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.

Tunable ohmic van der Waals-type contacts in monolayer C3N field-effect transistors.

Monolayer (ML) C3N, a novel two-dimensional flat crystalline material with a suitable bandgap and excellent carrier mobility, is a prospective channel material candidate for next-generation field-effect transistors (FETs). The contact properties of ML C3N-metal interfaces based on FETs have been comprehensively investigated with metal electrodes (graphene, Ti2C(OH/F)2, Zr2C(OH/F)2, Au, Ni, Pd, and Pt) by employing ab initio electronic structure calculations and quantum transport simulations. The contact properties of ML C3N are isotropic along the armchair and zigzag directions except for the case of Au. ML C3N establishes vertical van der Waals-type ohmic contacts with all the calculated metals except for Zr2CF2. The ML C3N-graphene, -Zr2CF2, -Ti2CF2, -Pt, -Pd, and -Ni interfaces form p-type lateral ohmic contacts, while the ML C3N-Ti2C(OH)2 and -Zr2C(OH)2 interfaces form n-type lateral ohmic contacts. The ohmic contact polarity can be regulated by changing the functional groups of the 2D MXene electrodes. These results provide theoretical insights into the characteristics of ML C3N-metal interfaces, which are important for choosing suitable electrodes and the design of ML C3N devices.

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.

Reinterpreting the Intercalation-Conversion Mechanism of FeP Anodes in Lithium/Sodium-Ion Batteries from Evolution of the Magnetic Phase.

Batteries with intercalation-conversion-type electrodes tend to achieve high-capacity storage, but the complicated reaction process often suffers from confusing electrochemical mechanisms. Here, we reinterpreted the essential issue about the potential of the conversion reaction and whether there is an intercalation reaction in a lithium/sodium-ion battery (LIB/SIB) with the FeP anode based on the evolution of the magnetic phase. Especially, the ever-present intercalation process in a large voltage range followed by the conversion reaction with extremely low potential was confirmed in FeP LIB, while it is mainly the conversion reaction for the sodium storage mechanism in FeP SIB. The insufficient conversion reaction profoundly limits the actual capacity to the expectedly respectable value. Accordingly, a graphene oxide modification strategy was proposed to increase the reversible capacity of FeP LIB/SIB by 99% and 132%, respectively. The results facilitate the development of anode materials with a high capacity and low operating potential.

Revealing the effect of LiOH on forming a SEI using a Co magnetic "probe".

The solid-electrolyte-interphase (SEI) plays a critical role in lithium-ion batteries (LIBs) because of its important influence on electrochemical performance, such as cycle stability, coulombic efficiency, etc. Although LiOH has been recognized as a key component of the SEI, its influence on the SEI and electrochemical performance has not been well clarified due to the difficulty in precisely controlling the LiOH content and characterize the detailed interface reactions. Here, a gradual change of LiOH content is realized by different reduction schemes among Co(OH)2, CoOOH and CoO. With reduced Co nanoparticles as magnetic "probes", SEI characterization is achieved by operando magnetometry. By combining comprehensive characterization and theoretical calculations, it is verified that LiOH leads to a composition transformation from lithium ethylene di-carbonate (LEDC) to lithium ethylene mono-carbonate (LEMC) in the SEI and ultimately results in capacity decay. This work unfolds the detailed SEI reaction scenario involving LiOH, provides new insights into the influence of SEI composition, and has value for the co-development between the electrode materials and electrolyte.

Chinese Herbal Medicine Dingji Fumai Decoction for Ventricular Premature Contraction: A Real-World Trial.

BACKGROUND: Chinese herbal medicine Dingji Fumai Decoction (DFD) is widely clinically used for ventricular premature contraction (VPC). This real-word trial was designed to assess the safety and effectiveness of DFD for VPC. METHODS: This was a double-blinded, randomized placebo-controlled trial. Patients with VPC were randomized (1 : 1) to treatment with DFD combined with metoprolol (DFD arm) or metoprolol combined with placebo (MET arm). A primary end point was a composite of clinical symptoms and signs determined by the traditionalChinese medicine syndrome score and the number of VPC determined by the Holter examination. Second outcomes were adverse events, medication compliance, and laboratory examination. RESULTS: 144 patients were randomized to DFD arm (76 patients) or MET arm (68 patients), and 136 cases (71 in DFD arm and 65 in MET arm) finally completed this trial. After a 12-week follow-up, DFD arm significantly decreased traditional Chinese medicine syndrome score and the number of VPC compared with MET arm (P = 0.003 and 0.034, respectively). There was no adverse drug effect and patient medication compliance was good. CONCLUSIONS: Superiority with DFD arm for VPC was demonstrated over MET arm for both the safety and effectiveness end points.