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We report on electrical gating of superconducting bilayer NbSe2 using dual-gate field-effect transistors constructed by the van der Waals assembly of mechanically exfoliated NbSe2 and SrTiO3 thin films grown by molecular beam epitaxy. Charge carrier doping, but not a pure electric field, was found to induce changes to the superconducting resistive transition, reaching a 190 mK modulation of the critical temperature and excluding the Rashba effect. The phase space for the superconducting state beyond the Pauli limit under in-plane magnetic fields expands when the critical temperature is enhanced. Quantitative comparison with theory suggests the presence of intervalley scattering, which competes with Ising spin–orbit coupling to set the superconducting-normal phase boundary. The gating method demonstrated here may be applied to study other van der Waals layered superconductors. [ABSTRACT FROM AUTHOR]

Ferroelectric materials have shown great value in the modern semiconductor industry and are considered important function materials due to their high dielectric constant and tunable spontaneous polarization. A ferroelectric field effect transistor (FeFET) is a field effect transistor (FET) with ferroelectric polarization field introduced to regulate carriers in semiconductors. With the coupling of ferroelectric and semiconductor, FeFETs are attractive for advanced electronic and optoelectronic applications, including emerging memories, artificial neural networks, high-performance photodetectors, and smart sensors. In this review, representative research results of FeFETs are reviewed from the perspective of structures and applications. Here, the background and significance of ferroelectrics and FeFETs are given. Furthermore, methods of building FeFETs in different structures and physical models describing the characteristics of FeFET are introduced. Important applications of FeFETs in electronics and optoelectronics are presented, with a comparison of performance between FeFETs and FETs without ferroelectrics, including memories and memristive devices, photodetectors, negative capacitance FETs, sensors, and multifunctional devices. Finally, based on the above discussions, promising applications and challenges of FeFETs are summarized. [ABSTRACT FROM AUTHOR]

A transparent, flexible graphene field effect transistor (GFET) based on ferroelectric gate is demonstrated. In this device, the single layer graphene was fabricated by chemical vapor deposition method, and transferred to the polyethylene terephthalate substrate. Then the poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric polymer layer film was used as the gate dielectric for the graphene FET. Based on the P(VDF-TrFE)/graphene heterojunction FET, Hall Bar structure was fabricated. The transport properties of the graphene channel at low temperature and retention characteristics at different temperature are investigated in detail. These special properties indicated that the GFET might be useful for many particular applications, such as a non-volatile memories, flexible electronic devices and phototransistors. [ABSTRACT FROM AUTHOR]

Low-abundance biomolecule detection is very crucial in many biological and medical applications. In this paper, we present a novel electrolyte-gated graphene field-effect transistor (EGFET) biosensor consisting of acoustic tweezers to increase the sensitivity. The acoustic tweezers are based on a high-frequency bulk acoustic resonator with thousands of MHz, which has excellent ability to concentrate nanoparticles. The operating principle of the acoustic tweezers to concentrate biomolecules is analyzed and verified by experiments. After the actuation of acoustic tweezers for 10 min, the IgG molecules are accumulated onto the graphene. The sensitivities of the EGFET biosensor with accumulation and without accumulation are compared. As a result, the sensitivity of the graphene-based biosensor is remarkably increased using SMR as the biomolecule concentrator. Since the device has advantages such as miniaturized size, low reagent consumption, high sensitivity, and rapid detection, we expect it to be readily applied to many biological and medical applications. [ABSTRACT FROM AUTHOR]