Stopping power and straggling of energetic light ion beams in yttrium

Energy loss and straggling for protons, deuterons and α-particles in yttrium were measured in the energy region between 0.15 MeV and 2.5 MeV. The measured stopping powers of the hydrogen ions agree reasonably well with the semi-empirical values of Andersen and Ziegler, although better agreement was found with the values of Janni. For helium ions there are a marked difference with the values of Ziegler. Below 200 keV/amu the stopping ratios of the helium and hydrogen ions are lower than Ziegler's master curve. The straggling values of the hydrogen ions are about 15% lower than the Bohr estimate, while the straggling of the helium ions reach the Bohr value at about 0.2 MeV/amu.     

MeV能量离子在生物样品中的能量损失与能量离散

为了研究 MeV能量离子在生物样品中的能量损失与能量离散, 分别使用1.0, 1.8和2.8 MeV质子和4.5 MeV氦离子分别辐照不同质量厚度的洋葱内表皮膜。 当质子穿过该生物样品后, 可以利用透射能谱测量透射离子的能量损失和能量离散。 实验结果显示, 在以上的生物样品中, MeV能量离子的能量损失值和TRIM程序模拟的结果相吻合, 但是透射离子的能量离散值却与TRIM程序模拟结果有很大的不同。 结合生物样品的结构不均匀的特性, 对Bohr能量离散理论进行了修正, 并发现修正后的Bohr能量离散理论计算结果与实验值符合得很好。     

铒离子注入6H-SiC的横向离散研究

利用离子注入掺杂技术设计、制作半导体集成器件时,了解离子注入半导体材料的射程分布、射程离散和横向离散规律等是很重要的.用400 keV能量的铒(Er)离子分别与样品表面法线方向成0°,45°和 60°倾角注入碳化硅(6H-SiC)晶体中,利用卢瑟福背散射技术研究了剂量为5×10¹⁵ cm^-2 的400 keV Er离子注入6H-SiC晶体的横向离散.测出的实验值与TRIM98和SRIM 2006得到的理论模拟值进行了比较,发现实验值跟TRIM98和SRIM 关键词： 离子注入 6H-SiC 卢瑟福背散射技术 横向离散     

Range of Er ions in amorphous Si

We have measured the range and range straggling for energetic 100-900 keV Er ions in amorphous Si by means of Rutherford backscattering followed by spectrum analysis. The results are compared with other experimental data and Monte Carlo (SRIM-2003) calculations. Our experimental results show that, although the measured values for both range and range straggling exceed the SRIM predictions, they are nevertheless consistent with trends that have been previously observed. We see no anomalous trends in range and range straggling parameters for the rare earth ions for implant energies E ≥ 100 keV. We present a detailed consideration of ⁴He stopping powers in Si due to its crucial impact on RBS range measurements.     

Increase in the superconducting transition temperature in Zr-Hf alloys due to <Emphasis Type="Italic">s-d</Emphasis> electron transfer under pressure

Correlation between the roughness of neighboring interfaces (roughness cross correlation) in a Ni/C X-ray multilayer mirror (XMM) prepared by laser ablation was studied by measuring X-ray diffuse scattering (XDS). The XDS intensities in the vicinity of the first Bragg reflection were measured at different photon energies: slightly below (8.325 keV) and slightly above (8.350 keV) the nickel photoabsorption K edge. The effective screening of the contribution from the deep layers to the XDS cross section due to the strong damping of the wave field at a photon energy higher than the photoabsorption edge allowed information on the character of the in-depth roughness cross correlation in the sample to be obtained. In particular, the characteristic lateral correlation length of the roughness was 0.35 µm at a photon energy of 8.325 keV (the contribution to the XDS cross section of the entire XMM volume), and it increased to 0.4 µm at a photon energy of 8.350 keV (predominantly the contribution from the upper layers). These data give direct evidence for the mechanism of smoothing of the interfacial roughness in the process of Ni/C XMM growth on anomalously large (up to micron) spatial scales. It was found that only rough large-scale defects with sizes of ≥10 µm are reproduced reasonably well from layer to layer. The processes of viscous flow and (or) reevaporation of high-energy target ions during deposition, which is characteristic of the laser method of XMM preparation, may serve as a possible explanation of the observed phenomenon.     

Energy loss straggling of fast charged particles

Energy loss straggling of fast charged particles colliding with atoms have been considered in the eikonal approximation. The result is represented in the form of the Fano formula with a nonperturbative correction. The known nonperturbative Titeica formula (which is transformed to the Fano formula when perturbation theory is applicable) is obtained only under certain approximations in eikonal calculations. It has been shown that straggling calculated with allowance for nonperturbative effects at large charges of the projectile can be significantly different (by an order of magnitude) from the results obtained by Titeica, Fano, and Bohr. Energy loss straggling of fast highly charged ions on hydrogen and copper atoms have been calculated. The latter results are compared to experimental data.     

Mechanism of ion-induced mixing phenomena in Gold–Nickel bilayer on Si substrate

Gold/Nickel bilayer thin films deposited on Si(100) substrates are bombarded by 100 keV ⁴⁰Ar⁺, 260 and 300 keV ⁸⁴Kr²⁺ and 400 keV ¹³²Xe³⁺ ions which deposit maximum energy across the Gold/Nickel interface and hence produce maximum atomic transport within two sides of the interface. However, due to the energy of the projectile ions some Si atoms have also gained energy, which, in turn, displaces the atoms. The atomic displacements caused by the projectile in the system has been analyzed using RBS, XRD, SEM/EDS and AFM/MFM techniques. The relative change in the variance of the intermixed region across the Au–Ni–Si interfaces excluding the irradiation-induced surface roughness has been calculated and it was observed that it increases linearly with ion fluence. The measured athermal mixing rates which vary between 3.7 and 6.9 nm⁴, have been explained by various existing phenomenological models. It shows that local or global thermal spike models are most suitable for explaining the ion beam-induced mixing of systems with strong thermochemical properties of the constituents. The mixing efficiency of this system has been calculated and found to be 1.2 nm⁵/keV.     

Investigation by ellipsometry of the damage in GaAs bombarded with low-energy Ar ions

The crystalline-amorphous transition in GaAs induced by Ar ions (energy 1–3 keV) has been investigated using single-wavelength ellipsometry. The experiments have been performed in-situ at room temperature. Ion damage straggling, amorphization threshold and critical energy density have been derived by means of a simple analytical model for the growth of the amorphous layer. This model is discussed and the corresponding calculations are found to be in satisfactory agreement with experimental data.     

Energy loss straggling in collisions of fast finite-size ions with atoms

The influence of ion size on straggling of energy losses by fast partially stripped ions is studied using the nonperturbative approach based on the eikonal approximation. It is shown that such a consideration of collisions of ions with complex atoms can lead to considerable corrections in calculating root-mean-square straggling of energy losses by fast ions compared to the results obtained for point ions. The root-mean-square straggling of energy losses are calculated for bromide and iodine ions in collisions with copper, silver, and aluminum atoms. It is shown that allowance for the size of the electron “coat” of an ion noticeably improves the agreement with experimental data.     

Carbon auger electron line shape after beam-foil excitation of molecular ions

Auger electrons of beam-foil excited C-projectiles and C-fragments of Coulomb exploding molecular CO-projectiles at 83 keV/u yield information on the excitation mechanisms and the interaction with the solid. A numerical procedure is developed to calculate the mean energy of the Coulomb explosion, the charge states of the fragment ions and their angular straggling behaviour inside the solid. The calculated results are compared with experimental data. From a detailed line shape calculation the magnitude of directional effects induced by the Wake-potential can be predicted.     

Description of Ion Energy Straggling after Penetration through Thin Target

The energy loss straggling for fast ions is simulated using the Monte Carlo method in the case of large and small transferred momenta. The interval of applicability of the Bohr approximation is determined for frequently used solid targets. The asymmetry in the distribution of ion energy losses is related to the influence of large transferred momenta and is observed in wide intervals of ion energy and target thicknesses.     

The ISAC post-accelerator

The acceleration chain of the ISAC facility boosts the energy of both radioactive and stable light and heavy ions for beam delivery to both a medium energy area in ISAC-I and a high energy area in ISAC-II. The post-accelerator comprises a 35.4 MHz RFQ to accelerate beams of A/q ≤ 30 from 2 keV/u to 150 keV/u and a post stripper, 106.1 MHz variable energy drift tube linac (DTL) to accelerate ions of A/q ≤ 6 to a final energy between 0.15 MeV/u to 1.5 MeV/u. A 40 MV superconducting linac further accelerates beam from 1.5 MeV/u to energies above the Coulomb barrier. All linacs operate cw to preserve beam intensity.     

Drastic enhancement of energy-loss straggling of relativistic heavy ions due to charge-state fluctuations

Stopping power and energy-loss straggling of 197Au, 208Pb, and 209Bi projectiles have been measured in different solids (4相似文献   

Ranges of implanted atoms under polyatomic cluster bombardment of the Cu (111) surface

A computer simulation of the bombardment of the Cu (111) surface with Cu_N and Au_N polyatomic clusters differing in size (N = 1, 6, and 13) with energies of 0.5 and 5 keV/atom has been performed in the framework of classical molecular dynamics. The spatial distribution of the implanted atoms, their ranges, and range fluctuations (straggling) depending on the size N and energy E/N of the incident cluster has been investigated. It has been shown that an increase in the mean range and range straggling is observed at a fixed energy per incident atom as the cluster size N increases. At the same time, the effect of an increase in the range (at a specified value of E/N) gradually disappears with increasing cluster energy, whereas the effect of an increase in straggling is retained. These tendencies qualitatively agree with the available experimental observations. It has been shown that the dominating contribution to the increase in the atom range of the implanted cluster is made by the so-called clearing-the-way effect, which is weakened with increasing the incident cluster energy. The effect of the range straggling increasing is significantly due to the presence of nonlinear “spike” effects at the bombarded target.     

铒离子注入碳化硅的射程和退火行为研究

用300—500 keV能量的铒(Er)离子注入碳化硅(6H-SiC)晶体中,利用卢瑟福背散射技术研究了剂量为5×10¹⁵ cm^-2 的Er离子注入6H-SiC晶体的平均投影射程R_p和射程离散ΔR_p,将测出的实验值和TRIM软件得到的理论模拟值进行了比较,发现R_p的实验值与理论值符合较好,ΔR_p的实验值和理论值差别大一些 关键词： 离子注入 投影射程和射程离散 退火行为 卢瑟福背散射技术     

Angular distribution of atoms sputtered from germanium by 1–20 keV Ar ions

The angular distribution of atoms sputtered from germanium under 1–20 keV Ar⁺ ion bombardment (normal incidence) has been studied experimentally and using computer simulations. A collector technique combined with Rutherford backscattering to analyze the distribution of collected material was used. In addition, the surface topography was under control. It was found that the experimental angular distribution of sputtered atoms (E ₀=3–10 keV) could be approximated by the function cos ⁿ θ with n≈ 1.65. Such a high value of n is connected with the surface scattering of ejected atoms and a noticeable contribution of backscattered ions to the formation of the sputter flux (the mass effect). The target surface was found to be practically flat even at ion fluencies ～10¹⁸ ions/cm². The results obtained are compared with data from the literature, including our recent data on Si sputtering.     

Double scattering of ions from polycrystalline materials

In this paper double scattering of ions from polycrystalline materials has been theoretically investigated. It is shown that double collision events contribute to the yield at low energy as well as to the high energy flanks of the peaks depending on whether or not the azimuthal angle ø₁ is greater than or less than a critical angle ø_1c at a given first scattering angle θ₁. There are various combinations of first scattering angle θ₁ and second scattering angle θ₂ which give the required retained energy in two successive collisions. Scattering cross sections derived from the Bohr potential and a double interpolation sub-routine are used to calculate the scattering yield at various angles. Two systems, Ne⁺ scattered from copper and Ar⁺ scattered from gold, each at 30 keV primary energy, have been compared with experimental results.