MoTe₂ on ferroelectric single-crystal substrate in the dual-gate field-effect transistor operation

An exfoliated MoTe₂ flake in contact with a ferroelectric single-crystal substrate was studied to examine its charge carrier modulation by neighboring ferroelectric polarization. A MoTe₂ field-effect transistor was fabricated, having a hexagonal-BN (hBN) flake and a ferroelectric substrate employed as top and bottom gate dielectrics. In the dual-gate operation, the charge conduction exhibited an ambipolar behavior with large hysteresis during the gate voltage sweep. It mainly originates from the ferroelectric nature in combination with the charge trap phenomena at the interfaces. Interestingly, we found out that holes are more easily trapped than electrons, and charge carriers in MoTe₂ are easily modulated through the top hBN gate when the electron conduction is predominantly set by the bottom ferroelectric field. However, the controllability becomes much weaker under opposing ferroelectric polarizations. This unbalanced controllability reveals the interfacial hole-trap effect resulting from ferroelectric polarization.