Understanding the Intrinsic Water Wettability of Molybdenum Disulfide (MoS2)
2015
Kozbial, Andrew | Gong, Xiao | Liu, Haitao | Li, Lei
2D semiconductors allow for unique and ultrasensitive devices to be fabricated for applications ranging from clinical diagnosis instruments to low-energy light-emitting diodes (LEDs). Graphene has championed research in this field since it was first fabricated; however, its zero bandgap creates many challenges. Transition metal dichalcogenides (TMDCs), e.g., MoS₂, have a direct bandgap which alleviates the challenge of creating a bandgap in graphene-based devices. Water wettability of MoS₂ is critical to device fabrication/performance and MoS₂ has been believed to be hydrophobic. Herein, we report that water contact angle (WCA) of freshly exfoliated MoS₂ shows temporal evolution with an intrinsic WCA of 69.0 ± 3.8° that increases to 89.0 ± 3.1° after 1 day exposure to ambient air. ATR-FTIR and ellipsometry show that the fresh, intrinsically mildly hydrophilic MoS₂ surface adsorbs hydrocarbons from ambient air and thus becomes hydrophobic.
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