Spin-Valve Effect in FeGeTe/MoS/FeGeTe van der Waals Heterostructures.

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 MoS with vdW ferromagnetic metal FeGeTe (FGT) flakes. The linear current-voltage curves illustrate that Ohmic contacts are formed in FGT/MoS interfaces, while the temperature dependence of the junction resistance further demonstrates that the MoS interlayer acts as a conducting layer instead of a tunneling layer.

From two- to multi-state vertical spin valves without spacer layer based on FeGeTe van der Waals homo-junctions.

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 FeGeTe 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 FeGeTe nanoflakes, respectively.

Fast gate-tunable photodetection in the graphene sandwiched WSe/GaSe heterojunctions.

We investigated electrical and photoelectrical properties of graphene sandwiched WSe/GaSe van der Waals heterojunctions. The device showed a high rectification ratio up to 300 at V = 1.5/-1.

Fast, multicolor photodetection with graphene-contacted p-GaSe/n-InSe van der Waals heterostructures.

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.