电子束曝光机的偏转系统

电子束曝光机的偏转系统控制电子束偏转扫描。像差低、偏转灵敏度高、扫描速度快是它的基本要求。对各种偏转器、偏转方式进行分析、比较,从偏转器空间场的数值计算方法、偏转系统的优化、像差校正、偏转器制作工艺、电气参数等方面阐述设计过程和工程实现上一些值得注意的问题。综合考虑偏转器和偏放电路的设计可以得到最优性能的系统。     

Spectral properties of nanoengineered Ag/Au bilayer rods fabricated by electron beam lithography

Ag/Au bimetallic nanoparticles possess the combinatory advantages of Au and Ag nanoparticles and can also be utilized to tune the properties of localized surface plasmon resonance. Ag/Au bilayer nanorods were prepared by electron beam lithography, and their spectral properties were investigated. Compared with Ag monolayer nanorods, Ag/Au bilayer nanorods show broader localized surface plasmon resonance bands, and the longitudinal mode and transverse mode localized surface plasmon bands show blueshift and redshift, respectively. The maximum near-field intensity of the longitudinal mode of the Ag/Au nanorod is less than half that of the Ag/Au nanorod without gold layer. Shape-induced modification of Ag/Au bilayer nanorods on their spectral properties was also discussed.     

Electron beam lithography developed resist profile improved by quality analysis

A numerical experiment of electron beam lithography (EBL) using the computer simulation tool SELID is presented and analysed. A layout of parallel lines with 0.3 μm width, situated 0.4 μm from each other, is obtained through exposure and development of the positive resist PMMA. Through a model-based approach an analysis of the influence of the exposure dose, the acceleration voltage and the resist thickness on: (i) the width of the developed resist profile, measured at the interface between the resist and the substrate, (ii) the measured width at a height of 5% of the initial resist thickness from the substrate, (iii) the average sidewall angle of the developed resist trench edge and (iv) the thickness loss of the developed resist in the non-irradiated areas is made. Concrete conclusions concerning the role of these factors are drawn. Optimisation is done using the quality criteria of obtaining developed resist profiles with parallel sidewalls. In order to find the parameter areas where the deviation from the target values of the performance characteristics above will be minimal in mass production two models, for the mean value and the variance, are proposed and estimated for tolerance limits of the factors of about 5%. The proposed approaches can be applied also with other simulation models, parameters and resists, as well as with real experimental EBL data.     

Combinatorial optimization of a molecular glass photoresist system for electron beam lithography

Electron beam lithography is a powerful technique for the production of nanostructures but pattern quality depends on numerous interacting process variables. Orthogonal gradients of resist composition, baking temperatures, and development time as well as dose variations inside writing fields are used to prepare ternary combinatorial libraries for an efficient stepwise optimization of a molecular glass negative tone resist system.     

电子束辐照法合成钴纳米粒子的表征

本文论述了在常温常压、无任何催化剂的条件下,通过电子束辐照制备纳米钴。利用X射线衍射仪（XRD）、透射电子显微镜（TEM）和差热分析仪（DSC）分别分析了纳米钴的结构、行貌、大小和熔点。利用激光散射粒度分布仪（LSPSDA）观察了纳米钴的粒度分布,并用样品振荡磁力计（VSM）分析了纳米钴的磁性。结果表明实验所制得的纳米钴粒子平均粒径32nm,粒度分布窄,熔点显著降低。最后,探讨了纳米钴的形成机理。     

Effect of molecular adsorption on the electrical conductance of single au nanowires fabricated by electron-beam lithography and focused ion beam etching

Metal nanowires are one of the potential candidates for nanostructured sensing elements used in future portable devices for chemical detection; however, the optimal methods for fabrication have yet to be fully explored. Two routes to nanowire fabrication, electron-beam lithography (EBL) and focused ion beam (FIB) etching, are studied, and their electrical and chemical sensing properties are compared. Although nanowires fabricated by both techniques exhibit ohmic conductance, I-V characterization indicates that nanowires fabricated by FIB etching exhibit abnormally high resistivity. In addition, the resistivity of nanowires fabricated by FIB etching shows very low sensitivity toward molecular adsorption, while those fabricated by EBL exhibit sensitive resistance change upon exposure to solution-phase adsorbates. The mean grain sizes of nanowires prepared by FIB etching are much smaller than those fabricated by EBL, so their resistance is dominated by grain-boundary scattering. As a result, these nanowires are much less sensitive to molecular adsorption, which mediates nanowire conduction through surface scattering. The much reduced mean grain sizes of these nanowires correlate with Ga ion damage caused during the ion milling process. Thus, even though the nanowires prepared by FIB etching can be smaller than their EBL counterparts, their reduced sensitivity to adsorption suggests that nanowires produced by EBL are preferred for chemical and biochemical sensing applications.     

Reversible formation of CdSe nanoparticles in aqueous solutions by high-energy electron beam irradiation

An unusual reversible effect was observed in the synthesis of CdSe nanoparticles in the aqueous tertiary butanol solutions containing equimolar Cd[NH₃]₄SO₄ and Na₂SeSO₃ by the high-energy electron beam irradiation. These nanoparticles were found to be unstable in the aqueous solutions and decomposed upon exposure to air/oxygen. However, they were stable in the de-aerated aqueous solutions and both aerated and de-aerated organic solvents. The decomposed aqueous solutions again produced these nanoparticles upon irradiation with the electron beam. On the contrary, the cadmium selenide nanoparticles synthesized with the cobalt-60 γ-irradiation, were stable under ambient conditions and did not exhibit any reversible behavior. This was attributed to the vast differences in the dose rates involved in the two types of synthetic processes, leading to a remarkable variation in the crystal structure and size of the nanoparticles.     

Control of the electron beam active zone position in electron beam welding processes

It is known that charged particles emitted from the region of electron beam (EB) interaction with the material being processed, are an important source of information for the understanding of EB welding processes. Measurements for the three largest groups of charged particles, namely, backscattered electrons, true secondary electrons and ions are presented here. It was estimated that only the signals of the direct component amplitude of these particles’ currents, processed by neural networks, could be used to effectively control the EB welding process. Computer simulations of various models of neural networks are described. The best result was obtained for a network that determines an optimal value of focusing current for the weld being made, based on the amplitude of signals measured with a moderately defocused EB.     

Effect of electron beam irradiation on the electrical and optical properties of ITO/Ag/ITO and IZO/Ag/IZO films

We have investigated the effect of electron beam irradiation as well as insertion of a Ag layer on the electrical and optical properties of the ITO or IZO films. The results show that electron beam irradiation as well as inserting a very thin Ag layer can significantly reduce sheet resistance of the ITO/Ag/ITO and IZO/Ag/IZO films. The electron beam irradiation also increases light transmittance and optical band gap of the ITO/Ag/ITO multilayer films; meanwhile, it has not influence on the transmittance of the IZO/Ag/IZO films. These results can be explained by that In and Zn cation in IZO film have strong tendency to preserve their coordination with oxygen.     

Osteoprogenitor response to low-adhesion nanotopographies originally fabricated by electron beam lithography

It is considered that cells can use filopodia, or microspikes, to locate sites suitable for adhesion. This has been investigated using a number of mature cell types, but, to our knowledge, not progenitor cells. Chemical and topographical cues on the underlying substrate are a useful tool for producing defined features for cells to respond to. In this study, arrays of nanopits with different symmetries (square or hexagonal arrays with 120 nm diameters, 300 nm center–centre spacings) and osteoprogenitor cells were considered. The pits were fabricated by ultra-high precision electron-beam lithography and then reproduced in polycarbonate by injection moulding with a nickel stamp. Using scanning electron and fluorescence microscopies, the initial interactions of the cells via filopodia have been observed, as have subsequent adhesion and cytoskeletal formation. The results showed increased filopodia interaction with the surrounding nanoarchitecture leading to a decrease in cell spreading, focal adhesion formation and cytoskeletal organisation.     

Nanostructures and functional materials fabricated by interferometric lithography

Interferometric lithography (IL) is a powerful technique for the definition of large-area, nanometer-scale, periodically patterned structures. Patterns are recorded in a light-sensitive medium, such as a photoresist, that responds nonlinearly to the intensity distribution associated with the interference of two or more coherent beams of light. The photoresist patterns produced with IL are a platform for further fabrication of nanostructures and growth of functional materials and are building blocks for devices. This article provides a brief review of IL technologies and focuses on various applications for nanostructures and functional materials based on IL including directed self-assembly of colloidal nanoparticles, nanophotonics, semiconductor materials growth, and nanofluidic devices. Perspectives on future directions for IL and emerging applications in other fields are presented.     

Production of silver nano-powders by electron beam evaporation

Evaporation of metallic silver was performed in Ar, N₂ and He using the ELV-6 electron accelerator. The obtained ultra-dispersed powders with a particle size of 70-80 nm were investigated by XRD, HREM and UV-Vis spectroscopy. The structure of Ag(Ar) powder was shown to differ substantially from that of Ag(N₂) by the presence of small oxide-like species of 10-20 nm on the particle surface. Catalytic activity of the powders in the reaction of ethylene epoxidation was also studied.     

Magnetization reversal in nanotriangles fabricated by nanosphere lithography

We report on the magnetization reversal behavior of sub 100-nm triangular shaped Ni₈₀Fe₂₀ dot array fabricated by nanosphere lithography. Hysteresis loops measured by magneto-optical Kerr effect magnetometry are classified into single and double-switched loops in 45 nm, 80 nm and 100 nm triangular nanomagnets. Micromagnetic simulations show that a plateau observed in the double-switched loop in the 100-nm triangular nanomagnet is due to the formation of a metastable mediating V state.     

A new generation of power supplies for electron beam welding machines

Widely used electron beam welding machines are equipped with heavy power supplies, located in a special oil tank and connected with an electron gun to a high-voltage cable. A special system detects electric discharges in the electron gun space, which may arise during welding and then it tries to switch off the high voltage to interrupt an electric arc. Such disadvantages have been eliminated with the novel power supply described here. The Q of resonance circuit of this supply is stabilized and as a result circulating power appears. During an electric discharge in the gun, power is not sent to the electron gun but circulates between the electronic parts of the resonance circuit without losses and “waits” for the break in the short circuit. The power supply is much smaller and lighter than supplies of similar rating used nowadays. It is connected directly to the electron gun chamber without a high-voltage cable. The first construction of the supply was designed for electron beam welding machine of 5 kW power and 60 kV accelerating voltage. Tests of the new power supply in laboratory and industrial conditions have shown its usefulness for electron beam welding.     

Pronounced effects of anisotropy on plasmonic properties of nanorings fabricated by electron beam lithography

Gold nanoring dimers were fabricated via EBL with dimensions of 127.6 ± 2.5 and 57.8 ± 2.3 nm for the outer and inner diameters, respectively, with interparticle separations ranging from 17.8 ± 3.4 to 239.2 ± 3.7 nm. The coupling between the inner and outer surfaces of a single nanoring renders it very sensitive to any anisotropy. We found that anisotropy in the particle geometry and anisotropy introduced by the substrate combine to create very unique spectral features in this system.     

Patterning of polymer nanocomposite resists containing metal nanoparticles by electron beam lithography

Poly(vinyl pyrrolidone) (PVP)-stabilized silver nanoparticles (NPs) were used as a new nanocomposite resist for electron beam lithography. A nanocomposite resist prepared by reducing silver nitrate in an alcoholic PVP solution was patterned by using a scanning electron microscope equipped with a nanometer pattern generation system. Well-defined negative tone patterns with a good sensitivity of 200 microC/cm2 and a contrast of 2.83 were obtained using the prepared nanocomposite resist. In addition, the changes in the morphology and structure of the resist patterns with a thermal treatment temperature were investigated by a FE-SEM with an EDX. The results revealed that the patterns of Ag NPs were formed through sintering the formed resist patterns at above 300 degrees C.     

Preparation of PbSe nanoparticles by electron beam irradiation method

A novel method has been developed by electron beam irradiation to prepare PbSe nanoparticles. 2 MeV 10mA GJ-2-II electronic accelerator was used as radiation source. Nanocrystalline PbSe was prepared rapidly at room temperature under atmospheric pressure without any kind of toxic reagents. The structure and morphology of prepared PbSe nanoparticles were analysed by X-ray diffraction, transmission electron microscope and atomic force microscope. The results indicated that the obtained materials were cubic nanocrystalline PbSe with an average grain size of 30 nm. The optical properties of prepared PbSe nanocrystalline were characterized by using photoluminescence spectroscopy. The possible mechanism of the PbSe grain growth by electron beam irradiation method is proposed.     

Design optimization of a hairpin electron source for electron beam welding

We report the optimization of the design and performance of recently reported hairpin tungsten electron source as a cathode in diode type geometry of the gun. The temperature maximum has been shifted close to the crown of the source. Focusing of the beam has been achieved up to 1 mm in diameter with Gaussian profile of the beam at the target. The perveance and power density measured are 10⁻⁵ A V^−3/2 and 10⁶ W cm⁻², respectively.     

Step-wise Ag thin film patterns fabricated by holographic lithography

A laser-induced thermo-elastic removal was used to pattern nanostructured silver thin films solution-deposited on the glass substrate. We show that sharp-edged patterns can be fabricated under an interference-generated gradual intensity profile. The etching behavior and the resulting pattern morphology were very sensitive to the cohesion of the film and its adhesion to the substrate, being both modified by the post-deposition annealing process. The fabrication of step-wise one-dimensional (1D) and 2D patterns at the micrometer scales is demonstrated by holographic lithography using an Nd:YAG pulsed laser, along with a discussion on the effect of film cohesion and adhesion.