Abstract
The alkali metals Cs and Rb are the only surfaces which are not wetted by liquid 4He below a certain temperature. Especially for the system 4He–Cs this has been observed many times. However, there exist discrepancies in the measured contact angles and accompanying hysteresis, and in the movement of helium contact lines. Surface roughness is expected to have a significant influence on the wetting properties, but the working mechanism is not clearly understood yet. For this reason we have developed a special low temperature setup, which allows simultaneously an in situ evaporation of the alkali metals and an investigation of the substrate surface using a scanning tunneling microscope (STM). A characterization of quench-condensed Cs substrates is given and a manipulation of their surfaces on the nanometer scale is demonstrated. These investigations contain the first STM images of such a Cs surface at low temperatures.
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