Institute for Solid State Research , Leibniz Institute for Solid State and Materials Research , Helmholtzstrasse 20 , D-01069 Dresden , Germany.
Institute of Ion Beam Physics and Materials Research , Helmholtz-Zentrum Dresden-Rossendorf , Bautzner Landstrasse 400 , D-01328 Dresden , Germany.
Nano Lett. 2018 Aug 8;18(8):4777-4784. doi: 10.1021/acs.nanolett.8b01270. Epub 2018 Jul 17.
The nondestructive 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 three-dimension 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.
从功能电位的角度对纳米级器件（如基于半导体纳米线的器件）进行非破坏性表征，对于将器件特性与其形态/材料特征相关联，以及对于精确调整和优化其生长过程至关重要。电子全息断层扫描（EHT）过去曾被用于重建三维总势分布，但迄今为止缺乏一种定量方法来分离由于化学成分变化（平均内电势，MIP）和空间电荷引起的电势变化。在这封信中，我们将 EHT 和高角度环形暗场扫描透射电子显微镜（HAADF-STEM）断层扫描结合并关联在单个 ⟨111⟩取向 GaAs-AlGaAs 核-壳多壳纳米线（NW）上。我们在确定 AlGaAs 壳内的 Al 浓度以及作为量子阱管的几纳米薄 GaAs 壳的厚度变化方面，两种方法都得到了很好的一致性。从 STEM 断层扫描中减去确定的 MIP，使我们能够观察到 NW 表面和 Au-NW 界面处的功能电位，这两个电位都归因于半导体费米能级的表面/界面钉扎。
