兰州大学机构库 >物理科学与技术学院
用KINETIC MONTE CARLO方法模拟薄膜生长
Alternative TitleKINETIC MONTE CARLO SIMULATION OF THIN FILM GROWTH
张佩峰
Thesis Advisor贺德衍
2004-05-10
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
KeywordKINETIC MONTE CARLO方法 薄膜生长
Abstract计算机模拟是计算机技术的一个重要应用领域,具有高效、快捷、经济等多方面的优点。用计算机模拟研究材料是集计算机科学、计算数学、 材料科学、表面科学、物理化学于一体的一门新兴的交叉学科,用Monte Carlo算法模拟薄膜生长是计算材料科学的一个研究热点。目前国际上主要是借助于具有强大运算能力的中小型计算机和商业化的软件包进行相关方面的研究,这对资金、硬件平台等都有较高的要求。同时,已有的软件包开发往往是建模与编程分离,所以,无法及时地把新的研究成果升级到软件中,更不可能创建新的模型或修改模型。虽然近年来有些科研机构自行编写了一些模拟软件,但因为硬件环境、算法实现等多方面的问题使得模型设计过于简单,反而在一定程度上延缓了研究的步伐。 本文在充分调研国际最新研究动态的基础上,用Kinetic Monte Carlo算法以Cu薄膜为例模拟了薄膜生长的随机过程,并利用计算机图形学原理和数据库技术从定性和定量两个方面直观而又准确的展示了模拟结果。 首先,设计了一个更为合理、完善的模型。在合理选择原子间相互作用计算方法的基础上,考虑到原子的吸附、迁移、迁移所导致的近邻原子连带效应以及原子的脱附等过程,给出了一个有效的激活能计算方法。 其次,对模拟算法进行了构造和优化。因为Monte Carlo方法作为一种反映随机规律的思想,不可能对所有的随机过程给出现成的具体算法,所以,我们根据设计的模型,构造并优化了具体的算法,实现了可行性编程并保证了程序在较低成本的硬件环境中快速运行。 最后,我们利用计算机图形学、数据库技术等编写了一整套包含过程模拟、数据处理、三维成像、岛核认证等功能齐全的软件包。 在以上工作的基础上,我们模拟计算了薄膜的初期成核、表征薄膜生长表面状况的表面粗糙度以及表征薄膜内部晶格完整性的相对密度。结果表明, 1)随着衬底温度的升高或入射率的降低,沉积在衬底上的原子由离散分布逐步聚集形成一些岛核,并且逐步由二维岛核向三维岛核过渡; 2)在原子入射率确定的情况下,存在着三个特征温度,成核率最高时对应的最佳成核温度Tn,薄膜的表面粗糙度最低时对应的生长转变温度Tt,相对密度趋近于1时对应的相对密度饱和温度Td。这三个特征温度数值基本相同,同时发现,它们的平均值最佳生长温度Topt与入射率的对数成正比; 3)随着温度的增加,粗糙度先减小后增大。虽然在低温和高温情况下表面都比较粗糙,但表面形态截然不同。低温时表面因为形成许多蘑菇状的突起而变得粗糙,而高温时表面因形成少量具有规则晶面的大岛核而变得粗糙不平。 4)随着入射率的增大,相对密度不断减小。温度较低时,随着入射率的增大,成核率基本不变,但表面粗糙度不断增大;温度较高时,随着入射率的增大,成核率显著增大,但表面粗糙度不断减小。 5)随着平均厚度的增加,表面粗糙度不断增大。相对密度在温度较低时不断减小,当达到某一温度后,变化明显趋缓。
Other AbstractComputer simulation technique is playing a very important role in the field of computational material science. Particularly, it has been demonstrated that Monte Carlo simulation is well suited for studying the growth processes of the films. It offers a potential way to explore the growth mechanism of the films and predicts the film properties. Currently, most of the works about Monte Carlo simulation of the film growth depend on the existing huge computer and software package. Therefore, it is impossible to modify the model and the software by absorbing the obtained results to date. Some researchers designed their model and edited some software, but it is too simple to simulate the real growth processes. This thesis is based on a wide investigation on the up-to-date reports on actuality and simulates of the random process of Cu film growth. It is very intuitional to show the simulation results from qualitative and quantitative points of view. A three-dimensional kinetic Monte Carlo technique has been developed for simulating growth of thin films firstly. The model involves incident atom attachments, diffusion of the atoms on the growing surface, and detachment of the atoms from the growing surface. The related effect by surface atom diffusion was taken into account. A significant improvement was made on calculation of the activation energy for atom diffusion based on a reasonable assumption of interaction potential between atoms. A more optimum arithmetic was designed and a package of software was edited by taking advantage of computer graph technique and database technique. All software including simulating process, dealing with data and three-dimensional formation of images can run on a low-cost hardware setting. The nucleation rate at the early stage, the surface roughness and the relative density of the films were simulated as functions of growth substrate temperature and deposition rate. The main results we obtained are as following. 1)At the early stage of the growth, the higher temperature or the lower deposition rate, the larger size the islands. Also, we observed an island shape transition from 2-dimension to 3-dimension. 2)There exist three character growth temperatures at a given deposition rate, namely Tn at which the nucleation rate maximizes, Tt at which the surface roughness minimizes and Td at which the relative density approaches to saturation. The three character temperatures are close to equal. The optimum Topt, which is th...
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/229075
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
张佩峰. 用KINETIC MONTE CARLO方法模拟薄膜生长[D]. 兰州. 兰州大学,2004.
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