共查询到19条相似文献,搜索用时 203 毫秒
1.
针对SiC外延生长中微观原子动力学过程,建立了一个三维蒙特卡罗模型来研究偏向■或■方向4H-SiC(0001)邻晶面上台阶形貌演化过程,并且利用Burton-Cabera-Frank理论分析了其形成机理.在蒙特卡罗模型中,首先建立了一个计算4H-SiC晶体生长过程的晶格网格,用来确定Si原子和C原子晶格坐标以及联系它们之间的化学键;其次,考虑了原子在台阶面上的吸附、扩散,原子在台阶边上的附着、分离以及传输等过程;最后,为了更加详细地捕捉微观原子在晶体表面的动力学过程信息,该模型把Si原子和C原子分别对待,同时还考虑了能量势垒对吸附原子影响.模拟结果表明:在偏向■方向的4H-SiC(0001)邻晶面,有一个晶胞高度的聚并台阶形貌形成,而对于偏向■方向的邻晶面,出现了半个晶胞高度的聚并台阶形貌,该模拟结果与实验中观察到的结果相符合.最后,利用Burton-Cabera-Frank理论对聚并台阶形貌演化机理进行了讨论. 相似文献
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利用分子动力学中的静态结构计算方法对Pd,Ag及Cu原子在面心立方铜的台阶表面扩散过程中的Ehrlich-Schwoebel(ES)势垒进行了模拟计算,研究了各种台阶表面情况下增原子扩散过程中的ES势垒;讨论了与衬底互溶的金属和与衬底不互溶的金属增原子扩散的ES势垒的异同,并将模拟结果与同质情况的研究结果进行了对比. 结果表明: 1)在同质和异质扩散过程中ES势垒随着台阶高度的变化关系是相似的,即随着台阶高度的增加,ES势垒逐渐增加;当台阶高度达到某一高度时ES势垒将趋于定值. 2)在跳跃机理下,与Cu互溶的金属(Pd)在Cu表面台阶上扩散的ES势垒最大,其次是Cu,最小的是与Cu不互溶的金属 (Ag);而在交换机理下,与Cu不互溶的金属(Ag)在Cu表面台阶上扩散的ES势垒最大,其次是Cu,最小的是与Cu互溶的金属(Pd). 3)对大多数台阶的情况,交换机理支配着原子在台阶边缘的扩散行为;且表面台阶高度对交换扩散过程影响较大. 相似文献
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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 相似文献
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动力学晶格蒙特卡洛方法模拟Cu薄膜生长 总被引:2,自引:1,他引:2
利用动力学晶格蒙特卡洛方法模拟了Cu薄膜在Cu(100)面上的三维生长过程。模型中考虑了四个动力学过程:原子沉积、增原子迁移、双原子迁移和台阶边缘原子迁移,各动力学过程发生的概率由多体势函数确定。讨论了基底温度、沉积速率及原子覆盖率对Cu原子迁移、成核和表面岛生长等微观生长机制的影响;获得了Cu薄膜的表面形貌图并计算了表面粗糙度。模拟结果表明,随基底温度升高或沉积速率下降,岛的平均尺寸增大,数目减少,形状更加规则。低温时,Cu薄膜表现为分形的离散生长,高温时,Cu原子迁移能力增强形成密集的岛。Cu薄膜表面粗糙度随着基底温度的升高而迅速减小;当基底温度低于某一临界温度时,表面粗糙度随原子覆盖率或沉积速率的增大而增大;当基底温度超过临界温度时,表面粗糙度随原子覆盖率或沉积速率的变化很小,基本趋于稳定。 相似文献
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本文提出了一个新的基于扩散界面的相场模型来描述外延生长中岛的形核、生长及熟化过程. 该模型同时考虑了弹性场、表面能、沉积、扩散、解吸和能量势垒等热力学及动力学过程对表面纳米形貌的影响. 采用经典的BCF模型来描述生长中的扩散形核过程, 而采用一个新的包含弹性应变能的自由能函数, 通过变分得到一个描述多层岛生长的相场方程, 该方法可以有效地描述外延生长中复杂的外延形貌. 采用有限差分格式对非线性耦合方程组进行求解. 数值结果显示, 该模型可以真实地再现外延生长中多层岛结构(即山丘状形貌)的演化过程, 模拟结果与已有实验结果一致. 同时模拟了生长过程中随外延形貌演化而形成的复杂生长应力, 研究表明, 在生长过程中, 岛中存在着复杂的应力分布, 且在岛边界处应力达到局部最大, 这与实验结果定性一致. 此外, 本文的重要发现是, 外延生长中的应力演化明显地影响原子的扩散过程, 当应力存在时, 外延结构变化较无弹性场时变快. 该项研究对理解外延生长中各物理机理的协同作用有重要的指导意义. 相似文献
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为了研究离子注入对外延磁性薄膜面内磁各向异性的影响,用离子加速器对在有错切角的Si(111)面上外延生长的Fe膜进行了N~+注入实验.随着N~+注入剂量的增加,外延生长的Fe膜的面内磁各向异性逐渐从二重对称改变为六重对称.通过透射电子显微镜和刻蚀实验验证,发现离子辐照改变了Fe膜表面和界面的状态.未辐照Fe膜面内二重磁对称来自于由于Si(111)面的错切使得在薄膜界面和表面处形成的原子台阶.N~+注入的溅射作用使得Fe膜表面的原子台阶被擦除,N~+注入使得缓冲层和Fe膜界面处相互扩散导致界面处原子台阶消失.因此,外延Fe膜在大剂量N~+注入后表现出Fe(111)面诱导的六重磁对称.研究结果对于提高面内磁记录密度有潜在的应用价值. 相似文献
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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 相似文献
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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: 相似文献
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The energies of magnetic interactions between Co adatoms at the vicinal Cu(111) surface are calculated in the framework of the density functional theory using the Korringa-Kohn-Rostoker type Green’s functions. It is demonstrated that the interactions between Co adatoms appreciably depend on the distance from a surface step. Our calculations show that the magnitude of the repulsive barrier related to the surface step is larger for Co adatoms located at the upper surface terrace than for those located at the lower surface terrace. 相似文献
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We consider the wandering instability of steps due to a gap in the lifetime of adatoms for evaporation on the upper and the lower terraces. Our study is meant to explain the step wandering observed in the growth of Si(1 1 1) surface near its structural transition temperature. With a linear stability analysis and Monte Carlo simulations, we show that the instability of an isolated step occurs in growth if adatoms on the upper terrace evaporate more easily than those on the lower terrace. For the instability of a vicinal face, additional features are considered as the motion of the phase boundary and the mass flow across it during the phase transformation. It is found that steps and phase boundaries wander in-phase with a rather well-defined periodicity when evaporation is weak. We compare the result with that for a system with a gap in the diffusion coefficient. The simulation results show that the first mechanism is more effective to make the wandering steps in-phase and that the second mechanism induces step wandering in a wider range of parameters. 相似文献
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S. Schinzer S. Köhler G. Reents 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):161-168
We examine the step dynamics in a 1+1-dimensional model of epitaxial growth based on the BCF-theory. The model takes analytically
into account the diffusion of adatoms, an incorporation mechanism and an Ehrlich-Schwoebel barrier at step edges. We find
that the formation of mounds with a stable slope is closely related to the presence of an incorporation mechanism. We confirm
this finding using a solid-on-solid model in 2+1 dimensions. In the case of an infinite step edge barrier we are able to calculate
the saturation profile analytically. Without incorporation but with inclusion of desorption and detachment we find a critical
flux for instable growth but no slope selection. In particular, we show that the temperature dependence of the selected slope
is solely determined by the Ehrlich-Schwoebel barrier which opens a new possibility in order to measure this fundamental barrier
in experiments.
Received 11 May 1999 and Received in final form 6 November 1999 相似文献
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We study the behavior of single atoms on an infinite vicinal surface assuming certain degree of step permeability. Assuming
complete lack of re-evaporation and ruling out nucleation the atoms will inevitably join kink sites at the steps but will
do many attempts before that. Increasing the probability for step permeability or the kink spacing lead to increase of the
number of steps crossed before incorporation of the atoms into kink sites. The asymmetry of the attachment-detachment kinetics
(Ehrlich-Schwoebel effect) suppresses the step permeability and completely eliminates it in the extreme case of the infinite
Ehrlich-Schwoebel barrier. A negligibly small drift of the adatoms in a direction perpendicular to the steps leads to a significant
asymmetry of the distribution of the permeability events, the atoms thus visiting more distant steps in the direction of the
drift. The curves are fitted with an exponential function containing a constant which can be considered as a length scale
of the effect of the drift. Some conclusions concerning the stability of the vicinals are drawn.
相似文献
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A kinetic Monte Carlo simulation is performed in order to study the effect of Sb atoms as a surfactant on the growth of Ag on Ag(111).In our model the repulsive mechanism in which the surfactant Sb atoms repel diffusing Ag adatoms,and the exchange mechanism between Ag and Sb atoms,are considered.Our simulations show that the effects of Sb atoms for Ag/Ag(111) growth system are mainly to increase the chances for Ag atoms to overcome the Ehrlich-Schwoebel barrier both in the interlayer growth and along the edge diffusion.The influence of the coverage of Sb atoms and substrate temperature on the growth of Ag/Sb/Ag(111) is discussed. 相似文献
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K. Morawetz C. Olbrich S. Gemming 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):311-317
The coverage of vicinal, stepped surfaces with molecules is simulated with
the help of a two-dimensional Ising model including local distortions and
an Ehrlich-Schwoebel barrier term at the steps. An effective two-spin model is capable
to describe the main properties of this distorted Ising model. It is employed
to analyze the behavior of the system close to the critical points.
Within a well-defined regime of bonding strengths and Ehrlich-Schwoebel barriers we
find a reduction of coverage (magnetization) at low temperatures due to the
presence of the surface step. This results in a second, low-temperature
transition besides the standard Ising order-disorder transition.
The additional transition is characterized by a divergence of the
susceptibility as a finite-size effect. Due to the
surface step the mean-field specific heat diverges with a power law. 相似文献
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We fabricated monatomic Fe wires on vicinal Au(111) surfaces and found that decoration of step edges with Fe adatoms has a significant influence on the behavior of surface state electrons confined between regularly arranged steps. On a surface with Fe monatomic rows, angle-resolved photoemission spectra measured in the direction perpendicular to the steps shows parabolic dispersion, in contrast to one-dimensional quantum-well levels observed on a clean surface. Simple analysis using a one-dimensional Kronig-Penney model reveals potential barrier reduction from 20 to 4.6 eV A, suggesting an attractive nature of the Fe adatoms as scatterers. 相似文献
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We study the onset and development of ledge instabilities during growth of vicinal metal surfaces using kinetic Monte Carlo simulations. We observe the formation of periodic patterns at [110] close packed step edges on surfaces vicinal to fcc(001) under realistic molecular beam epitaxy conditions. The corresponding wavelength and its temperature dependence are studied in detail. Simulations suggest that the ledge instability on fcc(1,1,m) vicinal surfaces is controlled by the strong kink Ehrlich-Schwoebel barrier, with the wavelength determined by dimer nucleation at the step edge. Our results are in agreement with recent continuum theoretical predictions, and experiments on Cu(1,1,17) vicinal surfaces. 相似文献
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Mass transport of Ag and In on vicinal Si(111) has been investigated by scanning Auger microscopy (SAM). Highly anisotropic surface diffusion and surface electromigration due to direct current were observed for Ag and In adatoms on 0°−, 0.5°−, 3°− and 6°−off vicinal Si(111) surfaces. The diffusion on the intermediate layer is strongly enhanced in the direction parallel to the step edge for Ag adatoms, while it is remarkably suppressed in the direction perpendicular to the step edge for In adatoms. The activation energy of the diffusion for the Ag adatoms ranged between 0.81 and 1.3 eV, while that for In adatoms increased from 0.31 to 0.66 eV with increasing the vicinal angle. The anisotropic diffusion transport is explained in terms of the step structure and the difference in the binding energy at the step site and the terrace site. 相似文献