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<jats:p>Since the discovery of magnetism in two dimensions, effective manipulation of magnetism in van der Waals magnets has always been a crucial goal. Ionic gating is a promising method for such manipulation, yet devices gated with conventional ionic liquid may have some restrictions in applications due to the liquid nature of the gate dielectric. Lithium-ion conducting glass-ceramics (LICGC), a solid Li<jats:sup>+</jats:sup> electrolyte, could be used as a substrate while simultaneously acts as a promising substitute for ionic liquid. Here we demonstrate that the ferromagnetism of Fe<jats:sub>3</jats:sub>GeTe<jats:sub>2</jats:sub> (FGT) could be modulated via LICGC. By applying a voltage between FGT and the back side of LICGC substrate, Li<jats:sup>+</jats:sup> doping occurs and causes the decrease of the coercive field (<jats:italic>H</jats:italic> <jats:sub>c</jats:sub>) and ferromagnetic transition temperature (<jats:italic>T</jats:italic> <jats:sub>c</jats:sub>) in FGT nanoflakes. A modulation efficiency for <jats:italic>H</jats:italic> <jats:sub>c</jats:sub> of up to ∼ 24.6% under <jats:italic>V</jats:italic> <jats:sub>g</jats:sub> = 3.5 V at <jats:italic>T</jats:italic> = 100 K is achieved. Our results provide another method to construct electrically-controlled magnetoelectronics, with potential applications in future information technology.</jats:p>

<jats:p>The two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have been recently proposed as a promising class of materials for spintronic applications. Here, we report on the all-2D van der Waals (vdW) heterostructure spin valve device comprising of an exfoliated ultra-thin WS<jats:sub>2</jats:sub> semiconductor acting as the spacer layer and two exfoliated ferromagnetic Fe<jats:sub>3</jats:sub>GeTe<jats:sub>2</jats:sub> (FGT) metals acting as ferromagnetic electrodes. The metallic interface rather than Schottky barrier is formed despite the semiconducting nature of WS<jats:sub>2</jats:sub>, which could be originated from the strong interface hybridization. The spin valve effect persists up to the Curie temperature of FGT. Moreover, our metallic spin valve devices exhibit robust spin valve effect where the magnetoresistance magnitude does not vary with the applied bias in the measured range up to 50 μA due to the Ohmic property, which is a highly desirable feature for practical application that requires stable device performance. Our work reveals that WS<jats:sub>2</jats:sub>-based all-2D magnetic vdW heterostructure, facilitated by combining 2D magnets, is expected to be an attractive candidate for the TMDCs-based spintronic applications.</jats:p>

<jats:p>Spin orbit torques (SOTs) in ferromagnet/heavy-metal heterostructures have provided great opportunities for efficient manipulation of spintronic devices. However, deterministically field-free switching of perpendicular magnetization with SOTs is forbidden because of the global two-fold rotational symmetry in conventional heavy-metal such as Pt. Here, we engineer the interface of Pt/Ni heterostructures by inserting a monolayer MoTe<jats:sub>2</jats:sub> with low crystal symmetry. It is demonstrated that the spin orbit efficiency, as well as the out-of-plane magnetic anisotropy and the Gilbert damping of Ni are enhanced, due to the effect of orbital hybridization and the increased spin scatting at the interface induced by MoTe<jats:sub>2</jats:sub>. Particularly, an out-of-plane damping-like torque is observed when the current is applied perpendicular to the mirror plane of the MoTe<jats:sub>2</jats:sub> crystal, which is attributed to the interfacial inversion symmetry breaking of the system. Our work provides an effective route for engineering the SOT in Pt-based heterostructures, and offers potential opportunities for van der Waals interfaces in spintronic devices.</jats:p>

<jats:p>Exploring two-dimensional (2D) magnetic heterostructures is essential for future spintronic and optoelectronic devices. Herein, using first-principle calculations, stable ferromagnetic ordering and colorful electronic properties are established by constructing the VS<jats:sub>2</jats:sub>/C<jats:sub>3</jats:sub>N van der Waals (vdW) heterostructure. Unlike the semiconductive properties with indirect band gaps in both the VS<jats:sub>2</jats:sub> and C<jats:sub>3</jats:sub>N monolayers, our results indicate that a direct band gap with type-II band alignment and p-doping characters are realized in the spin-up channel of the VS<jats:sub>2</jats:sub>/C<jats:sub>3</jats:sub>N heterostructure, and a typical type-III band alignment with a broken-gap in the spin-down channel. Furthermore, the band alignments in the two spin channels can be effectively tuned by applying tensile strain. An interchangement between the type-II and type-III band alignments occurs in the two spin channels, as the tensile strain increases to 4%. The attractive magnetic properties and the unique band alignments could be useful for prospective applications in the next-generation tunneling devices and spintronic devices.</jats:p>

<jats:p>Two-dimensional (2D) magnetic materials have aroused tremendous interest due to the 2D confinement of magnetism and potential applications in spintronic and valleytronic devices. However, most of the currently 2D magnetic materials are achieved by the exfoliation from their bulks, of which the thickness and domain size are difficult to control, limiting the practical device applications. Here, we demonstrate the realization of thickness-tunable rhombohedral Cr<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> nanosheets on different substrates via the chemical vapor deposition route. The magnetic transition temperature at about 75 K is observed. Furthermore, van der Waals heterostructures consisting of Cr<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> nanosheets and monolayer WS<jats:sub>2</jats:sub> are constructed. We observe the magnetic proximity effect in the heterostructures, which manifests the manipulation of the valley polarization in monolayer WS<jats:sub>2</jats:sub>. Our work contributes to the vapor growth and applications of 2D magnetic materials.</jats:p>

<jats:p>We perform first-principles calculations and coherent laser-matter interaction analyses to investigate the laser-induced ultrafast spin flip on graphene nanoflakes (GNFs) with transition metal elements attached on the boundary [TM&amp;GNFs (TM = Fe, Co, Ni)]. It is shown that the spin-flip process on TM&amp;GNFs is highly influenced by the involved element species and the position attached to the nanoflakes. Furthermore, taking Ni&amp;GNF as an example, the first-principles tensile test predicts that the variation of the C–Ni bond length plays an important role in the spin density distribution, especially for the low-lying magnetic states, and can therefore dominate the spin-flip processes. The fastest spin-flip scenario is achieved within 80 fs in a Ni&amp;GNF structure under 10% tensile strain along the C–Ni bond. The local deformation modulation of spin flip provides the precursory guidance for further study of ultrafast magnetization control in GNFs, which could lead to potential applications in future integrated straintronic devices.</jats:p>

<jats:p>The optical properties of materials are of great significance for their device applications. Different numbers of krypton ions are doped into high-quality Zn-polar ZnO films fabricated by molecular beam epitaxy (MBE) on sapphire substrates through ion implantation. Krypton is chemically inert. The structures, morphologies, and optical properties of films are measured. The x-ray diffraction (XRD) spectra confirm the wurtzite structures of Zn-polar ZnO films. Atomic force microscopy (AFM) results show that the films have pit surface structure and higher roughness after Kr ion implantation. A detailed investigation of the optical properties is performed by using the absorption spectrum, photoluminescence (PL), and spectroscopic ellipsometry (SE). The absorption spectrum is measured by UV-visible spectrophotometer and the bandgap energy is estimated by the Tauc method. The results show that the absorption increases and the bandgap decreases after Kr ion implantation. Moreover, the Kr ion implantation concentration also affects the properties of the film. The ellipsometry results show that the films’ refractive index decreases with the Kr ion implantation concentration increasing. These results can conduce to the design and optimization of Kr ion-implanted polar ZnO films for optoelectronic applications.</jats:p>

<jats:p>In citric acid-based carbon dots, molecular fluorophore contributes greatly to the fluorescence emission. In this paper, the nitrogen and sulfur co-doped carbon dots (N,S-CDs) were prepared, and an independent sulfur source is selected to achieve the doping controllability. The influence of sulfur doping on the molecular fluorophore was systematically studied. The introduction of sulfur atoms may promote the formation of molecular fluorophore due to the increased nitrogen content in CDs. The addition surface states containing sulfur were produced, and S element exists as –SO<jats:sub>3</jats:sub>, and –SO<jats:sub>4</jats:sub> groups. Appreciate ratio of nitrogen and sulfur sources can improve the fluorescence emission. The photoluminescence quantum yields (PLQY) is increased from 56.4% of the single N-doping CDs to 63.4% of double-doping CDs, which ascribes to the synergistic effect of molecular fluorophores and surface states. The sensitivity of fluorescence to pH response and various metal ions was also explored.</jats:p>

<jats:p>The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, GaAs based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells, photodetectors, and other photoelectric devices.</jats:p>

<jats:p>The absorption coefficient is usually considered as a constant for certain materials at the given wavelength. However, recent experiments demonstrated that the absorption coefficient could be enhanced a lot by the PN junction. The absorption coefficient varies with the thickness of the intrinsic layer in a PIN structure. Here, we interpret the anomalous absorption coefficient from the competition between recombination and drift for non-equilibrium carriers. Based on the Fokker–Planck theory, a non-equilibrium statistical model that describes the relationship between absorption coefficient and material thickness has been proposed. It could predict the experimental data well. Our results can give new ideas to design photoelectric devices.</jats:p>