State of the art two-dimensional materials-based photodetectors: Prospects, challenges and future outlook

Inert-Atmosphere Microfabrication Technology for 2D Materials and Heterostructures

Most 2D materials are unstable under ambient conditions. Assembly of van der Waals heterostructures in the inert atmosphere of the glove box with ex situ lithography partially solves the problem of device fabrication out of unstable materials. In our paper, we demonstrate an approach to the next-generation inert-atmosphere (nitrogen, <20 ppm oxygen content) fabrication setup, including optical contact mask lithography with a 2 μm resolution, metal evaporation, lift-off and placement of the sample to the cryostat for electric measurements in the same inert atmosphere environment. We consider basic construction principles, budget considerations, and showcase the fabrication and subsequent degradation of black-phosphorous-based structures within weeks. The proposed solutions are surprisingly compact and inexpensive, making them feasible for implementation in numerous 2D materials laboratories.

Bias-Modified Schottky Barrier Height-Dependent Graphene/ReSe2 van der Waals Heterostructures for Excellent Photodetector and NO2 Gas Sensing Applications

Herein, we reported a unique photo device consisting of monolayer graphene and a few-layer rhenium diselenide (ReSe₂) heterojunction. The prepared Gr/ReSe₂-HS demonstrated an excellent mobility of 380 cm²/Vs, current on/off ratio ~ 10⁴, photoresponsivity (R ~ 74 AW^-1 @ 82 mW cm^-2), detectivity (D^* ~ 1.25 × 10¹¹ Jones), external quantum efficiency (EQE ~ 173%) and rapid photoresponse (rise/fall time ~ 75/3 µs) significantly higher to an individual ReSe₂ device (mobility = 36 cm² V^-1s^-1, Ion/Ioff ratio = 1.4 × 10⁵-1.8 × 10⁵, R = 11.2 AW^-1, D* = 1.02 × 10¹⁰, EQE ~ 26.1%, rise/fall time = 2.37/5.03 s). Additionally, gate-bias dependent Schottky barrier height (SBH) estimation for individual ReSe₂ (45 meV at V_bg = 40 V) and Gr/ReSe₂-HS (9.02 meV at V_bg = 40 V) revealed a low value for the heterostructure, confirming dry transfer technique to be successful in fabricating an interfacial defects-free junction. In addition, HS is fully capable to demonstrate an excellent gas sensing response with rapid response/recovery time (39/126 s for NO₂ at 200 ppb) and is operational at room temperature (26.85 °C). The proposed Gr/ReSe₂-HS is capable of demonstrating excellent electro-optical, as well as gas sensing, performance simultaneously and, therefore, can be used as a building block to fabricate next-generation photodetectors and gas sensors.

Performance tunability of field-effect transistors using MoS2(1-x)Se2xalloys

Ultra-thin channel materials with excellent tunability of their electronic properties are necessary for the scaling of electronic devices. Two-dimensional materials such as transition metal dichalcogenides (TMDs) are ideal candidates for this due to their layered nature and great electrostatic control. Ternary alloys of these TMDs show composition-dependent electronic structure, promising excellent tunability of their properties. Here, we systematically compare molybdenum sulphoselenide (MoS_2(1-x)Se_2x) alloys, MoS₁Se₁and MoS_0.4Se_1.6. We observe variations in strain and carrier concentration with their composition. Using them, we demonstrate n-channel field-effect transistors (FETs) with SiO₂and high-kHfO₂as gate dielectrics, and show tunability in threshold voltage, subthreshold slope (SS), drain current, and mobility. MoS₁Se₁shows better promise for low-power FETs with a minimum SS of 70 mV dec^-1, whereas MoS_0.4Se_1.6, with its higher mobility, is suitable for faster operations. Using HfO₂as gate dielectric, there is an order of magnitude reduction in interface traps and 2× improvement in mobility and drain current, compared to SiO₂. In contrast to MoS₂, the FETs on HfO₂also display enhancement-mode operation, making them better suited for CMOS applications.

Interface design of carbon filler/polymer composites for electromagnetic interference shielding

The main three methods of interface design for carbon/polymer composites for different carbon materials.

Design and synthesis of a 3D flexible film electrode based on a sodium carboxymethyl cellulose–polypyrrole@reduced graphene oxide composite for supercapacitors

A novel, environmentally friendly and freestanding 3D flexible film electrode (CMC–PPy@RGO) was prepared by a simple vacuum filtration method.