Tuning the Electronic Structures of Atomic Layer MoS2 on Different Substrates Using Scanning Tunneling Microscopy/Spectroscopy

MoS2 ultra-thin films were prepared on different substrates, including highly doped p-Si (P-sample), highly doped n-Si (N-sample) and SiO2/Si substrate (C-sample), in order to form vertical stacking junctions. Using these different junctions, the electronic structures of MoS2 in different junctions are characterized by scanning tunneling microscopy/spectroscopy. The nominated bandgap is found to be about 1.0-2.5eV for the atomic layer MoS2 on different substrates. In the range of atomic layers, the work function decreases with decreasing thickness. Comparing the films with similar thickness, the trend of the selected bandgap E-g and work function phi are found to be E-gN>E-gC>E-gP and phi(P)>phi(N)>phi(C), respectively. Based on our results, electronic structures of atomic layer MoS2 can be tuned by different substrates, and the selected bandgap and work function are different using different substrates. The presence of tip-induced band bending has been confirmed to contribute to the measured bandgap and work function values. Our results offer valuable reference to the influence of substrates on electronic structure of MoS2 films.