Strain-driven InAs island growth on top of GaAs(111) nanopillars
Strain-driven InAs island growth on top of GaAs(111) nanopillars
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DOI：
10.1103/physrevmaterials.4.014602
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发表时间：
2019-09
影响因子：
3.4
通讯作者：
T. Riedl;V. Kunnathully;A. Trapp;T. Langer;D. Reuter;J. Lindner
中科院分区：
文献类型：
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作者：
T. Riedl;V. Kunnathully;A. Trapp;T. Langer;D. Reuter;J. Lindner
本文从实验和理论两方面分析了圆柱形GaAs(111)A纳米柱顶部表面的异质外延InAs岛的形状和位置。低温下无催化剂分子束外延生长的InAs在GaAs纳米柱上得到了直径< 30 nm的InAs岛，其平面内形状主要为圆形三角形。岛屿显示出从中心向柱边缘偏移的位置生长的趋势。原子分子静力学模拟证明，以柱轴为中心、直径小于纳米柱的三角形棱柱岛在能量上是有利的。此外，我们还揭示了离轴岛位的最小能态的存在，与实验结果一致。这些发现是通过评价空间应变分布和表面原子断裂键的数量作为表面能的测量来解释的。首选的离轴孤岛位置可以理解为，由于靠近自由表面，孤岛下方的砷化镓纳米柱的顺应性增加，从而导致应变能降低。讨论了表面台阶对系统能量的影响。
We analyze the shape and position of heteroepitaxial InAs islands on the top face of cylindrical GaAs(111)A nanopillars experimentally and theoretically. Catalyst-free molecular beam epitaxial growth of InAs at low temperatures on GaAs nanopillars results in InAs islands with diameters < 30 nm exhibiting predominantly rounded triangular in-plane shapes. The islands show a tendency to grow at positions displaced from the center towards the pillar edge. Atomistic molecular statics simulations evidence that triangular-prismatic islands centered to the pillar axis with diameters smaller than that of the nanopillars are energetically favored. Moreover, we reveal the existence of minimum-energy states for off-axis island positions, in agreement with the experiment. These findings are interpreted by evaluating the spatial strain distributions and the number of broken bonds of surface atoms as a measure for the surface energy. The preferred off-axis island positions can be understood in terms of an increased compliancy of the GaAs nanopillar beneath the island because of the vicinity of free surfaces, leading to a reduction of strain energy. The influence of surface steps on the energy of the system is addressed as well.