Reconstruction of Crystalline Ice Surface Revealed by Atomic Force Microscopy

Naoya Kawakami^1*, Akitoshi Shiotari¹, Yoshiaki Sugimoto¹

¹Dept. Adv. Matter. Sci., Univ. of Tokyo, Chiba, Japan

* Presenter:Naoya Kawakami, email:kawakami@afm.k.u-tokyo.ac.jp

It has been gradually apparent that ice surfaces act as a field of various chemical reactions. For unveiling the reaction mechanisms in detail, surface structures of ice surfaces should be identified at the atomic level. However, it is still unclear whether the arrangement of H bonds in the bulk is retained at the surface or rearranged. This is because conventional experimental methods (e.g., low energy electron diffraction and scanning tunneling microscopy) had poor sensitivity to H atoms or were ineligible for measuring insulating materials. In contrast, atomic force microscopy (AFM) must be suitable for studying ice surfaces because it can be applied to atomic scale observation of insulators and it is sensitive to H atoms at the surface. We investigated the surface of crystalline ice grown on Pt(111) with frequency modulation AFM under ultra-high vacuum conditions. In AFM images of the ice surfaces, protrusions are arranged in a (2×2) short-range order relative to the ideal lattice of ice Ih(0001), which reflects the arranged H atoms. The density of H atoms was lower than the value expected from ideal surface. This result indicates that the ice surface is reconstructed in order to reduce the number of H atoms on the surface.

Keywords: AFM, ice, Surface reconstruction