FIBSIM – dynamic Monte Carlo simulation of compositional and topography changes caused by focused ion beam milling

A new simulation program is presented for focused ion beam (FIB) induced sputtering in two-dimensional targets. The model combines dynamic Monte Carlo simulation of the collision cascades with cell-based topography simulation. This approach takes the nonlocal nature of the sputtering process into account, and treats doping, damage formation and compositional changes self-consistently with the evolution of the surface. Two applications are presented: erosion of a sample edge, and milling of a hole into a multilayer target.     

环氧树脂分子量对电子束辐射固化效果的影响

研究了分子量对于环氧树脂电子束辐射固化行为的影响规律。环氧树脂体系的辐射反应速率随分子量增加而下降,在低辐射剂量下,高分子量树脂的固化度和固化层厚度较小,提高辐射剂量,分子量的影响减弱。对于辐射固化程度较高的样品,其玻璃化温度(Tg)和贮能模量(E’)主要受固化度控制。电子束辐射固化的环氧树脂进行热处理后,样品的玻璃化温度和高温E’均有所提高,低分子量树脂的热处理效果更为明显。     

Ion beam irradiation of nanostructures - A 3D Monte Carlo simulation code

A computer code for the simulation of ion beam irradiation of nanostructures has been developed. The code simulates the transport of energetic ions through matter by means of a Monte Carlo algorithm, similar to the often-used TRIM code (Ziegler et al. (1985) [1]). New effects occur compared to bulk, when irradiating nanostructures, which are of the same size as the ion range or the damage cascade. To account for these effects, the target in our code does not consist of layers like in TRIM but can be defined as an arbitrary 3-dimensional structure. This allows to obtain more accurate 3D distributions of implanted ions and implantation damage for nanostructures, which cannot be described by a stack of layers. We demonstrate the functionality of the code by comparing simulations with ion beam implantation into nanowires.     

Gate/Geant4-based Monte Carlo simulation for calculation of dose distribution of 400 MeV/u carbon ion beam and fragments in water

The applications of carbon ion beam in tumor therapy have attracted more attention in recent years.Monte Carlo simulation is an important approach to obtain accurate radiotherapy parameters. In this work, a400 Me V/u carbon ion beam incident on water phantom was simulated with Gate/Geant4 tools. In methods, the authors set up a carbon ion beam source according to the experiment parameters of Haettner, defined the geometries and materials, set up the physics processes, and designed the means of information collection. In results,the authors obtained the longitudinal dose distribution, the lateral dose distribution, and the relative uncertainty of dose. The dose contributions of all kinds of fragments were calculated detailedly and compared with the Francis results. This work is helpful for people's understanding of the dose distributions produced by carbon ion beam and fragments in water. The simulation method is also significative for radiotherapy treatment planning of carbon ion beam, and it is easy to extend. For obtaining a special result, we may change the particle energy, particle type,target material, target geometry, physics process, detector,etc.     

Spectroscopic analysis and mechanical properties of electron beam irradiated polypropylene/epoxidized natural rubber (PP/ENR) polymer blends

Polymer blends based on different ratios of polypropylene (PP) and epoxidized natural rubber (ENR) were prepared by melt extrusion into sheets. The PP/ENR blends were exposed to various dose of accelerated electrons. The formation of free radicals during and after electron beam irradiation was illustrated by electron spin resonance (ESR). Also, the effect of electron beam irradiation on the mechanical and structural morphology was investigated by stress-strain behavior and scanning electron microscope (SEM). The ESR spectra indicated the formation of alkyl and allyl radicals during electron beam irradiation and peroxyl radicals during the post effect. The rate of radical decay was found to be second-order kinetics. The improvement in mechanical properties and structural morphology was confirmed to be due to the effect of electron beam irradiation.     

电子束注入PMMA空间电荷分布的Monte-Carlo模拟与实验验证

精确控制和测量电子束注入样品后电荷量以及电荷的沉积分布,对于进行高压电力电缆材料的击穿以及航空器受到高能宇宙射线破坏的研究有着非常重要的意义。本工作结合空间电荷对固体电介质材料击穿影响的研究课题,利用Monte-Carlo方法模拟计算了电子束注入聚甲基丙烯酸甲脂(PMMA)样品中电荷的沉积分布,并通过激光感应压力波法(LIPP)对电子束注入后的PMMA进行测量;实验验证计算结果,吻合较好,为以后实验参数的设计提供了重要依据。     

重离子束辐照细胞研究的文献计量学分析

应用文献计量学方法和相应的应用软件,借助Web of Science平台对重离子束辐照细胞这一研究主题的相关文献、作者、期刊、机构以及关键词进行定量和系统考察。结果显示,重离子束辐照细胞研究在1990年之后日益活跃并深入;不同品质的重离子束辐照诱导不同类型细胞会产生不同的生物学效应、旁观者效应及其机制、重离子束辐照细胞生物学效应评估模型、重离子束治疗癌症过程中辐照品质选择与控制模型以及相应的计算机程序是该研究主题的重要内容;引入特定指数推测所得该研究主题重要学术期刊与Nature,Proceedings of the National Academy of Sciences of the United States of America,Cancer Research等期刊之间有较高的共被引频次,表明更多科学前沿的突破性成果和思路应用于该主题研究中;此外,该研究主要集中于少数国家、少数机构、少数作者,并且合作相对较少。     

A Monte Carlo study of surface sputtering by dual and rotated ion beams

Several, recently proposed methods of surface manufacturing based on ion beam sputtering, which involve dual beam setups, sequential application of ion beams from different directions, or sample rotation, are studied with the method of kinetic Monte Carlo simulation of ion-beam erosion and surface diffusion. In this work, we only consider erosion dominated situations. The results are discussed by comparing them to a number of theoretical propositions and to experimental findings. Two ion-beams aligned opposite to each other produce stationary, symmetric ripples. Two ion beams crossing at right angle will produce square patterns only, if they are exactly balanced. In all other cases of crossed beams, ripple patterns are created, and their orientations are shown to be predictable from linear continuum theory. In sequential ion-beam sputtering we find a very rapid destruction of structures created from the previous beam direction after a rotation step, which leads to a transient decrease of overall roughness. Superpositions of patterns from several rotation steps are difficult to obtain, as they exist only in very short time windows. In setups with a single beam directed towards a rotating sample, we find a non-monotonic dependence of roughness on rotation frequency, with a very pronounced minimum appearing at the frequency scale set by the relaxation of prestructures observed in sequential ion-beam setups. Furthermore we find that the logarithm of the height of structures decreases proportional to the inverse frequency.     

Radiation hardness of polysiloxane scintillators analyzed by ion beam induced luminescence

The radiation hardness of polysiloxane based scintillators has been measured by ion beam induced luminescence (IBIL). The light intensity as a function of the irradiation fluence with an He⁺ beam at 1.8 MeV (1.0 μA/cm²) has been measured on undoped polymers synthesized with different amounts of phenyl units and on polysiloxanes doped with two different dye molecules (BBOT and Lumogen Violet) sensitizing the scintillation yield.     

微波离子枪离子束光学的数值模拟

用数值模拟方法研究了聚焦离子束系统中微波离子枪的束光学性能，将离子枪看作由源等离子体极和Ｏｒｌｏｆｆ－Ｓｗａｎｓｏｎ透镜组成的双级加速系统，分析了各参对束发射特性的影响。结果展示出引出束光学主要取决于引出导流系数和电势分布，在一定条件下可获得发散度小的离子束。     

离子束诱导电荷显微术的现状与发展趋势

离子束诱导电荷显微术（IBIC）是核子微探针显微成像技术的又一新发展，它具有低束流（fA量级），高效率的特点，已被广泛应用于半导体材料和微电子材料研究中。本文简述了离子束诱导电荷显微术（IBIC）的原理和实验方法，综述了IBIC 研究的现状和进展。     

低能氮离子束注入固态5＇－dTMP的辐照损伤研究

对３０ｋｅＶ氮离子束辐照５’ｅｄＴＭＰ核苷酸引起的无机磷和碱基的释放进行了多方面的研究，得到无机磷产率和碱基产生量的剂量效应曲线。以及０．１ｍｏｌ／ＬＮａＯＨ碱处理对它们的影响。碱处理不仅增加了无机磷的释放量，而且还使辐照产生的游离碱基受到损伤而裂解。碱处理后立刻测量得知，受辐照样品的碱溶液中无机磷的含量为其水溶液中的１７倍，而样品碱溶液中的碱基浓度却只有其水溶液中的０．５倍左右，碱处理４０ｍｉｎ后，受辐照样品之碱溶液中无机磷含量则增至其水溶液中的２．８倍左右。另外，离子束辐照作用主要是直接作用，具有较高的Ｇ（Ｐｉ）值，达０．４４分子／１００ｅＶ以上。     

伽玛刀体模剂量分布的Monte Carlo模拟

运用Ｍｏｎｔｅ Ｃａｒｌｏ方法模拟了伽玛刀Ｌｅｋｓｅｌｌ ｇａｍｍａ ｕｎｉｔ在体模中的吸收剂量的分布，计算结果与实验结果基本相符。     

Mapping ion beam induced current changes in a commercial MOSFET

We demonstrate a novel nuclear microprobe imaging and analysis modality for micrometre-scale field effect transistor devices probed with focused beams of MeV ions. By recording the drain current as a function of time during ion irradiation it is possible to identify current transients induced by the passage of single ions through the sensitive structures of the device. This modality takes advantage of the fact that the ionization produced by the passage of a single ion acts in an equivalent way to a transient change in the gate bias which therefore modulates the drain current as a function of time. This differs from the traditional ion beam induced charge technique where the ionization drifts in an internal electric field and induces a single charge pulse in an electrode applied to the device. Instead a richer variety of phenomena are observed, with different time constants which depend on the proximity of the ion strike to the channel of the device. The signals may be used to examine device function, radiation sensitivity or to count ion impacts within the channel.     

Simulation of ion beam induced crystallization and amorphization in (0 0 1) silicon

The ion beam induced epitaxial crystallization (IBIEC) and the ion beam induced interfacial amorphization (IBIIA) in (0 0 1) silicon caused by 3 MeV Si⁺ and 3 MeV Au⁺ irradiation at 293 K and 623 K are investigated by using a combination of binary collision MC simulations and MD simulations. The energy and angular distribution of the primary recoils is calculated by TRIM and the subcascades caused by the primary recoils are treated by classical MD simulations using a correspondingly large MD cell with 49152 atoms. The resulting topological interface structure is analyzed and compared with that obtained by thermally activated solid phase epitaxy. The rates of crystallization and amorphization are calculated and compared with experimental data. Especially, their dependence on the nuclear deposited energy is discussed.     

离子束混合及离子注入陶瓷材料表面改性研究概述

对离子注入陶瓷材料引起的辐照损伤和材料力学性能、摩擦学性能的改善及陶瓷基体上金属薄膜的离子束混合增强粘着研究的进展进行了综述。     

Ion beam induced formation of nanocrystalline silicon in pulsed laser deposited SiOX thin films

Synthesis and structural studies of nanocrystalline silicon grown in pulsed laser deposited SiO_X films is reported. The effect of high energy heavy ion beam irradiation on these films is studied using 100 MeV Ag ions. The structural studies were carried out using micro Raman spectroscopy, GAXRD, FTIR, TEM, HRTEM, SAED and EDX. The occurrence of phase separation in non-stoichiometric silicon oxide by means of ion beam irradiation leading to the formation of silicon nanocrystals in the films is confirmed by the results. HRTEM results reveal the structure of silicon phase formed after ion beam treatment and the particle size can be controlled up to 2-3 nm. A detailed analysis by micro Raman and HRTEM studies suggest the presence of crystallite size distribution. The results of GAXRD and SAED confirm the formation of cubic phase of silicon with two different lattice parameters. The studies conclude that the size of the nanocrystals can be controlled by varying deposition and ion irradiation parameters.     

离子束注入酪氨酸分子的剂量效应研究

研究发现，氮离子束注入酪氨酸（Ｔｙｒ）样品具有与传统的γ射线不同的剂量效应规律。并从物理机制入手分析了这一特殊规律形成的根源，导出了这一规律所遵循的数学解析式，体现了质量沉积效应的重要性。     

离子束注入抗生素产生菌的ESR研究

用ＥＳＲ波说仪测定了室温下氮离子注入核糖霉素产生菌、卡那霉素产生菌和卡那霉素抗株产生菌所引起的自由基。实验结果表明，氮离子注入上述三种菌种能产生大量的自由基，自由基产额随注入剂量的增加而增加。菌种死亡率随自由基产额的增加而上升。     

Effect of different ion beam energy on properties of amorphous carbon film fabricated by ion beam sputtering deposition (IBSD)

Amorphous carbon (a-C) films were fabricated by ion beam sputtering technique. The influence of sputtering ion beam energy on bonding structure, morphologic, mechanical properties, tribological properties and corrosion resistance of a-C films are investigated systematically. Morphology study shows that lowest surface roughness exists for mid-ion beam energy. Improved adhesion is observed for the films that are prepared under high ion beam energy, attributed to film graphitization, low residual stress and mixed interface. Relatively, a-C films prepared with ion beam energy of 2 keV exhibits optimum sp³ bond content, mechanical properties and corrosion resistance. It is found that the wear rate of DLC films decrease with increased ion beam energy in general, consistent with the varied trend of the H/E value which has been regarded as a suitable parameter for predicting wear resistance of the coatings. The correlation of the sp³ bond fraction in the films estimated from Raman spectroscopy with residual stress, nanohardness and corrosion resistance has been established.