薄膜生长中的表面动力学(Ⅱ)

本文较全面地从理论上研究了薄膜生长过程中原子在表面上的各种动力学表现，涉及的内容包括亚单层生长时，原子在表面上的扩散，粘接，成核，以及已经形成的原子岛之间的相互作用，兼并，失稳，退化等一系列过程。在第一部分(即0—6章，刊登在《物理学进展》23卷1期上)介绍了薄膜生长动力学的基础之后，从第7章开始我们侧重研究一个在向同性和各向异性表面都普遍成立的原子岛尺寸大小及密度分布的标度定律；建立了一套研究在各向同性和各向异性表面上二维原子岛退化过程的广义动力学标度理论。基于对层间质量扩散通道的研究，本文提出了两种不同的原子下跃机制，既任意跃迁机制和选择跃迁机制，并做了进一步的实验验证。利用这一新的层间质量扩散机制，我们成功地解释了实验上观测到的三维原子岛的退化规律。更加有趣的是，本文讨论了应力对岛的形状和各种动力学规律的影响。在最后我们还提出了一个利用凝聚能转化来控制二维原子岛生长的方法，其目的是希望能够找到一种人为有效地在表面上制备低维量子结构的方法。

ATOMIC-SCALE STUDY OF KINETIES IN FILM GROWTH

A systematic study of the kinetic and dynamic behavior of surface atoms during film growth is presented. The paper investigates the diffusion,attachment,and nucleation of the atoms on surface,as well as the interaction,aggregation,instability,and decay of the formed islands in submonolayer growth. At first,we study various theoretical methods,such as ab-initio calculations,molecular dynamics,kinetic Monte Carlo simulation,rate equation theory,and transition state theory(TST). A novel model for reaction limited aggregation(RLA)is introduced to study the effect of a monolayer surfactant on the formation of two-dimensional islands in epitaxy. The key finding of the RLA theory is a counterintuitive fractal-to-compact island shape transition can be induced either by increasing deposition flux or by decreasing growth temperature,which is contrary to the predication of the classic diffusion-limited-aggregation(DLA)theory. A generic scaling law has been developed in describing the size distribution and dynamical evolution of islands on both isotropic and anisotropic surfaces. The decay characteristics of three-dimensional islands formed on surfaces are investigated by considering two-types of interlayer transport mechanisms. In addition,we discuss the long-range interaction of surface atoms on the island shape and kinetic properties. Finally we show that a small amount of transfer from the condensation energy of deposited adatoms into adatom motion is sufficient to induce a net adatom current from the illuminated edge of a two-dimensional island to the other edges,thereby breaking the island symmetry.