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.

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。

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.

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.

Effects of operating conditions on the performance degradation and anode microstructure evolution of anode-supported solid oxide fuel cells

Performance degradation shortens the life of solid oxide fuel cells in practical applications.Revealing the degradation mechanism is crucial for the continuous improvement of cell durability.In this work,the effects of cell operating conditions on the terminal voltage and anode microstructure of a Ni-yttria-stabilized zirconia anode-supported single cell were investigated.The microstructure of the anode active area near the electrolyte was characterized by laser optical microscopy and focused ion beam-scanning electron microscopy.Ni depletion at the anode/electrolyte interface region was observed after 100 h discharge tests.In addition,the long-term stability of the single cell was evaluated at 700℃for 3000 h.After an initial decline,the anode-supported single cell exhibits good durability with a voltage decay rate of 0.72%/kh and an electrode polarization resistance decay rate of 0.17%/kh.The main performance loss of the cell originates from the initial degradation.

原子力显微镜-扫描电子显微镜共定位表征系统的研发与应用

微纳加工过程中,常有样品需要进行聚焦离子束(FIB)溅射、切割,扫描电子显微镜(SEM)以及原子力显微镜(AFM)表征,而这三类仪器都需要将样品固定在样品台上才可测试,固定不佳会影响表征结果.但固定好的样品在不同仪器之间转移、拆卸、再固定的过程中极易受到破坏.基于以上问题,设计了AFM-SEM-FIB样品共定位系统,可实现样品在此三种仪器之间的无损转移及共定位,避免珍贵样品破坏及目标丢失,以及解决AFM扫描无法控制方向、迅速调整位点等问题.在微纳表征中有优异的表现,系统已被开发成产品并量产销售.

光子晶体Micro LED微显示阵列加工及光学特性分析

Micro LED器件具有高亮度、低功耗和高可靠性等优点,但Micro LED显示像素巨量转移和光提取效率低的问题为其应用带来挑战。开发了具有高转移效率和出光效率的单片64×64 Micro LED微显示阵列,提出了倒装型GaN基单片Micro LED微显示阵列芯片和Si基驱动电路的设计方法及集成工艺。通过时域有限差分(FDTD)方法对Micro LED微显示阵列光学特性进行了建模分析,设计了一种提高Micro LED微显示阵列出光效率的光提取结构。结合仿真结果,开发了一种在Micro LED蓝宝石衬底表面制备光子晶体结构的聚焦离子束(FIB)微纳加工工艺,并进行了器件加工。测试结果表明,蓝宝石衬底上加工的光子晶体结构可以提高Micro LED器件的表面出光效率,光功率平均值提升了16.36%,对Micro LED微显示阵列加工及微显示像素光提取问题具有借鉴意义。

高侧壁垂直度超浅铌酸锂光栅耦合器的加工工艺及耦合效率

利用聚焦离子束(FIB)在铌酸锂(LN)表面形成100 nm及以下深度的超浅光栅耦合器结构。为了提高刻蚀侧壁垂直度、避免开口展宽效应对光栅形貌的影响,在LN表面覆盖非晶硅(α-Si)作为掩膜层,实际刻蚀深度为α-Si层厚度和LN表面目标刻蚀深度之和,且刻蚀过程中产生的开口效应仅存在于α-Si层。通过氢氧化钾(KOH)溶液选择性地去除α-Si层,留下的LN表面结构侧壁陡直且无开口展宽效应。制备了刻蚀深度108 nm的超浅光栅耦合器,在924 nm波长处,其耦合效率为23.3%。制备了刻蚀深度70 nm的超浅光栅耦合器,在935 nm波长处,其耦合效率为14.4%。该研究为LN光栅耦合器的发展与应用提供了有益指导。

聚焦离子束加工的硅酸钇波导中铕离子的光学与超精细跃迁

量子存储是大尺度量子网络的重要组成部分,基于波导等微纳结构的可集成量子存储可以提供更好的可扩展性并实现更低的光电能耗.在众多量子存储候选介质中,^(151)Eu^(3+):Y_(2)SiO_(5)晶体具有长达6 h的自旋相干寿命和1 h的相干光存储时间,成为长寿命存储的优异候选材料.本文通过聚焦离子束在^(151)Eu^(3+):Y_(2)SiO_(5)晶体表面加工出三角形悬梁臂波导,波导截面的边长为2μm,长度为20μm,并对三角形悬梁臂波导中的^(151)Eu^(3+)离子的^(7)F_(0)-^(5)D_(0)光学跃迁以及^(7)F_(0)基态的超精细跃迁开展了研究.结果显示,在2μm尺度的悬梁臂波导中^(151)Eu^(3+)离子基本保持了和块状晶体中^(151)Eu^(3+)离子一致的跃迁展宽及相干寿命,可以支持量子存储任务的实现.该工作为实现纳米尺度的^(151)Eu^(3+)离子可集成量子存储器以及单个^(151)Eu^(3+)离子的探测打下基础.

体电子显微成像技术在肝癌细胞超微结构分析中的应用研究

体电子显微成像技术(volume electron microscopy)可以在更大三维空间中对样品进行纳米分辨率三维结构分析,获取样品内部结构的三维模型和各结构之间的位置关系、体积比例等信息,更加全面地反映样品的超微结构与功能的关系。本文利用基于聚焦离子束扫描电镜的体电子显微成像技术对人源肝癌细胞的三维超微结构进行分析,获得了多种细胞器包括细胞核、线粒体、内质网和高尔基体等的高分辨率三维结构模型。

聚焦离子束工艺参数对单像素线刻蚀的影响

单像素线刻蚀是制备微纳米器件中的基本单元及加工其他复杂结构的基础,对聚焦离子束(FIB)加工具有重要的意义。通过改变离子束流的大小、驻留时间、扫描步长百分比及离子剂量等参数,对硅表面进行单像素线刻蚀的研究。结果表明,在聚焦离子束加工中,离子剂量与刻蚀线条宽度和深度之间呈正相关,与宽深比之间呈负相关;离子束流大小的变化对刻蚀深度影响不明显,但刻蚀宽度和宽深比随离子束流的增大而增大。此外,随着离子束流驻留时间增加,刻蚀宽度增大而深度减小;随着扫描步长百分比的增大,刻蚀深度增大,刻蚀宽度减小,分析结果表明这些变化与加工过程中再沉积作用有关。本研究成果为后续复杂图形的精密加工提供了重要参考依据。

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.

基于双束切槽法的DZ125镍基合金喷丸残余应力的研究

喷丸是提高零部件抗疲劳强度的重要工艺,其中喷丸引入的残余应力对其有着巨大影响。目前,人们对喷丸的残余应力研究仍然不足,主要是因为各种测试方法存在各自的缺陷,无法满足工程的实际需要。针对工程实际中喷丸部件长时间处于热暴露工作环境的情况,基于双束切槽法研究高温时效对DZ125镍基合金喷丸残余应力的影响。结果表明,高温时效会大幅降低喷丸引入的残余压应力。

润滑油添加剂对齿轮微点蚀的影响研究

探索建立微牵引力测定仪(MTM)、聚离子束、扫描电子显微镜、透射电子显微镜和能量色散光谱相结合的方法对齿轮微点蚀进行识别和评价。研究发现:添加剂的减摩性能和抗磨性能是影响其抗微点蚀性能的关键因素,在MTM试验中存在一个摩擦轨迹宽度不大于400μm、摩擦因数不小于0.097的微点蚀易产生区域,添加剂和配方的研发应避开这个微点蚀易产生区域,综合平衡减摩性和抗磨性;添加剂所形成的耐机械剪切的摩擦膜抗磨性能越好,使得MTM试验中的摩擦轨迹更窄,应力更集中,更易产生微点蚀;在产生微点蚀的润滑体系中引入降低体系摩擦因数的添加剂可改善其抗微点蚀性能。

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。

双束电子显微镜在锂离子电池研究中的应用

锂离子电池技术作为新能源储存领域重要的电池技术,具有广阔的发展前景.近年来,电极材料的开发和制备工艺的优化成为了锂离子电池技术的研究重点.双束电子显微镜又称聚焦离子束–扫描电子显微镜(focused ion beam-scanning electron microscope,FIB-SEM),是一种兼具微纳加工和显微成像功能的显微分析仪器,具有精确定点加工、高分辨扫描成像、适用多种类样品等优点,可为锂离子电池材料表征提供重要的技术支撑.对锂离子电池材料研究中FIB-SEM的应用场景进行了总结,归纳了FIB-SEM和其他仪器联用可实现的拓展功能.最后,对FIB-SEM在锂离子电池材料研究中的潜在应用进行了展望.