超薄膜外延生长的Monte Carlo模拟

用MonteCarlo(MC)方法对超薄膜外延生长过程进行了计算机模拟.模型中引入Morse势描述粒子间的相互作用,考虑粒子的沉积、吸附粒子的扩散和蒸发三个过程.研究了粒子间相互作用范围α和允许粒子行走的最大步数对薄膜生长形貌的影响.结果表明:在不同的α值下,随粒子行走步数的增加,薄膜的生长经历了从分散、分形、混合到团聚的过程;其中α=6时,基本观察不到粒子的分散生长过程;α值越小且粒子行走步数越小的情况下,薄膜越易趋向于分散生长 关键词： 超薄膜 MonteCarlo方法 外延生长 Morse势 分形     

基于Monte Carlo方法模拟薄膜生长

本文运用Monte Carlo方法,通过计算机模拟研究了真空镀膜过程中沉积速率、自由粒子迁移率、粒子沿分形迁移等对薄膜生长过程的影响。     

非均一相互作用能对超薄膜生长影响的Monte Carlo模拟研究

利用Monte Carlo (MC)模拟技术研究了非均一的吸附原子与基底相互作用能在一定的生长条件下对超薄膜生长过程的影响.非均一相互作用能是由基底表面原子在垂直和水平方向上实际位置与理想晶格原子位置的偏差所造成.本文用高斯分布来表示这种非均一相互作用能.模拟结果表明:非均一相互作用能对超薄膜的生长过程及薄膜的形貌有显著的影响.这种影响同时受到生长条件的限制,在中等温度时相互作用能的非均一性对岛的个数、平均大小的影响最显著;温度的增加在一定程度上可抵御相互作用能的非均一性对薄膜生长的影响. 关键词： 薄膜生长 Monte Carlo 模拟 相互作用能     

高温下金属薄膜生长初期的模拟研究

采用实际的生长模型和物理参量,用Monte Carlo方法对高温下金属薄膜的生长过程进行了模拟研究.综合考虑了原子沉积、扩散、成核、生长和扩散原子的再蒸发、原子沿岛周界扩散和岛的合并等众多过程后,模拟得到与实验结果相当一致的薄膜生长形貌及其相应的定量结果.通过动态统计薄膜生长过程中的岛数目及薄膜生长率,得到实验中不易直接获得的高温下薄膜生长的许多细节,如岛数目和薄膜生长率随表面温度、覆盖度变化的详细情况等 关键词： 薄膜 Monte Carlo模拟 成核 岛密度 薄膜生长率     

沉积粒子能量对薄膜早期生长过程的影响

利用Monte Carlo(MC)模型研究了能量粒子对薄膜生长的初始阶段岛膜的形貌和岛的尺寸的影响,沉积粒子的能量范围为:0—0.7eV.在模型中考虑了原子沉积、吸附原子扩散和蒸发等过程,并详细考虑了临近和次临近原子的影响.结果表明,在所采用的参量范围内不同的基底温度情况下,能量粒子的影响有很大的区别.低基底温度情况下,沉积粒子强烈地影响着薄膜的生长过程中,岛膜的形貌、数量和尺寸随能量粒子的能量增加而有很大的变化.分析表明,这些变化都是由于能量粒子的介入使得表面吸附粒子的扩散能力增强所致 关键词： 薄膜生长 Monte Carlo方法 扩散     

载能原子沉积Au/Au(100)外延薄膜生长的计算机模拟

在分子动力学研究的基础上建立了载能原子的沉积动力学物理模型,并根据在局域环境下的表面原子扩散模型,通过运动学Monte Carlo方法研究了载能粒子沉积Au/Au(100)薄膜的初期生长过程,探讨了载能粒子沉积对薄膜生长的影响及其随基体温度的变化.通过计算机模拟发现：载能粒子沉积的Au/Au(100)薄膜生长仍然呈现层状生长-三维岛状生长-准二维层状.在薄膜生长初期,载能粒子的作用是促进表面原子的成核,增加基体表面的缺陷;在薄膜的生长阶段,载能粒子通过抑制三维岛的生长速率起着平滑薄膜表面形貌的作用.载能粒 关键词：     

六方晶格基底上薄膜生长的Monte Carlo模拟研究

利用Monte Carlo（MC）方法,模拟研究了六方晶格基底上薄膜生长的初始阶段岛的形貌和岛的尺寸与薄膜覆盖度以及入射粒子沉积速率之间的关系. 结果表明在基底温度为300K时,岛的形貌主要表现为分形生长,随着薄膜覆盖度的增加,岛的分形枝簇变大,岛的数目不断减少. 在同样的温度下,随着入射粒子沉积速率的增大,薄膜表面的形貌逐步由少数聚集型岛核分布状态向众多各自独立的离散型岛核分布状态过渡. 进一步研究得出,薄膜覆盖度和入射粒子沉积速率对粒子扩散能力的影响最终导致岛的形貌发生了改变.     

具有幂次相互作用的磁性粒子凝聚过程的数值研究

在扩散限制凝聚模型的基础上引入粒子的自旋自由度(包括自旋向上和向下),并假设粒子间存在幂次Ising磁相互作用,采用Monte Carlo方法研究了在不同相互作用力程情况下磁性粒子的分形生长规律.模拟结果表明,当粒子间以反铁磁方式耦合时,凝聚体中的粒子自旋交替凝聚.当粒子间以铁磁方式耦合时,凝聚体中粒子的自旋分布与相互作用力程有关:对于短程作用系统,凝聚体中存在大小不同的自旋畴块,即为铁磁生长;而对于长程相互作用系统,凝聚体中的自旋出现反常分布,即中心区域是近似反铁磁生长的结构,其外围后续生长的粒子却保持 关键词： 幂次相互作用 扩散限制凝聚模型 自旋     

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     

基底显微结构对薄膜生长影响的Monte Carlo模拟研究

利用Monte Carlo方法研究了基底显微结构对薄膜生长的影响. 对不同显微结构基底上薄膜生长的初始阶段岛的形貌和尺寸与薄膜覆盖度和入射粒子沉积速率之间的关系进行了模拟和分析. 模型中考虑了粒子沉积、吸附粒子扩散和蒸发等过程. 结果表明,基底显微结构对薄膜生长具有明显影响. 当沉积温度为300K、沉积速率为0.005ML/s（Monolayer/second,简称ML/s）、覆盖度为0.05ML时,四方基底上薄膜生长呈现凝聚生长. 随着覆盖度增加,岛的尺寸变大,岛的数目减少. 而对于六方基底,当覆盖度从0.05ML变化到0.25ML时,薄膜生长经历了一个从分散生长过渡到分形生长的过程. 无论是四方还是六方基底,随着沉积速率的增加,岛的形貌由少数聚集型岛核分布状态向众多各自独立的离散型岛核分布状态过渡.     

Fractal structure of films deposited in a tokamak

The surface of amorphous films deposited in the T-10 tokamak was studied in a scanning tunnel microscope. The surface relief on a scale from 10 nm to 100 μm showed a stochastic surface topography and revealed a hierarchy of grains. The observed variety of irregular structures of the films was studied within the framework of the concept of scale invariance using the methods of fractal geometry and statistical physics. The experimental probability density distribution functions of the surface height variations are close in shape to the Cauchy distribution. The stochastic surface topography of the films is characterized by a Hurst parameter of H = 0.68–0.85, which is evidence of a nontrivial self-similarity of the film structure. The fractal character and porous structure of deposited irregular films must be considered as an important issue related to the accumulation of tritium in the ITER project. The process of film growth on the surface of tokamak components exposed to plasma has been treated within the framework of the general concept of inhomogeneous surface growth. A strong turbulence of the edge plasma in tokamaks can give rise to fluctuations in the incident flux of particles, which leads to the growth of fractal films with grain dimensions ranging from nano-to micrometer scale. The shape of the surface of some films found in the T-10 tokamak has been interpreted using a model of diffusion-limited aggregation (DLA). The growth of films according to the discrete DLA model was simulated using statistics of fluctuations observed in a turbulent edge plasma of the T-10 tokamak. The modified DLA model reproduces well the main features of the surface of some films deposited in tokamaks.     

Influence of the angular distribution function of incident particles on the microstructure and anomalous scaling behavior of thin films

The microstructure and the scaling properties of films grown by plasma enhanced chemical vapor deposition are reproduced with a discrete model that takes into account the angular distribution function of the particles and the lateral growth of the films. Both the experimental and simulated surfaces exhibit a granular microstructure and an anomalous scaling behavior characterized by values of the growth exponent beta that vary with the scale of measurement. Depending on the angular distribution function used in the model, values of beta ranging from 0.86 to 0.2 are obtained.     

Morphology and electronic structure of nanostructured carbon films embedding transition metal nanoparticles

Inclusions of metals in the growth process of carbon cluster assembled materials (ns-C) induce modifications in the structural and electronic properties of the material. A novel pulsed microplasma cluster source (PMCS) is able to deliver highly intense, collimated and stable beams suitable for producing bulk quantities of cluster-assembled nanocomposite films. Loading of metal nanoparticles into carbon cluster based films is obtained either by mixing a gas phase metallorganic compound with the carrier gas (He) before entering into the source (for example molybdenum (V) isopropoxide), or by using a double component sputtering target (metal (Ti, Ni)/graphite). The study of film morphology on nanometer scale, carried out by transmission electron microscopy (TEM), reveals the dispersion in a ns-C matrix of metallic particles and, in the case of molybdenum containing films, also of carbide particles. Spatially resolved ultraviolet photoemission spectroscopy confirms the segregation of metal particles and exhibits evident anisotropy in the Mo:ns-C films, mainly ascribable to the formation of carbide nanoparticles.     

Particle Systems Analysis by Using Skeletonization and Exact Dilations

This paper describes how the formation of particle systems can be investigated by using computer vision techniques, namely effective exact dilations and multiscale skeletonization. By assuming that all particles started to grow at the same time and had the same growth rate, a hypothesis that can be validated later, it becomes possible to infer the shape and distribution of the particles in the initial system configuration. Multiscale skeletons are obtained for each individual particle, and a suitable overall spatial scale, i.e. those best approximating the initial configuration, is determined as that immediately before the smallest particle fades. The thus obtained skeletons provide an estimate of the shape and position of the initial particles before uniform expansion. By using exact dilations, a generalized Dirichlet tessellation reconstruction of the particle system is obtained from these skeletons, and the similarity between this reconstruction and the original system can be used to validate the assumptions about the growth conditions. The proposed methodology is illustrated with respect to KC1 polycrystalline thin films.     

Hydrogen template assisted electrodeposition of sub-micrometer wires composing honeycomb-like porous Pb films

High surface area porous Pb films are electrodeposited using a hydrogen bubble dynamic template. The influence of the experimental parameters on the morphology features such as the pore size, wall thickness, and sub-micrometer size features is investigated. Two structural transformations between sub-micrometer wires and particles obtained by adjusting the HClO₄ concentration are observed. At a low HClO₄ concentration, the growth of sub-micrometer wires is favored. The deposition of particles or wires covered by particles is observed at higher H⁺ concentrations. The addition of sodium citrate as an additive facilitates the preservation of Pb in the form of wires. Adjusting the concentration of Pb(ClO₄)₂·3H₂O influences the mass transfer of Pb and affects its morphology. At low concentrations, the deposition of porous Pb films composed of porous wires is shown. The additional deposition of particles on wires is observed at high concentrations. The formation process of honeycomb-like porous structures is revealed by analysis of films deposited during different deposition time. The influence of the current density on the micro and sub-micrometer scale morphologies is presented.     

Plasma‐Substrate Interaction during Plasma Deposition on Polymers

The initial stage of film growth during plasma deposition on polymers determines many film properties such as morphology and structure, interphase formation and adhesion. Therefore, the plasma‐substrate interaction is investigated regarding the energy density during film growth, which is defined by the energy flux per depositing atom. The flux of film‐forming species and the flux of energetic particles were determined for metal sputtering (silver films) and plasma polymer deposition (amino‐functional hydrocarbon films). It is shown that enhanced energy densities can be obtained during the initial film growth due to reduced deposition rates and mixing with the polymer substrate (interphase formation). Thus, good adhesion on polymers such as polyethylene terephthalate (PET) has been achieved. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the phenomena occurring at the interface between iron and iron–platinum thin films

FePt films were rf sputtered at room temperature and 550?C on MgO monocrystalline substrates. Room temperature films were post-annealed at 550?C. The high temperature growth induces a tetragonal distortion of the structure with the formation of L1₀-FePt phase. Soft iron layers, with different thickness, were e-beam deposited on these hard films. The phenomena occurring at the interface have been analysed and connected with the final magnetic behaviour of the system. It has been found that a strong exchange coupling between soft and hard layers has been established through the formation of an interfacial layer constituted by FePt small particles.     

Structural and magnetic properties of <Emphasis Type="Italic">L</Emphasis>1<Subscript>0</Subscript>–FeCoPt nanoparticles prepared by rf-sputtering

L1₀ ordered Fe–Co–Pt magnetic nanoparticles were fabricated using radio frequency sputtering at 613 K on single-crystalline NaCl and MgO substrates. The growth of particles was studied by varying the sputtering gas pressure and sputtering duration. High-resolution electron microscopy and electron diffraction studies revealed a formation of particles with L1₀-related variant domains. The structure and magnetic studies showed the preferential in-plane formation of the magnetic easy axis. The coercivity of the films increased with annealing at 773 K. The Co addition to the FePt alloy increased the saturation magnetization to 1300 emu/cm³.     

pH and temperature dependence of particle size in Pb1−xFexS nanoparticle films

The growth mechanism of Pb_1−xFe_xS nanoparticle films in chemical deposition is discussed. Grain growth for the Pb_1−xFe_xS films with increasing temperature of the chemical bath is observed to be due to the phenomenon of coalescence and formation of bigger particles at higher pH is possibly due to aggregation.     

Structure and magnetism of electrodeposited ZnSe–Co granular films

ZnSe–Co granular films have been electrodeposited under potentiostatic condition on polished stainless steel substrates. X-ray diffraction and transmission electron microscopy measurements indicate the formation of polycrystalline granular films with Co particles dispersed in an ZnSe matrix without evidence of intermediate compound formation. Magnetic measurements reveal low values of coercive field and remanence, indicating that the overall magnetic response of the deposited films is determined by multidomain nanosized particles.