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arXiv 1107.5677cond-mat.mtrl-sci
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量子点相干生长中的第二层成核

Second-layer nucleation in coherent Stranski-Krastanov growth of quantum dots

J. E. Prieto, I. Markov

摘要:

我们研究了相干Sttranski-Krastanov生长情况下的单层-双层转变。我们发现第二层核的形成能在第一层岛的中心最大,在岛的角上最小。因此,预期成核发生在角部(或边缘)处,而不是在同质外延的情况下发生在岛的中心处。临界核除了具有紧凑的形状外还具有一个原子,其形状可以是i*i的正方形或i*(i-1)个原子的矩形,其中i>1是整数。当初始单层岛的边缘远大于临界核尺寸时,临界核尺寸总是一个矩形加上一个附加原子,吸附在较长的边缘上,产生一个新的原子排,以便将矩形转变为平衡的正方形。

英文摘要:

We have studied the monolayer-bilayer transformation in the case of the coherent Stranski-Krastanov growth. We have found that the energy of formation of a second layer nucleus is largest at the center of the first-layer island and smallest on its corners. Thus nucleation is expected to take place at the corners (or the edges) rather than at the center of the islands as in the case of homoepitaxy. The critical nuclei have one atom in addition to a compact shape, which is either a square of i*i or a rectangle of i*(i-1) atoms, with i>1 an integer. When the edge of the initial monolayer island is much larger than the critical nucleus size, the latter is always a rectangle plus an additional atom, adsorbed at the longer edge, which gives rise to a new atomic row in order to transform the rectangle into the equilibrium square shape.

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