Yuguang Wu

Electrical properties of polymer modified by metal ion implantation

Abstract Polyethylene terephthalate (PET) has been modified by Ag, Cr, Cu and Si ion implantation with a dose range from 1×10 16 to 2×10 17 ions cm −2 using a metal vapor vacuum arc (MEVVA) source. The electrical properties of PET have been changed after metal ion implantation. The resistivity of implanted PET decreased obviously with an increase of ion dose. When metal ion dose of 2×10 17 cm −2 was selected, the resistivity of PET could be less than 10 Ω cm, but when Si ions are implanted, the resistivity of PET would be up to several hundred Ω cm. The results show that the conductive behavior of a metal ion implanted sample is obviously different from Si implantation one. The changes of the structure and composition have been observed with transmission electron microscope (TEM) and X-ray diffraction (XRD). The surface structure is varying after ion implantation and it is believed that the change would cause the improvement of the conductive properties. The mechanism of electrical conduction will be discussed.

Behavior of PET implanted by Ti, Ag, Si and C ion using MEVVA implantation

Abstract Polyethylene terephthalane (PET) has been modified with Ti, Ag, Si and C ions from a metal vapor arc source (MEVVA). Ti, Ag, Si and C ions were implanted with acceleration voltage 40 kV to fluences ranging from 1×1016 to 2×1017 cm−2. The surface of implanted PET darkened with increasing ion dose, when the metal ion dose was greater than 1×1017 cm−2 the color changed to metallic bright. The surface resistance decreases by 5–6 orders of magnitude with increasing dose. The resistivity is stable after long-term storage. The depth of Ti- and Ag-implanted layer is approximately 150 and 80 nm measured by Rutherford backscattering (RBS), respectively. TEM photos revealed the presence of Ti and Ag nano-meter particles on the surface resulting from the high-dose implantation. Ti and Ag ion implantations improved conductivity and wear resistance significantly. The phase and structural changes were obtained by X-ray diffraction (XRD). It can be seen that nano-meter particles of Ti precipitation, TiO2 and Ti-carbides have been formed in implanted layer. Nano-hardness of implanted PET has been measured by a nano-indenter. The results show that the surface hardness, modulus and wear resistance could be increased.

Nano-phases and corrosion resistance of C+Mo dual implanted steel

The corrosion resistance of C+Mo dual-implanted H13 steel was studied using multisweep cyclic voltammetry. The phase formation conditions for corrosion resistance and its effects were researched. The super-saturation solid station solution of Mo+ and C+ atoms was formed in Mo+C dual implanted steel. Precipitate phase with nanometer size Fe2Mo, FeMo, MoC, Fe5C3 and Fe7C3 were formed in dual implanted layer. The passivation layer consisted of these nanometer phases. The corrosion resistance of the dual implanted layer was better than that of single Mo implantation.Jp of the Mo implanted sample is 0.55 times that of H13 steel. The corrosion resistance of the dual implantation was enhanced when ion dose increased. When the Mo+ ion dose was 6×1017/cm2 in the dual implantation,Jp of the dual implanted sample was only 0.11 times that in H13 steel. What is important is that pitting corrosion properties of dual implanted steel were improved obviously.

THE INFLUENCE OF HIGH-DOSE AND ELEVATED-TEMPERATURE IMPLANTATION ON PN-JUNCTION LEAKAGE CURRENT DURING RAPID THERMAL ANNEALING

The electrical properties of the pn junction formed by As implantation and rapid thermal annealing (RTA) have been studied in this article. It is found that the behavior of the pn junction formed by As implantation at elevated temperature (573 K) after RTA is better than that of room-temperature (RT) implantation. The changes of density of residual defects and motion of the defects for different annealing time were observed by TEM. The results of implanting at 5 × 1015 or 1.0 × 1016 cm−2 show that the density of residual defects for elevated-temperature (ET) implantation is lower than that of RT implantation. The carrier concentration profiles for different annealing times were measured by a spreading resistance probe (SRP). It is shown that the carrier concentration profile of elevated-temperature implantation is broader than that of RT implantation. The leakage current decreases with increasing RTA time and temperature. The depth of the pn junction (0.6 μm) for elevated-temperature implantation is larger than that of RT implantation (0.4 μm). The pn-junction leakage current of elevated-temperature implantation is several times lower than that of RT implantation. The influence of change of defect density on the leakage current of the pn junction was analyzed using these results. If the dose is as high as 5 × 1016 cm−2 for implantation, the result is different from that for a dose of 5 × 1015 cm−2, except for elevated-temperature implantation. The results from channeling measurements show that the lattice stress increases with increasing RTA time. Therefore the leakage current of the pn junction also increases with increasing RTA time. The minimum leakage current is obtained for RTA during 5 s.

Formation of nanometer embedded phases during high-energy Ti-implanted and annealed steel

Abstract Observation by transmission electron microscope (TEM) indicated the formation of FeTi2 phase of 3.5–20 nm in diameter embedded in a high-energy Ti-implanted layer. The nanometer phases were embedded among dislocations and grain boundaries in Ti-implanted steel at 400°C. It has good wear resistance. The embedded structure changes after annealing. The structure changed slightly after annealing at temperature ranging from 350°C to 500°C, while the hardness of the implanted layer increased greatly. The maximum of hardness is obtained when the sample was annealed at 500°C for 20 min and the Ti phases had an average diameter of 8 nm. Dislocations disappeared and the diameter of nanometer phases increased to 10 and 16 nm after annealing at temperature of 750°C and 1000°C, respectively. The average densities of the nanometer phases are 8.8×1010 and 6.5×10 10 cm −2 , respectively for both annealing temperatures.