III-V核-壳纳米线的三维组成和电势分布的相关STEM和全息层析成像
Three-dimensional composition and electric potential mapping of III-V core-multishell nanowires by correlative STEM and holographic tomography
摘要：
纳米器件的非破坏性表征，如那些基于半导体纳米线，在功能潜力方面是至关重要的关联设备属性与它们的形态/材料特征，以及精确调整和优化其生长过程。电子全息层析成像（EHT）在过去已被用来重建3D的总电位分布，但迄今为止缺乏一个定量的方法来分离由于化学成分的变化（平均内部电位- MIP）和空间电荷的电位变化。在这封信中，我们结合和关联EHT和高角度环形暗场扫描透射电子显微镜（HAADF-STEM）断层扫描在一个单独的<111>取向GaAs-AlGaAs核多壳纳米线（NW）。我们得到了很好的协议，这两种方法在确定的铝浓度内的AlGaAs壳，以及作为量子阱管的几个纳米薄GaAs壳的厚度变化。减去MIP确定的STEM断层图像，使我们能够观察到在NW表面和在Au-NW接口，都归因于半导体费米能级的表面/接口钉扎的功能电位。
英文摘要：
The non-destructive characterization of nanoscale devices, such as those based on semiconductor nanowires, in terms of functional potentials is crucial for correlating device properties with their morphological/materials features, as well as for precisely tuning and optimizing their growth process. Electron holographic tomography (EHT) has been used in the past to reconstruct the total potential distribution in 3D but hitherto lacked a quantitative approach to separate potential variations due to chemical composition changes (mean inner potential - MIP) and space charges. In this letter, we combine and correlate EHT and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) tomography on an individual <111> oriented GaAs-AlGaAs core-multishell nanowire (NW). We obtain excellent agreement between both methods in terms of the determined Al concentration within the AlGaAs shell, as well as thickness variations of the few nanometer thin GaAs shell acting as quantum well tube. Subtracting the MIP determined from the STEM tomogram, enables us to observe functional potentials at the NW surfaces and at the Au-NW interface, both ascribed to surface/interface pinning of the semiconductor Fermi level.
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