Observation of large in-plane anisotropic transport in van der Waals semiconductor Nb_(2)SiTe_(4)

Two-dimensional(2D)van der Waals material is a focus of research for its widespread application in optoelectronics,memories,and spintronics.The ternary compound Nb_(2)SiTe_(4) is a van der Waals semiconductor with excellent air stability and small cleavage energy,which is suitable for preparing a few layers counterpart to explore novel properties.Here,properties of bulk Nb_(2)SiTe_(4) with large in-plane electrical anisotropy are demonstrated.It is found that hole carriers dominate at a temperature above 45 K with a carrier active energy of 31.3 meV.The carrier mobility measured at 100 K is about 213 cm^(2)·V^(-1)·s^(-1) in bulk Nb_(2)SiTe_(4),higher than the reported results.In a thin flake Nb_(2)SiTe_(4),the resistivity ratio between the crystalline axes of a and b is reaching about 47.3 at 2.5 K,indicating that there exists a large anisotropic transport behavior in their basal plane.These novel transport properties provide accurate information for modulating or utilizing Nb_(2)SiTe_(4) for electronic device applications.

Tunable Superconductivity in 2H-NbSe2 via In Situ Li Intercalation

Using the newly-developed solid ionic gating technique,we measure the electrical transport property of a thinflake NbSe2 superconductor(Tc=6.67 K)under continuous Li intercalation and electron doping.It is found that the charge-density-wave transition is suppressed,while at the same time a carrier density,decreasing from7×10^14 cm^-2 to 2×10^14 cm^-2 also occurs.This tunable capability in relation to carrier density is 70%,which is 5 times larger than that found using the liquid ionic gating method[Phys.Rev.Lett.117(2016)106801].Meanwhile,we find that the scattering type of conduction electrons transits to the s-d process,which may be caused by the change of the occupied states of 4 d-electrons in Nb under the condition of Li intercalation.Simultaneously,we observe a certain decrement of electron-phonon coupling(EPC),based on the electron-phonon scattering model,in the high temperature range.Based on data gathered from in situ measurements,we construct a full phase diagram of carrier density,EPC and Tc in the intercalated NbSe2 sample,and qualitatively explain the variation of Tc within the BCS framework.It is our opinion that the in situ solid ionic gating method provides a direct route to describing the relationship between carrier density and superconductivity,which is helpful in promoting a clearer understanding of electronic phase competition in transition metal dichalcogenides.

Composition,Microstructure,Phase Constitution and Fundamental Physicochemical Properties of Low-Melting-Point Multi-Component Eutectic Alloys

Low-melting-point alloys have an extensive applications in the fields of materials processing, phase change energy storage, electronic and electrical automatic control, continuous casting simulation, welding, etc. Specifically, the eutectic compositions make up a large number of low-melting-point alloys that are ex- ploited because of their desirable features like single melting peaks, excellent operational reliability, and casting fluidity. However, the fundamental physicochemical properties from the current available liter- ature on low-melting-point multi-component eutectic alloys （LMP-MCEAs） are rather rare and lowly accurate, including the exact melting temperatures and compositions, constituent phases, microstruc- tures and morphologies, melting enthalpies, specific heats, densities, and so on. This lack of information seriously limits the development and application of low-melting-point multi-component eutectic alloys. In this paper, the low-melting-point multi-component eutectic alloys composed of Bi, Cd, Sn, Pb, and In elements synthesized by high vacuum induction melting and fundamental data were investigated by scan- ning electron microscopy （SEM）, energy dispersive spectrometry （EDS）, X-ray diffraction （XRD）, differential scanning calorimetry （DSC）, and density analysis instrument. Most of the LMP-MCEAs with complex eu- tectic morphology structures and XRD diffraction patterns could be explained with the fact that they were three-phase eutectic alloys with mixed growth way. Generally, LMP-MCEAs present an extremely low melting point between 48.3 and 124 ℃ and high density between 8 and 10 g/cm3.