Multifield Control of the Electronic Properties in Monolayer GeS and Its Applications in Logic Device

The development of multifunctional nanoelectronic devices requires multiple strategies to modulate the material’s electronic properties. Here, we systematically investigate the controllable electronic properties of the ferroelectric GeS monolayer by flexoelectric field, polarization field, and external electric fields, using first-principles calculations. The results show that GeS shows Type-I band alignment as the monolayer bends along the nonpolar direction. However, owing to the strong coupling between the intrinsic in-plane polarization field and the strain-gradient-induced flexoelectric field, monolayer GeS shows Type-II band alignment with spatial separation of HOMO and LUMO while bending along the polar direction. Critically, a tiny external electric field can drive a material with large bending (possessing a large flexoelectric field) to transfer from Type-II to Type-III band alignment. Based on this multifield control, we further investigate the transport properties and propose the design of a novel mechano-electric OR logic gate where the output current is independently controlled by mechanical flexure or electrical gate voltage. Our findings provide a novel pathway for designing multimodal logic circuits based on a single material.