Co-doped BaFe_(2)As_(2) Josephson junction fabricated with a focused helium ion beam

Josephson junction plays a key role not only in studying the basic physics of unconventional iron-based superconductors but also in realizing practical application of thin-film based devices,therefore the preparation of high-quality iron pnictide Josephson junctions is of great importance.In this work,we have successfully fabricated Josephson junctions from Co-doped BaFe_(2)As_(2)thin films using a direct junction fabrication technique which utilizes high energy focused helium ion beam(FHIB).The electrical transport properties were investigated for junctions fabricated with various He^(+)irradiation doses.The junctions show sharp superconducting transition around 24 K with a narrow transition width of 2.5 K,and a dose correlated foot-structure resistance which corresponds to the effective tuning of junction properties by He^(+)irradiation.Significant J_c suppression by more than two orders of magnitude can be achieved by increasing the He^(+)irradiation dose,which is advantageous for the realization of low noise ion pnictide thin film devices.Clear Shapiro steps are observed under 10 GHz microwave irradiation.The above results demonstrate the successful fabrication of high quality and controllable Co-doped BaFe_(2)As_(2)Josephson junction with high reproducibility using the FHIB technique,laying the foundation for future investigating the mechanism of iron-based superconductors,and also the further implementation in various superconducting electronic devices.

Half-integer Shapiro steps in MgB_(2) focused He ion beam Josephson junctions

Half-integer microwave induced steps(Shapiro steps)have been observed in many different Josephson junction systems,which have attracted a lot of attention because they signify the deviation of current phase relation(CPR)and uncover many unconventional physical properties.In this article,we first report the discovery of half-integer Shapiro steps in MgB_(2)focused He ion beam(He-FIB)Josephson junctions.The half-integer steps'dependence on microwave frequency,temperature,microwave power,and magnetic field is also analyzed.We find that the existence of half-integer steps can be controlled by the magnetic field periodically,which is similar to that of high temperature superconductor(HTS)grain boundary junctions,and the similarity of the microstructures between gain boundary junctions and He-FIB junctions is discussed.As a consequence,we mainly attribute the physical origin of half-integer steps in MgB_(2)He-FIB junctions to the model that a He-FIB junction is analogous to a parallel junctions'array.Our results show that He-FIB technology is a promising platform for researching CPR in junctions made of different superconductors.

Annealing treatment of focused gallium ion beam processing of SERS gold substrate

Raman spectroscopy is a type of inelastic scattering spectroscopy that is widely used in determining and analyzing molecular structure.It also has a number of practical applications in evaluating food safety,medicine,and forensics.The Raman spectral signal is weak,but the development of the surface-enhanced Raman scattering(SERS)technique has overcome this problem and led to further developments in Raman spectroscopy.This paper describes a fundamental study of the use of focused ion beam(FIB)direct writing for preparing gold substrates for SERS.Molecular dynamics and Monte Carlo simulation methods are used to investigate the damage induced by gallium ion implantation of a gold substrate.Based on characterization by x-ray photoelectron spectroscopy(XPS)and scanning electron microscopy,the mechanism by which ion implantation and annealing influence the damage induced by a gallium FIB is analyzed.After annealing at 350 XC,a mixture of metallic gallium,its oxide Ga2O3 conforming to the stoichiometric ratio,and its sub-stable oxide(Ga2Ox)in sub-stoichiometric ratio precipitated on the surface are detected by XPS.Annealing treatment can effectively reduce the effect of gallium ion implantation on a SERS substrate fabricated by FIB direct writing.

High-Temperature Superconducting YBa_(2)Cu_(3)O_(7-δ)Josephson Junction Fabricated with a Focused Helium Ion Beam

As a newly developed method for fabricating Josephson junctions,a focused helium ion beam has the advantage of producing reliable and reproducible junctions.We fabricated Josephson junctions with a focused helium ion beam on our 50 nm YBa_(2)Cu_(3)O_(7-δ)(YBCO)thin films.We focused on the junction with irradiation doses ranging from 100 to 300 ions/nm and demonstrated that the junction barrier can be modulated by the ion dose and that within this dose range,the junctions behave like superconductor–normal conductor–superconductor junctions.The measurements of the I–V characteristics,Fraunhofer diffraction pattern,and Shapiro steps of the junctions clearly show AC and DC Josephson effects.Our findings demonstrate high reproducibility of junction fabrication using a focused helium ion beam and suggest that commercial devices based on this nanotechnology could operate at liquid nitrogen temperatures.

Ordered SrTiO_3 Nanoripples Induced by Focused Ion Beam

Ordered nanoripples on the niobium-doped SrTiO_3 surfaces were fabricated through focused ion beam bombardment. The surface morphology of the SrTiO_3 nanoripples was characterized using in situ focused ion beam/scanning electron microscopy. The well-aligned SrTiO_3 nanostructures were obtained under optimized ion irradiation conditions. The characteristic wavelength was measured as about 210 nm for different ion beam currents. The relationship between the ion irradiation time and current and SrTiO_3 surface morphology was analyzed. The presented method will be an effective supplement for fabrication of SrTiO_3 nanostructures that can be used for ferroelectric and electronic applications.

Three-dimensional vertical ZnO transistors with suspended top electrodes fabricated by focused ion beam technology

Three-dimensional(3D)vertical architecture transistors represent an important technological pursuit,which have distinct advantages in device integration density,operation speed,and power consumption.However,the fabrication processes of such 3D devices are complex,especially in the interconnection of electrodes.In this paper,we present a novel method which combines suspended electrodes and focused ion beam(FIB)technology to greatly simplify the electrodes interconnection in 3D devices.Based on this method,we fabricate 3D vertical core-double shell structure transistors with ZnO channel and Al_(2)O_(3) gate-oxide both grown by atomic layer deposition.Suspended top electrodes of vertical architecture could be directly connected to planar electrodes by FIB deposited Pt nanowires,which avoid cumbersome steps in the traditional 3D structure fabrication technology.Both single pillar and arrays devices show well behaved transfer characteristics with an Ion/Ioff current ratio greater than 106 and a low threshold voltage around 0 V.The ON-current of the 2×2 pillars vertical channel transistor was 1.2μA at the gate voltage of 3 V and drain voltage of 2 V,which can be also improved by increasing the number of pillars.Our method for fabricating vertical architecture transistors can be promising for device applications with high integration density and low power consumption.

聚焦离子束(Focused Ion Beam)原理与其在半导体工业之应用

聚焦离子束被广泛应用于芯片电路修改、研磨、沉积和二次电子/离子成像。FIB对于新原型电路设计的修改以及离子间交互作用的基础研究具有独特之性能。使用极细的聚焦离子束,FIB技术可以进行比从前更加精确的产品失效分析。操作者可以快速地、选择性地去除绝缘层或金属层,以便进行集成电路下层信号的点针探测或材质分析。集成电路的断面切割还可以达到亚微米的精度。

Monte Carlo Si mulation of Damage Depth in Focused Ion Beam Milling Si_3N_4 Thin Film

The damage properties of Focused Ion Beam(FIB) milling Si3N4 thin film are investigated by the detailed analyzing images of nanoholes and simulation of Monte Carlo. The damage depth in the Si3N4 thin film for two different ion species(Gallium and Arsenic) under various parameters(ion energy, angle of incidence) are investigated by Monte Carlo method. The simulations show the damage depth increases with the increasing ion energy, the damage depth is dependent on the angle of incident ion, the curves of the damage depth for Ga ion and As ion at 30 keV nearly superpose, while the damage depth for Ga with 90 keV ion is more than that for As ion with the same energy.

Control of beam halo-chaos by sample function

The K-V beam through an axisymmetric uniform-focusing channel is studied using the particle-core model. The beam halo-chaos is found, and a sample function controller is proposed based on mechanism of halo formation and strategy of controlling halo-chaos. We perform multiparticle simulation to control the halo by using the sample function controller. The numerical results show that our control method is effective. We also find that the radial ion density changes when the ion beam is in the channel： not only can the halo-chaos and its regeneration be eliminated by using the sample function control method, but also the density uniformity can be found at the beam＇s centre as long as an appropriate control method is chosen.

Control of Beam Halo-Chaos for an Intense Charged-Particle Beam Propagating Through Double Periodic Focusing Field by Soliton

We study an intense beam propagating through the double periodic focusing channel by the particle-coremodel,and obtain the beam envelope equation.According to the Poincare-Lyapunov theorem,we analyze the stabilityof beam envelope equation and find the beam halo.The soliton control method for controlling the beam halo-chaos isput forward based on mechanism of halo formation and strategy of controlling beam halo-chaos,and we also prove thevalidity of the control method,and furthermore,the feasible experimental project is given.We perform multiparticlesimulation to control the halo by using the soliton controller.It is shown that our control method is effective.We alsofind the radial ion density changes when the ion beam is in the channel,not only the halo-chaos and its regeneration canbe eliminated by using the nonlinear control method,but also the density uniformity can be found at beam's centre aslong as an appropriate control method is chosen.

基于MD模拟的低能FIB辐照金刚石靶材亚表层损伤形成机理研究

聚焦离子束(focused Ion beam,FIB)作为一种用于金刚石微铣刀的特种加工方式,其引发的损伤程度直接关联到刀具的加工性能和寿命。课题组采用LAMMPS软件进行分子动力学(Molecular Dynamics,MD)模拟,结合SRIM软件的分析结果,探究单晶金刚石亚表层损伤的形成机理和入射离子能量对损伤深度和范围的影响。模拟结果表明:随着入射离子能量的提升,离子束在材料内的渗透深度及引起的非晶层和点缺陷损伤均有所增加;进一步的研究发现损伤形成过程中材料局部温度的上升可能诱发自退火现象,且与离子入射能量成正比,该现象对于理解聚焦离子束加工引起的损伤有着至关重要的意义;而势能的变化与损伤形成之间的显著对应关系揭示了第一邻近原子的势能明显高于第二邻近原子,进而高于Other类型原子,这一发现有助于深入理解损伤形成的微观过程。因此,精确控制入射能量是实现金刚石材料高精度聚焦离子束加工的关键,且对自退火效应和势能变化的研究对损伤监控与控制同样重要。

Imaging the interphase of carbon fiber composites using transmission electron microscopy:Preparations by focused ion beam, ion beam etching, and ultramicrotomy

Three sample preparation techniques, focused ion beam （FIB）, ion beam （IB） etching, and ultramicrotomy （UM） were used in comparison to analyze the interphase of carbon fiber ＇epoxy composites using transmission electron microscopy. An intact interphase with a relatively uniform thickness was obtained by FIB. and detailed chemical analysis of the interphase was investigated by electron energy loss spectroscopy. It shows that the interphase region is 200 mn wide with an increasing oxygen-to-carbon ratio from 10% to 19% and an almost constant nitrogen-to-carbon ratio of about 3%. However, gallium implantation of FIB tends to hinder fine structure analysis of the interphase. For IB etching, the interphase region is observed with transition morphology frona amorphous resin to nano-crystalline carbon fiber, but the uneven sample thickness brings difficulty for quantitative chemical analysis. Moreover, UM tends to cause damage and/or deformation on the interphase. These results are meaningful for in-depth understanding on the interphase characteristic of carbon fiber composites.

聚集离子束扫描电镜(FIB-SEM)在页岩纳米级孔隙结构研究中的应用

页岩中大量发育的纳米级孔隙组成了页岩气储集的主要空间。聚集离子束扫描电镜(FIB-SEM)通过对页岩样品的连续切割和成像,能够在纳米尺度上三维重建页岩的空间分布。依据不同岩石组分灰度值的差异,可以将页岩内的孔隙、有机质、黄铁矿等分割提取出来,不仅可以三维展示其空间分布形态,还可以对孔隙的分布特征和孔隙度等参数进行定量计算。聚集离子束扫描电镜在页岩纳米孔隙中的应用,将给页岩微观结构的深入研究提供新的研究手段。

高性能聚焦离子束(FIB)系统及其在材料科学领域的应用

采用液态镓作为离子源的FIB系统在材料科学研究领域可以起非常重要的作用。离子束聚焦于样品表面,在不同大小、束流及通入不同辅助气体的情况下,可分别实现图形刻蚀、绝缘和金属膜的沉淀,扫描离子成像等功能。该系统有三大用途:形貌观察,分辨率高达5nm;微刻蚀以及微沉淀。本文介绍了FIB技术的应用。

聚焦离子束(FIB)刻蚀在光电子器件方面的应用

聚焦离子束无掩模微细加工技术逐渐引起人们的兴趣，它包括聚焦离子束无掩模刻蚀、注入、往积、光刻等。聚焦离子束刻蚀能在半导体激光器材料上加工得到具有光学精度的表面。首先论述聚焦离子束刻蚀的特点，然后概括说明目前它在光电子器件方面的若干应用。

FIB加工、扫描及透射电子显微镜相结合的复杂合金相层状组织表征

扫描电子显微镜(SEM)与聚焦离子束(FIB)可集成为双束系统,实现微区形貌观察与样品加工一体化,同时也可实现截面薄样品的定位提取。利用该技术并结合透射电镜(TEM)技术研究了Al-Pd-Fe复杂合金系铸态组织中层片结构的构成与分布特征。结果表明,铸态Al_(75)Pd_(15)Fe_(10)合金中的层片组织由M-Al_(13)Fe_4相与准晶相构成。通过对比发现,相同层片组织在背散射电子像与透射电镜观察下呈现出明显不同的分布特征。结合扫描与透射电子显微学成像原理,阐明了SEM和TEM两种表征方式产生不同结果的原因,指出了通过SEM,FIB以及TEM相结合对表征微细多相混合组织真实三维空间分布特征的必要性和有效性。

FIB/SEM双束系统在微纳米材料电学性能测试中的应用

电学性能测试是微纳米材料物性研究的重要组成部分,测试电极的制备是其中一个难点。光学光刻、电子束曝光或聚焦离子束加工是三种不同的电极制备技术。每种技术都有自己的特点,采用何种技术取决于微纳米材料的尺寸、形态及测试目的等诸多因素。此外,选择适当的制样方法对后续的电学性能测试也很关键。本文以一台配备了电子束曝光功能附件的聚焦离子束(FIB)/扫描电子显微镜(SEM)双束系统为工具,结合光学光刻等其它加工技术,详细介绍了其针对不同类型微纳米材料进行电极制备的过程和方法。

FIB/SEM双束系统在微纳加工与表征中的应用

简要回顾了聚焦离子束/扫描电子显微镜双束系统在国家纳米科学中心的应用。围绕透射电镜样品制备、扫描电子显微镜与扫描离子显微镜、纳米材料的二维与三维表征等材料表征,以及离子束直接刻蚀加工如光子晶体阵列器件原型加工、材料沉积加工如用于电学性能测试的四电极制作、指定点加工如原子力显微镜针尖修饰、三维加工、电子束曝光及其与聚焦离子束联合加工等纳米结构加工两方面,以些具体实例分类进行了介绍。针对限制其应用的些不利因素,如加工效率低、面积小、精度不足、加工损伤等问题,些新技术如新型离子源Plasma、He+/Ne+离子等与现有Ga+聚焦离子束系统配合将成为未来发展方向。

基于FIB加工和SEM-EDS技术联用对共格BCC/B2高熵合金的元素分布表征分析

BCC/B2高熵合金中体心立方结构(body centered cube, BCC)纳米粒子影响其软磁性能和高温力学性能。然而,扫描电子显微镜-能量色散谱仪(scanning electron microscopy-X-ray energy dispersive spectroscopy, SEM-EDS)难以表征BCC纳米粒子的元素分布。本文利用聚焦离子束(focused ion beam, FIB)和SEM-EDS联用,制备BCC/B2高熵合金的纳米尺度薄片,并对其元素分布进行了研究。结果表明,AlCoFeCr高熵合金微观组织是由B2相与共格的BCC相构成,其中BCC粒子约为20~40 nm。对比SEM-EDS对块体试样和FIB制备的纳米尺度的薄片元素分布结果,FIB制备的纳米薄片提高了EDS的分辨率,BCC纳米粒子富集Cr元素,且B2基体相富集Al、Co和Fe元素。电子的加速电压和束流强度影响纳米薄片中BCC纳米粒子元素分布表征结果的准确性,其中30 kV 6.4 nA下元素分布表征结果的准确度最高。

Fabrication of Windowed Very-Small-Aperture Laser Diodes

A windowed very small aperture laser (VSAL) source for use in high resolution near field optical data storage is fabricated.The windowed regions are introduced to avoid shorting the pn junction with metal coating and suppress the COD effect.It facilitates producing VSAL by simplified technology and improves the laser performance.A VSAL with 400nm small aperture is demonstrated by focused ion beam (FIB) and the output power is 0 3mW at 31mA.