Interfacial optical sensing of ferroelectricity in freestanding perovskite oxides with monolayer Transition Metal Dichalcogenides*

In this work, we integrate monolayer MoSe₂ with a free-standing BaTiO₃ (BTO) membrane and study the ferroelectricity induced PL modulation in WSe₂. Two-dimensional (2D) transition-metal dichalcogenides (TMDs) can be easily integrated with other functional materials due to their lack of dangling bonds. Also, owing to their atomic thickness, electronic and photoluminescence (PL) properties of 2D TMDs can be modulated by external perturbations, which opens new avenues for quantum sensing and tunable optoelectronic devices [1,2,3]. Recent studies show that BTO can be separated from its oxide substrate using a sacrificial oxide layer, which opens new opportunities in material integration [4,5]. Using this method, we fabricated a dual gate field effect device where the BTO polarization can be switched and sensed simultaneously with monolayer MoSe₂ in-situ. We observe that the relative density of charge carriers in MoSe₂ changes as the polarization switches, and this gives rise to PL intensity modulation. The relative emission intensity of neutral and charged excitons show gate dependent hysteresis, which confirms that MoSe₂ senses and optically reads out the ferroelectricity in BTO.