Polarization charge coupling effect in 2D van der Waals-ferroelectric heterostructure

In two-dimensional (2D) layered semiconducting materials, charge distribution is controlled by ferroelectric polarization and inequivalent charge distribution is obtained vertically. Ferroelectric polarization induced accumulation or depletion in 2D semiconductors resulting in polarization charge coupling effect. In this study, 2D semiconductors (n-type MoS₂ and p-type WSe₂) and ferroelectric PbTiO₃ (PTO) thin films were integrated vertically. We used conductive atomic force microscopy to study vertical transport and light illumination effect is also studied. Enhanced resistive switching effect was obtained and polarization was exploited to control resistive switching characteristics. In addition, charge separation is effectively obtained due to built-in interfacial electrical field at interface between 2D semiconductor and PTO thin films. In particular, photovoltaic response is obtained in the heterostructure and polarization can behave as a physically-doped electrode. Polarization gives stable and additional separation of electron-hole pairs in 2D semiconductors and increase of photoresponse is obtained. Therefore, we can expect application for a photo-memristor and suggest new memory and photovoltaic devices by integrating 2D semiconductors and ferroelectrics.