Imaging and atomic structure engineering of quasi-two-dimensional materials encapsulated between graphene sheets

石墨烯片封装的准二维材料的成像和原子结构工程

• 批准号: 345789964
• 负责人: Professorin Dr. Ute Kaiser
• 金额: --
• 依托单位: Institut für Ionenstrahlphysik und Materialforschung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/345789964?language=en
• 关键词: Imaging; atomic; structure; engineering; quasi; Imaging; atomic; structure; engineering; quasi

Graphene sheets are mechanically robust and chemically inert membranes consisting of a single atomic layer. Owing to these properties, graphene has been proven to be an ideal substrate for imaging molecules and nanostructures using aberration-corrected transmission electron microscopy (AC-TEM). Experiments have shown that graphene reduces knock-on and electron-beam-induced ionization damage if the object is encapsulated between two sheets of graphene. This procedure enables the visualization of the atomic structure which otherwise is not possible. Because graphene and other two-dimensional (2D) materials, such as hexagonal BN and transition metal dichalcogenides, are impermeable for water and aqueous solutions, they can be used for confining liquid materials. Owing to this ability, the incident electrons can induce within the encapsulated materials the formation of new 2D phases which may not be stable otherwise.In this project, we aim to combine AC-high-resolution (HR) TEM experiments with atomistic simulations. This approach will enable us to unravel the formation process, the structure, and the properties of the new 2D materials between the sheets of graphene and other 2D materials. Since these encapsulated structures would otherwise be unstable, we call them quasi 2D materials. Specifically, water, aqueous solutions of salts, and metals with low melting temperature (mercury, gallium) will be encapsulated and studied using HRTEM in a wide range of temperatures and low electron voltages in the range of 20-80 kV. For the first time, we will use our newly developed SALVE machine, which provides exceptional resolution, because it is equipped with a spherical and chromatic aberration corrector. Since electron irradiation induces the formation of defects in the encapsulated materials through several mechanisms and chemical reactions, we will use the electron beam for engineering new confined nanostructures and quasi-2D crystals. To obtain complete understanding of the beam-induced transformations and the role of radiation-induced defects, multiscale atomistic simulations will be carried out. Specifically, we will develop new computational techniques based on the non-adiabatic Ehrenfest dynamics combined with time-dependent density-functional theory, implement them in the dedicated computer software (applicable also to bulk materials and bio systems), and connect them to the kinetic Monte-Carlo schemes to describe the evolution of the system on a macroscopic time scale. We will also carry out extensive calculations of the properties of the quasi-2D materials using standard techniques including DFT and analytical potential approaches. Our results should not only provide fundamental insights into the physics of confined low-dimensional systems on an atomic scale, but also enable us to explore promising avenues for engineering the structure and properties of novel encapsulated nanostructures.

石墨烯片是机械稳健的，化学惰性膜由单个原子层组成。由于这些特性，石墨烯已被证明是使用像差校正的透射电子显微镜（AC-TEM）成像分子和纳米结构的理想底物。实验表明，如果将物体封装在两片石墨烯之间，石墨烯会减少敲入和电子束诱导的电离损伤。此过程使原子结构可视化，否则就不可能。由于石墨烯和其他二维（2D）材料（例如六角型BN和过渡金属二核苷）对于水和水溶液不可渗透，因此它们可用于限制液体材料。由于这种能力，入射电子可以在封装的材料中诱导新的2D相的形成，否则可能不会稳定。在该项目中，我们旨在将AC-高分辨率（HR）TEM实验与原子模拟相结合。这种方法将使我们能够阐明石墨烯片和其他2D材料之间新2D材料的结构和特性。由于这些封装的结构否则将是不稳定的，因此我们称它们为准2D材料。具体而言，将使用较大温度的HRTEM封装并研究水，盐的水溶液和熔融温度低的金属（汞，耐加仑），并且在20-80 kV范围内的水范围范围很广。我们将首次使用新开发的Salve Machine提供出色的分辨率，因为它配备了球形和色差校正器。由于电子辐照通过几种机制和化学反应诱导封装材料中缺陷的形成，因此我们将使用电子束进行工程新的粘纳米结构和准2D晶体。为了完全了解梁诱导的转换和辐射诱导的缺陷的作用，将进行多尺度原子模拟。具体而言，我们将基于非绝热EHRENFEST动力学开发新的计算技术，并结合时间依赖性密度功能理论，在专用的计算机软件（也适用于批量材料和生物系统）中实现它们，并将它们连接到动力学的蒙特 - 卡洛（Monte-Carlo）方案中，以描述系统在宏观科目时尺度上的进化。我们还将使用包括DFT和分析潜在方法在内的标准技术对准2D材料的性质进行广泛的计算。我们的结果不仅应该在原子量表上提供对限制低维系统的物理学的基本见解，而且还使我们能够探索有希望的途径，以设计新型封装纳米结构的结构和特性。