Ferroelectricity of monolayer α-In₂Se₃ between electrodes from first principles

In conventional ferroelectrics, the polarization is reduced or disappears altogether in thin films of several-unit-cell thickness due to the depolarization field and interface effects. In contrast, 2D van der Waals materials have been shown to have robust polarization in a single van der Waals layer. In particular, a In₂Se₃ monolayer possesses both spontaneous out-of-plane and in-plane polarization. Here, using first-principles calculation, we investigate the ferroelectric properties of monolayer In₂Se₃ between graphene and ZrTe₂ electrodes, with a focus on the role of screening the depolarization fields. We find a substantial increase in polarization, compared with that of the freestanding monolayer. The polarization defined in terms of the charge transfer between the electrodes and its change on switching is discussed.