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1.
低能Pt原子与Pt(111)表面相互作用的分子动力学模拟   总被引:4,自引:0,他引:4       下载免费PDF全文
张超  吕海峰  张庆瑜 《物理学报》2002,51(10):2329-2334
利用分子动力学模拟方法详细研究了低能Pt原子与Pt(111)表面的相互作用所导致的表面吸附原子、溅射原子、表面空位的产生及分布规律,给出了表面吸附原子产额、溅射原子产额和表面空位产额随入射Pt原子能量的变化关系.模拟结果显示:溅射产额、表面吸附原子产额和表面空位产额随入射原子的能量的增加而增加,溅射原子、表面吸附原子的分布花样呈3度旋转对称性质;当入射粒子能量高于溅射阈值时,表面吸附原子主要是基体最表面原子的贡献,入射粒子直接成为表面吸附原子的概率很小.其主要原因是:当入射粒子能量高于溅射能量阈值时,入射 关键词: 分子动力学 低能粒子 表面原子产额 空位缺陷 溅射  相似文献   

2.
本文主要介绍了入射离子能量为64和67MeV时,12C+197Au反应中出射的α粒子的能谱和角分布,以及能量为71.5MeV时该反应中出射的α、Be和B等粒子的能谱和角分布。给出了6Li粒子的产额和使用α-α粒子符合技术,在相对于东流方向成90°处测得的反应中出射的8Be分裂开的α粒子的能谱和产额。反应中出射的各种粒子的最可几能量,随着入射离子能量的降低而降低,角分布都是大约在擦边角附近出现峰值,当入射离子能量从71.5MeV降到64MeV时,其峰位大约从80°移到120°,显示出转移反应的特征。我们对实验结果作了一些简要的分析讨论。  相似文献   

3.
本文用基于两体碰撞的蒙特-卡罗方法研究α粒子轰击固体靶的位移原子深度分布,并分析了位移原子深度分布与固体中能量沉积的关系。文中给出入射α粒子能量、入射角及靶材料的改变对位移原子深度分布的影响。结果表明,位移原子数与轰击离子在靶中的弹性能量损失密切相关。聚变α粒子在SiC中产生的位移损伤远小于它在不锈钢材料中的位移损伤。  相似文献   

4.
利用MeV能量的准直质子束,在不同的质子能量下,测定了α-LiIO_3单晶<001>向的轴沟道参数角度半宽度ψ1/2和产额极小值χ_(min)。在向静电场作用卞,首次观察到入射质子与表面处的Ⅰ原子沟道-背散射产额随电场作用时间而增加,并定量计算了表面无序Ⅰ原子数随静电场作用时间的关系。另外,入射质子与~7Li原子沟道-核反应[~7Li(p,α)~4He]产生的α粒子产额也随电场作用时间而增加。  相似文献   

5.
朱勇  李宝华  谢国锋 《物理学报》2012,61(4):46103-046103
本文先应用分子动力学模拟BaTiO3体系在初级击出原子(primary knock-on atom, PKA)轰击下缺陷产生和复合的动力学过程, 模拟结果表明:PKA的方向和能量对缺陷数目有重要影响, 并计算了Ba, O和Ti原子的平均位移阈能分别为69 eV, 51 eV和123 eV, 远大于SRIM程序默认的位移阈能25 eV. 然后应用蒙特卡罗软件包SRIM, 模拟质子在BaTiO3薄膜中的能量损失过程, 比较位移阈能对模拟结果的影响, 分析质子能量和入射角度对空位数量以及分布的影响. 结果表明空位数量随着质子能量增加而增加, 增加的速率随能量的增加是降低的;当入射角度大于60°, 空位数量随入射角增大而明显减少.  相似文献   

6.
核温度测量与粒子能量的关系   总被引:1,自引:1,他引:0  
提取了30MeV/u 40Ar+natAg反应中后角出射的同位素(6,7Li,3,4He)产额比温度为5MeV.观察到这一同位素产额比温度随阈值能量Ecut/A的增加而逐渐由5MeV上升到6MeV.为进一步研究这一变化关系,用Monte Carlo方法模拟了热核蒸发粒子的过程,表明随粒子能量的增加,发射该能量粒子的发射源平均温度也在增加.说明高温热核发射高能量粒子的几率大.  相似文献   

7.
不同电荷态低速离子(Arq+,Pbq+)轰击Si(110)晶面,测量不同入射角情况下的次级粒子的产额. 通过比较溅射产额与入射角的关系,证实沟道效应的存在. 高电荷态离子与Si相互作用产生的沟道效应说明溅射产额主要是由动能碰撞引起的. 在小角入射条件下,高电荷态离子能够增大溅射产额. 当高电荷态离子以40°—50°入射时,存在势能越高溅射产额越大的势能效应. 关键词: 高电荷态离子 溅射 沟道效应  相似文献   

8.
本文用基于两体碰撞的蒙特-卡罗方法研究α粒子轰击固体靶的位移原子深度分布,并分析了位移原子深度分布与固体中能量沉积的关系。文中给出入射α粒子能量、入射角及靶材料的改变对位移原子深度分布的影响。结果表明,位移原子数与轰击离子在靶中的弹性能量损失密切相关。聚变α粒子在SiC中产生的位移损伤远小于它在不锈钢材料中的位移损伤。 关键词:  相似文献   

9.
 先进燃料D-3He聚变产生的高能带电粒子在本底等离子体中慢化时间的准确性直接影响到能量平衡和高能离子压强的计算结果。结果表明:高能带电粒子与本底等离子体的离子相互作用的库仑对数量子力学效应明显。应使用高能带电粒子库仑对数力学效应来研究聚变产生的高能端部粒子慢化过程;能量大于等于25Z2iZ2iAi keV的高能粒子与本底等离子体中离子的相互作用库仑对数最好也使用量子截断。  相似文献   

10.
在入射能量E为40和100MeV/u时,对112Sn+112Sn和124Sn+124Sn两个反应系统在不同碰撞参数下进行了同位旋相关的量子分子动力学模型计算,系统研究了阻塞率、线性动量转移、荷电粒子多重性、轻荷电粒子多重性、中子多重性以及束缚核总电荷Zbound随碰撞参数的变化规律,结果表明,中子多重性对碰撞参数的依赖在两个能量下都存在着明显的同位旋效应,Zbound在E为40MeV/u时存在着同位旋效应.同时讨论了在较低和较高能量时如何更合理地确定反应事件的碰撞参数.  相似文献   

11.
Abstract

Earlier measurements of sputtering efficiency of polycrystalline targets (fraction of impinging ion energy leaving the target through sputtering and backscattering) have been extended to higher energies. Lead and copper targets were bombarded with several different projectiles with energies between 80 and 1200 keV. The sputtering efficiency decreases with increasing energy. This decrease is ascribed to the combined influence of changes in the scattering cross section with energy, and to electronic stopping. The results may be described as a function of the mass ratio M 2/M 1 and the reduced energy ? only.

The sputtering efficiency was measured as a function of angle of incidence of the bombarding ions. To ensure complete collection of sputtered and backscattered particles, it was possible to cover only the region of incidence angle from 0° to 45°. Targets of copper, silver, and lead were investigated with 17 different ion-target combinations. The sputtering efficiency increased with angle of incidence. This increase is described well by a simple interpolation formula by Sigmund.  相似文献   

12.
Two modifications of Sigmund's sputtering formula, viz. by Bohdansky and by Yamamura et al. are compared with an α-adaptation of Sigmund's original formula to 620 experimental sputtering yields taken from literature. Using the α-values for the comparison, it was found that the considerable scatter of these values (averaged for given M1, Z1, M2, Z2) is not reduced by either of the two modifications, except for values in the range M2/M1 > 100. In each of the three versions the scatter is systematic, however, in as far as certain target elements yield average values of α which are consistently high, low or intermediate over a wide range of M2/M1 ratios.  相似文献   

13.
Molecular dynamics simulations of the 20-keV C60 bombardment at normal incidence of Si, SiC, diamond and graphite targets were performed. The unique feature of these targets is that strong covalent bonds can be formed between carbon atoms from the C60 projectile and atoms in the solid material. The mesoscale energy deposition footprint (MEDF) model is used to gain physical insight into how the sputtering yields depend on the substrate characteristics. A large proportion of the carbon atoms from the C60 projectile are implanted into the lattice structure of the target. The sputtering yield from SiC is ∼twice that from either diamond or Si and this can be explained by both the region of the energized cylindrical tract created by the impact and the number density. On graphite, the yield of sputtered atoms is negligible because the open lattice allows the cluster to deposit its energy deep within the solid. The simulations suggest that build up of carbon with a graphite-like structure would reduce any sputtering from a solid with C60+ bombardment.  相似文献   

14.
The energy distribution and yields of the α-particles emitted in the thermal-neutron fission of 235U were measured with the same detector system for the cases when the average angles between fragments and α-particles were 90°, 46°, 27° and 11°. The data were analysed by the Monte Carlo method to take into account the effects of the finite size of the source and the various detectors, and the following results were obtained: (i) Even at small angles with respect to the fission axis the yield of the α-particles is about 2–3 % of the yield at 90°, and does not go to zero as would be expected for a true Gaussian angular distribution of a variance which fits the data around 90°. (ii) At these angles where most of the α-particle yield belongs to the non-Gaussian component, the α-particle energy distribution has a significantly higher most probable energy but the FWHM of the energy distribution is not significantly different, (iii) The rms width σθ of the Gaussian angular distribution is found to increase for very high (Eα > 20 MeV) α-particle energies and also to a lesser extent for very low (Eα < 15 MeV) energies. The origin of the yield of the α-particles at small angles, and the dependence of the rms width σθ on the energy are discussed.  相似文献   

15.
A quartz crystal microbalance (QCM) has been used to determine total-mass sputtering yields of PMMA films by 1-16 keV C60+,2+ ion beams. Quantitative sputtering yields for PMMA are presented as mass loss per incident ion Ym. Mass-lost rate QCM data show that a 13 keV C60 cluster leads to emission equivalent to 800 PMMA molecules per ion. The power law obtained for the increase in sputtering yield with primary ion energy is in good agreement those predicted by “thermal spike” regime and MD models, when crater sizes are used to estimate sputtering.  相似文献   

16.
The sputtering yield angular distributions have been calculated on the basis of the ion energy dependence of total sputtering yields for Ni and Mo targets bombarded by low-energy Hg+ ions. The calculated curves show excellent agreement with the corresponding Wehner's experimental results of sputtering yield angular distributions. This fact clearly demonstrates the intrinsic relation between the ion energy dependence of total sputtering yields and the sputtering yield angular distribution. This intrinsic relation had been ignored in Yamamura's papers [Yamamura, Y. (1982). Theory of sputtering and comparison to experimental data, Nucl. Instr. and Meth., 194, 515–522; Yamamura, Y. (1981). Contribution of anisotropic velocity distribution of recoil atoms to sputtering yields and angular distributions of sputtered atoms, Rad. Eff., 55, 49–55.] due to some obvious mistakes.  相似文献   

17.
The computer simulation program MARLOWE which follows the trajectories of energetic ions and recoiling target atoms in solids has been used to calculate sputtering yields for low energy (0.1–10keV) light ions (H, D, T,4He). Recoil energy densities were calculated for comparison with analytical theories. The sputtering yields obtained for amorphous Fe agree within a factor of two with experimentally measured values for polycrystalline stainless steel, while the calculated yields for protons on amorphous molybdenum are more than twice the experimental values on polycrystalline material. The calculations show that in the parameter range investigated, ions backscattered in the solid contribute a major part to sputtering. This result confirms earlier calculations of the threshold energy for sputtering which are in agreement with recent measurements. Operated for the United States Department of Energy by the Union Carbide Corporation.  相似文献   

18.
19.
TiO2 thin films were grown by ion beam sputter deposition (IBSD) using oxygen ions, with the ion energy and geometrical parameters (ion incidence angle, polar emission angle, and scattering angle) being varied systematically. Metallic Ti and ceramic TiO2 served as target materials. The thin films were characterized concerning thickness, growth rate, surface topography, structural properties, mass density, and optical properties. It was found that the scattering geometry has the main impact on the film properties. Target material, ion energy, and ion incidence angle have only a marginal influence. Former studies on reactive IBSD of TiO2 using Ar and Xe ions reported equivalent patterns. Nevertheless, the respective ion species distinctively affects the film properties. For instance, mass density and the refractive index of the TiO2 thin films are remarkably lower for sputtering with oxygen ions than for sputtering with Ar or Xe ions. The variations in the thin film properties are tentatively attributed to the angular and the energy distribution of the film-forming particles, especially, to those of the backscattered primary particles.  相似文献   

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