Qi Tianyu, Cheng Yongfa, Cheng Feng, Li Luying, Li Chen, Jia Shuangfeng, Yan Xin, Zhang Xia, Wang Jianbo, Gao Yihua
Center for Nanoscale Characterization & Devices (CNCD), Wuhan National Laboratory for Optoelectronics (WNLO) and School of Physics, Huazhong University of Science and Technology (HUST), Luoyu Road 1037, Wuhan 430074, People's Republic of China.
Nanotechnology. 2020 Mar 27;31(24):245701. doi: 10.1088/1361-6528/ab767e. Epub 2020 Feb 14.
The configurations of core/shell nanowires (NWs) and quantum dots (QDs) decorating NWs have found great applications in forming optoelectronic devices thanks to their superior performances. The combination of the two configurations would expect to bring more benefits, however, the nanometer-scale electrostatic properties of the QD/buffer layer/NW heterostructures are still unrevealed. In this study, the InAs QDs decorating GaAs/AlAs core/shell NWs are systemically studied both experimentally and theoretically. The layered atomic structures, chemical information, and anisotropic strain conditions are characterized by comprehensive transmission electron microscopy (TEM) techniques. Quantitative electron holography analyses show a large number of electrons accumulating in the InAs QD, especially at the dot apex, and charges of reversed signs and similar densities are observed to distribute at the sequential interfaces, leaving great amounts of holes in the NW core. Theoretical calculations including simulated heterostructural band structures, interfacial charge transfer, and chemical bonding analysis are in good accordance with the experimental results, and prove the important role of the AlAs buffer layer in adjusting the heterostructural band structure as well as forming stable InAs QDs on the NW surfaces. These results could be significant for achieving related optoelectronic devices with better stability and higher efficiency.
由于其卓越的性能，核壳纳米线（NWs）以及装饰纳米线的量子点（QDs）的结构在光电器件的形成中得到了广泛应用。这两种结构的结合有望带来更多益处，然而，量子点/缓冲层/纳米线异质结构的纳米级静电特性仍未被揭示。在本研究中，对装饰有GaAs/AlAs核壳纳米线的InAs量子点进行了系统的实验和理论研究。通过综合透射电子显微镜（TEM）技术对分层原子结构、化学信息和各向异性应变条件进行了表征。定量电子全息分析表明，大量电子聚集在InAs量子点中，尤其是在量子点顶点，并且观察到相反符号和相似密度的电荷分布在连续界面处，在纳米线核心留下大量空穴。包括模拟异质结构带结构、界面电荷转移和化学键分析在内的理论计算与实验结果高度吻合，并证明了AlAs缓冲层在调节异质结构带结构以及在纳米线表面形成稳定的InAs量子点方面的重要作用。这些结果对于实现具有更好稳定性和更高效率的相关光电器件可能具有重要意义。
