Large Band Offset in Monolayer MoS2 on Oppositely Polarized BiFeO3(0001) Polar Surfaces

Integrating two-dimensional materials with ferroelectrics has attracted much attention in recent years. Here, we present first-principles calculations for an MoS2 monolayer on BiFeO3(0001) polar surfaces. For the oppositely polarized BiFeO3(0001) surfaces, which are thermodynamically favorable under most chemical conditions, we demonstrate the existence of a considerable electrostatic potential difference. The weak van der Waals interaction between the MoS2 monolayer and the BiFeO3(0001) surface facilitates electrostatic modulation of the MoS2 electronic properties. Our results indicate that the MoS2 monolayer on the BiFeO3(0001) negative surface maintains its intrinsic semiconducting character, whereas the MoS2 monolayer on the positive surface shows an n-type conducting behavior. A remarkable band offset of 0.9 eV is predicted in the MoS2 monolayer on the oppositely polarized BiFeO3(0001) substrates. Our results reveal that seamless n-i (intrinsic) homojunctions in the MoS2 monolayer can be made by patterning the domain structure of the oppositely polarized BiFeO3(0001) substrate.