A few-layer MoS2 photodetector driven by poly(vinylidene fluoride-trifluoroethylene) ferroelectrics is achieved. The detectivity and responsitivity are up to 2.2 × 10(12) Jones and 2570 A W(-1), respectively, at 635 nm with ZERO gate bias. E(g) of MoS2 is tuned by the ultrahigh electrostatic field from the ferroelectric polarization. The photoresponse wavelengths of the photodetector are extended into the near-infrared (0.85-1.55 μm).

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Van der Waals heterostructures based on 2D layered materials have received wide attention for their multiple applications in optoelectronic devices, such as solar cells, light-emitting devices, and photodiodes. In this work, high-performance photovoltaic photodetectors based on MoTe /MoS vertical heterojunctions are demonstrated by exfoliating-restacking approach. The fundamental electric properties and band structures of the junction are revealed and analyzed. It is shown that this kind of photodetectors can operate under zero bias with high on/off ratio (>10 ) and ultralow dark current (≈3 pA). Moreover, a fast response time of 60 µs and high photoresponsivity of 46 mA W are also attained at room temperature. The junctions based on 2D materials are expected to constitute the ultimate functional elements of nanoscale electronic and optoelectronic applications.

We investigate the electron tunneling through a normal-metal-quantum-dot-superconductor ͑N-QD-S͒ system where multiple discrete levels of the QD are considered. By using the nonequilibrium-Green's-function method, the current I and the probability of the Andreev reflection T A () are derived and studied in detail. In addition to the resonant behavior of the Andreev tunneling as obtained in previous works, we find that the current I versus the gate voltage v g exhibits different kinds of peaks, depending on the bias voltage, the level spacing of the QD, and the energy gap of the superconducting electrode. Besides, in I-V characteristics extra peaks superimposed on the conventional current plateaus emerge, which stem from the resonant Andreev reflections. In the case with strongly asymmetric barriers, the BCS spectral density can be obtained directly from the I-V characteristics.