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目前在原子尺度上人们对量子点分子束外延生长过程了解很少,所有关于量子点外延生长的理论模型和计算机模拟都是建立在传统的外延生长理论框架内。在传统理论框架内,量子点的生长过程被理解为发生在生长表面上一系列的单一的原子事件,如原子沉积、扩散、聚集等。在这种理论中,外延生长表面原子之间的相互作用被忽略;另外,按照这种理论,量子点生长过程必须是一个相对缓慢的过程。这种理论模型不可能恰当地解释所观察到的大量复杂的量子点外延生长实验现象。作者在两个实验现象基础上,提出了在InAs/GaAs(001)体系中量子点外延生长过程的新模型。这两个实验现象分别是在InAs/GaAs(001)生长表面有大量的“浮游”In原子,一个量子点的生长过程可以在很短的时间内完成(<10-4 s)。在提出的新模型中,量子点的自组装过程是一个大数量原子的集体、协调运动过程。
At present, little is known about the molecular beam epitaxy growth at the atomic scale. All the theoretical models and computer simulations about the growth of quantum dots are based on the traditional theory of epitaxial growth. Within the framework of traditional theory, the growth of quantum dots is understood as a series of single atomic events occurring on the growth surface, such as atomic deposition, diffusion, aggregation and the like. In this theory, the interaction between epitaxial growth surface atoms is neglected; in addition, according to this theory, the quantum dot growth process must be a relatively slow process. This theoretical model can not properly explain the observed large number of complex experimental phenomena of quantum dot epitaxial growth. Based on the two experimental phenomena, the authors propose a new model for quantum dot epitaxial growth in InAs / GaAs (001) system. The two experimental phenomena are a large number of “floating” In atoms on the InAs / GaAs (001) growth surface, and the growth of a quantum dot can be completed in a very short time (<10-4 s). In the proposed new model, the self-assembly of quantum dots is a collective, coordinated movement of a large number of atoms.