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<jats:p>The drying of liquid droplets is a common phenomenon in daily life, and has long attracted special interest in scientific research. We propose a simple model to quantify the shape evolution of drying droplets. The model takes into account the friction constant between the contact line (CL) and the substrate, the capillary forces, and the evaporation rate. Two typical evaporation processes observed in experiments, i.e., the constant contact radius (CCR) and the constant contact angle (CCA), are demonstrated by the model. Moreover, the simple model shows complicated evaporation dynamics, for example, the CL first spreads and then recedes during evaporation. Analytical models of no evaporation, CCR, and CCA cases are given, respectively. The scaling law of the CL or the contact angle as a function of time obtained by analytical model is consistent with the full numerical model, and they are all subjected to experimental tests. The general model facilitates a quantitative understanding of the physical mechanism underlying the drying of liquid droplets.</jats:p>

<jats:p>The electronic structures and magnetic properties of diverse transition metal (<jats:italic>TM</jats:italic> = Fe, Co, and Ni) and nitrogen (N) co-doped monolayer MoS<jats:sub>2</jats:sub> are investigated by using density functional theory. The results show that the intrinsic MoS<jats:sub>2</jats:sub> does not have magnetism initially, but doped with <jats:italic>TM</jats:italic> (<jats:italic>TM</jats:italic> = Fe, Co, and Ni) the MoS<jats:sub>2</jats:sub> possesses an obvious magnetism distinctly. The magnetic moment mainly comes from unpaired Mo:4d orbitals and the d orbitals of the dopants, as well as the S:3p states. However, the doping system exhibits certain half-metallic properties, so we select N atoms in the V family as a dopant to adjust its half-metal characteristics. The results show that the (Fe, N) co-doped MoS<jats:sub>2</jats:sub> can be a satisfactory material for applications in spintronic devices. On this basis, the most stable geometry of the (2Fe–N) co-doped MoS<jats:sub>2</jats:sub> system is determined by considering the different configurations of the positions of the two Fe atoms. It is found that the ferromagnetic mechanism of the (2Fe–N) co-doped MoS<jats:sub>2</jats:sub> system is caused by the bond spin polarization mechanism of the Fe–Mo–Fe coupling chain. Our results verify that the (Fe, N) co-doped single-layer MoS<jats:sub>2</jats:sub> has the conditions required to become a dilute magnetic semiconductor.</jats:p>

<jats:p>At least four two- or quasi-one-dimensional allotropes and a mixture of them were theoretically predicted or experimentally observed for low-dimensional Te, namely the <jats:italic>α</jats:italic>, <jats:italic>β</jats:italic>, <jats:italic>γ</jats:italic>, <jats:italic>δ</jats:italic>, and chiral-<jats:italic>α</jats:italic> + <jats:italic>δ</jats:italic> phases. Among them the <jats:italic>γ</jats:italic> and <jats:italic>α</jats:italic> phases were found to be the most stable phases for monolayer and thicker layers, respectively. Here, we found two novel low-dimensional phases, namely the <jats:italic>ε</jats:italic> and <jats:italic>ζ</jats:italic> phases. The <jats:italic>ζ</jats:italic> phase is over 29 meV/Te more stable than the most stable monolayer <jats:italic>γ</jats:italic> phase, and the <jats:italic>ε</jats:italic> phase shows comparable stability with the most stable monolayer <jats:italic>γ</jats:italic> phase. The energetic difference between the <jats:italic>ζ</jats:italic> and <jats:italic>α</jats:italic> phases reduces with respect to the increased layer thickness and vanishes at the four-layer (12-sublayer) thickness, while this thickness increases under change doping. Both <jats:italic>ε</jats:italic> and <jats:italic>ζ</jats:italic> phases are metallic chains and layers, respectively. The <jats:italic>ζ</jats:italic> phase, with very strong interlayer coupling, shows quantum well states in its layer-dependent bandstructures. These results provide significantly insight into the understanding of polytypism in Te few-layers and may boost tremendous studies on properties of various few-layer phases.</jats:p>

<jats:p>Being parent materials of two-dimensional (2D) crystals, van der Waals layered materials have received revived interest. In most 2D materials, the interaction between electrons is negligible. Introducing the interaction can give rise to a variety of exotic properties. Here, via intercalating a van der Waals layered compound VS<jats:sub>2</jats:sub>, we find evidence for electron correlation by extensive magnetic, thermal, electrical, and thermoelectric characterizations. The low temperature Sommerfeld coefficient is 64 mJ⋅K<jats:sup>−2</jats:sup>⋅mol<jats:sup>−1</jats:sup> and the Kadowaki–Woods ratio <jats:italic>r</jats:italic> <jats:sub>KW</jats:sub> ∼ 0.20<jats:italic>a</jats:italic> <jats:sub>0</jats:sub>. Both supports an enhancement of the electron correlation. The temperature dependences of the resistivity and thermopower indicate an important role played by the Kondo effect. The Kondo temperature <jats:italic>T</jats:italic> <jats:sub>K</jats:sub> is estimated to be around 8 K. Our results suggest intercalation as a potential means to engineer the electron correlation in van der Waals materials, as well as 2D materials.</jats:p>

<jats:p>Due to their unique characteristics, two-dimensional (2D) materials have drawn great attention as promising candidates for the next generation of integrated circuits, which generate a calculation unit with a new working mechanism, called a logic transistor. To figure out the application prospects of logic transistors, exploring the temperature dependence of logic characteristics is important. In this work, we explore the temperature effect on the electrical characteristic of a logic transistor, finding that changes in temperature cause transformation in the calculation: logical output converts from ‘AND’ at 10 K to ‘OR’ at 250 K. The transformation phenomenon of temperature regulation in logical output is caused by energy band which decreases with increasing temperature. In the experiment, the indirect band gap of MoS<jats:sub>2</jats:sub> shows an obvious decrease from 1.581 eV to 1.535 eV as the temperature increases from 10 K to 250 K. The change of threshold voltage with temperature is consistent with the energy band, which confirms the theoretical analysis. Therefore, as a promising material for future integrated circuits, the demonstrated characteristic of 2D transistors suggests possible application for future functional devices.</jats:p>

<jats:p>Effective improvement in electrical properties of NO passivated SiC/SiO<jats:sub>2</jats:sub> interface after being irradiated by electrons is demonstrated. The density of interface traps after being irradiated by 100-kGy electrons decreases by about one order of magnitude, specifically, from 3×10<jats:sup>12</jats:sup> cm<jats:sup>−2</jats:sup>⋅eV<jats:sup>−1</jats:sup> to 4×10<jats:sup>11</jats:sup> cm<jats:sup>−2</jats:sup>⋅eV<jats:sup>−1</jats:sup> at 0.2 eV below the conduction band of 4H-SiC without any degradation of electric breakdown field. Particularly, the results of x-ray photoelectron spectroscopy measurement show that the C–N bonds are generated near the interface after electron irradiation, indicating that the carbon-related defects are further reduced.</jats:p>

<jats:p>Memristive devices have attracted intensive attention in developing hardware neuromorphic computing systems with high energy efficiency due to their simple structure, low power consumption, and rich switching dynamics resembling biological synapses and neurons in the last decades. Fruitful demonstrations have been achieved in memristive synapses neurons and neural networks in the last few years. Versatile dynamics are involved in the data processing and storage in biological neurons and synapses, which ask for carefully tuning the switching dynamics of the memristive emulators. Note that switching dynamics of the memristive devices are closely related to switching mechanisms. Herein, from the perspective of switching dynamics modulations, the mainstream switching mechanisms including redox reaction with ion migration and electronic effect have been systemically reviewed. The approaches to tune the switching dynamics in the devices with different mechanisms have been described. Finally, some other mechanisms involved in neuromorphic computing are briefly introduced.</jats:p>

<jats:p>Two-dimensional (2D) crystals are known to have no bulk but only surfaces and edges, thus leading to unprecedented properties thanks to the quantum confinements. For half a century, the compression of <jats:italic>z</jats:italic>-dimension has been attempted through ultra-thin films by such as molecular beam epitaxy. However, the revisiting of thin films becomes popular again, in another fashion of the isolation of freestanding 2D layers out of van der Waals (vdW) bulk compounds. To date, nearly two decades after the nativity of the great graphene venture, researchers are still fascinated about flattening, into the atomic limit, all kinds of crystals, whether or not they are vdW. In this introductive review, we will summarize some recent experimental progresses on 2D electronic systems, and briefly discuss their revolutionizing capabilities for the implementation of future nanostructures and nanoelectronics.</jats:p>

<jats:p>Grouping different oxide materials with coupled charge, spin, and orbital degrees of freedom together to form heterostructures provides a rich playground to explore the emergent interfacial phenomena. The perovskite/brownmillerite heterostructure is particularly interesting since symmetry mismatch may produce considerable interface reconstruction and unexpected physical effects. Here, we systemically study the magnetic anisotropy of tensely strained La<jats:sub>2/3</jats:sub>Sr<jats:sub>1/3</jats:sub>Co<jats:sub>1 – <jats:italic>x</jats:italic> </jats:sub>Mn<jats:sub> <jats:italic>x</jats:italic> </jats:sub>O<jats:sub>2.5 + <jats:italic>δ</jats:italic> </jats:sub>/La<jats:sub>2/3</jats:sub>Sr<jats:sub>1/3</jats:sub>MnO<jats:sub>3</jats:sub>/La<jats:sub>2/3</jats:sub>Sr<jats:sub>1/3</jats:sub>Co<jats:sub>1 – <jats:italic>x</jats:italic> </jats:sub>Mn<jats:sub> <jats:italic>x</jats:italic> </jats:sub>O<jats:sub>2.5 + <jats:italic>δ</jats:italic> </jats:sub> trilayers with interface structures changing from perovskite/brownmillerite type to perovskite/perovskite type. Without Mn doping, the initial La<jats:sub>2/3</jats:sub>Sr<jats:sub>1/3</jats:sub>CoO<jats:sub>2.5 + <jats:italic>δ</jats:italic> </jats:sub>/La<jats:sub>2/3</jats:sub>Sr<jats:sub>1/3</jats:sub>MnO<jats:sub>3</jats:sub>/La<jats:sub>2/3</jats:sub>Sr<jats:sub>1/3</jats:sub>CoO<jats:sub>2.5 + <jats:italic>δ</jats:italic> </jats:sub> trilayer with perovskite/brownmillerite interface type exhibits perpendicular magnetic anisotropy and the maximal anisotropy constant is 3.385 × 10<jats:sup>6</jats:sup> erg/cm<jats:sup>3</jats:sup>, which is more than one orders of magnitude larger than that of same strained LSMO film. By increasing the Mn doping concentration, the anisotropy constant displays monotonic reduction and even changes from perpendicular magnetic anisotropy to in-plane magnetic anisotropy, which is possible because of the reduced CoO<jats:sub>4</jats:sub> tetrahedra concentration in the La<jats:sub>2/3</jats:sub>Sr<jats:sub>1/3</jats:sub>Co<jats:sub>1 – <jats:italic>x</jats:italic> </jats:sub>Mn<jats:sub> <jats:italic>x</jats:italic> </jats:sub>O<jats:sub>2.5 + <jats:italic>δ</jats:italic> </jats:sub> layers near the interface. Based on the analysis of the x-ray linear dichroism, the orbital reconstruction of Mn ions occurs at the interface of the trilayers and thus results in the controllable magnetic anisotropy.</jats:p>

<jats:p>Last decade has witnessed a rapid development of the generation of terahertz (THz) vortex beams as well as their wide applications, mainly due to their unique combination characteristics of regular THz radiation and orbital angular momentum (OAM). Here we have reviewed the ways to generate THz vortex beams by two representative scenarios, i.e., THz wavefront modulation via specific devices, and direct excitation of the helicity of THz vortex beams. The former is similar to those wavefront engineering devices in the optical and infrared (IR) domain, but just with suitable THz materials, while the latter is newly-developed in THz regime and some of the physical mechanisms still have not been explained explicitly enough though, which would provide both challenges and opportunities for THz vortex beam generation. As for their applications, thanks to the recent development of THz optics and singular optics, THz vortex beams have potentials to open doors towards a myriad of practice applications in many fields. Besides, some representative potential applications are evaluated such as THz wireless communication, THz super-resolution imaging, manipulating chiral matters, accelerating electron bunches, and detecting astrophysical sources.</jats:p>