/Ferroelectric Composite Structures*

Integrating layered van der Waals materials such as the transition metal dichalcogenides with ferroelectrics offers the opportunity to introduce new functionalities to the 2D platform, including nonvolatile memory and programmable junctions. In this work, we report a novel nonlinear optical response emerged at the interface between monolayer MoS₂ and ferroelectric thin films. We have pre-patterned ferroelectric domain structures with polarization up and down domains on epitaxial PbZr_0.2Ti_0.8O₃ (PZT) thin films using piezoresponse force microscopy, and then transferred on the top MoS₂ flakes. We then carried out second-harmonic generation (SHG) microscopy studies on the composite structures. In the reflection mode, we find that the SHG intensity on the ferroelectric domain wall (DW) is highly modulated compared with those on both polar domains, either significantly enhanced or suppressed depending on the chirality of the DW. Stacking angle dependence demonstrates that MoS₂ also tunes the polarity of the SHG response on the DW. Our study points to a new strategy to achieve tailored light polarity and intensity modulation via nanoscale ferroelectric control.