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arXiv 0912.0053cond-mat.mtrl-sci
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应变量子点形状转变的动力学蒙特卡罗模拟

Kinetic Monte Carlo simulation of shape transition in strained quantum dots

Chi-Hang Lam

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8 pages, 3 figures
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摘要：

采用一种新的结合有效表面重构的多态晶格模型，对Ge $_{x}$ Si $_{1-x}$ on Si（100）中由金字塔量子点上的阶跃聚束引发的量子点到圆顶的转变进行了原子级模拟.结果解释了一个简单的理论基础上的浅岛近似。在给定的沉积条件下，在$d$尺寸，形状的转变被证明发生在岛的大小$n_c$以下$n_c^{1/d} \propto x^{-ζ}$独立的温度和沉积速率，其中$ζ\alt 2$和$x$是实际的锗在岛的浓度。该过渡具有由小面界面能主导的能垒。然而，快速沉积可能超过并延迟向更大岛尺寸的过渡。

英文摘要：

The pyramid-to-dome transition in Ge$_{x}$Si$_{1-x}$ on Si(100) initiated by step bunching on pyramidal quantum dots is atomistically simulated using a novel multi-state lattice model incorporating effective surface reconstructions. Results are explained by a simple theory based on a shallow island approximation. Under given deposition conditions in $d$ dimensions, the shape transition is shown to occur at island size $n_c$ following $n_c^{1/d} \propto x^{-ζ}$ independent of temperature and deposition rate, where $ζ\alt 2$ and $x$ is the actual Ge concentration in the island. The transition has an energy barrier dominated by the facet interface energy. Fast deposition however can out-run and delay the transition to larger island sizes.

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