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Surface Energy Engineering for Tunable Wettability through Controlled Synthesis of MoS2

MoS2 is one of the important members of transition metal dichalogenides which is emerging as a potential 2D atomically thin layered material for low power electronic and opto-electronic applications. However, for MoS2 a critical fundamental question of significant importance is how the surface energy and hence the wettability is altered in nanoscale -- in particular, the role of crystal quality in low dimensions. Present work reports the synthesis of large area MoS2 films on insulating substrates with different surface morphology via vapor phase deposition by varying the growth temperatures. The crystallinity of the samples is examined by transmission electron microscopy and Raman spectroscopy. From contact angle measurements, it is possible to correlate the wettability with crystallinity at nanoscale. The specific surface energy for few layers thick MoS2 is estimated to be around 46.5 mJ/m2. Our results shed light on the MoS2-water interaction which is significant for developing important devices based on MoS2 coated surfaces for micro-fluidic applications.