Multi-element focused ion beams using compact microwave plasma ion source

Focused ion beams (FIB) are widely used for research and applications in nanoscience and technology. We have developed a compact microwave plasma based multi element FIB (MEFIB) system in order to widen the applications and overcome the limitations faced by conventional Liquid Metal Ion Source (LMIS) based FIB systems, that provide primarily Ga ions. The MEFIB source provides high density plasmas (∼1.5 × 10¹¹ cm⁻³) in a compact cross section. Recently the ion energy spread in the plasma meniscus from where the beams are extracted is found to be small (∼5 eV) [1–3]. The beam extraction and focusing are carried out using electrostatic multi electrode assembly. AXCEL INP and SIMION simulation codes are employed for the design of electrostatic Einzel lenses for beam focusing. The beam focal point is measured using a specially designed three slit Faraday cup and the spot size is measured by the micrography of craters formed by the focused ion beams impinging on copper and aluminium substrates. The initial experimental results show a focused beam spot size of ∼ 25 micron which is in good agreement with the simulations. By further reduction of electrode apertures and operating the second Einzel lens at higher potentials, submicron focused ion beams can be expected.     

Generation of optical contrast in insulating materials by irradiation with focused ion beams

The optical properties of crystalline insulating materials can markedly be modified by irradiation with energetic ions. The exposed areas of such materials absorb and reflect light more strongly than non-irradiated ones. In this way, optical contrast is created. With modern equipment, ion beams of sufficient intensity can be focused to submicron dimensions. Thus, both analog and digital information can be recorded with pixel densities of Gbit/cm² to Tbit/cm². In particular, crystalline films of group-IV elements of the periodic system, such as Si, SiC and C_D (diamond), are best suited for this novel ionographic process. The physical foundations of this technology and the resulting properties of the recorded data will be discussed. Received: 11 July 2000 / Accepted: 13 July 2000 / Published online: 13 September 2000     

Microfabrication techniques using focused ion beams and emergent applications.

The application of focused ion beam (FIB) machining in several technologies aimed at microstructure fabrication is presented. These emergent applications include the production of micromilling tools for machining of metals and the production of microsurgical tools. An example of the use of microsurgical manipulators in a circulatory system measurement is presented. The steps needed to transform the laboratory fabrication of these tools and manipulators into a routine FIB production process are discussed. The ion milling of three-dimensional cavities by the exact solution of a mathematical model of the FIB deflection is demonstrated. A good agreement between the model calculation and the ion beam control has been obtained for parabolic and cosine cross-section features with planes of symmetry.     

Processing of vacuum microelectronic devices by focused ion and electron beams

Localized physical and chemical reactions induced by focused ion and electron beams, i.e. dual beams, have been used to fabricate field emitters (FEs) and their arrays, field-emitter arrays (FEAs), without masking and annealing processes. Issues arising from beam processing such as beam-induced damage and contamination were eliminated to provide FEAs with low leakage current. Quick prototyping and repairing processes of FEs and FEAs using dual-beam processing have been demonstrated. Nb- or Au-gated Pt FEAs have been fabricated using dual beams. The fabricated FEAs showed a turn-on voltage of 40 V for field emission with a typical emission current of about 1 μA/tip. Received: 21 August 2002 / Accepted: 21 August 2002 / Published online: 12 February 2003 RID="*" ID="*"Corresponding author. Fax: +81-6/6850-6662, E-mail: takai@rcem.osaka-u.ac.jp     

New parameter correlations for deep penetration welding with high energy focused beams

As a result of the unification of two models previously described by the author, a three-dimensional treatment of the workpiece temperature distribution, which takes into consideration the solid to liquid phase change of the processed material, is presented for deep penetration welding (d.p.w.) with high energy focused beans.The new model improves the accuracy of weld geometry prediction by better correlating the shape, width and depth of the cross-section of the resolidified weld with beam characteristics, material thermophysical properties, workpiece velocity and preheating temperature.     

Workpiece temperature distribution for deep penetration welding with high energy focused beams

A solution for the two-dimensional temperature field in a workpiece at welding by laser or electron beams, which takes into consideration the solid-to-liquid phase change of the material, is presented. This leads to more precise process parameter correlations.     

CCD detector for high time resolution experiments with SR beams

A detector for fast diagnostics of particle beams in storage rings using an optical component of synchrotron radiation (SR) is developed. The detector records a limited series of one-dimensional or small two-dimensional images at a rate of (1?10) × 10⁶ frames/s. It can also be used for investigating fast processes in X-ray SR beams. In particular, matched with a structured scintillation screen (with low deexcitation time), this detector provides a recording with an SR flash rate of shadowgraph images (for axially symmetric objects, initial data for tomograms) or a record of the distribution of small-angle X-ray scattering. It is also possible to apply this detector as a dispersion-free image spectrometer; this would make it possible to perform pulsed X-ray diffraction studies with ??white?? SR beams. In the single-flash mode this would provide a record of the formation and behavior of crystalline phases in shock and detonation waves with a time resolution of up to 1 ns.     

High resolution in EUV spectroscopy of foil-excited fast ion beams

In high-resolution spectra of fast ion beams, employing a grating of high groove density in a 2m grazing-incidence monochromator, asymmetric line broadening has been observed. The effect is explained in terms of Doppler broadening and atomic lifetimes. Various procedures to reduce the broadening by narrowing the angular acceptance of the detection system have been applied. Line widths (FWHM) ofΔλ=3 pm at 8<λ/nm<17 have been obtained. Fine structure-resolvedn=2 ton=3 transitions in one-, two- and three-electron ions ofO andF are shown, demonstrating the feasibility of high resolution EUV spectroscopy using fast ion beams.     

The preheating temperature parameter for deep penetration welding with high energy focused beams

The effects of workpiece preheating at steady state deep penetration welding with high energy focused beams upon weld cross-section width and depth are investigated theoretically.Parameter correlations, with special attention focused on the preheating of the workpiece are presented as analytic expressions and visualized in a nomograph. Preheating leads to weld width and depth increase. The theoretical correlations are in qualitative agreement with experimental results reported in the literature.     

Spatial structure of high intensity focused ultrasound beams of various geometry

The influence of nonlinear and diffraction effects on distortion of the spatial structure of peak positive and negative pressures in focused acoustic beams was studied for a weakly dissipative propagation medium. The problem was solved numerically based on the Khokhlov-Zabolotskaya-Kuznetsov equation for beams with uniform and Gaussian distributions of the harmonic signal amplitude at the source.     

高功率离子束的应用研究

给出用“闪光二号”加速器高功率离子束轰击19F靶产生6~7MeV准单能脉冲γ射线的实验结果;提出采用离子束传输法分离和降低轫致辐射干扰的方法,利用闪烁体探测器和半导体探测器,测出质子传输不同距离后轰击C2F4靶产生的6~7MeV准单能脉冲γ射线信号以及相比轫致辐射的延迟时间;介绍了模拟材料的软X射线的热 力学效应等方面的高功率离子束的应用,给出一些实验和理论计算结果。     

高功率离子束的应用研究

 给出用“闪光二号”加速器高功率离子束轰击19F靶产生6~7MeV准单能脉冲γ射线的实验结果；提出采用离子束传输法分离和降低轫致辐射干扰的方法，利用闪烁体探测器和半导体探测器，测出质子传输不同距离后轰击C₂F₄靶产生的6~7MeV准单能脉冲γ射线信号以及相比轫致辐射的延迟时间；介绍了模拟材料的软X射线的热 力学效应等方面的高功率离子束的应用，给出一些实验和理论计算结果。     

分段表面放电沉积效率研究

利用一种结构紧凑的分段表面放电辐射源模块，详细研究了在不同电压、电容、气压实验条件下回路等效电阻、等效电感及放电能量沉积效率的变化规律，利用四分幅相机拍摄获得了不同实验条件下的放电等离子体通道图像，分析讨论了放电等离子体运动对放电能量沉积效率的影响，提出了提高能量放电沉积效率的有效途径。     

脉冲高功率离子二极管的动力学模拟

基于等离子体的爆炸发射模型,利用自洽的2.5维的胞中粒子（PIC）模拟程序MAGIC模拟了平板型磁绝缘离子二极管中电子和质子的动力学特性。给出了电压为300kV,外加磁场为2倍临界磁场情况下的二极管特性,阴阳极间隙中带电粒子的空间和相空间分布,以及净电荷密度分布和电场分布,结果表明,引出束流密度比单离子Child-Langmuir公式计算的结果大5倍;外加磁场导致在阴极附近形成虚阴极。空间电荷使得阴阳极间隙中电场扰动和增强。     

Imaging with unfocused regions of focused ultrasound beams

This article gives an analytical, computational, and experimental treatment of the spatial resolution encoded in unfocused regions of focused ultrasound beams. This topic is important in diagnostic ultrasound since ultrasound array systems are limited to a single transmit focal point per acoustic transmission, hence there is a loss of spatial resolution away from the transmit focus, even with the use of dynamic receive focusing. It is demonstrated that the spatial bandwidth of a Gaussian-apodized beam is approximately constant with depth, which means that there is just as much encoded spatial resolution away from the transmit focus as there is in the focal region. The practical application of this principle is discussed, an algorithm for retrospectively focusing signals from unfocused regions of fixed-focus beams is presented, and a quantitative comparison between the authors' methods and dynamic-receive beamforming is provided.     

Fabrication of high quality plan-view TEM specimens using the focused ion beam

We describe a technique using a focused ion beam instrument to fabricate high quality plan-view specimens for transmission electron microscopy studies. The technique is simple, site-specific and is capable of fabricating multiple large, >100 μm² electron transparent windows within epitaxially grown thin films. A film of La_0.67Sr_0.33MnO₃ is used to demonstrate the technique and its structural and functional properties are surveyed by high resolution imaging, electron spectroscopy, atomic force microscopy and Lorentz electron microscopy. The window is demonstrated to have good thickness uniformity and a low defect density that does not impair the film's Curie temperature. The technique will enable the study of in-plane structural and functional properties of a variety of epitaxial thin film systems.     

High vacuum ionization chamber with high spatial resolution for monitoring synchrotron radiation beams

The possibility of using an ionization chamber with a cutting collectorin vacuum (10⁻⁴–10⁻⁵ Pa) for online monitoring of the position of a synchrotron radiation (SR) beam is studied experimentally The possibility of measuring the vertical position of the SR beam with a precision of up to several micrometers is demonstrated in the high vacuum conditions of an open channel in the VEPP-4M storage ring (in the absence of a beryllium window). Two such ionization chambers operating synchronously and situated one after another can serve as a basis for the SR beam stabilization system in neighboring channels.     

Formation of two-dimensional photonic-crystal structures in silicon for near-infrared region using fine focused ion beams

One of the two variants of producing two-dimensional photonic crystals in silicon is the formation of ordered macropore structures in a silicon substrate. The characteristic pore dimensions (the diameter and the wall thickness between pores) determine the wavelength range in which such a pore structure exhibits the properties of a photonic crystal. For the near-infrared region, these dimensions approach 1 μm or fall in a submicron region. An ordered structure of macropores with such dimensions is formed in this work using fine focused ion beams to provide the stimulating effect of implanted ions on pore nucleation in given sites on the silicon substrate surface. Pores are shown to nucleate at sites subjected to ion irradiation even at a low implantation dose (2×10¹³ ion/cm²). A model describing the orienting effect of ion irradiation on pore nucleation is proposed. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 1, 2004, pp. 35–38. Original Russian Text Copyright ? 2004 by Vyatkin, Gavrilin, Gorbatov, Starkov, Sirotkin.