Weiming Lv

Te‐Doped Black Phosphorus Field‐Effect Transistors

Element doping allows manipulation of the electronic properties of 2D materials. Enhanced transport performances and ambient stability of black-phosphorus devices by Te doping are presented. This provides a facile route for achieving airstable black-phosphorus devices.

Carbonaceous photonic crystals as ultralong cycling anodes for lithium and sodium batteries

Via carbonization of butterfly wings, carbonaceous photonic crystals (CPCs) were derived as anode materials for lithium and sodium ion batteries (LIB and NIB) with ultralong cycling stability. Owing to the CPCs inheritance of the wings unique photonic structure, the periodically interconnected ridges and ribs serve as perfect channels for electron transportation and allow the presence of cross-linked macropores for facile electrolyte access and ion diffusion. The carbonization-induced micro- and mesopores in the ridges and ribs can further facilitate electrolyte penetration and thus shorten the ion diffusion distances. Moreover, depending on the carbonization temperature, rich contents of O and N heteroatoms on the carbon surfaces can offer extra sites for reversible Li+/Na+ adsorption and enhance the electrochemical reactivity and electronic conductivity. For LIB/NIB applications, the derived CPC (CPC800) by carbonization at 800 °C delivers the best performances. CPC800 offers high specific capacities of 590 mA h g−1 (LIB) and 235 mA h g−1 (NIB) with ∼100% coulombic efficiencies at 0.05 A g−1. More impressively, CPC800 displays ultralong cycling stability for LIB and NIB applications, sustaining more than 10000 cycles at 5 A g−1 (LIB) and 1 A g−1 (NIB) with no evident observation of the fading of capacity and ∼100% coulombic efficiencies.

Electric-Field Control of Spin–Orbit Torques in WS2/Permalloy Bilayers

Transition metal dichalcogenides (TMDs) have drawn great attention owing to their potential for electronic, optoelectronic, and spintronic applications. In TMDs/ferromagnetic bilayers, an efficient spin current can be generated by the TMDs to manipulate the magnetic moments in the ferromagnetic layer. In this work, we report on the electric-field modulation of spin-orbit torques (SOTs) in WS2/NiFe bilayers by the spin-torque ferromagnetic resonance technique. It is found that the radio frequency current can induce a spin accumulation at the WS2/NiFe interface because of the interfacial Rashba-Edelstein effect. As a consequence, the SOT ratio between the field-like and antidamping-like torques can be effectively controlled by applying the back-gate voltage in WS2/NiFe bilayers. These results provide a strategy for controlling the SOT by using semiconducting TMDs.

Sulfur-Doped Black Phosphorus Field-Effect Transistors with Enhanced Stability

Black phosphorus (BP) has drawn great attention owing to its tunable band gap depending on thickness, high mobility, and large Ion/ Ioff ratio, which makes BP attractive for using in future two-dimensional electronic and optoelectronic devices. However, its instability under ambient conditions poses challenge to the research and limits its practical applications. In this work, we present a feasible approach to suppress the degradation of BP by sulfur (S) doping. The fabricated S-doped BP few-layer field-effect transistors (FETs) show more stable transistor performance under ambient conditions. After exposing to air for 21 days, the charge-carrier mobility of a representative S-doped BP FETs device decreases from 607 to 470 cm2 V-1 s-1 (remained as high as 77.4%) under ambient conditions and a large Ion/ Ioff ratio of ∼103 is still retained. The atomic force microscopy analysis, including surface morphology, thickness, and roughness, also indicates the lower degradation rate of S-doped BP compared to BP. First-principles calculations show that the dopant S atom energetically prefers to chemisorb on the BP surface in a dangling form and the enhanced stability of S-doped BP can be ascribed to the downshift of the conduction band minimum of BP below the redox potential of O2/O2-. Our work suggests that S doping is an effective way to enhance the stability of black phosphorus.

Magnetoresistance Effect in NiFe/BP/NiFe Vertical Spin Valve Devices

Two-dimensional (2D) layered materials such as graphene and transition metal dichalcogenides are emerging candidates for spintronic applications. Here, we report magnetoresistance (MR) properties of a black phosphorus (BP) spin valve devices consisting of thin BP flakes contacted by NiFe ferromagnetic (FM) electrodes. The spin valve effect has been observed from room temperature to 4 K, with MR magnitudes of 0.57% at 4 K and 0.23% at 300 K. In addition, the spin valve resistance is found to decrease monotonically as temperature is decreased, indicating that the BP thin film works as a conductive interlayer between the NiFe electrodes.

Ultrahigh-photoresponsive UV photodetector based on a BP/ReS2 heterostructure p–n diode

The van der Waals (vdW) heterostructure, made up of two dissimilar two-dimensional materials held together by van der Waals interactions, has excellent electronic and optoelectronic properties as it provides a superior interface quality without the lattice mismatch problem. Here, we report the development and photoresponse characteristics of a p-n diode based on a stacked black phosphorus (BP) and rhenium disulfide (ReS2) heterojunction. The heterojunction showed a clear gate-tunable rectifying behavior similar to that of the conventional p-n junction diode. Under UV illumination, the BP/ReS2 p-n diode displayed a high photoresponsivity of 4120 A W-1 and we were able to modify the photoresponse properties by adjusting the back gate voltage. Moreover, an investigation of various channel lengths yielded the highest photoresponsivity of 11 811 A W-1 for a BP length of 1 μm. These results suggested vdW 2D materials to be promising for developing advanced heterojunction devices for nano-optoelectronics.