Graphene and other two-dimensional materials have received considerable attention regarding their potential applications in nano-electronics. Here, we report top-gate nonvolatile memory field-effect transistors (FETs) with different layers of MoSe ₂ nanosheets channel gated by ferroelectric film. The conventional gate dielectric of FETs was replaced by a ferroelectric thin film that provides a ferroelectric polarization electric field, and therefore defined as an Fe-FET where the poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) was used as the gate dielectric. Among the devices with MoSe ₂ channels of different thicknesses, the device with a single layer of MoSe ₂ exhibited a large hysteresis of electronic transport with an over 10 ⁵ write/erase ratio, and displayed excellent retention and endurance performance. The possible mechanism of the device’s good properties was qualitatively analyzed using band theory. Additionally, a comprehensive study comparing the memory properties of MoSe ₂ channels of different thicknesses is presented. Increasing the numbers of MoSe ₂ layers was found to cause a reduced memory window. However, MoSe ₂ thickness of 5 nm yielded a write/erase ratio of more than 10 ³ . The results indicate that, based on a Fe-FET structure, the combination of two-dimensional semiconductors and organic ferroelectric gate dielectrics shows good promise for future applications in nonvolatile ferroelectric memory.

Conventional field-effect transistors (FETs) are not expected to satisfy the requirements of future large integrated nanoelectronic circuits because of these circuits’ ultra-high power dissipation and because the conventional FETs cannot overcome the subthreshold swing (SS) limit of 60 mV/decade. In this work, the ordinary oxide of the FET is replaced only by a ferroelectric (Fe) polymer, poly(vinylidene difluoride-trifluoroethylene) (P(VDF-TrFE)). Additionally, we employ a two-dimensional (2D) semiconductor, such as MoS₂and MoSe₂, as the channel. This 2D Fe-FET achieves an ultralow SS of 24.2 mV/dec over four orders of magnitude in drain current at room temperature; this sub-60 mV/dec switching is derived from the Fe negative capacitance (NC) effect during the polarization of ferroelectric domain switching. Such 2D NC-FETs, realized by integrating of 2D semiconductors and organic ferroelectrics, provide a new approach to satisfy the requirements of next-generation low-energy-consumption integrated nanoelectronic circuits as well as the requirements of future flexible electronics.

We propose a theoretical model based on the concept of multiferroic tunnel junction. The model is capable of producing eight different logic states by combining the spin-filter effect and the screening of polarization charges between two electrodes through a general spintronic tunneling. The dependence of the conductance ratio with very large magnitude on electric polarization, exchange splitting, barrier width, and bias voltage is investigated. The result may provide some insights into the realization of octal data storage (namely, the eight different logic states are used as octal code), which could lead to the tremendous increase of memory storage density.

Superconductivity has attracted much interest in two-dimensional (2D) compounds because of their application in constructing nano-superconducting devices. Based on the crystal structure prediction method and first-principles calculations, we obtain two new 2D molybdenum boride structures of tetr- and tri-Mo₂B₂. Then, we calculate their electronic structures, phonon spectra, electron–phonon coupling (EPC), and superconducting properties. The results show that both tetr- and tri-Mo₂B₂ are intrinsic phonon-mediated superconductors with superconducting transition temperatures (T_c) of 3.9 and 0.2 K, respectively. We demonstrate that the EPC is mainly from the low-frequency phonon vibrations of Mo atoms. Our findings will enrich 2D superconducting materials and stimulate more efforts in this field.

Two dimensional superconductors are demonstrated in our predicted rect-, hex-GaB ₆ , rect- and hex-InB ₆ systems, with superconducting transition temperatures of 1.67, 14.02, 7.77 and 4.83 K, respectively.