Controlling the twist angle between two stacked van der Waals (vdW) crystals is a powerful approach for tuning their electronic and photonic properties. Hyperbolic media have recently attracted much attention due to their ability to tailor electromagnetic waves at the subwavelength-scale which, however, usually requires complex patterning procedures. Here, we demonstrate a lithography-free approach for manipulating the hyperbolicity by harnessing the twist-dependent coupling of phonon polaritons in double-layers of vdW α-MoO3, a naturally biaxial hyperbolic crystal. The polariton isofrequency contours can be modified due to this interlayer coupling, allowing for controlling the polaritonic characteristics by adjusting the orientation angles between the two layers. Our findings provide opportunities for control of nanoscale light flow with twisted stacks of vdW crystals.

Due to their optical magnetic and electric resonances associated with the high refractive index, dielectric silicon nanoparticles have been explored as novel nanocavities that are excellent candidates for enhancing various light-matter interactions at the nanoscale. Here, from both of theoretical and experimental aspects, we explored resonance coupling between excitons and magnetic/electric resonances in heterostructures composed of the silicon nanoparticle coated with a molecular J-aggregate shell. The resonance coupling was originated from coherent energy transfer between the exciton and magnetic/electric modes, which was manifested by quenching dips on the scattering spectrum due to formation of hybrid modes. The influences of various parameters, including the molecular oscillation strength, molecular absorption line width, molecular shell thickness, refractive index of the surrounding environment, and separation between the core and shell, on the resonance coupling behaviors were scrutinized. In particular, the resonance coupling can approach the strong coupling regime by choosing appropriate molecular parameters, where an anticrossing behavior with a mode splitting of 100 meV was observed on the energy diagram. Most interestingly, the hybrid modes in such dielectric heterostructure can exhibit unidirectional light scattering behaviors, which cannot be achieved by those in plexcitonic nanoparticle composed of a metal nanoparticle core and a molecular shell.

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Flexible supercapacitors, which can sustain large deformations while maintaining normal functions and reliability, are playing an increasingly important role in portable electronics. Here we report the preparation of a three-dimensional α-Fe 2 O 3 /carbon nanotube (CNT@Fe 2 O 3 ) sponge electrode with a porous hierarchical structure, consisting of a compressible, conductive CNT network, coated with a layer of Fe 2 O 3 nanohorns. The specific capacitance of these hybrid sponges has been significantly improved to above 300 F/g, while the equivalent series resistance remains at about 1.5 Ω. The highly deformed CNT@Fe 2 O 3 sponge retains more than 90 % of the original specific capacitance under a compressive strain of 70% (corresponding to a volume reduction of 70%). The hybrid sponge still works stably and sustains similar specific capacitance as initial value even after 1000 compression cycles at a strain of 50%. The outstanding properties of this hybrid sponge make it a highly promising candidate for flexible energy devices.

TMDCs, [7][8][9] the quantum spin Hall effect, [10] the valleytronics, [11,12] as well as the 2D superconductivity, [13] implying extensive potential applications. In contrast to graphene, monolayer TMDCs with suitable bandgaps have demonstrated the state-of-the-art characteristics for integrated circuits (IC), i.e., high on/ off ratio (>10 7 ) and record drive current density (100 µA µm −1 ). [14,15] So far, a number of approaches have been developed to obtain TMDCs, including the micromechanical cleavage method [16] and liquid-phase exfoliation [17][18][19] due to the weak van der Waals interactions between the neighboring layers. Among them, chemical vapor deposition (CVD) has been widely demonstrated to be an effective technique to synthesize highquality TMDCs as well as their in-plane and vertical heterostructures by using different precursors, [20,21] such as the solid powders of MoO 3 , [22][23][24][25] MoO 3 solution, [26,27] MoCl 5 , [28] WO 3 , [29,30] WS 2 , WSe 2 , MoS 2 , and MoSe 2 [31][32][33] with the additional alkali metal halides as the growth promoters, [2,34] the gaseous chemical precursors including molybdenum hexacarbonyl (MHC), [4] as well as the liquid precursors like the solution of ammonium thiomolybdate (NH 4 ) 2 MoS 4 , [35,36] ammonium molybdate tetrahydrate (NH 4 ) 6 Mo 7 O 24 •4H 2 O and ammonium tungstate hydrate Chemical vapor deposition (CVD) has been widely used to synthesize highquality 2D transition-metal dichalcogenides (TMDCs) from different precursors. At present, quantitative control of the precursor with high precision and good repeatability is still challenging. Moreover, the process to synthesize TMDCs with designed patterns is complicated. Here, by using an industrial inkjet-printer, an in situ aqueous precursor with robust usage control at the picogram (10 −12 g) level is achieved, and by precisely tuning the inkjetprinting parameters, followed by a rapid heating process, large-area patterned TMDC films with centimeter size and good thickness controllability, as well as heterostructures of the TMDCs, are achieved facilely, and high-quality single-domain monolayer TMDCs with millimeter-size can be easily synthesized within 30 s (corresponding to a growth rate up to 36.4 µm s −1 ). The resulting monolayer MoS 2 and MoSe 2 exhibits excellent electronic properties with carrier mobility up to 21 and 54 cm 2 V −1 s −1 , respectively. The study paves a simple and robust way for the in situ ultrafast and patterned growth of high-quality TMDCs and heterostructures with promising industrialization prospects. Moreover, this ultrafast and green method can be easily used for synthesis of other 2D materials with slight modification.

Janus transition-metal dichalcogenides (TMDCs) are emerging as special 2D materials with different chalcogen atoms covalently bonded on each side of the unit cell, resulting in interesting properties. To date, several synthetic strategies have been developed to realize Janus TMDCs, which first involves stripping the top-layer S of MoS2 with H atoms. However, there has been little discussion on the intermediate Janus MoSH. It is critical to find the appropriate plasma treatment time to avoid sample damage. A thorough understanding of the formation and properties of MoSH is highly desirable. In this work, a controlled H2-plasma treatment has been developed to gradually synthesize a Janus MoSH monolayer, which was confirmed by the TOF-SIMS analysis as well as the subsequent fabrication of MoSSe. The electronic properties of MoSH, including the high intrinsic carrier concentration (∼2 × 1013 cm–2) and the Fermi level (∼ – 4.11 eV), have been systematically investigated by the combination of FET device study, KPFM, and DFT calculations. The results demonstrate a method for the creation of Janus MoSH and present the essential electronic parameters which have great significance for device applications. Furthermore, owing to the metallicity, 2D Janus MoSH might be a potential platform to observe the SPR behavior in the mid-infrared region.

For newly developed semiconductors, obtaining high‐performance transistors and identifying carrier mobility have been hot and important issues. Here, large‐area fabrications and thorough analysis of InGaZnO transistors with enhanced current by simple encapsulations are reported. The enhancement in the drain current and on–off ratio is remarkable in the long‐channel devices (e.g., 40 times in 200 µm long transistors) but becomes much less pronounced in short‐channel devices (e.g., 2 times in 5 µm long transistors), which limits its application to the display industry. Combining gated four‐probe measurements, scanning Kelvin‐probe microscopy, secondary ion mass spectrometry, X‐ray photoelectron spectroscopy, and device simulations, it is revealed that the enhanced apparent mobility up to several tens of times is attributed to the stabilized hydrogens in the middle area forming a degenerated channel area while that near the source‐drain contacts are merely doped, which causes artifact in mobility extraction. The studies demonstrate the use of hydrogens to remarkably enhance performance of oxide transistors by inducing a new mode of device operation. Also, this study shows clearly that a thorough analysis is necessary to understand the origin of very high apparent mobilities in thin‐film transistors or field‐effect transistors with advanced semiconductors.

The ability to engineer microscale and nanoscale morphology upon metal nanowires (NWs) has been essential to achieve new electronic and photonic functions. Here, this study reports an optically programmable Plateau−Rayleigh instability (PRI) to demonstrate a facile, scalable, and high-resolution morphology engineering of silver NWs (AgNWs) at temperatures <150 °C within 10 min. This has been accomplished by conjugating a photosensitive diphenyliodonium nitrate with AgNWs to modulate surface-atom diffusion. The conjugation is UV-decomposable and able to form a cladding of molten salt-like compounds, so that the PRI of the AgNWs can be optically programmed and triggered at a much lower temperature than the melting point of AgNWs. This PRI self-assembly technique can yield both various novel nanostructures from single NW and largearea microelectrodes from the NW network on various substrates, such as a nanoscale dot-dash chain and the microelectrode down to 5 μm in line width that is the highest resolution ever fabricated for the AgNW-based electrode. Finally, the patterned AgNWs as flexible transparent electrodes were demonstrated for a wearable CdS NW photodetector. This study provides a new paradigm for engineering metal micro-/nanostructures, which holds great potential in fabrication of various sophisticated devices.