Search

The manipulation of spin and valley degree of freedom in two-dimensional materials is desirable for emerging applications in next-generation electronics. Here, we report a regulation of the spin splitting in monolayer antiferromagnetic MnPSe3 through stacking van der Waals (vdW) heterostructures with transition-metal dichalcogenides (TMDs). Different TMDs including Janus MoSSe, MoSe2, and MoS2 are engaged and the spin and valley dependences on stacking configurations, interfacial atoms, and interlayer spacings are comprehensively investigated based on first-principles calculations. The results show that spin degeneracy of MnPSe3 can be lifted through the interfacial interaction in the vdW heterostructures. Compared with the MnPSe3 interfacing with traditional TMDs (MoSe2 and MoS2), those with Janus TMDs (MoSSe or MoSeS) have larger spin splitting. A maximal spin splitting of 50.8 meV at valence band maximum is achieved in MoSSe/MnPSe3 heterostructure, and such splitting is further enhanced to 243.0 meV when the interlayer spacing is reduced to 2.9 Å. It is found that the different hybridizations between the d-orbitals of the two inequivalent Mn atoms in MnPSe3 and the above TMDs lead to the occurrence of net magnetic moments, and thus induce spin splitting. This work paves a novel way to modify the spin-valley properties of two-dimensional semiconductors.

Memristors are excellent candidates for non-volatile memory and neuromorphic computing. Controlling the resistive switching polarity in certain materials holds great promise for the design and integration of multifunctional memristors. Here, bipolar and unipolar nonvolatility were realized by modulating the crystal structures, which exhibit high switching ratios, desirable cyclability, and long retention. By investigating the defect level and conductivity difference in single-crystal and polycrystal ReS2, the competition between electric field and Joule heat effects were revealed as the essential mechanism governing the switching process and memristive polarities. These results promote the design of two-dimensional memristors with controllable polarity.

The breakdown characteristics of AlGaN/GaN high-electron-mobility transistors are one of the most important parameters for practical applications when used as power devices. In this study, the relationship between the relative permittivity of the passivation layers and the breakdown voltages in the off state was investigated in detail using TCAD simulations. An embedded double-passivation layer was proposed to enhance the breakdown voltage of the devices. This device structure was realized using an additional step of etching and opening holes on the edge of the gate metal, followed by the deposition of the embedded passivation films. The extracted electric field shows that this embedded passivation layer not only can improve the breakdown characteristics of the device like using a single high-k passivation film but also presents as the function of the ‘Metal Field Plate’, additionally resulting in the enlarged breakdown voltage. Further theoretical simulations indicated that the greater the difference between the dielectric constants of the high/low passivation materials, the higher the breakdown voltage can be obtained.

In this work, the electronic and spintronic properties of GaSe/HfSe2 heterostructure under different strains are investigated through first-principles calculations. The results indicate that GaSe/HfSe2 heterostructure has an intrinsic type I band alignment, and the band structure is sensitive to the strain. A transition from type-I to type-II band alignment is found under a tensile stress. The evolution of the band structures is analyzed by the decomposed-projected band structures. Moreover, switchable spin textures of GaSe/HfSe2 heterostructure with different strains are also predicted. The controllable electronic spintronic properties of GaSe/HfSe2 heterostructure hold a great promise in applications of nanoelectronics and spintronics.

Development of two-dimensional (2D) nanoelectronics is appealing for electrically tunable properties in 2D materials. By means of density functional theory computations, we systematically study the modulation of vertical electric field on the electronic structure and spintronic properties of monolayer GaGeTe. A transition from indirect to direct bandgap is realized with an electric field of 0.11 V A−1. The direct bandgap monotonously diminishes due to the giant Stark effect with a Stark coefficient of 3.68 A. A critical electric field of 0.43 V A−1 is predicted, at which the semiconductor-to-metal transition occurs, and the effective mass of holes is correspondingly tuned to as low as 0.16 m 0. Electric-field-induced SOC plays an important role in the spintronic properties of monolayer GaGeTe so that a widely tunable SOC splitting from 0 to 78.3 meV is achieved, and switchable spin-polarization features are also predicted in the spin texture. The spin splitting is attributed to the Rashba effect with the Rashaba contribution coefficients tuned from 0 eVA to 0.15 eVA. As the all-electrical control method is demonstrated, the physical mechanism related to the redistribution of the electronic states is further revealed. The outstanding electronic and transport features as well as the widely controllable spintronic properties of monolayer GaGeTe hold a great promise for their applications in the field of 2D nanoelectronics and spintronics.

Perpendicular magnetic anisotropy is significantly important for realizing a long-term retention of information for spintronics devices. Inspired by 2D graphene with its high charge carrier mobility and long spin diffusion length, we report a first-principles design framework on perpendicular magnetic anisotropy engineering of a Fe atom adsorbed graphene by employing a O-terminated MgO (1 1 1) substrate. Determined by the adsorption sites of the Fe atom, a tunable magnetic anisotropy is realized in Fe/graphene/MgO (1 1 1) structure, with the magnetic anisotropy energy of −0.48 meV and 0.23 meV, respectively, corresponding to the in-plane and out of plane easy magnetizations. Total density of states suggest a half-metallicity with a 100% spin polarization in the system. Decomposed densities of Fe-3d states reveal the orbital contributions to the magnetic anisotropy for different Fe adsorption sites. Bonding interaction and charge redistribution regulated by MgO substrate are found responsible for the novel perpendicular magnetic anisotropy engineering in the system. The effective manipulation of perpendicular magnetic anisotropy in present work offers some references for the design and construction of 2D spintronics devices.