超冷离子源研究进展

纳米离子束是制备束斑直径在微纳米尺度荷能离子束的先进技术,主要应用于高分辨和高精度的离子束分析、离子束加工和离子束材料改性研究,在材料分析、微纳加工、微电子器件制造和量子计算等方面发挥着重要的作用.高品质离子源作为纳米离子束装置的关键部件,其性能指标直接决定着该装置的技术水平.然而,目前常用的传统离子源存在离子种类单一、能散高和结构复杂等问题,已经难以满足新应用场景下的多离子种类和高分辨的要求,突显出研发新型离子源的重要性和迫切性.随着激光冷却技术的日臻成熟,基于光电离冷原子和激光冷却离子技术可以获得温度在mK甚至μK量级的超冷离子,其低温和易于操控等典型特征极大地促进了超冷离子源的发展.超冷离子具有极小的横向速度发散,可以显著提升离子源的亮度和发射度等品质参数,为纳米离子束技术的革新带来了巨大的发展机遇.因此,超冷离子源的研究对于实现更高亮度、更小尺寸、更低能散、更多样化离子种类以及结构更简化的高品质离子源具有重要的意义.本文综述了近年来超冷离子源的研究进展,从制备原理、产生方式以及典型应用等方面介绍了磁光阱离子源、冷原子束离子源和超冷单离子源在基础研究和应用技术研发方面取得的重要成果,并对超冷离子源的未来发展和应用前景进行了展望.

Characterization of carbon encapsulated Fe-nanoparticles prepared by confined arc plasma

Carbon encapsulated Fe nanoparticles were successfully prepared via confined arc plasma method. The composition, morphology, microstructure, specific surface area and particle size of the product were characterized via X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectrometry and Brunauer-Emmett-Teller N2 adsorption. The experiment results show that the carbon encapsulated Fe nanoparticles have clear core-shell structure. The core of the particles is body centered cubic Fe, and the shell is disorder carbons. The particles are in spherical or ellipsoidal shapes. The particle size of the nanocapsules ranges from 15 to 40 nm, with the average value of about 30 nm. The particle diameter of the core is 18 nm, the thickness of the shells is 6-8 nm, and the specific surface area is 24 m2/g.

Gas-Phase Deposited Plasmonic Nanoparticles Supported on 3D-Graphene/Nickel Foam for Highly SERS Detection

In this work, we proposed a novel three-dimensional (3D) plasmonic nanostructure based on porous graphene/nickel foam (GNF) and gas-phase deposited Ag nanoparticles (NPs). Ag NPs with high density were directly deposited on the surface of 3D GNF by performing a novel cluster beam deposition approach. In comparison with traditional Ag substrate (SiO2/Ag), such hot-spots enriched 3D nanostructure showed extremely high electromag-netic field enhancement under incident light irradiation which could be used as a sensitive chemical sensor based on surface enhanced Raman scattering (SERS). The experimental results demonstrated that the proposed nanostructure showed superior SERS performance in terms of Raman signal reproducibility and sensitivity for the probe molecules. 3D full-wave simulation showed that the enhanced SERS performance in this 3D hierarchical plasmonic nanostructure was mainly obtained from the hot-spots between Ag NPs and the near-field coupling between Ag NPs and GNF sca olds. This work can provide a novel assembled SERS substrate as a SERS-based chemical sensor in practical applications.

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.

Modulating the threshold voltage of oxide nanowire field-effect transistors by a Ga^＋ ion beam

In this paper, we report a method to change the threshold voltage of SnO2 and In2O3 nanowire transistors by Ga^＋ ion irradiation. Unlike the results in earlier reports, the threshold voltages of SnO2 and In2O3 nanowire field-effect transistors （FETs） shift in the negative gate voltage direction after Ga^＋ ion irradiation. Smaller threshold voltages, achieved by Ga^＋ ion irradiation, are required for high-performance and low-voltage operation. The threshold voltage shift can be attributed to the degradation of surface defects caused by Ga＋ ion irradiation. After irradiation, the current on/off ratio declines slightly, but is still close to -106. The results indicate that Ga^＋ ion beam irradiation plays a vital role in improving the performance of oxide nanowire FETs.

Vectorial holography-mediated growth of plasmonic metasurfaces

Nowadays,the electromagnetic properties of artificial photonic materials can be well-tuned via designs over their composition and geometries.However,engineering the properties of artificial materials at the nanoscale is challenging and costly.Here we demonstrate a facile and low-cost method for fabricating large-area silver nanoparticle metasurfaces(AgNPMSs)by using the vectorial holography-mediated growth technique.The AgNPMS,which can be regarded as a hologram device,possesses excellent chiroptical properties.The vectorial holographic technique may open avenues for fabricating novel chiroptical metamaterials with large degrees of freedom,which can be further used for beam steering,photocatalysis,biosensing,etc.

Microstructure and mechanical properties of Ti Al Si N nano-composite coatings deposited by ion beam assisted deposition

TiA1SiN nano-composite coatings with Silicon contents from 4.1 to 23.9 at.% were deposited on Silicon wafers. The nano- hardness, microstructure, and adhesion force of the coatings were deeply affected by Silicon contents. The TiA1SiN with 9.0 at.% Silicon has a maximum hardness of 40.9 GPa, a highest adhesion force of 67 N and a lowest friction coefficient of 0.5. Microstructures show that Silicon doping increases the hardness of coating due to solid solution hardening effect and grain boundary enhancement effect. The amorphous Si3N4 matrix, which contains （Ti,Al）N nano-crystals, is formed as the Silicon content is increased. The matrix contributes to the nano-hardness and helps to resist surface oxidization. Especially, the matrix induces low surface roughness and decreases the friction coefficient.

Fabrication technique of micro/nano-scale speckle patterns with focused ion beam

The fabrication technique of micro/nano-scale speckle patterns with focused ion beam (FIB) system is studied for digital image correlation (DIC) measurement under a scanning electron microscope (SEM).The speckle patterns are fabricated by directly etching the counterpart of the specimen to the black part of a template.Mean intensity gradient is used to evaluate the quality of these SEM images of speckle patterns fabricated based on different templates to select an optimum template.The pattern size depending on the displacement measurement sensitivity is adjusted by altering the magnification of FIB according to the relation curve of the etching size versus magnification.The influencing factors including etching time and ion beam current are discussed.Rigid body translation tests and rotation tests are carried out under SEM to verify the reliability of the fabricated speckle patterns.The calculated values are in good agreement with the imposed ones.