Tornberg Marcus, Sjökvist Robin, Kumar Krishna, Andersen Christopher R, Maliakkal Carina B, Jacobsson Daniel, Dick Kimberly A
Centre for Analysis and Synthesis, Lund University, Box 118, 22100 Lund, Sweden.
NanoLund, Lund University, 22100 Lund, Sweden.
ACS Nanosci Au. 2021 Nov 4;2(1):49-56. doi: 10.1021/acsnanoscienceau.1c00021. eCollection 2022 Feb 16.
With the increased demand for controlled deterministic growth of III-V semiconductors at the nanoscale, the impact and interest of understanding defect formation and crystal structure switching becomes increasingly important. Vapor-liquid-solid (VLS) growth of semiconductor nanocrystals is an important mechanism for controlling and studying the formation of individual crystal layers and stacking defects. Using studies, combining atomic resolution of transmission electron microscopy and controlled VLS crystal growth using metal organic chemical vapor deposition, we investigate the simplest achievable change in atomic layer stacking-single twinned layers formed in GaAs. Using Au-assisted GaAs nanowires of various diameters, we study the formation of individual layers with atomic resolution to reveal the growth difference in forming a twin defect. We determine that the formation of a twinned layer occurs significantly more slowly than that of a normal crystal layer. To understand this, we conduct thermodynamic modeling and determine that the propagation of a twin is limited by the energy cost of forming the twin interface. Finally, we determine that the slower propagation of twinned layers increases the probability of additional layers nucleating, such that multiple layers grow simultaneously. This observation challenges the current understanding that continuous uniform epitaxial growth, especially in the case of liquid-metal assisted nanowires, proceeds one single layer at a time and that its progression is limited by the nucleation rate.
随着对纳米级III-V族半导体可控确定性生长的需求增加，理解缺陷形成和晶体结构转变的影响及重要性日益凸显。半导体纳米晶体的气-液-固（VLS）生长是控制和研究单晶层形成及堆垛缺陷的重要机制。通过结合透射电子显微镜的原子分辨率研究以及使用金属有机化学气相沉积的可控VLS晶体生长，我们研究了在砷化镓中形成的最简单可实现的原子层堆叠变化——单个孪晶层。利用不同直径的金辅助砷化镓纳米线，我们以原子分辨率研究单个层的形成，以揭示形成孪晶缺陷时的生长差异。我们确定孪晶层的形成比正常晶体层的形成要慢得多。为理解这一点，我们进行了热力学建模，并确定孪晶的传播受形成孪晶界面的能量成本限制。最后，我们确定孪晶层较慢的传播增加了额外层成核的概率，从而使得多层同时生长。这一观察结果挑战了当前的认识，即连续均匀的外延生长，特别是在液态金属辅助纳米线的情况下，是一次生长一个单层，并且其进程受成核速率限制。
