Hofer Christoph, Madsen Jacob, Susi Toma, Pennycook Timothy J
EMAT, University of Antwerp, Antwerp, Belgium.
Faculty of Physics, University of Vienna, Vienna, Austria.
J Microsc. 2025 Mar 21. doi: 10.1111/jmi.13404.
Electronic charge transfer at the atomic scale can reveal fundamental information about chemical bonding, but is far more challenging to directly image than the atomic structure. The charge density is dominated by the atomic nuclei, with bonding causing only a small perturbation. Thus detecting any change due to bonding requires a higher level of sensitivity than imaging structure and the overall charge density. Here we achieve the sensitivity required to detect charge transfer in both pristine and defected monolayer WS using the high dose efficiency of electron ptychography and its ability to correct for lens aberrations. Excellent agreement is achieved with first-principles image simulations including where thermal diffuse scattering is explicitly modelled via finite-temperature molecular dynamics based on density functional theory. The focused-probe ptychography configuration we use also provides the important ability to concurrently collect the annular dark-field signal, which can be unambiguously interpreted in terms of the atomic structure and chemical identity of the atoms, independently of the charge transfer. Our results demonstrate both the power of ptychographic reconstructions and the importance of quantitatively accurate simulations to aid their interpretation.
原子尺度上的电荷转移能够揭示有关化学键合的基础信息，但与原子结构相比，直接成像要困难得多。电荷密度主要由原子核决定，键合仅引起微小的扰动。因此，检测由于键合引起的任何变化需要比成像结构和整体电荷密度更高的灵敏度。在这里，我们利用电子叠层成像术的高剂量效率及其校正透镜像差的能力，实现了检测原始和有缺陷的单层WS中电荷转移所需的灵敏度。通过第一性原理图像模拟获得了极佳的一致性，其中包括通过基于密度泛函理论的有限温度分子动力学对热漫散射进行显式建模的情况。我们使用的聚焦探针叠层成像配置还提供了同时收集环形暗场信号的重要能力，该信号可以独立于电荷转移，根据原子的原子结构和化学特性进行明确解释。我们的结果展示了叠层成像重建的强大功能以及定量精确模拟对辅助解释的重要性。
