Cu薄膜三维生长的Monte Carlo模拟

利用蒙特卡罗(Monte Carlo)方法模拟了Cu薄膜在四方基底上的三维生长过程。模型中考虑了三个主要的原子热运动过程:原子沉积、原子扩散、原子脱附,各过程发生的概率是由各运动的速率来决定的。讨论了基底温度、沉积速率及原子覆盖度对Cu薄膜的表面形貌及表面粗糙度的影响。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,薄膜以层状生长方式生长;Cu薄膜表面粗糙度随温度的升高而减小,当基底温度处于某一临界温度之内时,表面粗糙度随沉积速率的变化很大,但当基底温度超过临界温度时,表面粗糙度随沉积速率的变化很小;薄膜的粗糙度与薄膜亚单层的形核密切相关。     

考虑二维ES势垒的薄膜生长动力学Monte Carlo模型

考虑了原子在发生层间扩散过程中Ehrlich-Schwoebel势垒的作用,构造了四边形基底表面上薄膜三维生长的动力学Monte Carlo(MC)模型。在这个模型中,原子表面运动的三种动力学过程包括沉积、扩散和脱附过程,它们相互影响又相互独立,依据各自的概率发生。在不同生长条件下,模拟出薄膜的三种生长模式以及相应的薄膜三维生长形貌图。对计算结果的分析表明,ES势垒和在ES势垒作用下基底温度和沉积速率等因素对薄膜的三维生长模式有重要影响。     

基于H—Si（100）表面上原子层沉积Al2O3的仿真研究

通过对原子层沉积过程的计算机仿真,分析不同沉积条件对沉积过程的影响.以H-Si(100)表面原子层沉积Al2O3的过程为基础,通过分析基片上不同表面功能团之间的相互作用,将整个沉积过程分为初始沉积和后续生长两个阶段.基于不同的阶段建立相应的前驱体到达事件模型、反应事件模型以及表面解吸事件模型.采用动力学晶格蒙特卡罗方法实现这一沉积过程的仿真.实现了不同温度、不同真空条件下Al2O3的原子层沉积仿真.结果表明:在一定的范围内,前驱体或基片的温度高,反应室真空度低,薄膜生长速率的增长快,表面粗糙度小;基片温度对于薄膜沉积过程的影响最大,其阈值约为200℃.而且薄膜的生长趋势由初始的三维岛状生长向二维层状生长逐渐转变.     

金属薄膜缺陷及生长模式的有限元模拟

为了从微观领域研究金属薄膜缺陷的形成和薄膜的初期生长模式,利用有限元法对金属薄膜沉积过程中的缺陷和生长模式进行了计算机模拟.以Pt原子为膜料粒子,采用刚性球入射到石墨基底,重点研究了在基底上形成的缺陷结果表明,在薄膜生长初期会形成"树桩"小岛,而当碳基底上沉积铂原子的能量值达到75 eV时,就有可能发生随机原子注入."树桩"小岛的形成使薄膜生长多为岛状生长机制,同时检验了有限元方法在微观领域中的合理性和适用性.     

薄膜生长初期形貌的计算机模拟与改进

本文模拟了在低温基底上超薄膜沉积初期表面形貌。文章模拟多个沉积原子同时移动的生长过程，引入了宏观量沉积流量影响。在此基础上讨论了各向异性的影响作用，并改进了模型，修改了基底吸附位置的排列方式，从而获得了与实验结果更相近的图样。     

各向异性胶体基底表面的分形凝聚体

对各向异性胶体基底表面的分枝状金原子凝聚体的生长机制进行了研究。沉积在无规杂质区域的熔融玻璃表面的金原子先形成网状结构的薄膜 ,然后逐渐演变成分枝状凝聚体。根据这一实验结果 ,建立了各向异性的团簇 团簇凝聚模型 ,对此类胶体基底表面的金原子分枝状凝聚体的生长全过程进行了计算机模拟 ,研究了杂质区域对凝聚体各种参数的影响 ,其结果与实验相符合     

薄膜生长初期形貌的计算机模拟与改进

本文模拟了在低温基底上超薄膜沉积初期表面形貌。文章模拟多个沉积原子同时移动的生长过程 ,引入了宏观量沉积流量影响。在此基础上讨论了各向异性的影响作用 ,并改进了模型 ,修改了基底吸附位置的排列方式 ,从而获得了与实验结果更相近的图样     

各向异性胶体基底表面的分形凝聚体

对各向异性胶体基底表面的分枝状金原子凝聚体的生长机制进行了研究，沉积在无规杂质区域的熔融玻璃表面的金原子先形成网状结构的薄膜，然后逐渐演变成分枝状凝聚体，根据这一实验结果，建立了各向异性的团簇-团簇凝聚模型，对此类胶体基底表面的金原子分枝状凝聚体的生长全过程进行了计算机模拟，研究了杂质区域对凝聚体各种参数的影响，其结果与实验相符合。     

沉积能量与沉积速率对薄膜生长形貌的影响

本文利用各向同性的周期性四方形基底,模拟了沉积能量与沉积速率对薄膜三维形貌的影响。模型主要分析了原子沉积、吸附原子扩散和原子脱附三个过程,同时详细地考虑了四方形基底的最近邻和次近邻的影响。结果表明:沉积能量对薄膜粗糙度、衬底填充比、岛的个数都有明显的影响。沉积速率对薄膜粗糙度的影响较小,在低沉积能量下对填充比和岛的个数影响较小,在高沉积能量下对填充比和岛的个数影响较大。在高沉积能量高沉积速率下,为了提高成膜质量,同时保证成膜效率,适当降低沉积速率比适当降低沉积能量更有效。     

分子动力学方法模拟GaN薄膜生长

采用分子动力学模拟方法,应用Buckingham经验势模型,模拟纤锌矿相GaN的薄膜晶格生长.研究了GaN薄膜生长的早期阶段的形貌特点、生长规律、表面结构及动力学特性.模拟发现,N原子与Ga原子按照晶格特征吸附在衬底上,作层状分布趋势并且薄膜层从下到上晶态特征逐渐减弱.观察每层沉积原子数、空位比、沉积原子团簇质心高度与沉积原子均方位移随时间的变化规律,发现了随着时间步数增加,原子团簇逐渐达到稳定,在5000步时前3层都达到了较稳定状态,且N原子比Ga原子能更快地找到平衡位置.     

Crystal growth study using combination of molecular dynamics and Monte Carlo methods

Molecular dynamics method although provides details of energies of the system as a function of time, is not suited to simulate the processes involving activation processes. Therefore, we attempted to combine the molecular dynamics and Monte Carlo methods. Using molecular dynamics, the energies of the system were calculated which were subsequently combined with Monte Carlo method using random numbers, epitaxial growth of (111) plane of copper, silver, and gold. While surface adsorption and surface diffusion for copper, silver, and gold were simulated by use of molecular dynamics method, the relation between the growth rate of thin films and the packing density of atoms were obtained using Monte Carlo simulation. Thus, by combining the results of the molecular dynamics method and the Monte Carlo method the growth process of thin films at elevated temperatures were obtained, which is too tedious to be calculated by molecular dynamics alone.     

Monte Carlo模拟薄膜生长的研究

阐述了Monte Carlo方法在薄膜生长中的应用和最新进展;简要论述了Monte Carlo算法的类型及各自的特点;结合MonteCarlo方法的特点,提出了模拟薄膜生长的模型以及处理方法.同时,归纳出MonteCarlo模拟薄膜生长需要解决的主要问题.     

Modeling and visualization of polycrystalline thin film growth

A novel polycrystalline thin film growth simulator, FACET, has been developed. FACET is a multi-scale model with two major components: an atomic level one-dimensional kinetic lattice Monte Carlo (1D KLMC) model and a real time feature scale two-dimensional facet nucleation and growth model.

The 1D KLMC model has been developed to calculate inter-facet diffusion rates. By inputting the diffusion activation energies, the model will calculate the inter-facet atomic flux between {1 0 0}, {1 1 0}, and {1 1 1} facets of FCC materials at any temperature. The results of the 1D KLMC model have been verified by comparison with a full three-dimensional kinetic lattice Monte Carlo (3D KLMC) model.

The feature scale polycrystalline thin film nucleation and growth model is based on describing grains in terms of two-dimensional faceted surfaces and grain boundaries. The profile of the nuclei are described by crystallographically appropriate facets. The position and orientation of the nuclei can be randomly selected or preferred textures can be created. Growth rates are determined from different deposition fluxes and surface diffusion effects. Quantitative microstructural characterization tools, including roughness analysis, average grain size analysis, and orientation distribution analysis, were incorporated into the model, which allows the users to design, conduct and analyze the virtual experiments within one integrated graphical user interface. Users can also visualize the nucleation and growth process of the film and obtain the final film microstructure. The effects of thickness, temperature, and deposition flux on thin film microstructures have been studied by FACET.     

Topology evolution of graphene in chemical vapor deposition, a combined theoretical/experimental approach toward shape control of graphene domains

Morphology control of thin film relies on understanding multiple ongoing processes during deposition and growth. To reveal the shape evolution of graphene domains on copper surfaces in chemical vapor deposition (CVD), a combinative study is performed on the CVD growth of graphene on copper surfaces. To identify the factors that influence the adsorption and diffusion of carbon atoms and further determine the domain shape, simulations based on kinetic Monte Carlo techniques are carried out. The results reveal the dependence of the graphene domain shapes on the crystalline orientation of the underlying copper substrate surfaces.     

薄膜生长的计算机模拟

薄膜技术在现代科技领域中有着广泛的应用。人们对薄膜的生长过程通过理论和实验进行了深入的研究，其中计算机模拟是重要的方法，本文概述了对薄膜生长过程的实验观察结果及其理论分析，主要讨论了薄膜生长的计算机模拟中经常采用的方法-蒙特卡罗法和分子动力学方法、描述衬底上成膜粒子运动的一些模型以及在计算机模拟中需注意的一些问题，其中主要包括粒子间的相互作用，入射粒子的能量和粒子上的衬底上的扩散运动。     

Simulation of structure evolution in Cu films

The Monte Carlo method was used to simulate grain growth in thin Cu films. The model, based on energetic principles, was compared with the evolution of measured film structures. Surface, interface, grain boundary, and elastic strain energies were applied to determine the preferred microstructure in terms of different annealing conditions and film thicknesses. Four microstructural cases, relating to different film thicknesses, were developed in this paper. Twinning in the Cu films is simulated by arbitrary re-assignment of randomly selected crystallite lattice orientations. The observed evolution in crystallographic texture for each film thickness can be obtained from the Monte Carlo simulations.     

Monte Carlo simulation of the growth of SrTiO3 thin film with molecular source

A three-dimensional model of SrTiO₃ thin film growth under ultraslow growth rate was proposed based on Monte Carlo method. The model is based on Solid on Solid (SOS) model with periodic boundary condition. The ideal molecular source is regarded as a mixture of predominantly SrTiO₃ molecules and a few SrO and TiO₂ molecules. Monte Carlo events consist of deposition, diffusion of molecules and generation of SrTiO₃ molecules. The results show that in the temperature range simulated, the binding possibility of SrO and TiO₂ to SrTiO₃ increases with the increase of the substrate temperature, resulting in the decrease of the number of SrO and TiO₂ molecules. When the substrates temperature reaches a special value (<800 K), all SrO and TiO₂ molecules may already convert to SrTiO₃, which agrees with our previous experiment. Thus, under ultraslow deposition rate and at the temperature beyond 800 K, a simplified Monte Carlo model consisting only of SrTiO₃ cell diffusion can be achieved. The dependence of morphology on the temperature is simulated and the results show that under ultraslow deposition rate, the SrTiO₃ thin film grows with layer-by-layer mode at higher temperature and with island mode at lower temperature, which is qualitatively consistent with the experiment.     

Monte Carlo simulation of nucleation and growth of thin films

We study thin film growth using a lattice-gas, solid-on-solid model employing the Monte Carlo technique. The model is applied to chemical vapour deposition (CVD) by including the rate of arrival of the precursor molecules and their dissociation. We include several types of migration energies including the edge migration energy which allows the diffusive movement of the monomer along the interface of the growing film, as well as a migration energy which allows for motion transverse to the interface. Several well-known features of thin film growth are mimicked by this model, including some features of thin copper films growth by CVD. Other features reproduced are—compact clusters, fractal-like clusters, Frank-van der Merwe layer-by-layer growth and Volmer-Weber island growth. This method is applicable to film growth both by CVD and by physical vapour deposition (PVD).