RESUMO
The integration of different two-dimensional materials within a multilayer van der Waals (vdW) heterostructure offers a promising technology for high performance opto-electronic devices such as photodetectors and light sources. Here we report on the fabrication and electronic properties of vdW heterojunction diodes composed of the direct band gap layered semiconductors InSe and GaSe and transparent monolayer graphene electrodes. We show that the type II band alignment between the two layered materials and their distinctive spectral response, combined with the short channel length and low electrical resistance of graphene electrodes, enable efficient generation and extraction of photoexcited carriers from the heterostructure even when no external voltage is applied. Our devices are fast (â¼2 µs), self-driven photodetectors with multicolor photoresponse ranging from the ultraviolet to the near-infrared and offer new routes to miniaturized optoelectronics beyond present semiconductor materials and technologies.
RESUMO
Different than covalently bonded magnetic multilayer systems, high-quality interfaces without dangling bonds in van der Waals (vdW) junctions of two-dimensional (2D) layered magnetic materials offer opportunities to realize novel functionalities. Here, we report the fabrication of multi-state vertical spin valves without spacer layers by using vdW homo-junctions in which exfoliated Fe3GeTe2 nanoflakes act as ferromagnetic electrodes and/or interlayers. We demonstrate the typical behavior of two-state and three-state magnetoresistance for devices with two and three Fe3GeTe2 nanoflakes, respectively. Distinct from traditional spin valves with sandwich structures, our novel homo-junction-based spin-valve structure allows the straightforward realization of multi-state magnetic devices. Our work demonstrates the possibility of extend multi-state, non-volatile spin information to 2D magnetic homo-junctions, and it emphasizes the utility of vdW interface as a fundamental building block for spintronic devices.
RESUMO
The van der Waals (vdW) materials offer an opportunity to build all-two-dimensional (all-2D) spintronic devices with high-quality interfaces regardless of the lattice mismatch. Here, we report on an all-2D vertical spin valve that combines a typical layered semiconductor MoS2 with vdW ferromagnetic metal Fe3GeTe2 (FGT) flakes. The linear current-voltage curves illustrate that Ohmic contacts are formed in FGT/MoS2 interfaces, while the temperature dependence of the junction resistance further demonstrates that the MoS2 interlayer acts as a conducting layer instead of a tunneling layer. In addition, the magnitude of the magnetoresistance (MR) of 3.1% at 10 K is observed, which is around 8 times larger than that of the reported spin valves based on MoS2 sandwiched by conventional ferromagnetic electrodes. The MR decreasing monotonically with increasing temperature follows the Bloch's law. As the bias current decreases exponentially, the MR increases linearly up to a maximum value of 4.1%. Our results reveal the potential opportunities of vdW heterostructures for developing novel spintronic devices.
RESUMO
We investigated electrical and photoelectrical properties of graphene sandwiched WSe2/GaSe van der Waals heterojunctions. The device showed a high rectification ratio up to 300 at Vds = 1.5/-1.5 V, which is attributed to the built-in electric field in the device. Due to the bipolar property of WSe2, gate-tunable rectification inversion was observed. Meanwhile, the graphene sandwiched heterojunction showed excellent performances on photodetection, where the photoresponsivity of (6.2 ± 0.2) A W-1 can be reached under Vds = -1.5 V and P = 0.2 µW. The device also showed great external quantum efficiency of (1490 ± 50)% and fast response time of â¼30 µs. Our study identified the graphene sandwiched heterojunctions based on 2D materials have great potential for gate-tunable electronic and optoelectronic applications.