Interfacial Properties of Anisotropic Monolayer SiAs Transistors.

The newly prepared monolayer (ML) SiAs is expected to be a candidate channel material for next-generation nano-electronic devices in virtue of its proper bandgap, high carrier mobility, and anisotropic properties. The interfacial properties in ML SiAs field-effect transistors are comprehensively studied with electrodes (graphene, V2CO2, Au, Ag, and Cu) by using ab initio electronic structure calculations and quantum transport simulation. It is found that ML SiAs forms a weak van der Waals interaction with graphene and V2CO2, while it forms a strong interaction with bulk metals (Au, Ag, and Cu). Although ML SiAs has strong anisotropy, it is not reflected in the contact property. Based on the quantum transport simulation, ML SiAs forms n-type lateral Schottky contact with Au, Ag, and Cu electrodes with the Schottky barrier height (SBH) of 0.28 (0.27), 0.40 (0.47), and 0.45 (0.33) eV along the a (b) direction, respectively, while it forms p-type lateral Schottky contact with a graphene electrode with a SBH of 0.34 (0.28) eV. Fortunately, ML SiAs forms an ideal Ohmic contact with the V2CO2 electrode. This study not only gives a deep understanding of the interfacial properties of ML SiAs with electrodes but also provides a guide for the design of ML SiAs devices.

Isotropic Contact Properties in Monolayer GeAs Field-Effect Transistors.

Owing to the tunable bandgap and high thermodynamic stability, anisotropic monolayer (ML) GeAs have arisen as an attractive candidate for electronic and optoelectronic applications. The contact properties of ML GeAs with 2D metal (graphene, Ti2CF2, V2CF2, and Ti3C2O2) and Cu electrodes are explored along two principal axes in field-effect transistors (FET) by employing ab initio electronic structure calculations and quantum transport simulations. Weak van der Waals interactions are found between ML GeAs and the 2D metal electrodes with the band structure of ML GeAs kept the same, while there is a strong interaction between ML GeAs and the Cu metal electrode, resulting in the obvious hybridization of the band structure. Isotropic contact properties are seen along the two principal directions. P-type lateral Schottky contacts are established in ML GeAs FETs with Ti3C2O2, graphene, and Ti2CF2 metals, with a hole Schottky barrier height (SBH) of 0.12 (0.20), 0.15 (0.11), and 0.29 (0.21) eV along the armchair (zigzag) direction, respectively, and an n-type lateral Schottky contact is established with the Cu electrode with an electron SBH of 0.64 (0.57) eV. Surprisingly, ML GeAs forms ideal p-type Ohmic contacts with the V2CF2 electrode. The results provide a theoretical foundation for comprehending the interactions between ML GeAs and metals, as well as for designing high-performance ML GeAs FETs.

Decoration of defective graphene with MoS2 enabling enhanced anchoring and catalytic conversion of polysulfides for lithium-sulfur batteries: a first-principles study.

The potential of carbon materials for electrochemical processes could be largely activated by the delicate regulation of their intrinsic defects, and this prospect could be further enhanced after hybridizing with other functional components. Herein, we, for the first time, systematically combine graphene possessing different intrinsic defects with MoS2 as a host material for sulfur in lithium-sulfur batteries using first-principles calculations. After introducing the intrinsic defects in graphene, the heterostructures provide moderate binding affinity to lithium polysulfides (LiPSs) and facilitate their chemical reactions due to the unsaturated coordination of defective carbon and the charge rearrangement inside the heterostructures. Specifically, graphene with intrinsic defects increases the active sites and improves the conductivity, while MoS2 can not only improve the adsorption for LiPSs, but also provide smooth Li diffusion pathways and catalyze the rapid conversion of LiPSs. Among all the calculated heterostructures, the single vacancy graphene/MoS2 heterostructure is considered to be the most promising sulfur host due to the strongest binding strength to LiPSs (3.10-0.72 eV) and the lowest free energy barrier for the sulfur reduction reaction (1.36 eV), which is attributed to the spin polarization near the carbon defect. This work could afford fruitful insights into the rational design of defect engineering in heterostructures.

Preparation of a hydrophilic and antibacterial dual function ultrafiltration membrane with quaternized graphene oxide as a modifier.

In order to improve the anti-biofouling performance of ultrafiltration membrane, quaternized graphene oxide (QGO) was synthesized as a membrane modifier by in-situ growth of quaternary ammonium salt on the graphene oxide surface. A hydrophilic and antibacterial dual functional membrane was prepared with this kind of modifiers by immersion phase inversion method. The modified membrane obviously exhibits enhanced hydrophilicity, antibacterial and mechanical properties than the unmodified Polyvinylidene fluoride (PVDF) membranes. At the same time, it is proved that graphene oxide, as a carrier of quaternary ammonium salt, can significantly reduce the loss of antibacterial substances from the membranes.