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Crystal Growth Theory with considerations of strain

考虑应变的晶体生长理论

基本信息

批准号：
12640380
负责人：
SAITO Yukio
金额：
$ 2.3万
依托单位：
Keio University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2003
项目状态：
已结题

项目摘要

Since it became possible to observe clean and flat surface in an atomic resolution, various growth modes are identified on the singular surface during heteroepitaxy, and morphological instabilities of steps are found an a vicinal surface. These self assembled nano structures are caused by the elastic strain in the crystal. So far the continuum elasticity (CE) approximation is used for the analysis, but for a crystal growth where a single atom processes as impingement or desorption are essential, an atomic-level model for elasticity is required. In the present project, I propose an elastic lattice model, and obtain interactions between surface defects as steps to detect the limit of CE theory. Furthermore, the effect of step interaction mediated by the strain is studied on the dynamical instabilities.Interaction induced by strain extends long-range, but for a thin substrate it is cut off at a separation about the thickness. On the other hand, thick substrate requires long CPU time for numerical simulation. The elastic lattice Green's function (GF) resolves this difficulty. By means of GF, steps across an island are found to interact differently from those across a pit when they are close to each other. After the finite size effect dies out, step interaction shows 1/r^2 behavior predicted by the CE, but its strength is weakened due to the atomic relaxation around the steps. On applying the model to two-dimensional heteroepitaxy, energy minimum configuration is traced systematically as a function of the coverage, and the possibility of a new growth mode is obtained.We also studied step instabilities on Si(001) vicinal surface, where surface reconstruction takes place, and the groove formation is concluded perpendicular to the steps. On a Si(111) surface where the surface phase transition occurs, the wandering instability of a step is explained close to the phase transition temperature, where two phases coexist.

由于它成为可能，以原子分辨率观察清洁和平坦的表面，各种生长模式被确定在异质外延过程中的奇异表面上，和形态的不稳定性的步骤被发现一个邻位表面。这些自组装纳米结构是由晶体中的弹性应变引起的。到目前为止，连续弹性（CE）近似用于分析，但对于晶体生长的一个单一的原子的碰撞或解吸过程是必不可少的，一个原子级的弹性模型是必需的。在本计画中，我提出一弹性晶格模型，并获得表面缺陷间的交互作用，作为检测CE理论极限的步骤。进一步研究了应变引起的阶跃相互作用对动力学不稳定性的影响，应变引起的阶跃相互作用扩展到长距离，但对于薄衬底，阶跃相互作用在厚度附近被截断。另一方面，厚衬底需要长的CPU时间进行数值模拟。弹性格点绿色函数（GF）解决了这一困难。通过GF的方式，跨岛的步骤被发现不同的相互作用时，跨坑彼此接近。在有限尺寸效应消失后，台阶相互作用表现出CE预测的1/r^2行为，但由于台阶周围原子的弛豫，其强度减弱。将该模型应用于二维异质外延，系统地追踪了能量最小组态与覆盖度的关系，得到了新生长模式的可能性，并研究了Si（001）邻面的台阶不稳定性，在那里发生表面重构，并得出垂直于台阶的凹槽形成。在发生表面相变的Si（111）表面上，在两相共存的相变温度附近解释了台阶的漂移不稳定性。