Zhang Huixing

Broad beam high average current metal ion source

For industrial application in material surface modification it is necessary to obtain higher average beam current for metal ion implantation. Two new versions of MEVVA ion source, MEVVA‐II and MEVVA‐IIA, in which the size of the extraction area is expanded to 60 mm in diameter have been developed, based on MEVVA‐I being constructed early. The sources are operated in pulsed mode with a maximum beam duty cycle of 6%. A time average beam current of up to 10–30 mA has been extracted from a range of different cathode materials, such as C, Mg, Al, Ti, V, Cr, Fe, Ni, Cu, Zn, Y, Zr, Mo, Nb, Sn, Ta, W, and Pb. In the MEVVA‐IIA, particularly, a movable cathode is used for compensating the consumption of the cathode material during the source operation, so that the running time may be extended, for example, it has been operated stably more than 16 h with a 10 mA beam current with a Ti cathode. In this paper, we will describe the source and some preliminary results.

High‐current metal‐ion source for ion implantation

High‐current metal‐ion beams, as needed for material modification of metal surfaces, can be produced using the MEVVA ion source. In this article a brief description of the ion source is given, and its operational characteristics and preliminary results are presented. A range of metal ions such as Cu, Ti, Al, Fe, Mo, and W, etc., have been extracted from the source. The ion‐beam current is 0.5–1 A (total current in all charge states) and is a function of the cathode material, arc current, and extractor voltage. The beam pulse width is 300–550 μs, the repetition rate several pulses per second, the extraction voltage about 30 kV, and the arc current 150–350 A. The extraction system has a set of three multiaperture extractor grids, including three different sizes: 37 holes 2 mm in diameter, and 207 and 495 holes 1 mm in diameter. The operating pressure is in the 2×10−6‐Torr range, obtained with a diffusion pump.

Influence of the structure of implanted steel with Y, Y + C and Y + Cr on the behaviors of wear, oxidation and corrosion resistance

Abstract New methods were studied to improve the properties of corrosion, wear and oxidation resistance of implanted H13 steel using ions of Y, Cr, Y + C and Y + Cr, produced by a pulsed metal ion source (MEVVA). The results show that the behaviors of wear, corrosion and oxidation resistance were improved obviously for four kinds of ion implantation into H13 steel. The oxidation resistance of single Y implantation at 25 μA cm −2 is better than at higher fluxes. The wear and oxidation resistance of Y + C are better than those of Cr, Y and Y + Cr implantation. The corrosion resistance of high dose implantation is better than that of low dose implantation. The structural changes of the implanted layer before and after oxidation were measured by X-ray diffraction. An improvement in the above-mentioned properties is closely related to the structural change of yttrium-iron alloy and yttrium-iron oxidation compounds. The compounds were formed during a short-time (10 min) oxidation. Because of the compound formation, a strong Y atom concentration profile appeared. The shape of the profile is constant during oxidation at 800 °C for 40 min. Finally, the mechanism of influence of the oxidation compounds and the strange shape of the profile on the properties of the implanted layer is discussed.

Industrialization of MEVVA source ion implantation

Abstract Ion implantation is being successfully applied for the reduction of corrosion, wear and oxidation of materials. As a result, ion implantation as an engineering tool is a powerful and relatively important technique. In order to develop applications of ion implantation for precision tooling, moulds and large number of engineering components, improvement in the MEtal Vapor Vacuum Arc (MEVVA) source implantor for industrial ion implantation now offers more attractive costs per unit area and a potentially greater throughput. Material modification was produced by MEVVA source implantation at high target temperature (200∼550°C) with high ion flux (25∼100 μA/cm 2 ). Metal ion implantation has yielded good results in the improvement of drills, cutters, dies, bearings and off-gas pumps for returnable artificial satellites using MEVVA source implantors. The results show that reduction of manufacturing costs and the challenges to improve component performance justify consideration of metal ion implantation in industrial processing. The ion implantation workshop was established with two implantors for industrial application. Millions of drills were processed per year. A large number of ion-implanted products have been exported up to now.

Influence of nanostructure on electrical and mechanical properties for Cu implanted PET

Abstract Polyethylene terephthalate (PET) has been modified by 40 KeV Cu ion using a metal vapor vacuum arc (MEVVA) source to fluence ranging from 1×10 16 to 2×10 17 ions/cm 2 . The surface morphology was observed by atomic force microscopy (AFM). The Cu atom precipitation and nano-structure of Cu implanted PET were observed. It is believed that the structure change improves the electrical properties and wear resistance of PET. The electrical properties of PET have been improved extremely after ion implantation. The surface resistance of implanted PET decreased obviously with an increase of ion dose. When metal ion dose was higher than 1×10 17 cm −2 , the surface resistivity of PET could be less than 0.1 Ω m. The results show that the conductive behavior of a Cu ion implanted sample is much better than that of non-metal Si- and C-ion implanted one. After Cu implantation, the surface hardness and Youngs modulus increase and the cross-section area of cutting groove is narrow and shallow comparing with the unimplanted PET. The modification mechanism of PET was discussed.

Polymer modification by MEVVA source deposited and ion implantation

Polyethylene terephthalate (PET) has been modified by Ti, Ni and W deposition using a metal vapor vacuum arc (MEVVA) source and implantation. The surface resistance of deposited PET could decrease to several hundred ohms. The adhesion of metal coating on polymers is very strong. The thickness of the deposited metal coating could be controlled from tens of nanometers to 1 μm. The hardness for thick Ti and W deposited PET is 3.81 and 2.54 GPa, which are several times greater than that of PET. The elastic modulus of deposited PET increases also. Similar results have been observed for other metal implanted PET. The thickness and atomic distribution of deposited metal coating was analyzed using RBS. The surface structure has varied after deposition and implantation. It is believed that the change would cause the improvement of the conductive properties and wear resistance.

The formation of metallic silicides of Ti, Y, Fe, Mo and W using metal vapour vacuum arc implantation

Abstract The formation of metallic silicides was studied using implantation into Si with ions of Ti, Y, Fe, Mo and W produced by a metal vapour vacuum arc ion source. The electrical properties were measured by four-probe and spread-resistance probe devices. The resistivities are from tens to hundreds of micro-ohm centimetres for the implantation of these ions. The resistivity of Ti-, Y- and Fe-implanted layers decreased obviously with increasing ion flux. In contrast, the lowest resistivity is found for Mo and W implantations at 50 μA cm-2. The glossy surface changes into a rough surface and the resistivity increases, if the ion flux of Mo and W is larger than 75 μA cm-2. The silicide phases were distinguished by X-ray diffraction and Rutherford backscattering spectrometry. The metallic silicides TiSi, TiSi2, YSi, YSi2, FeSi, FeSi2, MoSi2 and WSi2 were fully formed if the ion flux was as high as 50 μA cm-2. The surface atomic ratio was about 40%–60% for Ti, Y and Fe, and 20%–25% for Mo and W, if implanted doses of (3–5) × 1017 cm-2 were used. The distribution depth of the silicides was about 30–80 nm. The new process technique is suitable and can be employed for shallow junction technologies of very-large-scale integration.

The Beijing metal vapor vacuum arc ion source program

Work on metal vapor vacuum arc (MEVVA) ion source development was initiated at the Institute of Low Energy Nuclear Physics, Beijing Normal University, in 1988. MEVVA ion sources I, II, IIA, and III have been designed, fabricated, and tested, and an ion implantation facility with three MEVVA ion sources has been developed and is now undergoing testing. Here the status of the MEVVA ion source research and development program is described.

Metallic ion implantation by using a MEVVA ion source

Abstract Metallic ions (Ti, Mo, W, V, Ni, Y, Fe and Al) extracted from a MEVVA source have been implanted up to high doses (>1 × 1017 cm−2) into Al and H13 steel. Because of beam heating, rather low energy ions could penetrate quite deeper in the substrates than predicted, stable intermetallic compounds appear as fine precipitates in the doped region, and hence the retained concentration of implants even exceeds the sputter-limited maximum. Multiply charged beam, enhanced diffusion and chemical reaction give great influences to the concentration distribution of implants. All these features are strongly dependent on the chosen ion-target combination.

A modified, filtered, pulsed cathodic vacuum arc implantation and deposition apparatus with the filtering duct working as a second anode

Abstract A modified filtered pulsed cathodic vacuum arc implantation and deposition apparatus with the filtering duct biased positively 30–60 V relative to the cathode has been set up. Pulsed cathodic vacuum arc discharge between the duct and the cathode was observed. As a result of this, the cathode erosion rate and ion intensity at the substrate increased dramatically. The influence of the focusing magnetic field of the MEVVA plasma source as well as the positive bias and the guide magnetic field of the filtering duct on the arc discharge and the duct output were studied. Experimental results show that the output of the duct and the duct current increased with increasing duct potential and increasing arc source focusing magnetic field. It is also shown that the duct current decreased with an increase in the guiding magnetic filed, and 7–8 mT duct magnetic field is the optimum for the duct output.