Electronic structure of MoS2 with palladium adsorption

Metal contact on a two-dimensional semiconducting transition metal dichalcogenides (TMDs) is of fundamental importance for TMDs sprintronics devices. In this work, the occupied electronic states of a single crystal N-type MoS2 with palladium adsorption has been studied with angle-resolved spectroscopy (ARPES) along the gamma-K and and gamma-M directions of the brillouin zone in the vicinity of Fermi level. A very thin layer of palladium was being deposited on a single crystal pristine MoS2 with a good crystalline order and it's verified by low-energy electron diffraction (LEED). The interface between a semiconductor and a low or high work function metal are predominantly effective in electron injection into the conduction band or hole injection into the valence band respectively. The adsorption of palladium on a typical N-type semiconductor, MoS2, is expected to be blocking contact in this case. However, experimentally we have seen that, by comparing the top of the valence band of a pristine MoS2, the palladium adsorption on MoS2 has caused a downward shifting of the valence band, namely towards higher binding energy or away from the Fermi level, by roughly 0.2eV in both gamma-K and gamma-M directions. The valence band shift upon metal adsorption on different TMDs, Na on MoS2 and Co on WSe2, has been reported, and comparison can be made.<!--[if gte msEquation 12]> m:val="̅"/> style='mso-bidi-font-style:normal'>Γ style='mso-bidi-font-style:normal'>- m:val="̅"/> style='font-size:12.0pt;line-height:107%;font-family:"Cambria Math",serif;
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