Interfacial Charge Transfer Induced Electronic Property Tuning of MoS_2 by Molecular Functionalization

The modulation of electrical properties of MoS_2 has attracted extensive research interest because of its potential applications in electronic and optoelectronic devices.Herein,interfacial charge transfer induced electronic property tuning of MoS_2 are investigated by in situ ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy measurements.A downward band-bending of MoS_2-related electronic states along with the decreasing work function,which are induced by the electron transfer from Cs overlayers to MoS_2,is observed after the functionalization of MoS_2 with Cs,leading to n-type doping.Meanwhile,when MoS_2 is modified with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane(F_4-TCNQ),an upward band-bending of MoS_2-related electronic states along with the increasing work function is observed at the interfaces.This is attributed to the electron depletion within MoS_2 due to the strong electron withdrawing property of F_4-TCNQ,indicating p-type doping of MoS_2.Our findings reveal that surface transfer doping is an effective approach for electronic property tuning of MoS_2 and paves the way to optimize its performance in electronic and optoelectronic devices.

Development and Property Tuning of Refractory High-Entropy Alloys:A Review

In the past decade, multi-principal element high-entropy alloys (referred to as high-entropy alloys, HEAs) are an emerging alloy material, which has been developed rapidly and has become a research hotspot in the fi eld of metal materials. It breaks the alloy design concept of one or two principal elements in traditional alloys. It is composed of five or more principal elements, and the atomic percentage (at.%) of each element is greater than 5%but not more than 35%. The high-entropy eff ect caused by the increase of alloy principal elements makes the crystals easy form body-centered cubic or face-centered cubic structures, and may be accompanied by intergranular compounds and nanocrystals, to achieve solid solution strengthening,precipitation strengthening, and dispersion strengthening. The optimized design of alloy composition can make HEAs exhibit much better than traditional alloys such as high-strength steel, stainless steel, copper-nickel alloy, and nickel-based superalloy in terms of high strength, high hardness, high-temperature oxidation resistance, and corrosion resistance. At present,refractory high-entropy alloys (RHEAs) containing high-melting refractory metal elements have excellent room temperature and high-temperature properties, and their potential high-temperature application value has attracted widespread attention in the high-temperature fi eld. This article reviews the research status and preparation methods of RHEAs and analyzes the microstructure in each system and then summarizes the various properties of RHEAs, including high strength, wear resistance, high-temperature oxidation resistance, corrosion resistance, etc., and the common property tuning methods of RHEAs are explained, and the existing main strengthening and toughening mechanisms of RHEAs are revealed. This knowledge will help the on-demand design of RHEAs, which is a crucial trend in future development. Finally, the development and application prospects of RHEAs are prospected to guide future research.

Effect of layer sliding on the interfacial electronic properties of intercalated silicene/indium selenide van der Waals heterostructure

Methods capable of tuning the properties of van der Waals(vdW)layered materials in a controlled and reversible manner are highly desirable.Interfacial electronic properties of two-dimensional vdW heterostructure consisting of silicene and indium selenide(InSe)have been calculated using density functional theory-based computational code.Furthermore,in order to vary the aforementioned properties,silicene is slid over a InSe layer in the presence of Li intercalation.On intercalation of the heterostructure,the buckling parameter associated with the corrugation of silicene decreases from 0.44A to 0.36A,whereas the InSe structure remains unaffected.Potential energy scans reveal a significant increase in the sliding energy barrier for the case of intercalated heterostructure as compared with the unintercalated heterostructure.The sliding of the silicene encounters the maximum energy barrier of 0.14 eV.Anisotropic analysis shows the noteworthy differences between calculated in-plane and out-of-plane part of dielectric function.A variation of the planar average charge density difference,dipole charge transfer and dipole moment have been discussed to elucidate the usability spectrum of the heterostructure.The employed approach based on intercalation and layer sliding can be effectively utilized for obtaining next-generation multifunctional devices.

New Janus structure photocatalyst having widely tunable electronic and optical properties with strain engineering

Photoelectrochemical water splitting using solar energy,generating oxygen and hydrogen is one of the clean fuel production processes.Inspired by surface-dependent characteristics of Janus structures,a newly designed Janus monolayer Silicon Phosphorous Arsenide(SiPAs)was analyzed with Density Functional Theory(DFT)methods.Hybrid exchange-correlation functional(HSE06)combined with Wannier90-based analysis for electronic and optical properties of SiPAs reveals that it can act as a photocatalyst.SiPAs show an indirect bandgap of 1.88 eV,absorbing visible light range is 350 to 500 nm.The phonon spectrum confirms dynamic stability.The exciton binding energy is computed with GW/BSE methods.The electronic band edge positions are at-5.75 and-4.43 eV,perfectly straddling the water redox potentials.Interestingly the strain application modifies the bandgap and also non-homogenously widens the absorption band.A novel range of photocatalyst designs with Group IV-V elements with great promise for water-splitting,photovoltaic,and narrow bandgap semiconductor(optoelectronics)applications may be feasible.

Synthesis of magnetic two-dimensional materials by chemical vapor deposition

The development of magnetic two-dimensional(2D)materials in its infancy has generated an enormous amount of attention as it offers an ideal platform for the exploration of magnetic properties down to the 2D limit,paving the way for spintronic devices.Due to the nonnegligible advantages including time efficiency and simplified process,the facile bottom-up chemical vapor deposition(CVD)is regarded as a robust method to fabricate ultrathin magnetic nanosheets.Recently,some ultrathin magnets possessing fascinating properties have been successfully synthesized via CVD.Here,the recent researches toward magnetic 2D materials grown by CVD are systematically summarized with special emphasis on the fabrication methods.Then,heteroatoms doping and phase transition induced in CVD growth to bring or tune the magnetic properties in 2D materials are discussed.Characterizations and applications of these magnetic materials are also discussed and reviewed.Finally,some perspectives in need of urgent attention regarding the development of CVD-grown magnetic 2D materials are proposed.

Strain-sensitive ferromagnetic two-dimensional Cr_(2)Te_(3)

Searching for room temperature magnetic two-dimensional(2D)materials is a charming goal,but the number of satisfied materials is tiny.Strain can introduce considerable deformation into the lattice structure of 2D materials,and thus significantly modulate their intrinsic properties.In this work,we demonstrated a remarkable strain-modulated magnetic properties in the chemical vapor deposited Cr_(2)Te_(3) nanoflakes grown on mica substrate.We found the Curie temperature of Cr_(2)Te_(3) nanoflakes can be positively and negatively modulated under tensile and compressive strain respectively,with a maximum varied value of -40 and-90 K,dependent on the thickness of samples.Besides,the coercive field of Cr_(2)Te_(3) nanoflakes also showed a significant decrease under the applied strain,suggesting the decrease of exchange interaction or the change of the magnetization direction.This work suggests a promise to employ interfacial strain to accelerate the practical application of room temperature 2D magnetics.