共查询到18条相似文献,搜索用时 125 毫秒
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用分子动力学方法对5%负失配条件下面心立方晶体铝薄膜的原子沉积外延生长进行了三维模拟.铝原子间的相互作用采用嵌入原子法(EAM)多体势计算.模拟结果再现了失配位错的形成现象.分析表明,失配位错在形成之初即呈现为Shockley扩展位错,即由两个伯格斯矢量为〈211〉/6的部分位错和其间的堆垛层错组成,两个部分位错的间距、即层错宽度为1.8 nm,与理论计算结果一致;外延晶体薄膜沉积生长中,位错对会发生滑移,但其间距保持稳定.进一步观察发现,该扩展位错产生于一种类似于“局部熔融-重结晶”的表层局部无序紊乱-
关键词:
失配位错
外延生长
薄膜
分子动力学
铝 相似文献
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采用三维分子动力学模拟方法,使用Ercolessi和Adams建立的嵌入原子法(EAM)多体势函数,模拟了二维晶格失配铝膜晶体中失配位错的形成过程,通过体系结构和能量曲线两种方法研究了温度对位错出现厚度的影响。结果显示:温度对于失配位错的形成有影响。同等条件下,随着温度的增大,失配位错的出现厚度变薄。 相似文献
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运用分子动力学方法对纳米晶柱阵列衬底上铝簿膜的外延生长进行了模拟研究.所采用的原子间相互作用势为嵌入原子法(EAM)多体势.模拟结果表明:采用纳米晶柱阵列衬底可以在不形成失配位错的条件下释放其上生长的外延薄膜晶体中的失配应变,有效地抑制其中失配位错的形成,获得高质量的外延薄膜晶体;这种纳米晶柱阵列的几何设计应满足两个基本条件:1) 晶柱的横截面尺寸应大于对应温度下的晶柱热失稳临界尺寸,以克服纳米结构的热失稳,模拟显示700K下铝的热失稳临界尺寸为19nm;2) 晶柱的高度与间距之比应大于076,以保证
关键词:
失配位错
分子动力学
纳米晶柱
铝 相似文献
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高质量GaN外延薄膜的生长 总被引:1,自引:0,他引:1
综述了高质量GaN外延薄膜的生长研究工作的最新重要进展.主要采用的新工艺为:在较低温度下生长GaN缓冲层后再高温生长GaN外延薄膜,双气流金属有机化合物气相沉积(MOCVD),以及用开有窗口的SiO2膜截断穿过位错后横向覆盖外延生长(epitaxialylateralovergrowth).X射线衍射和高分辨电镜研究证实,上述工艺使GaN外延薄膜质量得到显著提高.利用这种薄膜研制成的蓝色激光管即将投放市场. 相似文献
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分子动力学模拟铜薄膜的热导率 总被引:1,自引:0,他引:1
采用分子动力学(MD)方法模拟铜薄膜的热导率,给出了厚度在100~400nm、温度在100~600K范围内铜薄膜热导率对尺寸及温度的依赖关系. 相似文献
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我们研究了各种淀积参数(衬底温度,沉积速度和薄膜厚度)对C60薄膜在云母及NaCl衬底上成膜的影响,并在云母(001)新鲜解理面上成功地制备出了高质量的C60外延薄膜,此外,我们还对C60薄膜可能的生长过程,薄膜与衬底的取向关系及其缺陷结构进行了一定的讨论。 相似文献
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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 相似文献
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Effect of H impurity on misfit dislocation in Ni-based single-crystal superalloy: molecular dynamic simulations 下载免费PDF全文
The effect of H impurity on the misfit dislocation in Ni-based single-crystal superalloy is investigated using the molecular dynamic simulation. It includes the site preferences of H impurity in single crystals Ni and Ni3Al, the interaction between H impurity and the misfit dislocation and the effect of H impurity on the moving misfit dislocation. The calculated energies and simulation results show that the misfit dislocation attracts H impurity which is located at the γ/γ' interface and Ni3Al and H impurity on the glide plane can obstruct the glide of misfit dislocation, which is beneficial to improving the mechanical properties of Ni based superalloys. 相似文献
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It is shown experimentally that, during annealing and creep under low applied stresses, matrix dislocation loops frequently cross-glide. The periodic length of the zigzag dislocations deposited in the interfaces is equal to that of the γ/γ′-microstructure. Initially, the zigzag dislocations move in the (001) interface by a combination of glide and climb but then they stop near the γ′-edges and align along ?100?. Reactions of such dislocations lead to the formation of square interfacial networks consisting of ?100? oriented edge dislocations. The complex dislocation movement is explained by the inhomogeneity of the misfit stresses between γ- and γ′-lattices. The tensile components of the stress tensor drive the dislocations through the channel, whereas the shear components near the γ′-edges cause the zigzag movement and the ?100? alignment. The total effect is the most efficient relaxation of the misfit stresses. The results are relevant, especially for single-crystal superalloys of the newest generations, which have an increased γ/γ′-misfit due to the high level of refractory elements. 相似文献
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Ghiath Monnet 《哲学杂志》2013,93(29):3810-3829
An investigation is reported of the probability and the probability density of thermal activation of stress-driven dislocation processes, as simulated using molecular dynamics (MD). Stochastic analyses of the survival probability are found to lead to simple relationships between the loading history and the distribution of the interaction time and strength. It is shown that the determination of the activation energy associated to a thermally activated event can be achieved by a reduction of the stochastic process to a process obeying the Poisson's distribution, preserving the activation probability at the survival time. The method is applied to the kink-pair mechanism for screw dislocations in iron. Predictions are compared with experimental results and with other methods reported in the literature, which allows the difference in the approximations and in the assumptions considered in these models to be underlined. 相似文献
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本文使用Stillinger-Weber势函数和周期性边界条件,通过在原子尺度上的分子动力学计算研究了60°位错的位错心能量和运动情况.首先提出了相对简单的建立位错偶极子的新方法.在此基础上,借助于最近得到的对周期性映像作用的评估理论,由不同大小的3维计算模型得到的位错心能量的平均值为0.43 eV,这一结果不同于先前文献中的报导.另一方面,为研究位错运动在较大温度和压力范围下的表现,提出了相应解决方法来避免位错心在高温模拟环境时测量的不精确性.模拟结果显示位错速度相对于温度的变化曲线表现为波动形式.而且,位错的速度随模拟温度的升高而降低,这一结果与声子拖拽模型相吻合. 相似文献
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We report a method to incorporate dislocation climb controlled by bulk diffusion in a three-dimensional discrete dislocation dynamics (DDD) simulation for fcc metals. In this model we couple the vacancy diffusion theory to the DDD in order to obtain the climb rate of the dislocation segments. The capability of the model to reproduce the motion of climbing dislocations is examined by calculating several test-cases of pure climb-related phenomena and comparing the results with existing analytical predictions and experimental observations. As test-cases, the DDD is used to study the activation of Bardeen–Herring sources upon the application of an external stress or under vacancy supersaturation. Loop shrinkage and expansion due to vacancy emission or absorption is shown to be well described by our model. In particular, the model naturally describes the coarsening of a population of loops having different sizes. 相似文献
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针对Ni基单晶合金建立初始压入γ 相的γ /γ' 模型和初始压入γ'相的γ'/γ 模型, 采用分子动力学方法模拟金刚石压头压入两种模型的纳米压痕过程, 计算两种模型[001]晶向硬度. 采用中心对称参数分析两种模型(001)相界面错配位错对纳米压痕过程的影响. 结果显示: 弛豫后, 两种模型(001)相界面错配位错形式不同, 其中γ'/γ 模型(001)相界面错配位错以面角位错形式存在; 压入深度在0.930 nm 之前, 两种模型(001)相界面错配位错变化不大, 压入载荷-压入深度及硬度-压入深度曲线较符合; 压入深度在0.930 nm之后, γ'/γ 模型(001)相界面错配位错长大很多, 导致相同压入深度时γ'/γ 模型比γ /γ'模型压入载荷和硬度计算结果小; 压入深度在2.055 nm之后, γ /γ'模型(001)相界面错配位错对γ 相中位错进入γ'相有阻碍作用, 但仍有部分位错越过(001) 相界面进入γ' 相中, γ'/γ 模型(001)相界面处面角位错对γ' 相中位错进入γ 相有更明显的阻碍作用, 几乎无位错越过(001) 相界面进入γ 相中, 面角位错的强化作用更明显, 所以γ'/γ 模型比γ /γ'模型压入载荷上升速度快. 相似文献