In photon upconverting core-shell nanoparticles, structure strongly dictates performance. Conventional imaging in scanning transmission electron microscopy has sufficient resolution to probe the atomic structure of these nanoparticles, but contrast, dose, and projection limitations make conventional imaging modes insufficient for fully characterizing these structures. Phase retrieval methods provide a promising alternative imaging mode, and in particular, multislice electron ptychography can recover depth-dependent information. Here, we study beam-sensitive photon upconverting core-shell nanoparticles with a multislice ptychography approach using a low electron dose to avoid damage. Large strain fields arise in these heterostructures due to the mismatch in lattice parameter between the core and the shell. We reconstruct both a nanoparticle that appears defect-free and one that has a large break in the side and map the distribution of strain in 3D by computing distortion fields from high-resolution potential images of each slice. In the defect-free nanoparticle, we observe twisting of the shell, while in the broken nanoparticle we measure the 3D position of the crack, the core, and dislocations. These results highlight the advantage of multislice electron ptychography to recover 3D information from a single scan, even under strict electron dose requirements from beam-sensitive samples.
Trade-off between interface morphology and compositional homogeneity in AlGaAs/GaAs quantum wells revealed by multislice electron ptychography
University of California, Irvine（加州大学尔湾分校）；University of Texas Austin（德克萨斯大学奥斯汀分校）；Irvine Materials Research Institute, University of California Irvine（加州大学尔湾分校欧文材料研究所）
Atomic-Scale Roughness of Freestanding Oxide Membranes Revealed by Electron Ptychography
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Department of Physics, National Cheng Kung University（台湾成功大学物理系）；State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University（清华大学物理系低维量子物理国家重点实验室）；Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University（台湾成功大学量子前沿研究与技术中心）
Near-Isotropic Sub-Ångstrom 3D Resolution Phase Contrast Imaging Achieved by End-to-End Ptychographic Electron Tomography
Institute of Micro- and Nanostructure Research (IMN)（微纳米结构研究所）；Center for Nanoanalysis and Electron Microscopy (CENEM)（纳米分析与电子显微镜中心）；Friedrich Alexander-Universität Erlangen-Nürnberg（埃尔朗根-纽伦堡弗里德里希·亚历山大大学）
