Effect of Ultraviolet-Ozone Treatment on MoS₂ Monolayers: Comparison of Chemical-Vapor-Deposited Polycrystalline Thin Films and Mechanically Exfoliated Single Crystal Flakes.

ABSTRACT: We report the different oxidation behavior between polycrystalline chemical-vapor-deposited and mechanically exfoliated single crystal MoS₂ monolayers by ultraviolet-ozone treatment. As ultraviolet-ozone treatment time increased from 0 to 5 min, photoluminescence emission and Raman modes of both MoS₂ disappeared, suggesting structural degradation by oxidation. Analysis with optical absorbance and X-ray photoelectron spectroscopy suggested the formation of MoO₃ in both MoS₂ after ultraviolet-ozone treatment. In addition, ultraviolet-ozone treatment possibly led to the formation of oxygen vacancies, molybdenum oxysulfide, or molybdenum sulfates in chemical-vapor-deposited MoS₂. The measurement of electrical resistance after ultraviolet-ozone treatment suggested the transformation of chemical-vapor-deposited MoS₂ into doped MoO₃ and of mechanically exfoliated MoS₂ into negligibly doped MoO₃. These results demonstrate that the crystallinity of monolayer MoS₂ can strongly influence the effect of ultraviolet-ozone treatment, providing important implications on the device integration of MoS₂ and other two-dimensional semiconductors.

SUBMITTER: Jung C 

PROVIDER: S-EPMC6695460 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature