Structure and dynamics of water at surface probed by scanning probe microscopy
Ying Jiang1*
1International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
* Presenter:Ying Jiang,
Water/solid interfaces are a central theme across an incredibly broad range of scientific and technological processes. Scanning probe microscopy (SPM) has been extensively applied to probe interfacial water in the past decades. However, there exist two longstanding limitations, which makes SPM fall short compared with conventional spectroscopic methods. First, H atoms of water molecule are very small and light, so it is very difficult to image them directly; Second, the water molecules are linked by weak H bonds, and it is highly possible to disturb the fragile water structure during the imaging process. In order to overcome these two grand challenges, we have developed a H-sensitive and weakly perturbative atomic force microscopy (AFM) based on a qPlus sensor [1]. The key lies in fine tuning the interplay between Pauli repulsive force and high-order electrostatic force using a CO-terminated tip. In this talk, I will first discuss the application of this technique to determine the microscopic structure of metastable water clusters [1]. In addition, we have unraveled the detailed atomic structures of ion hydrates at interfaces and the effect of hydration number on the ion transport [2]. Finally, I will show the ability of visualizing the growth of a two-dimensional ice in real space with atomic resolution, by capturing various metastable and intermediate structures during the ice growth at the ice edges [3].

[1] Peng et al., Nature Communications 9, 122 (2018).
[2] Peng et al., Nature 557, 701 (2018)
[3] Ma et al., Nature 577, 60 (2020)

Keywords: water, scanning probe microscopy, structure, dynamics