Enhanced Thermoelectric Performance and Ferroelectricity in 1T′-MoTe ₂ /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′-MoTe 2 ) 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′-MoTe 2 ) 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′-MoTe 2 ) 2 /(GeTe) 30 film exhibited markedly enhanced ferroelectric polarization as compared to the pristine GeTe film, with a large piezoelectric coefficient ( d 33 ) 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.