Wu Yuguang

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 ternary Ti (Zr, N) phases formation and modification of TiN coatings by Zr+ MEVVA ion implantation

Abstract The TEM observation shows that TiN coating changed over from columnar structure to compact texture after Zr + implantation. X-Ray analysis indicates that combining of N with Zr, Ti atoms and Ti 2 N would be transformed into TiN and ternary Ti (Zr, N) phases during Zr-implantation with high doses, high ion flux and annealing. Therefore, the wear resistance had improved obviously, the hardness of the TiN coating increased by 1.3–1.7 times after Zr + implantation. The wear resistance of implanted TiN coatings increased obviously. As an attractive procedure, the MEVVA source ion implantation of the TiN coatings would find new applications in many fields.

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.

Determination of rare earths and other trace elements in samples of Antarctica by neutron activation analysis

The concentrations of REE and other trace elements have been determined in samples of Antarctica by Instrumental Neutron Activation Analysis (INAA). The samples were collected from the West Lake area near Great Wall Station. The samples include sediment, residual plants, rock and soil taken from the bottom of the lake to 3.4 m deep. The amounts of samples were very rare. In order to get more information, reactor NAA using both short and long irradiations with “K0 standardization” has been adopted. Nine rare-earth elements (REE) namely La, Ce, Nd, Sm, Eu, Tb, Dy, Yb, and Lu as well as other trace elements (As, Au, Ba, Br, Co, Cr, Hf, Sc, Se, Th, V, Zn) have been determined. The concentrations and distribution patterns of REE in the samples have been given.

Carrier concentration profiles in multiply implanted silicon with 0.5–7.5 MeV phosphorus

Abstract MeV implantation is very important in fabricating semiconductor devices and VLSI. The carrier concentration profiles in high energy phosphorus implanted silicon have been investigated. Phosphorus with energies ranging from 0.5 to 7.5 MeV were implanted into Si with doses ranging from 2 × 10 12 to 1 × 10 13 /cm 2 . The results indicate that carrier concentration profiles consist of two half-Gaussians distribution with different stragglings σ f and σ b . According to these profiles the method of forming a uniform profile with multiple implantations was suggested. The various specific carrier concentration profiles can be got by multiple implantations with different energies, doses and masking technology with SiO 2 . Rapid thermal annealing has been used to obtain good reliability and reproducibility of their profiles. The residual defects of the samples were measured by 1000 kV TEM. Specific transistors produced with phosphorus multiple implantations have satisfactory characteristics.

Phase transition and pitting corrosion behaviour for Mo-implanted aluminium

Molybdenum ions are implanted into aluminium with high ion flux and high dose at elevated temperatures of 200?C, 400?C and 500?C. Due to the high temperature and high flux of vacancies and interstitial atoms, the atom diffusion and chemical effects are enhanced during the ion implantation. The effects increase with increasing ion flux and dose, so that new phase formation and phase transition emerge noticeably. X-ray diffraction analysis shows that when the aluminium is implanted with Mo ions at a low ion flux (25?A/cm2), the Al5Mo alloy is formed. The atomic ratio of Mo/Al of the Al5Mo phase is close to 20%. When the aluminium is implanted with Mo ions at a high ion flux (50?A/cm2), the phase transition from Al5Mo to Al12Mo appears and the latter is dominant, which is determined to be the final phase. The ratio of Mo/Al in Al12Mo is 7.7%. Rutherford backscattering spectroscopy indicates also that the Mo/Al atom ratio is ~7% to ~8% in Mo-implanted aluminium. The atomic ratios of the constituents in Al5Mo and Al12Mo are of stoichiometric composition for these alloys. The thicknesses of the Al12Mo alloy layers for Mo-implanted Al with ion doses of 3?1017/cm2 and 1?1018/cm2 are 550nm and 2000nm, respectively. The pitting corrosion potential Vp increases obviously. It is clear that due to the formation of Al12Mo alloy layer, the pitting corrosion resistance is enhanced.

Nanometer structure and conductor mechanism of polymer modified by metal ion implantation

Polyethylene terephthalate (PET) has been modified by Ag, Ti, Cu and Si ion implantation with a dose ranging from 1×1016 to 2×1017 ions/cm2 using a metal vapor vacuum arc (MEVVA) source. The electrical properties of PET have been improved by metal ion implantation. The resistivity of implanted PET decreased obviously with an increase in ion dose. The results show that the conductive behavior of a metal ion implanted sample is different from Si-implantation samples. In order to understant the mechanism of electrical conduction, the structures of implanted layer were observed in detail by XRD and TEM. The nano carbon particles were dispersed in implanted PET. The nano metallic particles were built up in metallic ion implanted layers with dose range from 1 × 1016 to 1 × 1017 ions/cm2. The nanometer metal net structure was formed in implanted layer when a dose of 2 × 1017ions/cm2 is reached. Anomalous fractal growths were observed. These surface structure changes revealed conducting mechanism evolution. It is believed that the change would result in an improvement of the conductive properties. The conducting mechanism will be changed with increasing metal ion dose.