An apparatus for preparing frozen solution samples in ultrahigh vacuum experiments

Here, we develop an apparatus for preparing frozen solution samples, which can be characterized by surface science techniques under ultrahigh vacuum (UHV) conditions. When a temperature-controlled substrate makes contact with a frozen solution at 77 K, the surface of the frozen solution is locally melted and then refreezes together with the substrate. By detaching the substrate from the frozen solution in situ in a high vacuum, the frozen solution is cleaved and transferred onto the substrate. Applying this method, we demonstrate transferring NaCl and LiNO3 frozen solutions onto an Au substrate and directly imaging the crystallization of NaCl and LiNO3 with atomic resolution using atomic force microscopy (AFM) in UHV at 5 K. This apparatus provides a new approach to transfer solution samples in their glassy states into the UHV environment while maintaining the cleanliness of the samples, laying the foundation for further research related to the solution environment in real life, such as crystallization, hydration, chemical reaction, materials synthesis, and bioimaging.