Photoemission Study of 1H-1T’ Phase-transition in Monolayer MoS₂ on Gold

We study the transition of monolayer-MoS₂ on gold (MoS₂/Au) from trigonal semiconducting 1H-phase to the distorted octahedral quasi-metallic 1T’-phase based on a high-temperature annealing-based process. Besides, we observe a tunable inverted gap（~0.50eV) in quasi-metallic (1T’-phase) monolayer-MoS₂ upon the phase transition. With the focus on verifying the phase transition of MoS₂/Au, we study the evolution of Mo-3d and S-2p core level, work function, and valence band spectra at different annealing temperatures using synchrotron-based photoemission spectroscopy. New spectra components at lower binding energies relative to the 1H-MoS₂ doublet grow in intensity upon annealing and are maximized at 250^oC. Combining our results with other experimental studies, we conclude that the temperature region of 250^oC. Our study provides a good verification of the 1H-1T’ phase-transition process of MoS₂/Au and that this annealing-based technique is a convenient and straightforward way of inducing a semiconductor-to-metal phase transition in 2D TMDs.