Scientific Reports (May 2017)

Adsorption energy of oxygen molecules on graphene and two-dimensional tungsten disulfide

  • Filchito Renee Bagsican,
  • Andrew Winchester,
  • Sujoy Ghosh,
  • Xiang Zhang,
  • Lulu Ma,
  • Minjie Wang,
  • Hironaru Murakami,
  • Saikat Talapatra,
  • Robert Vajtai,
  • Pulickel M. Ajayan,
  • Junichiro Kono,
  • Masayoshi Tonouchi,
  • Iwao Kawayama

DOI
https://doi.org/10.1038/s41598-017-01883-1
Journal volume & issue
Vol. 7, no. 1
pp. 1 – 10

Abstract

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Abstract Adsorption of gas molecules on the surface of atomically layered two-dimensional (2D) materials, including graphene and transition metal dichalcogenides, can significantly affect their electrical and optical properties. Therefore, a microscopic and quantitative understanding of the mechanism and dynamics of molecular adsorption and desorption has to be achieved in order to advance device applications based on these materials. However, recent theoretical calculations have yielded contradictory results, particularly on the magnitude of the adsorption energy. Here, we have experimentally determined the adsorption energy of oxygen molecules on graphene and 2D tungsten disulfide using temperature-programmed terahertz (THz) emission microscopy (TPTEM). The temperature dependence of THz emission from InP surfaces covered with 2D materials reflects the change in oxygen concentration due to thermal desorption, which we used to estimate the adsorption energy of oxygen molecules on graphene (~0.15 eV) and tungsten disulphide (~0.24 eV). Furthermore, we used TPTEM to visualize relative changes in the spatial distribution of oxygen molecules on monolayer graphene during adsorption and desorption. Our results provide much insight into the mechanism of molecular adsorption on the surface of 2D materials, while introducing TPTEM as a novel and powerful tool for molecular surface science.