Layer Dependence and Light Tuning Surface Potential of 2D MoS₂ on Various Substrates

Here surface potential of chemical vapor deposition (CVD) grown 2D MoS₂ with various layers is reported, and the effect of adherent substrate and light illumination on surface potential of monolayer MoS₂ are investigated. The surface potential of MoS₂ on Si/SiO₂ substrate decreases from 4.93 to 4.84 eV with the increase in the number of layer from 1 to 4 or more. Especially, the surface potentials of monolayer MoS₂ are strongly dependent on its adherent substrate, which are determined to be 4.55, 4.88, 4.93, 5.10, and 5.50 eV on Ag, graphene, Si/SiO₂ , Au, and Pt substrates, respectively. Light irradiation is introduced to tuning the surface potential of monolayer MoS₂ , with the increase in light intensity, the surface potential of MoS₂ on Si/SiO₂ substrate decreases from 4.93 to 4.74 eV, while increases from 5.50 to 5.56 eV on Pt substrate. The I-V curves on vertical of monolayer MoS₂ /Pt heterojunction show the decrease in current with the increase of light intensity, and Schottky barrier height at MoS₂ /Pt junctions increases from 0.302 to 0.342 eV. The changed surface potential can be explained by trapped charges on surface, photoinduced carriers, charge transfer, and local electric field.