SurfaceScience21 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

O: Fachverband Oberflächenphysik

O 16: Mini-Symposium: Free-standing functional molecular 2D materials II

O 16.2: Talk

Monday, March 1, 2021, 14:00–14:15, R2

Towards atomic-resolution HRTEM imaging of organic 2D materials — •Haoyuan Qi, Baokun Liang, David Mücke, and Ute Kaiser — Electron Microscopy Group of Materials Science, Universität Ulm, 89081 Ulm, Germany

Organic two-dimensional materials (O2DMs), such as 2D polymers, 2D covalent-organic frameworks (COFs), and 2D metal-organic frameworks (MOFs), open up the exciting possibility of crystal engineering tailored for next-generation applications. However, structural characterization of O2DMs via transmission electron microscopy (TEM) remains a formidable task. The main challenge arises from the strong interaction between incident electrons and the bonded hydrogen atoms. During TEM imaging, the incident electrons transfer kinetic energy to the atoms (i.e., knock-on damage) and may trigger bond dissociation and various chemical reactions degrading the structural integrity of O2DMs.

Here, we will present a comprehensive illustration of experimental techniques that are dedicated to enhancing achievable image resolution. For instance, through low-dose HRTEM imaging, a near-atomic resolution has been achieved on 2D polyimine under 300 kV. We further demonstrate that, by applying a mid-range acceleration voltage, i.e., 120 kV, the useful structural information per unit damage can be enhanced in several COFs, resulting in higher S/N ratio in the experimental images as compared to 300 kV. Besides, through a hydrogen-free structural design, MOFs' intrinsic stability can be significantly increased, allowing direct observation down to atomic scale.