Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA.
Phys Rev Lett. 2012 Sep 7;109(10):106103. doi: 10.1103/PhysRevLett.109.106103.
Using a multiscale approach combining continuum model with first-principles calculation, we develop a quantitative theoretical model for heterogeneous nucleation and the growth of a quantum dot molecule-a few islands "strain bonded" by a pit in heteroepitaxy of thin films, in contrast to homogeneous nucleation and growth of isolated strain islands on the surface. We show that the critical size and energy barrier for island nucleation next to a pit is substantially reduced with the increasing pit size, but the reduction approaches an upper bound of ~85% and ~72% for the size and barrier, respectively. Our model also predicts a self-limiting effect on island growth, resulting from an intriguing interplay between island-pit attraction and island-island repulsion, that drives the island size to increase linearly with the pit size, which explains a long-standing puzzle of experimental observation.
我们采用一种多尺度方法，将连续介质模型与第一性原理计算相结合，为异质外延薄膜中量子点分子的异质成核和生长——几个由位错“应变键合”的小岛，建立了一个定量的理论模型，与孤立应变小岛在表面上的均匀成核和生长形成对比。我们表明，靠近位错的小岛成核的临界尺寸和能垒随着位错尺寸的增加而显著降低，但尺寸和势垒的降低分别趋近于85%和72%的上限。我们的模型还预测了小岛生长的自限制效应，这是由于小岛-位错吸引和小岛-小岛排斥之间的有趣相互作用，导致小岛尺寸随位错尺寸线性增加，这解释了实验观察中长期存在的一个难题。
