A ferroelectric semiconductor field-effect transistor (FeS-FET) was proposed and experimentally demonstrated for the first time. In this novel FeS-FET, a two-dimensional (2D) ferroelectric semiconductor α-In2Se3 is used to replace conventional semiconductor as channel.α-In2Se3 is identified due to its proper bandgap, room temperature ferroelectricity, the ability to maintain ferroelectricity down to a few atomic layers and the feasibility for large-area growth.An atomic-layer deposition (ALD) Al2O3 passivation method was developed to protect and enhance the performance of the α-In2Se3 FeS-FETs. The fabricated FeS-FETs exhibit high performance with a large memory window, a high on/off ratio over 10 8 , a maximum on-current of 671 μA/μm, high electron mobility of 488 cm 2 /V•s, and the potential to exceed the existing Fe-FETs for non-volatile memory applications.

We demonstrate room-temperature ferroelectric field-effect transistors (Fe-FETs) with MoS and CuInPS two-dimensional (2D) van der Waals heterostructure. The ferroelectric CuInPS is a 2D ferroelectric insulator, integrated on top of MoS channel providing a 2D/2D semiconductor/insulator interface without dangling bonds. The MoS- and CuInPS-based 2D van der Waals heterostructure Fe-FETs exhibit a clear counterclockwise hysteresis loop in transfer characteristics, demonstrating their ferroelectric properties. This stable nonvolatile memory property can also be modulated by the back-gate bias of the MoS transistors because of the tuning of capacitance matching between the MoS channel and the ferroelectric CuInPS, leading to the enhancement of the on/off current ratio. Meanwhile, the CuInPS thin film also shows resistive switching characteristics with more than four orders of on/off ratio between low- and high-resistance states, which is also promising for resistive random-access memory applications.

Mixed-dimensional (0D, 1D, and 3D) heterostructures based on 2D layered materials have been proven as a promising candidate for future nanoelectronics and optoelectronics applications. In this work, it is demonstrated that 1D atomic chain based Se nanoplates (NPs) can be epitaxially grown on monolayer ReS 2 by a chemical transport reaction, thereby creating an interesting mixed-dimensional Se/ReS 2 heterostructure. A unique epitaxial relationship is observed with the (110) planes of the Se NPs parallel to the corresponding ReS 2 (010) planes. Experimental and theoretical studies reveal that the Se NPs could conjugate with underlying monolayer ReS 2 via strong chemical hybridization at heterointerface, which is expected to originate from the intrinsic defects of ReS 2 . Remarkably, photodetectors based on Se/ReS 2 heterostructures exhibit ultrahigh detectivity of up to 8 × 10 12 Jones, and also show a fast response time of less than 10 ms. These results illustrate the great advantage of directly integrated 1D Se based nanostructure on planar semiconducting ReS 2 films for optoelectronic applications. It opens up a feasible way to obtain mixed-dimensional heterostructures with atomic interfacial contact by epitaxial growth.

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