SEM as a Facile Tool for Real-Time Monitoring of Microcrystal Growth during Electrodeposition: The Merit of Ionic Liquids

Due
to the extremely low vapor pressure of ionic liquids (ILs),
electrochemical deposition/dissolution of hexagonal hollow CuSn alloy
tubes in IL can be real-time observed with a scanning electron microscope
(SEM). Two specially made electrochemical cells are used for the top-view
and side-view observations. A series of clear SEM images reveals the
hexagonal cones are formed prior to further developing hexagonal tubes.
At the beginning, many small nuclei are formed on the electrode surface.
Due to the electrodeposition rate being slow enough for the nuclei
to crystallize into hexagonal structures, the electrodeposition rate
is faster on the periphery than the inside of the structures. As the
electrodeposition progresses, the tube wall will grow thicker, and
a secondary tube emerges inside the primary tube. Finally, shell-by-shell
hexagonal tubes are formed. Furthermore, the in situ SEM observation
also reveals that the dissolution of tube starts from its inner wall
followed by a sudden collapse of its wall. In this paper, we establish
a simple and convenient method, which can be broadly applied to the
study of metal, alloy, and semiconductor growth in real time.