低能离子注入引起的植物种子微结构的变化

以植物干种子芸豆和花生为生物体材料，采用正电子湮没技术（PAT）测定了该两类生物样品的正电子湮没寿命谱（PAL）。测量结果表明，在芸豆和花生生物体内存在着大量微小的孔洞，孔洞的直径分别为0．48nm和0．7nm。植物种子的这类特殊的微孔结构是低能离子注入生物效应机理的基础。对注入200keV低能V离子的花生样品也测量了它的PAL谱，并与未经离子注入的花生样品的PAL谱作了比较。     

低能重离子注入花生干种子深度-浓度分布的方向效应研究

用双光子激光扫描显微镜技术观测200keV V⁺离子从不同方向注入花生干种子的 深度-浓度 分布，发现沿纵向和横向注入的离子在样品中的深度-浓度分布有显著差别，即分布具有方 向效应.初步分析了造成注入离子分布出现方向效应的原因. 关键词： 离子注入 植物种子 深度-浓度分布 方向效应     

低能N+注入植物种子射程分布的模拟计算

伴随着离子束生物技术的广泛应用, 国内许多单位开展了低能离子注入植物种子的实验研究. 其中关于低能离子注入植物种子诱变的物理机理, 集中在离子注入的深度-浓度分布上. 一些单位直接使用纵向非静态(LSS)理论和TRIM程序来计算低能离子注入植物种子的深度-浓度分布, 却发现计算结果与实验测量结果相差甚远. 所以在对植物种子靶材料进行处理和对LSS理论进行修正的基础上, 在二维近似情况下, 用蒙特卡罗方法分别模拟计算了200keV V⁺和20keV Ti⁺注入花生和棉花种子的射程分布, 得到了与实验结果较符合的曲线. 在此模型基础上, 计算了同样初始条件和理论计算模型下无法从实验上测量的N⁺注入植物种子的射程分布, 初步地为低能N⁺注入植物种子射程分布提供了一种理论计算方法.     

200 keV V+注入花生种子深度-浓度分布的蒙特卡罗模拟

在对植物种子靶材料进行处理和对LSS理论进行修正的基础上,用蒙特卡罗方法模拟计算了在一维和二维近似情况下,200 keV V⁺注入花生种子的深度-浓度分布,得到了与实验结果较符合的曲线.并在同样初始条件和理论模型下,计算了200 keV N⁺注入植物种子的深度-浓度分布,为研究低能离子注入植物种子深度-浓度分布提供了一种初步的理论计算方法.     

用高分辨率沟道背散射谱仪研究硅的低能氮离子氮化

用高分辨率沟道背散射技术研究了低能N离子注入单晶硅形成氮化硅的过程。测出了N和位移Si原子的深度分布。提出在N离子注入时同时存在着三个过程——注入、溅射和释放。由此建立了一个微分方程描写样品中剩余N的浓度变化,并讨论了氮化硅形成机制。 关键词：     

用掩蔽注入法研究钛注入H13钢的耐磨性

采用由金属蒸汽真空弧离子源引出的强束流钛、碳离子对H13钢进行表面改性研究.钛和碳离子注入剂量分别为3×1017和1×1017cm-2,引出电压分别为48和30kV，平均束流密度分别为47和20μA·cm-2.为了保持相同的摩擦磨损实验条件，注 入过程中采用掩蔽注入技术.摩擦磨损实验结果表明，钛离子注入H13钢提高了其耐磨性，并大幅度降低其摩擦系数.利用卢瑟福背散射谱测量了离子注入表面的成分，并采用逐层递推 法得出了钛在H13钢中的浓度深度分布，借助掠面x射线衍射考察了注入表面的相结构. 关键词： 钛离子注入 金属蒸汽真空弧 卢瑟福背散射 掠面x射线衍射     

纯锆上离子注入钇和镧后的表面分析

用金属蒸汽真空弧源，以40kV加速电压对纯锆样品分别进行了10¹⁶—10¹⁷/cm²的钇、镧离子注入，注入温度约为130℃.然后对注入样品进行表面分析.x射线光电子能谱分析表明，注入的钇以Y₂O₃形式存在，镧以La₂O₃形式存在.俄歇电子能谱表明，纯锆基体表面的氧化膜厚度随着离子注入剂量的增加而增加，当离子注入剂量达到10¹⁷/cm²时，氧化膜的厚度达到了最大值.卢瑟福背散射显示镧层的厚度约为30nm，同时直接观察到当离子注入剂量为(La+Y)10¹⁷/cm²时，纯锆样品表面发生了严重的溅射. 关键词： 纯锆 钇和镧离子共注入 卢瑟福背散射 x射线光电子能谱     

真空、低能离子注入后HeLa细胞的吸收光谱研究

在选用了石蜡油作为细胞耐受真空的保护剂基础上,分别采集了人宫颈癌细胞(HeLa细胞)经真空和不同剂量低能离子注入后的紫外吸收光谱.实验结果显示:HeLa细胞在202及260 nm附近均有特征性的吸收峰.数据的进一步分析发现:(1)HeLa细胞经真空处理后的紫外吸光值随着真空时间的延长而增加,且真空对细胞紫外吸收光谱的影响大于单纯的石蜡油浸泡影响;(2)真空对于HeLa细胞紫外吸光值的影响远低于低能离子注入的影响;(3)HeLa细胞在注入不同剂量的低能N+后,紫外吸光值会随着注入剂量的增大而增加.在上述分析的基础上,本文又探讨了低能N+束注入对肿瘤细胞的结构、各成分的组成比例及分子排列的影响,该研究为深入探索低能离子注入生物样品的作用机理奠定了基础.     

质量分离低能离子束沉积碳膜及离子轰击效应

用质量分离的低能离子束沉积技术得到了非晶碳薄膜,X射线衍射、Raman谱以及俄歇深度谱的线形表明,此种非晶碳膜中镶嵌着金刚石颗粒.碳离子的浅注入是该碳膜SP³形成的主要机理.从一个侧面说明了化学气相沉积法中偏压预处理增加金刚石成核的主要原因是因为离子轰击效应. 关键词： 非晶碳 离子轰击 质量分离低能离子束     

低能离子注入形成氮化硅薄膜特性的研究

低能离子束与表面相互作用主要呈现溅射、注入等现象。本文研究了在1.35keVN₂⁺离子注入形成氮化硅的特性,并研究了注入和溅射的并存过程。在高剂量、低能(<10keV)注入的情况下,提出了有效剂量的概念,并建立了刻蚀速率、射程与有效注入剂量的关系。还用俄歇电子能谱(AES)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、背散射分析(RBS)测定了薄膜的有关特性。 关键词：     

低能离子注入育种中次级效应影响的模拟研究

低能离子注入育种作为一种有效的育种方法在实践中进行了大量的尝试并取得了一系列重要成果,但其作用机理一直都存在着巨大的争议,特别是射程很短的低能重离子如何穿透到种子内部触发生物效应。本研究利用SRIM、CASINO、Geant4模拟程序对低能离子注入生物样品的离子注入深度进行模拟和定量分析,并对次级粒子可能产生的影响进行了定量模拟研究。结果显示,低能重离子本身射程一般都小于1 μm,选用轻离子、提高注入能量、采用干种子进行注入,都有利于增加穿透深度。次级过程中,反冲质子的最大射程比初级入射离子的稍大,不能显著提升穿透能力。次级过程产生的粒子中只有X射线可以明显提高穿透种子的深度,只要剂量足够大,总会有少量X射线穿透到很深的地方。The breeding method by low-energy ion implantation has been proved to be a valuable breeding method by a large number of practical attempts, but the mechanism of the method has always been in a large dispute. The most difficult thing to be understood is how the low energy heavy ion with such a short range (normally shorter than 1 μm) can penetrate into the inner part of seeds to trigger the biological effects. In this paper, simulations with quantitative analysis were performed for the low energy ion implantating into biological samples and the effects caused by the secondary particles using SRIM, CASINO and Geant4 simulation programs. The results showed that the ranges of low energy heavy ions are normally less than 1 μm. The ranges can become longer if dry seeds and light ions are used with a higher energy. The ranges of recoil protons are only a little longer than that of the primary ions. Among the secondary particles produced in the ion implanting process, only the X-ray can obviously increase the penetration depth in seeds. There always will be a small amount of X-rays which can penetrate into the deeper place in the seed if the ion dose is high enough.     

POSITRON ANNIHILATION STUDY ON SURFACE STRUCTURE OF BIOLOGICAL SAMPLES IMPLANTED BY IONS WITH LOW ENERGY

The organic materials of biological samples, such as lima bean and peanut, were implanted respectively by nitrogen ions with an energy of 100 keV and vanadium ions with an energy of 200 keV. The positron annihilation lifetime spectra of implanted and non-implanted samples were compared with each other especially in τ₃ and I₃. The experimental results showed that before implantation there were many small holes with diameters of 0.48 and 0.7 nm respectively in lima bean and peanut. After ion implantation, the size of holes would be changed because of organism cross linking and scission. The effective penetration range of implantation of ions with low energy into biological samples is about 200μm.     

The energy dependence and depth distribution of lattice disorder in ion-implanted silicon

Silicon single crystals were implanted at room temperature with Xe and I ions in the energy range 20 to 150 keV and with 20 to 50 keV P ions. The lattice disorder induced by these implants was measured by a combination of the channeling and Rutherford backscattering techniques. The disorder produced by implanting I and Xe ions exhibited a similar relationship with implantation energy to that previously established for bismuth implants. The P ion implants induced less lattice disorder per incident ion in the energy range studied. Integral depth distributions of the implanted ions and of the lattice disorder were obtained by combining a layer removal technique with radiotracer implants of 110 keV ¹³³Xe and 40 keV ³²P. The depth distributions showed that in both cases the ions penetrate deeper into the crystal than the damage they produce but that the separation is significantly greater for the P implant than for the Xe implant.     

Simple technique for measurement of energy spectra of ions from laser produced plasma

Old absorption technique is revived for measuring the energy spectra of ions arising from laser generated plasma. The technique suggested relies on implantation of produced ions into a light element target situated close to the ion production site. Then the ion energy spectra are reconstructed from the depth profile of the implanted ions measured by some of the common depth profiling techniques such as RBS or SIMS. Theoretical range vs. ion energy relations are used for this purpose. In this study the principles of the method are explained and its capabilities are assessed. The feasibility of the method is demonstrated on the energy spectra of Ta ions arising from the laser generated plasma.     

MeV能量离子辐照拟南芥干种子和含水种子存活曲线对比

离子束辐照植物种子所产生的水自由基对植物种子存活率会有影响, 实验中为了观察这种辐射效应, 采用6.5 MeV能量的质子分别辐照拟南芥干种子和含水种子。 这个能量点的质子无论对干种子还是含水种子都可以完全穿透, 减少了因损伤部位不同带来的差异。 实验中采用的质子注量从4×109 ions/cm2到1×1014 ions/cm2。 实验结果显示干种子和含水种子存活曲线均成肩形下降趋势,而且含水种子下降注量点明显低于干种子。 这是自由基作用结果。 同时在辐射生物学靶学说的基础上, 建立了模型, 通过参数的合理设置,很好地拟合了实验数据。 The dry and water saturated seeds of Arabidopsis thaliana were irradiated by H+ions with 6.5 MeV in atmosphere. The ion fluence used in this experiment was in the range of 4×109 —1×1014 ions/cm2. According to the structure of the seed and TRIM simulation, the ions with the energy of 6.5 MeV can penetrate the whole seed. The experiment shows that the fluence response curves for the dry seeds and water saturated seeds had distinct shoulders and reduced rapidly. The experimental results show that the water imbibed seeds were more sensitive than the dry seeds and the reason is from free radicals reaction. A model has been constructed, and primely simulates the experiment data.     

Variation of the saturation magnetization through a neon implanted YIG film

The saturation magnetization of a YIG film implanted with 5*10¹⁴ neon ions/cm² at an energy of 450 keV was studied. By removing very thin layers from the ion implanted part of the film the magnetization was found to change. As a result of the analysis of these changes in the saturation magnetization it was possible to establish a profile for the magnetization as a function of depth through the ion implanted part of the film. The profile is asymmetric and shows a decrease in the magnetization of up to 35 % of the initial value at a depth coinciding with the depth of maximum strain.     

Tomographic study of the three-dimensional distribution of a high-fluence implant in a polymer

6 Li⁺ ions were implanted into PMMA at high flux up to fluences of 1×10¹⁵ cm^-2 under angles of 0° to 70° towards the surface normal. The Li depth distributions were determined by means of neutron depth profiling, and compared with theoretical simulations. The three-dimensional Li distribution was reconstructed from the one-dimensional depth profiles by means of a tomographic technique. It turned out that the measured Li depth distributions can be described by a superposition of Gaussian and exponential functions. This points at considerable Li mobility during or after the ion implantation, with trapping in unsaturable traps in the ion-irradiated region which roughly follow the electronic energy transfer distribution. The Li redistribution is more pronounced along the track direction than transversely to it. The normalized Li distributions in various implantation directions were fed into our tomographic program to reconstruct the three-dimensional distribution of the deposited lithium. As expected, the lithium preferentially distributes along the ion tracks. This work is another hint that mobility of implanted ions in solids does not proceed isotropically, but is strongly influenced by the radiation-damage distributions. Received: 11 May 1998 / Accepted: 9 September 1998 / Published online: 24 February 1999