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The penetration depth of yttrium ions extracted at 30 kV from a metal vapor vacuum arc (MEVVA) source reaches approximately 50 nm in H13 steel. For a pre-set dose of 3×10 17 cm −2 , the retained dose decreases (1.04×10 17 –6.2×10 16 cm −2 ) with increasing beam flux (25–76 μA cm −2 ). During high temperature (600–800°C) oxidation, yttrium implants have no change in quantity, but migrate inwards and redistribute themselves. As the dose is increased (up to 1×10 18 cm −2 ) in-going yttrium is redistributed almost uniformly within the oxidation scale; when the beam flux is increased the peak of yttrium profile shifts to a much deeper position (245 nm for 76 μA cm −2 ). Yttrium redistribution is not sensitive to oxidation time. A tentative explanation is presented.

Iron was implanted to different implantation doses (1×10 17 –1×10 18 cm −2 ) at different average beam fluxes (25–76 μA cm −2 ) in high purity aluminum foil by using a metal vapor vacuum arc ion implanter. The maximum thickness of the implanted layer can range between 350 and 400 nm for the highest dose of 1×10 18 cm −2 . Upon implantation dose and average beam flux, the retained concentration of Fe implants ranges between 22 at.% and lower than 10 at.%. Two crystal phases, i.e. Fe 2 Al 5 and FeAl 6 , are formed in the samples which were implanted to a dose larger than or equal to 5×10 17 cm −2 at an average beam flux of 51 μA cm −2 . The ratio of Fe 2 Al 5 to FeAl 6 increases with increasing implantation dose and average beam flux. The effect of implantation conditions on Mossbauer parameters is given. Mossbauer measurement reveals that there exists an amorphous state in the specimen implanted to the lowest implantation dose of 1×10 17 cm −2 at the smallest average beam flux of 25 μA cm −2 .

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.

The resistances to wear, corrosion and oxidation of implanted H13 steel using pulsed Ti and Y ions were studied. The Ti and Y ions were produced from a metal vapor vacuum source (MEVVA). The instantaneous beam current was from 0.3 to 1 A and energy was from 25–50 keV. The target temperature was raised to 300°C for a flux of 38 μA cm−2 and to 600°C for a flux of 76 μA cm−2. The hardness of Ti-implanted steel increases with ion dose and decreases with ion flux. The wear resistance of Ti-implanted steel is 3–3.7 times that for the unimplanted steel. Precipitates of Fe2Ti were observed by X-ray diffraction and high energy electron microscopy (HVEM). The size and amount of Fe2Ti increases with increasing ion dose and ion flux. The oxidation barrier of Y-implanted H13 steel formed during oxidation at 800°C for 10 min was measured by RBS. The oxidation rate of Y-implanted steel was 8–10 times less than the unimplanted steel. The electrochemical properties of Ti and Y implanted steel in 1 mol H2SO4 or solution of NaCl were studied. The results show that the Y implantation is effective for improvement of corrosion inhibition of H13 steel, GCr15 and 304 stainless steel.

The penetration depth of Ti ions extracted at 30 kV from a metal vapour vacuum arc source reaches 130 nm in H13 steel for a 5 × 10 17 cm -2 doping and is reduced to 60 nm for 1.5 × 10 19 cm -2 . The retained concentration is 21 at.% and 49 at.% respectively. The substantial structural change is the formation and growth of Fe 2 Ti, FeTi etc., and Fe 2 Ti precipitate becomes dominant at very high doses. The local electronic environment around Fe sites is distinctly altered owing to the interactions with Ti and the bonding state of Fe atoms is greatly enhanced.

An advanced metal ion implantation system for studying surface modification of materials by metal ion implantation has been developed, and is equipped with three metal vapor vaccum arc (MEVVA) IIA-H ion sources. All three ion sources are mounted horizontally on a large target chamber 600 mm high and 800 mm in diameter. The MEVVA IIA-H source operates in a pulsed mode, with a pulse width of 1.2 ms and a repetition rate up to 50 Hz. A large variety of ion species have been extracted at voltage of 30–80 kV, including the metal, compound and alloy ions. The time-averaged beam current is 10 mA or more for most ion species mentioned above. The target chamber is evacuated by two mechanical vacuum pumps and two molecular pumps. The base pressure in the system is 4 × 10 -4 Pa. The implantation chamber has a hinged door, 500 mm high and 400 mm wide, used to insert the components to be treated. Two viewing ports 100 mm in diameter are provided on each side of the chamber. Two kinds of target holder can be used in the target chamber for implanting components of different shapes.

The penetration depth of yttrium ions extracted at 30 kV from a metal vapor vaccum arc source reaches about 150 nm in pure aluminum; the maximum retained concentration is 20-50 at.% for varying doses of 5×10 16 to 1×10 18 cm -2 . Upon post-annealing at 600 °C, the implantation-induced YAl 3 (rhombohedral Bravais lattice with 12 atoms per unit cell) transforms in part into YAl 3 (hexagonal Bravais lattice with eight atoms per unit cell); yttrium diffuses deep into the bulk aluminum (600 nm) with a diffusion coefficient of 3.56×10 -13 cm 2 s -1 ; the directive diffusion and incorporation of foreign iron atoms result in the production of YFe 3.5 Al x (x

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.

The MEWA ion source has stood out for the surface modification of materials by direct ion implantation. Concurrent implantation with multiple ion species is more efficient in tailoring the surface sensitive properties of solid materials. Ion beam assisted synthesis of surface coating layers has also found increasing applications. The achievements obtained in the past few years in China will be reviewed and successful examples are introduced.

Ion implantation is a non-equilibrium process. After annealing, the process proceeds from its non-equilibrium state and the radiation-induced damage will be removed gradually. The hardness of Ti-, N- and Ti + N-implanted layers of H13 steel as a function of the annealing temperature was obtained. The hardness increased with increasing annealing temperature ranging from 400 to 600 °C. The maximum hardness was obtained when annealing at a temperature of 500 °C for 20 min; this hardness is 62% greater than that of the unnealed specimens. The compounds Fe2Ti and Fe2N have been identified by X-ray diffraction and transmission electron microscopy. After annealing, the compounds still remain in the implanted layers. The H13 steel is strengthened by the compounds and the dislocations.

The lattice damage, small intermetallic compound (Fe 2 Ti), metallic compound (TiN, Fe 2 N) formation and supersaturated solutions of Ti or Ti + N-ion implanted into steel with various ion doses and energies were measured by TEM and X-ray diffraction Formation and growth of the metallic compound Has found to depend on ion dose and energy. Change of phases and microstructure were particularly enhanced with high dose and high energy. Metal hardening also increases with increasing ion dose, energy and the amount and size of metallic compounds. Specimens implanted at target temperature ranging from 300°C to 400°C (HT) or implanted at room temperature (RT) and then annealed at temperature ranging from 300 to 500°C, showed significant increase in hardness. The wear resistance of high energy and high dose implanted steel is better than that of low energy and lower dose implantation. The wear rate decreases 2–2.6 times for low temperature implantation, 10.4 times for HT implantation and high energy implantation. The Fe 2 Ti and TiC precipitates, phase and microstructural changes in the implanted layer are responsible for such a drastic reduction in wear.

Intermetallic compounds of molybdenum and tungsten implanted into H13 steel and aluminium were measured by transmission electron microscopy (TEM) and X-ray diffraction. Ions extracted from a metal vapour vacuum arc source with around 25–100 keV energy and a dose range (1–5) × 10 17 cm -2 were used for implantation. The ion fluxes were 25, 47, 68 and 320 μA cm -2 . It was found from the results that the target temperature increases with increasing ion flux from 310 °C (25 μA cm -2 ) to 580 °C (68 μA cm -2 ). Intermetallic compounds such as FeMo, Al 2 Mo, Al 12 Mo, Fe 7 W, Fe 2 W and Al 5 W, were easily observed by TEM and X-ray diffraction when the flux was greater than 47 μA cm -2 . In situ observation in a high voltage transmission electron microscope (HVEM) was used to investigate the structure and formation of intermetallic compounds of molybdenum-implanted H13 steel. The electron diffraction pattern of FeMo precipitates appeared at 500 °C. Recrystallization and grain growth occurred at 650 °C.

The depth profiles of metal ions implanted into steel and aluminium were measured by Rutherford backscattering (RBS). The ions of Mo, W and Y, produced by a metal vapour vacuum arc ion source (MEVVA) were implanted at an energy range from 25 to 50 keV for doses of (2–5)×1017 cm−2 into H13 steel and aluminium. Beam currents were from 0.5 to 1.0 A. The beam flux is in the range of 25 to 75 μAcm−2. In order to simulate the profiles, a formula which includes the sputtering yield, diffusion coefficients and reaction rate was obtained. The results demonstrate that the penetration depth and retained dose increase with increasing beam flux for Mo implanted into aluminum. The peak concentration of Mo implanted H13 steel increases with increasing ion flux. In contrast to this for Y implantation into steel, the peak concentration of Y decreases with increasing ion flux. For an ion flux of 25 μA cm−2 for Mo, Y and W implantation into steel, the penetration depth and retained dose are 3–5 times greater than the theoretical values. The diffusion coefficients are about 10−16 to 10−15 s−1. If the ion flux is greater than 47 μA cm−2, the penetration depth and retained dose are 5 to 10 times greater than the theoretical values for Mo implanted aluminium. The diffusion coefficients increase with increasing ion flux for Mo implanted aluminium. The diffusion coefficients hardly change with increasing ion flux for Y and Mo implanted H13 steel. The retained dose increases 0.43 to 1.16 times for Y implanted steel for an ion flux of 25 μA cm−2. Finally, the influence of phases precipitates, reaction rate and diffusion on retained dose, diffusion coefficient and penetration depth are discussed.

In situ observation in high voltage transmission electron microscope (HVEM) was used to investigate the structure of Mo implanted H13 steel. Instead of tempered Martensite structure, the implanted layer has a fine grain structure. When the implanted specimen is heated inside the HVEM, the fine grain structure does not change until 500°C. The electron diffraction pattern of precipitates FeMo appears at 500°C. Recrystallization and grain growth occur at 650°C.

A phototransistor of CE-PTHPT (punch-through heterojunction phototransistor with control electrode) with novel emitter control electrode and wide band gap emitter has been designed. The devices were working under the depletion on the base region. The base current is nearly zero and the output noise current decreases eventually so as to increase the optical gain greatly. There is an i type layer between the emitter and base region, low doped base region, implant isolated planar device and decreased emitter area in this device. The novel CE-PTHPT has been fabricated in this paper. The optical gain of GaAlAs/GaAs CE-PTHPT for the incident light power 1.3 and 43 nW with the wavelength of 0.8 /spl mu/m reached 1260 and 8108. The input noise current calculated is 3.7/spl times/10/sup -16/ A/H/sub Z//sup 1/2/. For polysilicon emitter CE-PTHPT, the optical gain is 3083 at the input power of 0.174 /spl mu/W. The optical gain of InGaAs/InP CE-PTHPT reaches 350 for an incident power of 0.3 /spl mu/W at the wavelength of 1.55 /spl mu/m.

SI-GaAs wafers have been implanted with 0.6 /spl I.itilde/ 7.0 MeV /sup 28/ Si /sup +/ ions and processed by rapid thermal annealing. The donor activation rate goes down from 60% to /spl I.itilde/ 20% with an increasing fluence of 1 x 10/sup 13/ /spl I.itilde/ 2 x 10/sup 14/ cm/sup -2/, at high doses it goes up slowly with increasing ion energies. The carrier profile spreads shallower than Si atomic profile. The activation proceeds by the exchange of interstitial Si with substitutional Ga. The poor activation rate results mainly from Si/sub Ga/ - Si/sub As/ pair formation.

A new ventilated surface ionizer has been developed for a 860A cesium sputter negative ion source operated at BNU. The new ionizer consists of a multi-laminate nickel wire mesh and a spiral heater, and is spherical in shape. Low pressure cesium vapour diffuses through the wire mesh to the extraction side of the ionizer, meanwhile the neutral cesium can be ionized. The ionizer is capable of producing a positive ion current up to milliampere range. The negative ion current is 50 μA for P− and more than 150 μA for 0− and Si−.

A punch-through type AlGaAs-GaAs heterojunction phototransistor with a guarding modulation electrode is analyzed by a numerical procedure. The augmented drift-diffusion model is regarded as a suitable model to describe the device, and the coupled equations are solved by the successive line overrelaxation method. The distribution of carriers and electric potential, transportation of non-equilibrium carriers and frequency characteristics are computed systematically. Preliminary results are presented and discussed briefly.

Water penetration into Na-beta-alumina has been followed by 1 H ( 15 N, α γ) 12 C reaction. The uptake of water by beta-alumina occurs in two steps and is reversible upon heating. The average intercalated water estimated from the hydrogen concentration is about 1 H 2 O per unit cell for the monocrystal. The diffusion coefficient deduced from the hydrogen profile in beta-ceramics is 2 × 10 −13 to 2.8 × 10 −13 cm 2 s −1 for rapid absorption and 5.9 × 10 −15 to 6.2 × 10 −15 cm s −1 for slow penetration. In the monocrystal, they are 4.5 × 10 −13 cm 2 s −1 and 2.5 × 10 −14 cm 2 s −1 , respectively.