implantation assisted by beam-line ion source

Plasma immersion ion implantation (PIII) is a promising surface treatment technique for the irregular-shaped components. However, it is difficult to achieve uniform implantation along the surface of a concave sample due to the propagation and overlapping effect of plasma sheath. In this paper, a new ion implantation process is presented for improving the dose uniformity, especially for enhancing the lateral dose of the samples with concavities. In PIII enhanced by beam-line ions process, a beam-line ion source with certain energy is introduced from an external source into the concavity to suppress the sheath propagation and consequently to improve the dose uniformity. The time-dependent evolution of the potential, electrical field and the particle movement surrounding the surface of concave sample is studied by a particle-in-cell/Monte Carlo collision (PIC/MCC) simulation during a single bias high voltage (HV) pulse. The simulation results show that the plasma sheath propagation surrounding the concave sample is suppressed effectively by beam-line ions, and can be quasi-steady state during a single HV pulse. The influence of the energy of induced beam-line ions on the incident ion dose and energy distribution is discussed. Compared with the traditional PIII process, the dose uniformity of the sample surface is improved obviously due to the increase of the ions implanted into the lateral surface.     

Electrochemical corrosion behavior of a novel antibacterial stainless steel

A novel antibacterial stainless steel (ASS) with martenstic microstructure has been recently developed, by controlled copper ion implantation, as a new functional material having broad-spectrum antibacterial properties. The electrochemical corrosion behavior of the ASS in 0.05 mol/L NaCl was assessed using linear polarization and electrochemical impedance spectroscopy (EIS) and compared with that of a conventional stainless steel (SS) without copper ion implantation. The ASS exhibited higher corrosion susceptibility in the chloride medium; with a more negative (active) corrosion potential, higher anodic current density and lower charge transfer and polarization resistance. This has been attributed to the occurrence of copper-catalyzed interfacial reactions. A functional tool, 3-D presentation of EIS data, has been employed in analyzing the electrochemical corrosion processes as well as probing complex interfacial phenomena.