电子束辐照制备纳米镍(英文)

在水溶液中,常温常压下不加入任何催化剂,用电子束加速器辐照作为一种新的方法可成功制备纳米镍。利用 X 射线衍射(XRD)、透射电子显微镜(TEM)、激光衍射粒度分布仪(LSPSDA)、紫外可见光分光光度计(UV)、样品振荡磁力计(VSM)和差热分析仪(DSC)来分别表征材料的结构、形貌、大小、粒径分布、光学特征、磁学性能以及材料的熔点。TEM 图像和 LSPSDA 分布图证明颗粒大小为 39nm,这与XRD 实验通过 Scherer 理论公式计算的结果相一致。

DY-2001A型纳米级电子束曝光机中静电偏转器的设计

基于纳米曝光要求和JSM-35CF型扫描电镜,设计了一组上下偏转器长度不一致的静电偏转器,使偏转灵敏度大大提高。采用二阶有限元法计算了八极静电偏转器的轴上场分布。高精度的场分布有利于高级像差。为了使系统的总体像差最小,结合具体电子光学系统,用最小二乘法对偏转器的激励强度、转角及其在系统中的位置进行优化,得到直至五级分量的像差。动态校正后,偏转场为80μm×80μm时,束斑分辨率约为3.2nm;偏转场大小为1mm×1mm时,束斑分辨率约为29.8nm。结果表明,应用该组静电偏转器的电子光学系统的分辨率满足纳米曝光的要求。

电子束纳米光刻技术研究

纳米光刻技术在微电子制作中起着关键作用 ,而电子束光刻在纳米光刻技术制作中是最好的方法之一。我们使用VB5电子束曝光系统 ,经过工艺研究 ,现已研究出最细分辨率剥离金属条为 17nm ,最小剥离电极间距为 10nm ,最细T型栅为 10 0nm。

运用精确电压衬度像技术实现精确定位的原位电子束纳米刻蚀：制造具有悬挂纳米线结构的纳米器件

本文演示了运用精确电压衬度像技术实现原位电子束纳米刻蚀技术的精确定位,并运用该技术制作成具有悬挂结构的纳米开关。通过运用精确电压衬度像定位技术,能够很好地控制偏转电极的定位,误差可减少到大约10nm。通过该技术,不用通过任何刻蚀过程只运用一次电子束纳米刻蚀,便可实现将分散的纳米线夹在两个电阻层中间形成悬挂结构。在原位电子束刻蚀的整个过程中,无需移动样品台从而消除了样品台的移动误差。因此,整个过程中不需要高精确的激光台和定位标记,从而简化了传统的电子束纳米刻蚀工艺。通过该方法制作的纳米开关随着施加电压的改变很好地实现了闭合和断开的状态。这种简化的过程提供了一种简单、低成本、快速的通过改装过的场发射扫描电子显微镜(FESEM)来制作纳米线悬挂结构的方法,并可运用该技术进一步制造多层结构和特殊的纳米器件。

镓填充二氧化硅纳米管的电子束诱导的反常膨胀

研究了镓填充二氧化硅纳米管的电子束诱导的膨胀现象，确认微球系统中镓液体在电子束辐照下存在反常膨胀现象．首先分析了相关的实验过程和现象，指出此膨胀过程可以视为准静态过程；然后根据傅里叶热传导定律，在准静态热力学的框架下定量讨论了该系统在电子束辐照下微球中镓液体相对体积随温度变化规律，进一步确定系统的相对膨胀率和系统的膨胀系数，发现反常膨胀系数是正常热膨胀系数的5—9倍．最后指出这种反常膨胀是由系统的电离效应和残存效应共同引起的，两者造成系统的粒子数密度急剧增加，从而导致系统的内部压强急剧增加，产生体积反常膨胀．

Effect of electron beam irradiation on multi-walled carbon nanotubes

Multi-walled carbon nanotubes （MWCNTs） were irradiated with focused electron beams in a transmission electron microscope at room temperature. The results showed that carbon nanotubes had no obvious structural damages but only shell bending under 100 keV electron beam irradiation. However, when the electron energy increased to 200 keV, the nanotubes were damaged and amorphization, pits and gaps were detected. Furthermore, generating of carbon onions and welding between two MWCNTs occurred under 200 keV electron irradiation. It was easy to destroy the MWCNTs as the electron beams exceeded the displacement threshold energy that was calculated to be 83-110 keV. Conversely, the energy of electron beams below the threshold energy was not able to damage the tubes. The damage mechanism is sputtering and atom displacement.

Nano-Level Electron Beam Lithography

The JEOL JBX-5000LS is a vector type machine.The system hardware features an ion-pumped column,a LaB 6 electron emitter,25kV and 50kV accelerating voltage,and a turbo-pumped sample chamber.The resolution,stability,stitching and overlay of this system are evaluated.The system can write complex patterns at dimensions down to 30nm.The demonstrated overlay accuracy of this system is better than 40nm.

Fabrication of Sub-20nm Metal Nanogaps from Nanoconnections by the Extended Proximity Effect

We describe the fabrication of metal nanogaps of sub-20nm in feature size using the proximity effect in electron beam lithography （EBL）. The proximity effect is extended to develop a flexible and practical method for preparing metal （e. g. Au or Ag） nanogaps and arrays in combination with a transfer process （e. g., deposition/lift-off）. Different from the direct gap-writing process,the nanogap precursor structures （nanoconnections） were designed by GDSII software and then written by electron beam. Following a deposition and lift-off process, the metal nanogaps were obtained and the nanogap size can be lowered to -10nm by controlling the exposure dose in EBL.

Fabrication of Silicon Crystal-Facet-Dependent Nanostructures by Electron-Beam Lithography

Silicon crystal-facet-dependent nanostructures have been successfully fabricated on a （100）-oriented silicon-oninsulator wafer using electron-beam lithography and the silicon anisotropic wet etching technique. This technique takes advantage of the large difference in etching properties for different crystallographic planes in alkaline solution. The minimum size of the trapezoidal top for those Si nanostructures can be reduced to less than 10nm. Scanning electron microscopy （SEM） and atomic force microscopy （AFM） observations indicate that the etched nanostructures have controllable shapes and smooth surfaces.

电子束光刻研制高分辨X射线波带片透镜最新进展

首先综述了当前X射线透镜的分辨率和效率的水平,预测并讨论了发展我国波带片透镜、赶超国际先进水平的技术路径图。在原有100 nm分辨率波带片和会聚透镜工艺基础上,综述了电子束光刻结合金电镀进一步发展30~70 nm分辨率的X射线波带片的最新进展。在研发30 nm分辨率的波带片中,电子束光刻中的邻近效应严重限制了波带高宽比,而现有商业软件(基于蒙特卡罗模型和显影动力学)的邻近效应修正在同时处理从微米到30 nm的各种图形时效果甚微。为此,本团队针对70 nm分辨率的硬X射线波带片采用了图形修正法,实现了20:1的波带高宽比,针对50 nm分辨率的硬X射线波带片采用了分区域修正法,获得了15:1的波带高宽比;30 nm波带片透镜的金属化摒弃了传统的直流电镀工艺,采用脉冲金电镀,实现了金环均匀电沉积,成功研制了30 nm分辨率的软X射线波带片透镜和30~100 nm的大高宽比分辨率测试卡。所有研制的波带片透镜在上海同步辐射装置得到了X射线光学成像验证。

Palladium-Carbon Composite Nanoparticle Films with Enhanced Electrocatalytic Activity for Hydrogen Peroxide Sensors

A nanocomposite electrocatalyst was prepared with the method of cluster beam deposition of palladium nanoparticle thin lms on carbon nanoparticle supporting layers and used as sensitive nonenzyme hydrogen peroxide sensors. An enhancement on the electrocatalytic activity of the palladium nanoparticles toward H2O2 reduction was observed, which was related to the coverage of the carbon nanoparticles. With one monolayer of carbon nanoparticles, the H2O2 detection sensitivity reached the maximum, which was more than twice of that of the pure Pd nanoparticles.

Simulation of Influence of Partially Coherent Gaussian Laser Beam on Gradient Force Acting on Dielectric Nanoparticle inside Random Medium

The partially coherent beams propagating through random media have been used in the past to enhance effect of nonlinear optical interaction. Moreover, after propagation through a random （or turbulent） medium the coherent beam becomes a partially coherent one. In this research, the analytical formula for the average intensity of Gaussian beam propagating through random medium is derived and the influence of coherent partiality on optical gradient force acting on dielectric particle rounded by a random media is investigated.

Chemical Composition and Mechanical Characteristic of Nitrogen Ion Beam Mixed Carbon Nanolayer

Ion beam methods for modification of nanohardness of surface nanolayers of the titanium alloy Ti6AI4V were applied. After deposition of carbon nanolayers by electron beam evaporation, the ion implantation of nitrogen into samples was carried out. The chemical composition of the modified surface area was investigated by AES （auger electron spectroscopy）. The nanohardness of resulted ion beam modified surface nanolayers were investigated by nanoindentation testing. The measured concentration profiles indicate the atomic mixing of carbon into the substrate. It was found that the modified samples had a markedly higher nanohardness than the unmodified samples. The increased nanohardness is attributed to the newly created phases in the surface area.

Catalytic Properties of Pt Cluster-Decorated CeO2 Nanostructures

Uniform clusters of Pt have been deposited on the surface of capping-agent-free CeO2 nanooctahedra and nanorods using electron beam （e-beam） evaporation. The coverage of the Pt nanocluster layer can be controlled by adjusting the e-beam evaporation time. The resulting e-beam evaporated Pt nanocluster layers on the CeO2 surfaces have a clean surface and clean interface between Pt and CeO2. Different growth behaviors of Pt on the two types of CeO2 nanocrystals were observed, with epitaxial growth of Pt on CeO2 nanooctahedra and random growth of Pt on CeO2 nanorods. The structures of the Pt clusters on the two different types of CeO2 nanocrystals have been studied and compared by using them as catalysts for model reactions. The results of hydrogenation reactions clearly showed the clean and similar chemical surface of the Pt clusters in both catalysts. The support- dependent activity of these catalysts was demonstrated by CO oxidation. The Pt/CeO2 nanorods showed much higher activity compared with Pt/CeO2 nanooctahedra because of the higher concentration of oxygen vacancies in the CeO2 nanorods. The structure-dependent selectivity of dehydrogenation reactions indicates that the structures of the Pt on CeO2 nanorods and nanooctahedra are different. Thes differences arise because the metal deposition behaviors are modulated by the strong metal-metal oxide interactions.

Direct observation of Pt nanocrystal coalescence induced by electron-excitation-enhanced van der Waals interactions

Nanocrystal coalescence has attracted paramount attention in nanostructure fabrication in the past decades. Tremendous endeavor and progress have been made in understanding its mechanisms, benefiting from the development of transmission electron microscopy. However, many mechanisms still remain unclear, especially for nanocrystals that lack a permanent dipole moment standing on a solid substrate. Here, we report an in situ coalescence of Pt nanocrystals on an amorphous carbon substrate induced by electron-excitation- enhanced van der Waals interactions studied by transmission electron microscopy and first principles calculations. It is found that the electron-beam-induced excitation can significantly enhance the van der Waals interaction between Pt nanocrystals and reduce the binding energy between Pt nanocrystals and the carbon substrate, both of which promote the coalescence. This work extends our understanding of the nanocrystal coalescence observed in a transmission electron microscope and sheds light on a potential pathway toward practical electron- beam-controlled nanofabrication.

Momentum-space imaging spectroscopy for the study of nanophotonic materials

The novel phenomena in nanophotonic materials, such as the angle-dependent reflection and negative refraction effect, are closely related to the photonic dispersions EepT. EepT describes the relation between energy E and momentum p of photonic eigenmodes, and essentially determines the optical properties of materials. As EepT is defined in momentum space(k-space), the experimental method to detect the energy distribution, that is the spectrum, in a momentum-resolved manner is highly required. In this review, the momentum-space imaging spectroscopy(MSIS) system is presented, which can directly study the spectral information in momentum space. Using the MSIS system, the photonic dispersion can be captured in one shot with high energy and momentum resolution. From the experimental momentumresolved spectrum data, other key features of photonic eigenmodes, such as quality factors and polarization states, can also be extracted through the post-processing algorithm based on the coupled mode theory. In addition, the interference configurations of the MSIS system enable the measurement of coherence properties and phase information of nanophotonic materials, which is important for the study of light-matter interaction and beam shaping with nanostructures. The MSIS system can give the comprehensive information of nanophotonic materials, and is greatly useful for the study of novel photonic phenomena and the development of nanophotonic technologies.

A Facile One-Step Synthesis of TiOe/Graphene Composites for Photodegradation of Methyl Orange

TiO2/graphene composite photocatalysts have been prepared by a simple liquid phase deposition method using titanium tetrafluoride and electron beam （EB） irradiation-pretreated graphene as the raw materials. The products were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The effects of varying the synthesis parameters such as graphene content, concentration of titanium tetrafluoride solution and irradiation dose were investigated. It was found that the preparation conditions had a significant effect on the structure and properties of the final products. The irradiated graphene was covered with petal-like anatase TiO2 nanoparticles, which were more uniform and smaller in size than those in products synthesized without EB irradiation-pretreated graphene. The photocatalytic activities of the products were evaluated using the photocatalytic degradation of methyl orange as a probe reaction. The results showed that the products synthesized using EB irradiation-pretreated graphene exhibited higher photocatalytic activities than those using graphene without EB irradiation pretreatment.

Non-thermal radiation heating synthesis of nanomaterials

The nanoscale effect enables the unique magnetic,optical,thermal and electrical properties of nanostructured materials and has attracted extensive investigation for applications in catalysis,biomedicine,sensors,and energy storage and conversion.The widely used synthesis methods,such as traditional hydrothermal reaction and calcination,are bulk heating processes based on thermal radiation.Differing from traditional heating methods,non-thermal radiation heating technique is a local heating mode.In this regard,this review summarizes various non-thermal radiation heating methods for synthesis of nanomaterials,including microwave heating,induction heating,Joule heating,laser heating and electron beam heating.The advantages and disadvantages of these non-thermal radiation heating methods for the synthesis of nanomaterials are compared and discussed.Finally,the future development and challenges of non-thermal radiation heating method for potential synthesis of nanomaterials are discussed.

Effects of vacancies on interwall spacings of multi-walled carbon nanotubes

We use molecular dynamics (MD) simulations to study the effects of vacancies on tube diameters and interwall spacings of multi-walled carbon nanotubes (MWCNTs). Two types of vacancies, double vacancy and three dangling-bond (3DB) single vacancy, are identified to have opposite effects on the tube size change, which explains the inconsistency of the experimentally measured interwall spacings of MWCNTs after electron beam irradiation. A theoretical model to quantitatively predict the shrunk structures of the irradiated MWCNTs is further developed. We also discuss the fabrications of prestressed MWCNTs, in which reduced interwall spacings are desired to enhance the overall elastic modulus and strength.