AN ALUMINUM OXYNITRIDE FILM

We report on an aluminum oxynitride (AlON) film which was successfully made using the reactiver r.f. sputtering method in an N2-O2 mixture. The fabrication process, atomic components, breakdown field and refractive index of the AlON film are shown in detail. The AlON film is a new polyfilm combining the good properties of Al2O3 and AlN, and it is very interesting with regard to optoelectronic devices and integrated optic circuits.

MBE of GaN with DC-plasma source for nitrogen activation

In this paper we report on the first results of epitaxial growth of GaN layers on GaAs (100) substrates using a modified MBE system, equipped with a DC-plasma source for nitrogen activation in configuration of reverse magnetron at ultra-low pressures.

A new structure of In-based ohmic contacts to n-type GaAs

Electrical, structural and reaction characteristics of In-based ohmic contacts to n-GaAs were studied. Attempts were made to form a low-band-gap interfacial phase of InGaAs to reduce the barrier height at the metal/semiconductor junction, thus yielding low-resistance, highly reliable contacts. The contacts were fabricated by e-beam sputtering Ni, NiIn and Ge targets on VPE-grown n(+)-GaAs film (approximate to 1 mu m, 2 x 10(18) cm(-3)) in ultrahigh vacuum as the structure of Ni(200 Angstrom)/NiIn(100 Angstrom)/Ge(40 Angstrom)/n(+)-GaAs/SI-GaAs, followed by rapid thermal annealing at various temperatures (500-900 degrees C). In this structure, a very thin layer of Ge was employed to play the role of heavily doping donors and diffusion limiters between In and the GaAs substrate. Indium was deposited by sputtering NiIn alloy instead of pure In in order to ensure In atoms to be distributed uniformly in the substrate; nickel was chosen to consume the excess indium and form a high-temperature alloy of Ni3In. The lowest specific contact resistivity (rho(c)) of (1.5 +/- 0.5)x 10(-6) cm(2) measured by the Transmission Line Method (TLM) was obtained after annealing at 700 degrees C for 10 s. Auger sputtering depth profile and Transmission Electron Microscopy (TEM) were used to analyze the interfacial microstructure. By correlating the interfacial microstructure to the electronical properties, InxGa1-xAs phases with a large fractional area grown epitaxially on GaAs were found to be essential for reduction of the contact resistance.

Determination of the interdiffusion coefficients of liquid Zn and Sn using Ta/Zn-Sn/Si trilayers

In this paper we present a new method for measuring diffusion coefficients in liquid metals under convection-less conditions with solid/liquid-liquid/solid trilayer. The advantage of this kind of trilayer is that effects from gravity-induced convection and Marangoni-convection can be omitted, so that the diffusion coefficient is determined more accurately. The Ta/Zn-Sn/Si trilayer were prepared with a multi-target ion-beam sputtering deposition technique and annealed in an electric furnace under an argon atmosphere. The interdiffusion of liquid zinc and tin at 500 degrees degree C was investigated. The diffusion concentration profiles were determined by energy dispersive spectroscopy. The interdiffusion coefficients range from 1.0x10(-6)cm(2)/s to 2.8x10(-6)cm(2)/s, which is less than previous values measured by capillary reservoir technique under 1g-environment where various convection exist. The precise interdiffusion coefficients of liquid zinc and tin result from the removing of disturbances of various kinds of convection.

Study of the interaction of highly charged ions with SiO2 surface

Highly charged ions (HCIs) AO(q+)/Pbq+ are extracted from ECR source and impacted on solid surface Of SiO2 Sputtering yield as a function of incident angle is measured by multi-channel plate (MCP). The results have been fitted by a new formula. We proposed the cooperation model to explain the formula. The results demonstrate that the potential assisted kinetic sputtering yield increases with the charge state and potential sputtering (PS) could be induced by impact of HCIs. At larger incident angles, the sputtering yield is dominated by elastic collision between HCIs and material atoms. It is found that, smaller the incident angle, larger the contribution from the potential sputtering. (C) 2009 Elsevier B.V. All rights reserved.

Simulation of the Lanzhou Penning Trap LPT

The LPT (Lanzhou Penning Trap) is under construction and its task is to perforin direct mass measurement of fusion-evaporation residue, and if possible for heavy isotopes. Detailed simulations have been clone for a good understanding to the ion's movement and mechanics in the trap. The optimizal ion of the LPT is also performed based on the simulation. With a scale of 0.5 mm per grid used in the, simulation and many other limitations a highest mass resolution has been achieved to be 1.9 x 10(-5). An unexpected behavioin in the simulation related to magnetron motion has been found.

Experiments and modification on electron cyclotron resonance ion sources at the Institute of Modern Physics

Uranium ion beams were produced from electron cyclotron resonance (ECR) ion sources by sputtering method this year at the Institute of Modern Physics. At first, we chose the Lanzhou ECR No. 3 ion source to implement the production experiment of U ion beams. Finally, 11 e mu A of U28+, 5 e mu A of U32+, and 1.5 e mu A of U35+ were obtained. A U26+ ion beam produced by the LECR2 ion source was accelerated successfully by the cyclotron. This means that the Heavy Ion Research Facility in Lanzhou (HIRFL) has accomplished the acceleration of the ion beam of the heaviest element according to the designed parameters. The Lanzhou ECR ion source No. 2 (LECR2), which was built in 1997, has served the HIRFL for eight years and needed to be upgraded to provide more intense high charge state ion beams for HIRFL cooling storage ring. We started the upgrading project of LECR2 last year, and the modified design just has been finished. (c) 2006 American Institute of Physics.

高电荷态离子与Si(110)晶面碰撞的沟道效应研究

不同电荷态低速离子(Arq+，Pbq+)轰击Si(110)晶面，测量不同入射角情况下的次级粒子的产额. 通过比较溅射产额与入射角的关系，证实沟道效应的存在. 高电荷态离子与Si相互作用产生的沟道效应说明溅射产额主要是由动能碰撞引起的. 在小角入射条件下，高电荷态离子能够增大溅射产额. 当高电荷态离子以40°—50°入射时，存在势能越高溅射产额越大的势能效应.

Structural and PL properties of Cu-doped ZnO films

Cu-doped ZnO films with hexagonal wurtzite structure were deposited on silicon (1 1 1) substrates by radio frequency (RF) sputtering technique. An ultraviolet (UV) peak at similar to 380nm and a blue band centered at similar to 430nm were observed in the room temperature photoluminescent (PL) spectra. The UV emission peak was from the exciton transition. The blue emission band was assigned to the Zn interstitial (Zn-i) and Zn vacancy (V-Zn) level transition. A strong blue peak (similar to 435 nm) was observed in the PL spectra when the alpha(Cu) (the area ratio of Cu-chips to the Zn target) was 1.5% at 100 W, and ZnO films had c-axis preferred orientation and smaller lattice mismatch. The influence of alpha(Cu) and the sputtering power on the blue band was investigated.

Research on metallic ion beam production at IMP

Since 1998, many experiments for metallic ion production have been done on LECR2 (Lanzhou ECR ion source NO.2), LECR3 (Lanzhou ECR ion source NO.3) and SECRAL (Superconductiong ECR ion source Advanced design in Lanzhou) at Institute of Modern Physics. The very heavy metallic ion beams such as those of uranium were also produced by the plasma sputtering method, and supplied for HIRFL (Heavy Ion Research Facility in Lanzhou) accelerators successfully. During the test, 11.5e mu AU(28+), 9e mu AU(24+) were obtained. Some ion beams of the metal having lower melting temperature such as Ni and Mg ion beams were produced by oven method on LECR3 too. The consumption rate was controlled to be lower for Mg-26 ion beams production, and the minimum consumption was about 0.3mg per hour. In this paper, the main experimental results are given. Some discussions are made for some experimental phenomena and results, and some conclusions are drawn.

近玻尔速度高电荷态离子与表面作用诱发的溅射离子能谱

近玻尔速度高电荷态离子在物质表面诱发的溅射离子能谱研究在理论和实验上尚是一片空白。本工作针对溅射离子能谱测量，设计、建立了一台径向位置灵敏127o柱形静电离子能谱仪。该谱仪结合位置灵敏探测器，克服了传统静电谱仪只能通过扫描电场单次、单能量点取谱的缺陷，实现了分段取谱——单次可获取宽为0.85Ec ≤ E ≤ 1.15Ec的能谱，极大提高了实验测量效率。利用该谱仪，首次获得了0.8至1.8倍玻尔速度Ar7，8，9+离子与金属铍靶和高定向性石墨靶碰撞产生的溅射离子能谱（入射角45o ，出射角135o）。结果表明：1）能谱分布很宽，其峰值位于130eV至600eV之间，远大于线性级联碰撞区的几到十几eV；且峰位随入射离子速度增加向高能方向略有移动。2）铍靶的溅射能谱呈一个极不对称的峰分布——高能部分有很长的尾巴，下降趋势服从E-n分布；其能谱与入射离子速度关联很大，小于vBohr时指数n与线性级联碰撞接近，而大于vBohr时非线性贡献明显。3）石墨靶的能谱峰位与入射离子动能、势能相关；其谱形在上升到最大值后均出现一个很宽的平台，表明该系列碰撞系统中，非线性效应占主导

高电荷态离子与固体表面作用的离子溅射和电子发射的实验研究

高电荷态离子与固体表面相互作用的研究是目前国际上广受关注的热点研究领域之一。本论文详细介绍了在兰州重离子加速器国家实验室ECR离子源上建成的高电荷态离子表面物理实验平台；着重叙述了在实验平台上完成的高电荷态离子在固体表面引起的离子溅射和电子发射的研究。我们用初动能Ek=216～720keV的高电荷态Pb36+离子和初动能为Ek=144～288keV的Arq+（q =11～16）离子以不同入射角度(Ψ＝15º～80º)作用于Nb、Si和SiO2表面，通过研究离子溅射产额与入射离子初动能、势能（电荷态）和入射角度的关系，得到了以下结论：离子溅射产额与炮弹离子的势能沉积和动能作用有关；对Ar离子，电荷态从11增加到16时，离子溅射产额是随之增长的。而对Pb36＋离子，表面离子溅射产额随入射离子初动能的变化关系跟核阻止能损随入射离子初动能的变化关系是一致的，离子溅射产额与核阻止能损是线性相关的。认为高电荷态引发的表面离子溅射过程是势能沉积作用与线性级联碰撞过程协同作用的结果。我们还测量了Heq+(q=1,2, Ek=12keV～48keV)，Neq+(q=2～8, Ek=18～192keV)，Arq+(q=3～12, Ek=72keV)离子垂直作用于Si, W, Au表面产生的电子发射产额。得到了纯粹势能电子发射产额与入射离子势能的定量关系，势能电子产额随入射离子势能的增加而线性增加，势能每增加1eV，单离子电子发射产额增加0.0088（以初动能为42keV的Neq+入射到W表面为例）。势能电子发射增量跟靶的性质有关，W表面对势能变化的响应最剧烈，其次是Si表面。通过引入纯粹动能电子产额与电子能损的比值B分析和研究了动能电子发射，随着入射离子原子序数和初动能的增加，B因子有缓慢降低的趋势；B因子与靶材料密切相关，Au靶的B因子明显大于Si靶和W靶；我们还首次把B因子的研究扩展到高电荷态离子领域，认为B因子与入射离子的势能（电荷态）无关

Fabrication of a miniature twin-fuel-cell on silicon wafer

The fabrication and performance evaluation of a miniature twin-fuel-cell on silicon wafers are presented in this paper. The miniature twin-fuel-cell was fabricated in series using two membrane-electrode-assemblies sandwiched between two silicon substrates in which electric current, reactant, and product flow. The novel structure of the miniature twin-fuel-cell is that the electricity interconnect from the cathode of one cell to the anode of another cell is made on the same plane. The interconnect was fabricated by sputtering a layer of copper over a layer of gold on the top of the silicon wafer. Silicon dioxide was deposited on the silicon wafer adjacent to the copper layer to prevent short-circuiting between the twin cells. The feed holes and channels in the silicon wafers were prepared by anisotropic silicon etching from the back and front of the wafer with silicon dioxide acting as intrinsic etch-stop layer. Operating on dry H-2/O-2 at 25 degreesC and atmospheric pressure, the measured peak power density was 190.4 mW/cm(2) at 270 mA/cm(2) for the miniature twin-fuel-cell using a Nafion 112 membrane. Based on the polarization curves of the twin-fuel-cell and the two single cells, the interconnect resistance between the twin cells was calculated to be in the range from 0.0113 Omega (at 10 mA/cm(2)) to 0.0150 Omega (at 300 mA/cm(2)), which is relatively low. (C) 2003 Elsevier Science Ltd. All rights reserved.

Fabrication of integrated microelectrodes for electrochemical detection on electrophoresis microchip by electroless deposition and micromolding in capillary technique

A new method for the fabrication of an integrated microelectrode for electrochemical detection (ECD) on an electrophoresis microchip is described. The pattern of the microelectrode was directly made on the surface of a microscope slide through an electroless deposition procedure. The surface of the slide was first selectively coated with a thin layer of sodium silicate through a micromolding in capillary technique provided by a poly(dimethylsiloxane) (PDMS) microchannel; this left a rough patterned area for the anchoring of catalytic particles. A metal layer was deposited on the pattern guided by these catalytic particles and was used as the working electrode. Factors influencing the fabrication procedure were discussed. The whole chip was built by reversibly sealing the slide to another PDMS layer with electrophoresis microchannels at room temperature. This approach eliminates the need of clean room facilities and expensive apparatus such as for vacuum deposition or sputtering and makes it possible to produce patterned electrodes suitable for ECD on microchip under ordinary chemistry laboratory conditions. Also once the micropattern is ready, it allows the researchers to rebuild the electrode in a short period of time when an electrode failure occurs. Copper and gold microelectrodes were fabricated by this technique. Glucose, dopamine, and catechol as model analytes were tested.

The fabrication of dipped CdS and sputtered ITO thin films for photovoltaic solar cells

Stable bilayer thin films of indium tin oxide (ITO) on CdS and CdS on ITO were formed for the window material of solar cells by chemical bath and sputtering methods. Scanning electron microscopy and X-ray diffraction studies have shown that both the ITO and CdS films are continuous, homogeneous, with high compactness. Measurement of the CdS film thickness across the 2 x 4 cm(2) reveals the good uniformity of these films. Four-point probe measurements show that the resistivity of a CdS film on an ITO surface is much better than that of the single CdS film The thermal stability of an ITO/CdS bilayer, interfacial reaction and optical transmittance were investigated at different annealing temperatures and environments (air, vacuum and N-2 + H-2). The results showed that the ITO/CdS bilayer film is a good window material for the CuInSe2 and CdTe cells. It is a simple method using a small amount of the cadmium compound.