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<jats:title>Abstract</jats:title> <jats:p>Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been proposed for a wide variety of applications, such as neuromorphic computing, flexible field effect transistors, photonics, and solar cells, among others. However, for most of these applications to be feasible, it is necessary to integrate these materials with the current existing silicon technology. Although chemical vapor deposition (CVD) is a promising method for the growth of high-quality and large-area TMD crystals, the high temperatures necessary for the growth make this technique incompatible with the processes used in the semiconductor industry. Herein, we demonstrate the possibility of low-temperature growth of TMDs, using tungsten selenide (WSe2) as a model, by simply using moisture-assisted defective tungsten oxide (WO3) precursor powders during the growth of these materials. DFT calculations reveal the mechanism by which moisture promotes the defect formation on the precursor crystal structure and how it dictates the reduction of the temperature of the growth. The results were compared with the standard growth at high temperatures and with a precursor mixture with alkali salts to show the high quality of the WSe2 grown at temperatures as low as 550 °C. To conclude, the work improves the understanding of nucleation and growth mechanisms of WSe2 at low temperatures and provides a useful strategy for the growth of TMDs at temperatures required for the back-end-of-line (BEOL) compatibility with current silicon technology.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Grain boundary roughness can affect electronic and mechanical properties of two-dimensional materials. This roughness depends crucially on the growth process by which the two-dimensional material is formed. To investigate the key mechanisms that govern the roughness, we have performed kinetic Monte Carlo simulations of a simple model that includes particle attachment, detachment, and diffusion. We have studied the closure of the gap between two flakes during growth, and the subsequent formation of the grain boundary (GB) for a broad range of model parameters. The well known near-equilibrium (attachment-limited) and unstable (diffusion-limited) growth regimes are identified, but we also observe a third regime when the precursor flux is sufficiently high to saturate the gap between the edges with diffusing species. This high deposition rate regime forms GBs with spatially uncorrelated roughness, which quickly relax to smoother configurations. Extrapolating the numerical results (with support from a theoretical approach) to edge lengths and gap widths of some micrometers, we confirm the advantage of this regime to produce GBs with minimal roughness faster than near-equilibrium conditions. This suggests an unexpected route towards efficient growth of two-dimensional materials with smooth GBs. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Lithium metal anodes, the promising anodes for next-generation batteries, are troubled by the instability and safety issues induced by the dendrite growth. Three-dimensional hosts are widely used to accommodate lithium metal to solve the above problems. However, they are constantly challenged by large thickness and excess space in the host, lowering the volumetric energy density of batteries. Here, we used the reduced graphene oxide membrane (rGOM) assembled with small graphene oxide sheets as the host and obtained a compact, ultrathin (&lt; 20 μm) and free-standing lithium metal-reduced graphene oxide composite anode with good flexibility and high volumetric capacity. The overlap sites derived from the stacking of small size of GO act as abundant diffusion channels for the gas release during the spark reduction process, producing narrow interlamellar space in the rGOM and thus enhancing the capillary molten Li infusion to form a compact composite anode. These sites also guide the uniform deposition of Li metal on the surface and interior of the membrane, effectively suppressing the dendrite growth. This compact composite anode delivers a high volumetric capacity (1223 mAh cm-3) and stable cycling performance in the symmetrical cells and the full cells coupled with high mass loading LiFePO4 cathode under a low N/P ratio</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Due to its ultra-thin nature, the study of graphene quantum optoelectronics, like gate-dependent graphene Raman properties, is obscured by interactions with substrates and surroundings. For instance, the use of doped silicon with a capping thermal oxide layer limited the observation to low temperatures of a well-defined Kohn-anomaly behavior, related to the breakdown of the adiabatic Born–Oppenheimer approximation. Here, we design an optoelectronic device consisting of single-layer graphene electrically contacted with thin graphite leads, seated on an atomically flat hexagonal boron nitride (hBN) substrate and gated with an ultra-thin gold (Au) layer. We show that this device is optically transparent, has no background optical peaks and photoluminescence from the device components, and no generation of laser-induced electrostatic doping (photodoping). This allows for room-temperature gate-dependent Raman spectroscopy effects that have only been observed at cryogenic temperatures so far, above all the Kohn-anomaly phonon energy normalization. The new device architecture by decoupling graphene optoelectronic properties from the substrate effects, allows for the observation of quantum phenomena at room temperature.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Manipulating the strength of the interlayer coupling is an effective strategy to induce intriguing properties in layered materials. Recently, enhanced superconductivity has been reported in Weyl semimetal MoTe<jats:sub>2</jats:sub> and WTe<jats:sub>2</jats:sub> via ionic liquid cation intercalation. However, how the superconductivity enhancement depends on the interlayer interaction still remains elusive. Here by inserting ionic liquid cations with different sizes into MoTe<jats:sub>2</jats:sub> through this strategy, we are able to tune the interlayer spacing of the intercalated MoTe<jats:sub>2</jats:sub> samples and reveal the dependence of superconducting transition temperature <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> on the interlayer spacing. Our results show that <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> increases with the interlayer spacing, suggesting that the weakened interlayer coupling plays an important role in the superconductivity. Interestingly, the intercalation induced superconductivity shows a high Ginzburg-Landau anisotropy, which suggests a quasi-two-dimensional nature of the superconductivity where the adjacent superconducting layers are coupled through Josephson tunneling. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the effects of Kohn anomalies on the superconducting properties in electron- and hole-doped cases of monolayer blue phosphorene, considering both adiabatic and non-adiabatic phonon dispersions using first-principle calculations. We show that the topology of the Fermi surface is crucial for the formation of Kohn anomalies of doped blue phosphorene. By using the anisotropic Eliashberg formalism, we further carefully consider the temperature dependence of the non-adiabatic phonon dispersions. In cases of low hole densities, strong electron-phonon coupling leads to a maximum critical temperature of Tc = 97 K for superconductivity. In electron-doped regimes, on the other hand, a maximum superconducting critical temperature of Tc = 38 K is reached at a doping level that includes a Lifshitz transition point. Furthermore, our results indicate that the most prominent component of electron-phonon coupling arises from the coupling between an in-plane (out-of-plane) deformation and in-plane (out-of-plane) electronic states of the electron (hole) type doping. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Porous MXene-polymer composites have gained attention due to their lightweight properties, large surface area, and high electrical conductivity, which can be used in applications such as electromagnetic interference (EMI) shielding, sensing, energy storage, and catalysis. High internal phase emulsions (HIPEs) can be used to template the synthesis of porous polymer structures, and when solid particles are used as the interfacial agent, composites with pores lined with the particles can be realized. Here, we report a simple and scalable method to prepare conductive porous MXene/polyacrylamide structures via polymerization of the continuous phase in oil/water HIPEs. The HIPEs are stabilized by salt flocculated Ti3C2Tz nanosheets, without the use of a co-surfactant. After polymerization, the polyHIPE structure consists of porous polymer struts and pores lined with Ti3C2Tz nanosheets, as confirmed by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The pore size can be tuned by varying the Ti3C2Tz concentration, and the interconnected Ti3C2Tz network allows for electrical percolation at low Ti3C2Tz loading; further, the electrical conductivity is stable for months indicating that in these composites, the nanosheets are stable to oxidation at ambient conditions. The Ti3C2Tz polyHIPEs also exhibit rapid radio frequency heating at low power (10 °C/s at 1W). This work demonstrates a simple approach to accessing electrically conductive porous MXene/polymer composites with tunable pore morphology and good oxidation stability of the nanosheets. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>The layered nanostructure of cobalt hydroxide has received great attention in the field of hybrid supercapacitor (SC). However, the poor electrical conductivity and cyclic stability hinder its practical applicability. Surface modification of electrodes is considered as one of the effective strategies to improve these properties. In this work, the surface of α-Co(OH)2 is modified via Ti3C2Tx MXene using a simple drop-casting method with different mass loadings and corresponding SC performance is evaluated. The α-Co(OH)2 surface modified with 0.05 mg cm-2 Ti3C2Tx MXene (CM0.05) shows the maximum specific capacity of 392 C g-1 at the current density of 3 A g-1. The hybrid aqueous SC fabricated with CM0.05 as a positive electrode and 2D (2-dimensional) Ti3C2Tx MXene nanosheets as a negative electrode outperforms the SC fabricated with the activated carbon (AC) as a negative electrode. The CM0.05//MXene hybrid SC shows the maximum energy density of 44.5 Wh kg-1 at the power density of 2762 W Kg-1. This SC also shows the appreciable stability of 72% even after 5000 cycles. The flexible SC fabricated using PVA: KOH gel electrolyte demonstrates a superior energy density of 1.17 mWh cm-2 at the power density of 11.9 mW cm-2 with a wide operating potential of 1.6 V. Therefore, MXene (Ti3C2Tx) modified α-Co(OH)2 can be considered as a promising electrode material for hybrid flexible SCs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Realizing effective manipulation and explicit identification of topological spin configurations are two crucial ingredients to make them as candidates for information carriers in topological magnetism-based spintronic devices. Particularly, electric-field controlling magnetism has been considered as the most dissipationless method compared with traditional regulations. However, the electric field does not break time-reversal symmetry directly. On the other hand, thermal fluctuations make it difficult for topological magnetic quasiparticles to maintain their distribution. For overcoming this problem, the experiment has proposed that utilization different types of chiral magnetic structures as ‘0’ and ‘1’ bit carriers, which naturally has high requirement of materials. Here, we demonstrate that topological spin textures and electronic properties can be regulated simultaneously by electrical polarization in the Janus magnet-based multiferroic heterostructure, LaClBr/In2Se3. The skyrmions embedded in domain walls with metal state are transformed into uniform ferromagnetism with anomalous valley Hall effect by switching the direction of ferroelectric polarization from down to up. Therefore, the skyrmionic and uniform ferromagnetic states are easily distinguished by transverse voltage of sample. Our work provides an alternative approach for data encoding, in which data are encoded by combing topological spin textures with detectable electronic transport. </jats:p>