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arXiv 0811.1475cond-mat.mtrl-scicond-mat.stat-mech
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Si(001)和Ge(001)表面(2x 1)-(1x 1)相变的相场晶体模拟

Phase-field-crystal modeling of the (2x1)-(1x1) phase-transitions of Si(001) and Ge(001) surfaces

Ye-Chuan Xu, Bang-Gui Liu

摘要:

提出了Si(001)和Ge(001)表面(2 $\times$ 1)-(1 $\times$ 1)相变的二维相场晶体模型.在2 $\times$ 1相的二聚化描述与相场晶体变量,这是通过求解来自自由能的演化方程确定。模拟的周期性阵列的二聚变量是一致的扫描隧道显微镜图像的两个二聚表面。计算的二聚参数的温度依赖性表明,正常的二聚体和破碎的共存之间的温度描述的特征温度的相变,$T_L$和$T_H$的宽度,和一级相变发生在它们之间的温度。测定了整个温度范围内的二聚反应。这些结果与实验相一致。这种相场晶体方法也适用于其它重构表面相的相变,特别是半导体$n\times$ 1重构表面相。

英文摘要:

We propose a two-dimensional phase-field-crystal model for the (2$\times$1)-(1$\times$1) phase transitions of Si(001) and Ge(001) surfaces. The dimerization in the 2$\times$1 phase is described with a phase-field-crystal variable which is determined by solving an evolution equation derived from the free energy. Simulated periodic arrays of dimerization variable is consistent with scanning-tunnelling-microscopy images of the two dimerized surfaces. Calculated temperature dependence of the dimerization parameter indicates that normal dimers and broken ones coexist between the temperatures describing the charactristic temperature width of the phase-transition, $T_L$ and $T_H$, and a first-order phase transition takes place at a temperature between them. The dimerization over the whole temperature is determined. These results are in agreement with experiment. This phase-field-crystal approach is applicable to phase-transitions of other reconstructed surface phases, especially semiconductor $n\times$1 reconstructed surface phases.

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