[20a-E319-1~7] 6.5 Surface Physics, Vacuum

▲ [20a-E319-7] In situ work function measurement in the transformation of MoS₂ to MoO₃ using ambient pressure X-ray photoelectron spectroscopy

〇(P)Dooyong Lee^1,4, Sehwan Song¹, Jiwoong Kim¹, Jouhahn Lee², Wooseok Song³, Satoshi Kera⁴, Beomgyun Jeong², Sungkyun Park¹ (1.Pusan National University, 2.Korea Basic Science Institute, 3.Korea Research Institute of Chemical Technology, 4.Institute for Molecular Science)

Keywords:Ambient pressure X-ray photoelectron spectroscopy, Work function, Chemical transformation

Chemical transformation of low-dimensional (2D) materials is useful in further expanding 2D material to realize layered transition metal oxides and their heterojunction. Recently, there have been few reports on a layered MoO₃ and a heterostructure MoO₃/MoS₂ from chemical transformation of MoS₂. However, the difficult to obtain the high-quality MoO₃/MoS₂ remained because there are unexpected sub-oxide defects (i.e., MoS_xO_1-x) during chemical transformation. Therefore, it is important to monitor the change in physical and chemical properties during the chemical transformation, simultaneously.
In this presentation, we showed the experimental result of the in-situ work function and the chemical state of MoS₂ under chemical transformation using the ambient pressure X-ray photoelectron spectroscopy. The chemical transformation of MoS₂ was performed under annealing temperature (RT ~ 350 ^oC) in 1 mbar O₂ gas +1 mbar Ar gas. As a result, we found that the chemical state of MoS₂ was unchanged. However, the work function increased owing to the decrease in carbon/H₂O contamination from RT to 200 ^oC. Further increased temperature, the MoS₂ partially transformed into MoO₃, resulting in the increased work function. At 350 ^oC, MoS₂ completely disappeared, and MoO₃ was formed. These results will provide a way for precise control of chemical transformation of 2D materials by in situ monitoring the physical and chemical properties.