Laboratoire de Photonique et de Nanostructures, CNRS, Université Paris-Saclay , Route de Nozay, 91460 Marcoussis, France.
Nano Lett. 2016 Mar 9;16(3):1917-24. doi: 10.1021/acs.nanolett.5b05121. Epub 2016 Feb 10.
The growth of III-III-V axial heterostructures in nanowires via the vapor-liquid-solid method is deemed to be unfavorable because of the high solubility of group III elements in the catalyst droplet. In this work, we study the formation by molecular beam epitaxy of self-catalyzed GaAs nanowires with AlxGa1-xAs insertions. The composition profiles are extracted and analyzed with monolayer resolution using high-angle annular dark-field scanning transmission electron microscopy. We test successfully several growth procedures to sharpen the heterointerfaces. For a given nanowire geometry, prefilling the droplet with Al atoms is shown to be the most efficient way to reduce the width of the GaAs/AlxGa1-xAs interface. Using the thermodynamic data available in the literature, we develop numerical and analytical models of the composition profiles, showing very good agreement with experiments. These models suggest that atomically sharp interfaces are attainable for catalyst droplets of small volumes.
通过汽液固方法在纳米线中生长 III-III-V 轴状异质结构被认为是不利的，因为 III 族元素在催化剂液滴中的溶解度很高。在这项工作中，我们通过分子束外延研究了具有 AlxGa1-xAs 插入物的自催化 GaAs 纳米线的形成。使用高角度环形暗场扫描透射电子显微镜以单层分辨率提取和分析组成分布。我们成功地测试了几种生长程序来锐化异质界面。对于给定的纳米线几何形状，用 Al 原子预填充液滴被证明是减小 GaAs/AlxGa1-xAs 界面宽度的最有效方法。利用文献中提供的热力学数据，我们开发了组成分布的数值和分析模型，与实验结果吻合得非常好。这些模型表明，对于小体积的催化剂液滴，可以实现原子级锐利的界面。
