05. Micro- and Nano-Scale Transport, MEMS

Van der Waals heterostructures (vdWHs), formed by vertically stacking different two-dimensional materials, have garnered significant attention as they hold the potential for novel properties and functionalities, thus paving the way for new material science discoveries. While the wetting behavior of 2D transition metal dichalcogenides (TMDs) supported on substrates and the changes in wettability with the number of TMDs layers have been reported, studies on the wettability of vertical heterostructures composed of different 2D TMDs and the effects of stacking are still lacking. Here, we report the observation of micro-droplets condensed on tungsten diselenide/molybdenum disulfide (WSe2/MoS2) heterostructures using an environmental scanning electron microscope (ESEM). Previous studies reported a water contact angle (WCA) of around 70° on 2D MoS2 films supported on the SiO2/Si. In contrast, we observed a significant reduction in the WCA to approximately 30° for droplets condensed on the WSe2/MoS2 heterostructure. This dramatic decrease in WCA cannot be explained by the "wetting transparency" commonly associated with the ultimate thinness of 2D materials, and suggests a tunable interaction between water and 2D TMDs with van der Waals stacking of different 2D materials.

Prof.

Yasumitsu Miyata