Surface reconstruction stability and configurational disorder on Bi-terminated GaAs(001)
Surface reconstruction stability and configurational disorder on Bi-terminated GaAs(001)
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DOI：
10.1103/physrevb.87.035313
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发表时间：
2013-01-28
影响因子：
3.7
通讯作者：
Millunchick, Joanna M.
中科院分区：
文献类型：
--
作者：
Duzik, Adam;Thomas, John C.;Millunchick, Joanna M.
利用密度泛函理论和团簇展开理论相结合的方法，建立了一种计算Bi/GaAs(001)的0K表面相图的严格而详尽的方法。在寻找低能表面结构原型的基态合金组态时，我们发现(2×1)、α2(2×4)和β2(2×4)结构只有几个稳定的组态，尽管每个结构在很大的化学势范围内都是稳定的。相比之下，c(4×4)和(4×3)结构表现出许多稳定的组态，表明它们在有限温度下倾向于组态无序。蒙特卡罗模拟证实，随着温度的升高，(4×3)重构连续无序，并在典型的MBE生长条件下完成，而(2×1)结构在高温下保持有序化。计算的零开尔文相图和有限温度蒙特卡罗结果与本工作中的扫描隧道显微镜和其他地方的实验观测结果非常吻合。此外，这些结果对GaAsBi合金生长所带来的挑战，即铋的掺入、CuPtB的有序和铋的聚集提供了重要的见解。DOI：10.1103/PhysRevB.87.035313
We developed a rigorous and exhaustive method for calculating the 0 K surface phase diagram of Bi/GaAs(001) by using density functional theory in conjunction with the cluster expansion formalism. In a search for ground- state alloy configurations of low energy surface structure prototypes, we found that the (2 x 1), alpha 2(2 x 4), and beta 2(2 x 4) structures possess only a few stable configurations, though each is stable over a wide range of chemical potential. In contrast, the c(4 x 4) and (4 x 3) structures exhibit many stable configurations, suggesting their tendency towards configurational disorder at finite temperature. Monte Carlo simulations confirm a continuous disordering of the (4 x 3) reconstruction with increasing temperature that comes to completion well below typical MBE growth conditions, in contrast to the (2 x 1) structure, which remains ordered at high temperature. The calculated zero Kelvin phase diagram and finite temperature Monte Carlo results are in excellent agreement with STM in this work and experimental observations seen elsewhere. Furthermore, these results provide important insights into challenges posed by growth of GaAsBi alloys, namely Bi incorporation, CuPtB ordering, and Bi clustering. DOI: 10.1103/PhysRevB.87.035313