Enhanced Thermoelectric Performance and Ferroelectricity in 1T'-MoTe₂/GeTe Superlattice Films

The superlattice engineering approach has proven effective in synergistically improving physical properties of multifunctional materials, yet its application in GeTe-based films remains unexplored. In this work, we fabricated (1T'-MoTe₂)_x/(GeTe)_y superlattice films with well-controlled periodic layering and good structural coherence periodicity via molecular beam epitaxy, demonstrating the simultaneous optimization of thermoelectric and ferroelectric properties through superlattice engineering. The improved thermoelectric performance in GeTe-based superlattices arose from the evolution of intrinsic point defects, interfacial charge transfer, and band-bending-induced energy filtering. Specifically, the (1T'-MoTe₂)₂/(GeTe)₈₀ film achieved a high carrier effective mass of 3.70 m* and a superior room-temperature power factor of 2.53 mW m^-1 K^-2, arising from an optimal balance between enhanced effective mass and hole density. Meanwhile, the (1T'-MoTe₂)₂/(GeTe)₃₀ film exhibited markedly enhanced ferroelectric polarization as compared to the pristine GeTe film, with a large piezoelectric coefficient (d₃₃) of 15.3 pm V^-1, which is likely attributed to interfacial charge-transfer-induced suppression of the depolarization field. This work highlights the efficacy of superlattice engineering in concurrently optimizing thermoelectric and ferroelectric properties of GeTe-based films, offering insights on performance optimization of multifunctional materials.