Electronic Structure of Monolayer Molybdenum Diselenide Epitaxially Grown on Au(111)

Guan-Hao Chen^1,2*, Li-Syuan Lu², Pei-Yu Chuang³, Yu-Shiuan Su^1,4, Juhn-Jong Lin^1,5, Cheng-Maw Cheng³, Chun-Liang Lin¹, Wen-Hao Chang^1,2,5

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
³National synchrotron radiation research center, Hsinchu, Taiwan
⁴Taiwan Instrument Research Institute, Hsinchu, Taiwan
⁵5Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinch, Taiwan

* Presenter:Guan-Hao Chen, email:a0913635603@gmail.com

Using scanning tunneling microscopy/spectroscopy (STM/STS) and angle-resolved photoemission spectroscopy (ARPES), we reveal the electronic structure of monolayer MoSe2 and its modification caused by substrate interactions with the Au(111) surface. High-quality monolayer MoSe2 was grown epitaxially on single-crystal Au(111) surfaces by direct selenization of embedded Mo in Au. After growth, the sample was transferred to an ultrahigh vacuum (UHV) chamber and annealed at 180 °C for 1 hr. The MoSe2 lattice with a 0.33 nm periodicity can be well-resolved by STM. Our STS results reveal an energy difference of 0.18 eV between the onsets of the K point and Г point in the valence bands, which is in good agreement with both ARPES observation and DFT calculation. Then we performed a second annealing process for the sample at a higher temperature 450 °C in the UHV chamber. After the 450 °C annealings, the STM image can visualize another supercell with a periodicity of 2.3 nm, which corresponds to the moiré pattern formed between the MoSe2 and the Au(111) surface atoms. Interestingly, the K-Гenergy difference is significantly increased to 0.48 eV as revealed by STS measurements. Therefore, our results suggest that the underlying moiré potential strongly modified the electronic structure of monolayer MoSe2. Moreover, we also found that the monolayer MoSe2 transforms into n-type from intrinsic semiconductor after the high-temperature annealing.

Keywords: Scanning Tunneling Microscopy, Angular Resolved Photoemission Spectroscopy, Molybdenum diselenide, Electronic structure, Moiré pattern