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The magnetic heterostructures provide flexible ways to realize particular magnetic properties that possess both scientific and practical significance. Here, by first-principles calculation, we predict strong Dzyaloshinskii–Moriya interactions (DMIs) by constructing CrI3/Metal heterostructures. The underlaying mechanisms are ascribed to the large spin-orbital coupling (SOC) of the I atom and the structural distortion in CrI3 layer caused by substrates. This is different from the traditional way that deposit magnetic films on substrate to generate DMI, wherein DMI is dominated by interlayer hybridization and large SOC of substrates. In addition, both Heisenberg exchange and magnetic anisotropy are modulated dramatically, such as Heisenberg exchange is nearly doubled on Au(111), and the out-of-plane magnetism is enhanced by 88% on Ir(111). Our work may provide a experimentally accessible strategy to induce DMI in layered magnetic materials, which will be helpful to the design of spintronics devices. [ABSTRACT FROM AUTHOR]

Forming a low-resistance semiconductor–metal contact is a critical step to achieve a high-performance two-dimensional (2D) semiconductor nanoelectronic device. Motivated by the recent discovery of monolayer γ-GeSe with exceptional high electrical conductivity reaching 105 S/m, we computationally investigate the interface contact properties of γ-GeSe with four representative classes of metallic systems, including 2D semimetal (graphene), 2D metal (NbS2), 3D semimetal (Bi), and 3D metal (Au) using first-principle density functional theory simulations. We found that these metals exhibit rich contact formation physics with 2D γ-GeSe, yielding contacts of heterostructures with weak and moderate couplings. Importantly, γ-GeSe/NbS2 is an Ohmic contact while γ-GeSe/Bi is an n-type Schottky contact with an ultralow barrier height of 0.07 eV. For γ-GeSe/graphene contact, the electronic properties can be adjusted via the interlayer distance or via an external electric field. Finally, we show that the contact properties can also be further controlled using layer-number engineering of γ-GeSe. Our findings provide a useful guideline for designing high-performance 2D nanoelectronics based on 2D γ-GeSe. [ABSTRACT FROM AUTHOR]

Recently, Janus two-dimensional (2D) materials have gained much attention due to their intrinsic vertical dipole. Here, we extensively investigate the electronic and magnetic properties of a new type of two-dimensional graphene-like Janus GaInSeTe monolayer by adopting the first-principles methods based on the density functional theory. It is found that 2D Janus GaInSeTe exhibits high dynamical stability and acts as a direct band gap semiconductor. The novel electronic and magnetic properties of the GaInSeTe nanosheet can be modulated via biaxial strain and atomic-sized structural defects. Specifically, the significant changes of semiconductor-to-metal and direct-to-indirect semiconductor transitions are driven by the biaxial strain. Our results also confirm that different types of single vacancy and multiple vacancy can effectively alter the electronic and magnetic properties of the GaInSeTe monolayer. Depending on the different vacancies, they induce metallic ( V Ga and V In ), direct band-gap semiconductive (V Se , V GaIn and V GaInTeSe ) and indirect band-gap semiconductor ( V Te , V TeSe ), respectively. It was also found that the inclusion of an In vacancy induces magnetism in the Janus GaInSeTe monolayer. Moreover, results show that the electronic and magnetic properties of Janus GaInSeTe monolayer are significantly modulated by vacancies and the external strains, and it displays varied band gaps of magnetic or nonmagnetic, multiple magnetic moments in semiconducting or metallic structures. These tunable electronic structure and magnetic properties of the Janus GaInSeTe monolayer can be utilized for the development of low-dimensional spintronics devices. The electronic and magnetic properties of a Janus GaInSeTe monolayer are significantly modulated by vacancies and the external strain, and it displays varied magnetic or nonmagnetic band gaps and multiple magnetic moments in semiconducting or metallic structures. [ABSTRACT FROM AUTHOR]

Porphine has a great potential application in molecular electronic devices. In this work, based on the density functional theory (DFT) and combining with nonequilibrium Green's function (NEGF), we study the transport properties of the molecular devices constructed by the covalent homocoupling of porphine molecules conjunction with zigzag graphene nanoribbons electrodes. We find that different couple phases bring remarkable differences in the transport properties. Different coupling phases have different application prospects. We analyze and discuss the differences in transport properties through the molecular energy spectrum, electrostatic difference potential, local density of states (LDOS), and transmission pathway. The results are of great significance for the design of porphine molecular devices in the future. [ABSTRACT FROM AUTHOR]

We investigate the magnetic transport properties for a molecular device model constructed by a carbon atomic chain embedding in two hydrogen-passivated graphene nanoribbons (GNRs) electrodes with sawtooth zigzag edges. The spin-dependent transport simulation is carried out by the first-principles approach based on the density functional theory combing with nonequilibrium Green's function formalism. It is found that the dual spin-filtering effect with the perfect efficiency up to 100 % , high-performance dual-spin diode effect with the rectification ratio reaches about 2.02 × 10 8 and obvious negative differential resistance behaviour with a peak-to-valley ratio near 3.24 × 10 6 are numerically observed in such proposed molecular device. Particularly, a giant magnetoresistance ratio approaching 2.38 × 10 7 % is also observed, which is two orders magnitude higher than the value of a zigzag-edge GNR. These findings suggest that our proposed device has multifunction with highly effective spin-filter, spin-diode, spin-valve performance. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) MoSi2N4 monolayer is an emerging class of air-stable 2D semiconductors possessing exceptional electrical and mechanical properties. Despite intensive recent research effort devoted to uncover the material properties of MoSi2N4, the physics of electrical contacts to MoSi2N4 remains largely unexplored thus far. In this work, we study van der Waals heterostructures composed of MoSi2N4 contacted by graphene and NbS2 monolayers using first-principles density functional theory calculations. We show that the MoSi2N4/NbS2 contact exhibits an ultralow Schottky barrier height (SBH), which is beneficial for nanoelectronics applications. For the MoSi2N4/graphene contact, the SBH can be modulated via the interlayer distance or via external electric fields, thus opening up an opportunity for reconfigurable and tunable nanoelectronic devices. Our findings provide insights into the physics of 2D electrical contacts to MoSi2N4 and shall offer a critical first step toward the design of high-performance electrical contacts to MoSi2N4-based 2D nanodevices. [ABSTRACT FROM AUTHOR]

Two-dimensional polyaniline with a C 3 N structure is a newly fabricated layered material that is expected to have fascinating electronic, thermal, mechanical, and chemical properties. By performing first-principles calculations based on density functional theory and the nonequilibrium Green's function, we first perform a stoichiometric study of the energy bands of armchair C 3 N nanoribbons (AC 3 NNRs) without and with H-passivation. The results show that the pristine AC 3 NNRs are metals, whereas the H-passivated nanoribbons are either direct or indirect band gap semiconductors with different edge configurations. Interestingly, additional transport calculations demonstrate that the AC 3 NNR-based heterojunction shows good rectification behavior. The average rectification ratio (RR) can reach up to 1 0 3 under voltage bias within the range from 0.2 to 0.4 V. In particular, extending the length of the scattering region in the heterojunction, which leads to a reduction in the current passing through the junction, allows the RR to be enlarged obviously. The average value of RR increases to a magnitude of the order of 1 0 4 under bias voltages in the range from 0.25 to 0.4 V, with a boosted maximum of up to 1 0 5 at 0.35 V. The findings of this work may be helpful in the design of functional nanodevices based on AC 3 NNRs in the future. [Display omitted] • First numerical simulation on the electronic property for armchair C 3 N nanoribbons without or with H passivation. • The planar heterojunctions show a diode behavior, this is mainly because of the internal Schottky barrier and the role of structural asymmetry. • Length-dependent channel effect of heterojunction has been observed with the rectification ratio reaching up to 105. [ABSTRACT FROM AUTHOR]

Highlights • First study on molecular junction of naphthalene diimide with graphene electrodes. • Systematical investigation on spintronic transport property in an organic molecular junction. • Perfect spin-filtering and -rectifying with efficiency approaching nearly 100%, GMR with ratios up to 106. Abstract Using the method of density function theory (DFT) in combination with none-equilibrium Green's functions, we investigate the behavior of spin-charge transport through a junction of a naphthalene diimide (NDI) between two graphene electrodes with different molecule-graphene linkers. We observe the obvious effects of spin-filtering and the spin-rectifying when the two electrodes are set in different spin configurations. Specifically, the ratio of spin-filtering can be up to almost 100% and the magnitude of magnetoresistance reaches 10 5 . More interestingly, we find that the apparent effect of negative differential resistance (NDR) in the junction only with the linking benzene under the parallel spin configuration. As the molecule-graphene linker is replaced by the carbon chain under the parallel configuration, the NDR behavior is almost disappeared. Therefore, our result concludes that the different molecule-graphene linkers can remarkably modulate the spin-charge transport property of molecular junction device. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • In MoS 2 , Al and Sb can play as good p-type dopants. • In WS 2 , Al dopes on cation site can perform as a good acceptor. • Halogen elements dope on the Te site in MoTe 2 are suitable n-type dopants; As and Sb are appropriate for p-type doping. • In WTe 2 , F is a suitable n-type dopant; P, As, Sb and Al are promising acceptors. Abstract Dopability in semiconductors plays a crucial role in device performance. Using the first-principles density-functional theory calculations, we investigate systematically the doping properties of layered MX 2 (M = Mo, W; X = S, Te) by replacing M or X with the groups III, V and VII elements. It is found that the defect B M is hard to form in MX 2 due to the large formation energy originating from the crystal distortion, while Al M is easy to realize compared to the former. In MoS 2 , WS 2 and MoTe 2 , Al is the most desirable p-type dopant under anion-rich conditions among the group III components. With respect to the doping of the group V elements, it is found that the substitutions on the cation sites have deeper defect levels than those on the anion sites. As Te and Sb Te in MoTe 2 and WTe 2 are trend to form shallow acceptors under cation-rich conditions, indicating high hole-concentrations for p-type doping, whereas Sb S in MoS 2 and P Te in WTe 2 are shown to be good p-type candidates under cation-rich conditions. In despite of that the substitutions of group VII on X site have low formation energies, the transition energies are too high to achieve n-type MoS 2 and WS 2. Nevertheless, for MoTe 2 , the substitutions with the group VII elements on the anion sites are suitable for n-type doping on account of the shallow donor levels and low formation energies under Mo-rich condition. As to WTe 2 , F is the only potential donor due to the shallow transition energy of F Te. Our findings of filtering out unfavorable and identifying favorable dopants in MX 2 are very valuable for experimental implementations. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMD) MoS 2 or graphene could be designed to metallic nanoribbons, which always have only one edge show metallic properties due to symmetric protection. In present work, a nanoribbon with two parallel metallic and magnetic edges was designed from a noble TMD PtS 2 by employing first-principles calculations based on density functional theory (DFT). Edge energy, bonding charge density, band structure, density of states (DOS) and simulated scanning tunneling microscopy (STM) of four possible edge states of monolayer semiconductive PtS 2 were systematically studied. Detailed calculations show that only Pt-terminated edge state among four edge states was relatively stable, metallic and magnetic. Those metallic and magnetic properties mainly contributed from 5 d orbits of Pt atoms located at edges. What's more, two of those central symmetric edges coexist in one zigzag nanoribbon, which providing two atomic metallic wires thus may have promising application for the realization of quantum effects, such as Aharanov–Bohm effect and atomic power transmission lines in single nanoribbon. [ABSTRACT FROM AUTHOR]

We study the electron spin-charge transport properties through an aromatic molecule between two pyridines in conjunction with graphene electrodes by applying the nonequilibrium Green's functions in combination with the density functional theory. The computational result shows that, the multi-functions of perfect spin-filtering and spin-rectifying with efficiency approaching nearly 100%, giant magnetoresistance with ratio up to 10 5 and negative differential resistance effects, are exhibited in this all-carbon system. Importantly, these functionalities can be qualitatively adjusted by the oxygen absorption on molecule, the variation of the electrode initial magnetic orientations and the molecule-pyridine connection, respectively. The physical and chemical mechanisms are revealed and discussed in terms of the spin-resolved transmission spectrum, the evolution of the frontier molecular orbitals, the local density of states around the Fermi level at zero bias, and the molecular projected self-consistent Hamiltonian. Our conclusion may indicate a direction for designing all-carbon spintronic nanodevices based on graphene. [ABSTRACT FROM AUTHOR]

Similar to pure graphyne, two-dimension carbon nitride graphyne also possesses exceptional properties and potential applications. In this work, by using the density functional theory (DFT) and combining with nonequilibrium Green's function (NEGF), we study the electronic band structures and transport properties of zigzag rhombic N-graphyne nanoribbons (ZrNGYNRs). Our results show that all of the ZrNGYNRs have similar metallic band structures in no magnetic and ferromagnetic configuration, while the transport properties are directly related to the symmetry of the systems. The electron band structure exhibits a distinct spin splitting in the ferromagnetic state. We propose a device by cutting the ZrNGYNRs in the central scattering region. Negative differential resistance, rectification effects, and spin-filtering effects can be observed in this device. This work highlights the outstanding physics of ZrNGYNRs, and suggest that the ZrNGYNRs is a very promising material in the application of nanoelectronics. • First numerical simulation on the electronic property for zigzag-edge rhombic N-graphyne nanoribbons. • A proposed junction based on zigzag-edge rhombic N-graphyne nanoribbon symmetrically with good circuit performance. • The spin-filtering efficiency can be up to 100%, and the maximum of rectification ratio reaches up to 107. [ABSTRACT FROM AUTHOR]