Charge state dependent energy deposition by ion impact

We report on a measurement of craters in thin dielectric films formed by Xe(Q+) (26 ≤ Q ≤ 44) projectiles. Tunnel junction devices with ion-irradiated barriers were used to amplify the effect of charge-dependent cratering through the exponential dependence of tunneling conductance on barrier thickness. Electrical conductance of a crater σ(c)(Q) increased by 4 orders of magnitude (7.9 × 10(-4) μS to 6.1 μS) as Q increased, corresponding to crater depths ranging from 2 to 11 ?. By employing a heated spike model, we determine that the energy required to produce the craters spans from 8 to 25 keV over the investigated charge states. Considering energy from preequilibrium nuclear and electronic stopping as well as neutralization, we find that at least (27 ± 2)% of available projectile neutralization energy is deposited into the thin film during impact.     

Distributions of the implanted impurity and energy release in high-energy ion implantation

A new model for high-energy ion implantation is proposed, based on the use of the Fokker-Planck equation. An efficient algorithm of the adaptive type is devised for the numerical solution of the problem. A simulation of the implantation of boron in silicon is carried out for energies ranging from 10 to 100 MeV. Good agreement is obtained with the experimental data and the results of Monte Carlo simulations. Zh. Tekh. Fiz. 67, 61–67 (January 1997)     

Effects of Beam Energy Spread on the Weibel Instability in Fast Ignitor Scenarios

The effects of transverse temperature distribution on the Weibel instability in a laser produced plasma are studied analytically by using a three dimensional waterbag model. It is found that the purely transverse Weibel instability can be stabilized for the case in which the electron beam has a more symmetric transverse temperature distribution. This analytical expectation is supported by our two dimensional particle-in-cell simulations.     

Parameterization of the energy spectrum of an impurity ion in a perturbing field

The method of parameterizing the energy spectrum for systems with symmetries of the simplest point groups (SR groups) in an external stationary perturbing field has been generalized to the third approximation. The sums over intermediate states are partially convolved in 3n coefficients. We retain sums of derivatives of the given matrix elements which refer to states of all possible energy levels which enter into the external parameters which represent the minimal set of parameters describing the corrections to the energy. We give formulas for calculating the external parameters and establish the connection with the internal parameters in the usual version of the stationary theory of perturbations. In determining the parameters from experimental data the advantage of our method is found in those cases where the number of external parameters is less than the number of internal ones, which is the usual case. The method is illustrated using the Zeeman and Stark effects for energy levels of the T_2g type for an impurity ion having O_h site symmetry, as an example.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 61–67, March, 1995.     

Tunneling energy levels of an off-center impurity of the hydroxyl ion in NaCl crystal

Fine structures of the vibrational spectrum of OH^– in NaCl have been investigated by their dependence on the OH^– concentration, temperature and uniaxial stress. The absorption bands of A and C at 3651. 2 and 3655.2 cm-1 are ascribed to the tunneling motion of the off-center impurity of OH^–. The stress splitting factor of the tunneling levels has been estimated to be B(S11–S12)=0.96±0.10 cm-1/10⁸ dyn cm-2 in the ground state and it is about 1.4 times larger in the vibrational excited state.     

Low energy ion impact phenomena on single crystal surfaces

The dynamics of a solid bombarded by a 600 eV Ar⁺ ion have been studied classically by computer simulation. The model uses a crystallite of about 250 atoms described by pair potentials derived from elastic constants and which reproduce the surface binding energy of the solid. The relative calculated yield of secondary atom emission from the three low index faces of Cu follow the previously determined experimental order (111) > (100) > (110). We find major differences in the sputtering mechanisms for these faces. On (110), the impacted atom is ejected most frequently, while on (111) and (100) it almost never leaves the solid. We report the energy distribution of the sputtered particles for each face. The simulation successfully predicts the shape of the curve including the low energy maximum which is observed experimentally near 2 eV. In addition our model shows that many low energy atoms attempt to leave the crystal but are subsequently trapped to the solid at large distances from their original sites. This mechanism of radiation enhanced diffusion inevitably occurs in conjunction with sputtering or any other heavy secondary particle emission or scattering process.     

闪锌矿GaN量子点中类氢杂质态的束缚能

在有效质量近似下,用变分法研究了闪锌矿GaN/AlxGa1-xN单量子点中的类氢杂质态。结果表明量子点中的杂质位置和量子点结构参数（量子点高度H、半径R及Al含量x）对施主束缚能有很大的影响。当杂质位于量子点中心时,施主束缚能 有最大值。此外,施主束缚能 随着量子点高度H（半径 ）的增大而减小,随着量子点中Al含量x的增大而增大。     

离子束修形中光学元件表面热量沉积数值模拟

根据Sigmund溅射能量沉积理论建立了低能离子入射光学元件引起的能量扰动层厚度模型．理论推导了离子束倾斜入射时光学元件表面的束流密度,并建立了低能离子束对光学元件的热量沉积模型．采用MonteCarlo方法模拟了低能离子与熔石英光学表面的相互作用．分析了离子能量、离子类型、入射角度等参数对光学元件热量沉积和扰动层深度的影响规律．以离子束沉积在工件的能量作为热源,采用有限元分析软件ANSYS模拟了离子束入射工件的温度场分布、温度梯度场分布和温度应力分布．入射表面温度和热梯度呈高斯分布,束斑中心最高并向工件边缘逐渐减小．入射表面束斑区域受热膨胀,其膨胀受到外环区域的制约,从中心区域到大约束斑半峰值半径的区域,所受环向应力为压应力,在大致束斑半峰值半径以外区域为拉应力．     

强流脉冲离子束辐照双层靶能量沉积的数值模拟

利用拟合实验测得的TEMP Ⅱ型加速器磁绝缘二极管电压波形及其焦点附近束流密度曲线,建立了Gauss分布模型.采用Monte Carlo方法研究了强流脉冲离子束与铝材镀有不同厚度金膜的双层靶(金膜与铝材合称为双层靶)之间的相互作用,模拟了能量沉积的演化过程和随不同金膜厚度的变化情况.对脉冲离子束强化薄膜粘结性进行了探讨. 关键词： 强流脉冲离子束 双层靶 能量沉积 Monte Carlo方法     

Simulation of dynamic changes in the surface composition of tungsten under ion irradiation with regard to carbon impurity deposition

Argon ion cleaning of a tungsten surface covered by a carbon film was simulated taking into account the redeposition of graphite. An increase in the argon ion energy from 200 to 1000 eV greatly enhances cleaning. The cleaning rate is lowered when the carbon flux to the surface increases.     

非晶氧化钛薄膜形成过程中钛离子能量对表面结构影响的机理

研究了非晶氧化钛薄膜沉积过程中入射钛离子能量对表面结构形成机理以及薄膜特性的影响.模拟结果表明,通过提高入射钛离子能量,可以有效降低成膜表面粗糙度,从而减小薄膜表面的光学散射损耗.研究发现,当入射离子能量提高后,薄膜生长模式从"岛"状生长过渡到了"层"状生长,且离子入射点附近的平均扩散系数也有显著增加,这有利于形成更加平整的高质量薄膜表面.     

离子辅助沉积中离子束流密度的作用

测量了End-Hall离子源在不同条件下的离子束流密度，在不同离子束流密度下进行了Ar离子辅助沉积ZrO2薄膜的实验，研究了离子束流密度对薄膜折射率、晶相的影响.根据动量传递模型分析了离子束流密度对薄膜折射率的作用;根据热尖峰理论证明了一定条件下离子束流密度不会影响薄膜晶体结构.     

磁约束等离子体中杂质离子的输运方程

以非平衡态统计理论为基础,从福克尔-普朗克动理学方程出发推导出了各种杂质离子、氘离子和电子的输运动力学方程,即特殊的多组分等离子体输运方程。各级电离过程中形成的带不同电荷杂质离子的输运动力学过程以及不同粒子间碰撞相互作用的贡献在文中进行了系统的分析。此外,在重新推导并优化的基本方程组基础上,得到了各种杂质离子的输运动力学方程。     

Nonaxisymmetric energy deposition pattern on ASDEX upgrade divertor target plates during type-I edge-localized modes

In the ASDEX Upgrade tokamak, complex power deposition structures on the divertor target plates during type-I edge-localized modes (ELMs) have been discovered by fast (few microseconds), two-dimensional (40 x 40 cm(2)) infrared thermography. In addition to the usual axisymmetric power deposition line near the separatrix, there appear, statistically distributed, several laterally displaced and inclined stripes, mostly well separated from each other and from the main strike zone. These structures are interpreted as footprints of approximately field aligned, helical perturbations at the low field side of the main plasma edge related to the nonlinear ELM evolution. Based on this picture, the ELM related mode structure can be derived from the target load pattern, yielding on average toroidal mode numbers in a range of 8-24.     

Strong impact of impurity bands on domain formation in superlattices

The formation of electric field domains in doped semiconductor superlattices is described within a microscopic model. Due to the presence of impurity bands in low-doped samples the current–voltage characteristic is essentially different compared to medium-doped samples.     

The binding energy of a hydrogenic impurity in self-assembled double quantum dots

The binding energy of a hydrogenic impurity in self-assembled double quantum dots is calculated via the finite-difference method. The variation in binding energy with donor position, structure parameters and external magnetic field is studied in detail. The results found are: (i) the binding energy has a complex behaviour due to coupling between the two dots; (ii) the binding energy is much larger when the donor is placed in the centre of one dot than in other positions; and (iii) the external magnetic field has different effects on the binding energy for different quantum-dot sizes or lateral confinements.     

The high-density symmetry energy in heavy ion collisions

The nuclear symmetry energy as a function of density is rather poorly constrained theoretically and experimentally both below saturation density, but particularly at high density, where very few relevant experimental data exist. We discuss observables which could yield information on this question, in particular, proton-neutron flow differences, and the production of pions and kaons in relativistic heavy ion collisions. For the meson production we investigate particularly ratios of the corresponding isospin partners π⁻/π⁺ and K⁰/K⁺, where we find that the kaons are an interesting probe to the symmetry energy. In this case we also discuss the influence of various choices for the kaon potentials or in-medium effective masses.     

Hydrogen impurity in aluminium: Calculation of the lattice relaxation energy

We present the first treatment of lattice relaxation around a single strong impurity within the “spherical solid model”. For a proton placed in the octahedral site of an f.c.c. aluminium lattice, we get 2.4% expansion for the first shell and a corresponding - 0.063 eV lowering of the heat of solution.     

Slowing down approximations to the boltzmann equation: I. Applications to energy deposition and ion implantation

An approximale method for solving the Boltzmann equation for fast particles slowing down in homogeneous media is described. The Boltzmann equation is used in its straight ahead form and the method of Goertzel and Greuling, developed for neutron transport calculations, is extended to cover the problem of ion slowing down and energy deposition. Solutions are obtained in a simple analytical form and compared with exact calculations. We observe that the error passes through a maximum as the index of anisotropy, m, goes from zero to unity. The limitations of simple áge theory are discussed and it is shown how these solutions become exact in the Coulomb limit. The additional problem of electronic stopping is included and its effect on the solution is assessed. Numerical examples are given to support the general conclusions; namely that the Goertzel-Greuling method provides a convenient way to obtain useful estimates of ion implantation profiles and energy deposition.