Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Moiré bands separated by the primary and secondary gaps emerge in the superlattices ofmonolayer (MLG) and bilayer graphene (BLG) aligned with the hexagonal boron nitride (BN). We study the tuning of the electronic and transport properties of such moiré superlattices through the periodic electrostatic potentials produced by the one-dimensional (1D) or two-dimensional (2D) patterned gating structure in the devices. The electrostatic potentials in graphene are produced by the spatially varying particle and hole doping due to the local quantum capacitance effect and can be modulated by the voltage (V<jats:sub>TG</jats:sub>) of the top patterned gating structure and that (V<jats:sub>BG</jats:sub>) of the uniform bottom gate. For the 1D devices of MLG/BN and BLG/BN, different sets of Fabry-Pérot interference like resistance patterns as a function of V<jats:sub>TG</jats:sub> and V<jats:sub>BG</jats:sub> can be observed when the Fermi level is shifted from the charge neutrality point (CNP) to the secondary gaps in MLG/BN and BLG/BN, and the overlapping regions of the patterns exhibit the highest resistance. The electronic states in these various regions of the resistance map show different moiré-band hybridization and spatial distribution. The secondary resistance patterns around the secondary gaps move away from the primary one with increasing twist angle (θ) between graphene and BN and their detailed patterns also depend on the orientation of the 1D potential with respect to that of the superlattice. The 2D periodic potentials can further split the subbands between CNP and the secondary gaps, depending on the commensurability of the moiré superlattice and the 2D potentials, and additional resistance peaks appear as a function of the gate voltages. The calculated resistance map for BLG/BN at θ ∼ 1° is roughly consistent with recent experimental observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Two-dimensional (2D) materials have received extensive research attentions over the past two decades due to their intriguing physical properties (such as the ultrahigh mobility and strong light-matter interaction at atomic thickness) and a broad range of potential applications (especially in the fields of electronics and optoelectronics). The growth of single-crystal 2D materials is the prerequisite to realize 2D-based high-performance applications. In this review, we aim to provide an in-depth analysis of the state-of-the-art technology for the growth and applications of 2D materials, with particular emphasis on single crystals. We first summarize the major growth strategies for monolayer 2D single crystals. Following that, we discuss the growth of multilayer single crystals, including the control of thickness, stacking sequence, and heterostructure composition. Then we highlight the exploration of 2D single crystals in electronic and optoelectronic devices. Finally, a perspective is given to outline the research opportunities and the remaining challenges in this field.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The frequent oil spill accidents during oil exploration and transportation have caused large economic loss and catastrophic environmental disasters. Due to low cost and simplicity, adsorption and filtration materials are often chosen to deal with oil spills, but the outcomes are not satisfactory mainly because of the awfully high viscosity of crude oil. Herein a photothermal ultra-high molecular weight polyethylene/MXene composite aerogel with a high light absorption (99.97%) and water repellency (water contact angle &gt;148°) is developed by thermally induced phase separation method. The composite aerogel endows durable hydrophobicity with which the water contact angle is more than 142° in acidic/alkaline environments, and the maximum absorption capacity of 81 g g<jats:sup>−1</jats:sup>. In addition, it exhibits an excellent photothermal performance, rising surface temperature to 70 °C within 60 s under 1 sun irradiation, that can drastically reduce the crude oil absorption time from 60 min to 60 s, saving 98% of absorption time and reaching a crude oil absorption capacity of 21 g g<jats:sup>−1</jats:sup>. More interestingly, the designed solar evaporation device with the obtained composite aerogel can achieve an evaporation rate of 1.15 kg m<jats:sup>−2</jats:sup>h<jats:sup>−1</jats:sup> and evaporation efficiency of 74%. The designed composite aerogel opens a possible pathway for solar-powered crude oil adsorption applications.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Herein, we established a synthetic route towards MXene/poly(ionic liquid) (PIL) composite porous membranes as a new platform of solar-thermal conversion materials. These membranes were made by a base-triggered ionic crosslinking process between a cationic PIL and a weak polyacid in solution in the presence of dispersed MXene nanosheets. A three-dimensionally interconnected porous architecture was formed with MXene nanosheets uniformly distributed within it. The unique characteristics of the as-produced composite membranes displays significant light-to-heat conversion and excellent performance for solar-driven water vapor generation. This facile synthetic strategy opens a new avenue for developing composite porous membranes as solar absorbers for the solar-driven water production from natural resources.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In recent years, graphene has been widely utilised as a supercapacitor electrode, and doping heteroatom on graphene is reported to enhance the pseudocapacitance of the electrode materials significantly resulting in a high energy density. However, the relationship and charge storage mechanism of a so-called ‘synergistic effect’ between those doped atoms including oxygen-, nitrogen-, and sulphur-doping on supercapacitor performances remain inscrutable. In this study, machine learning models are used to predict the capacitance of heteroatom-doped graphene-based supercapacitors and establish the effects of heteroatom-doping. Trained artificial neural network can accurately predict the capacitance of the electrode, drawing the best synthesis conditions for the heteroatom-doped graphene. Furthermore, we successfully demonstrate the synergistic effect that arises from co-doping nitrogen, sulphur, and locate the optimised region for N/S-co-doping with high capacitance, and high retention rate. Machine learning methods allow us to consider a much larger space of heteroatom-doping combinations to maximise the supercapacitor performances and provide a useful guideline for co-doping graphene-based supercapacitors.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Flexible broadband optoelectronic devices play a prominent role in the areas of daily life including wearable optoelectronic systems, health care, and bio-imaging systems. Two-dimensional (2D) narrow-bandgap materials with atomic thickness, adjustable bandgap, mechanical flexibility, as well as excellent optical and electrical properties exhibit great potential for applications in flexible optoelectronic devices. Here, we demonstrate a high-performance photodetector based on high-quality ternary Ta<jats:sub>2</jats:sub>NiSe<jats:sub>5</jats:sub> nanosheets with a narrow bandgap of 0.25 eV. The photodetectors exhibit broadband photodetection capability in the visible-infrared (IR) spectrum (405–2200 nm) at room temperature. The maximum values of responsivity can reach up to 280 A W<jats:sup>−1</jats:sup> at the wavelength of 405 nm. Meanwhile, the high responsivity of 63.9 A W<jats:sup>−1</jats:sup> and detectivity of 3.8 × 10<jats:sup>9</jats:sup> Jones are achieved at the wavelength of 2200 nm, respectively. In addition, the obtained Ta<jats:sub>2</jats:sub>NiSe<jats:sub>5</jats:sub>-based photodetector shows excellent flexibility and the photodetection performance is almost insignificantly degraded after 1000 bending cycles. These results indicate that the 2D Ta<jats:sub>2</jats:sub>NiSe<jats:sub>5</jats:sub> semiconductor has great potential in future wearable IR optoelectronic devices.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent experimental observations of current blockades in 2-D material quantum-dot platforms have opened new avenues for spin and valley-qubit processing. Motivated by experimental results, we construct a model capturing the delicate interplay of Coulomb interactions, inter-dot tunneling, Zeeman splittings, and intrinsic spin-orbit coupling in a double quantum dot structure to simulate the Pauli blockades. Analyzing the relevant Fock-subspaces of the generalized Hamiltonian, coupled with the density matrix master equation technique for transport across the setup, we identify the generic class of blockade mechanisms. Most importantly, and contrary to what is widely recognized, we show that conducting and blocking states responsible for the Pauli-blockades are a result of the coupled effect of all degrees of freedom and cannot be explained using the spin or the valley pseudo-spin only. We then numerically predict the regimes where Pauli blockades might occur, and, to this end, we verify our model against actual experimental data and propose that our model can be used to generate data sets for different values of parameters with the ultimate goal of training on a machine learning algorithm. Our work provides an enabling platform for a predictable theory-aided experimental realization of single-shot readout of the spin and valley states on DQDs based on 2D-material platforms.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this letter, we propose a mechanism to control the magnetic properties of topological quantum material (TQM) by using magnetoelectric coupling: this mechanism uses a heterostructure of TQM with two-dimensional (2D) ferroelectric material, which can dynamically control the magnetic order by changing the polarization of the ferroelectric material and induce topological phase transitions. This concept is demonstrated using the example of the bilayer MnBi2Te4 on ferroelectric In2Se3 or In2Te3, where the polarization direction of the 2D ferroelectrics determines the interfacial band alignment and consequently the direction of the charge transfer. This charge transfer, in turn, enhances the stability of the ferromagnetic state of MnBi2Te4 and leads to a topological phase transition between the quantum anomalous Hall (QAH) effect and the zero plateau QAH. Our work provides a route to dynamically alter the magnetic ordering of TQMsand could lead to the discovery of new multifunctional topological heterostructures.&amp;#xD;</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The quantum anomalous Hall (QAH) effect has attracted continuous attention due to its intriguing properties and potential applications in future electronics. Here, we present our investigation of the electronic and topological properties of a square-octagon Sb monolayer with Mo atoms adsorbed (Mo@so-Sb) using first-principles calculations. Our studies reveal how a trivial insulator can be first engineered into an unusual bipolar magnetic semiconductor (BMS) and then further tuned by strain into a spintronics-favorable half semiconductor (HS) or half metal (HM). Remarkably, with 3.7% compressive strain applied, we achieve a QAH state in Mo@so-Sb with a high Chern number (C=4) which is much larger than that (C=±1 or ±2) of the previously predicted Chern insulators. This QAH state is characterized by the appearance of four gapless chiral edge states within the nontrivial band gap, enabling a robust multi-channel low-power-consumption transport. Its nontrivial topology primarily originates from the band inversion between the non-degenerate Mo 4d and Sb 5p orbitals. Additionally, we demonstrate the interesting BMS, HS, and QAH states can be controlled by the Mo adsorption concentrations. Our findings not only provide a versatile means of transforming trivial insulators into the desired spintronics-favorable and topological states, but also open new possibilities for high-performance electronic devices.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a symmetry-based systematic approach to explore the structural and compositional richness of two-dimensional materials. We use a “combinatorial engine” that constructs candidate compounds by occupying all possible Wyckoff positions for a certain space group with combinations of chemical elements. These combinations are restricted by imposing charge neutrality and the Pauling test for electronegativities. The structures are then pre-optimized with a specially crafted universal neural-network force-field, before a final step of geometry optimization using density-functional theory is performed. In this way we unveil an unprecedented variety of two-dimensional materials, covering the whole periodic table in more than 30 different stoichiometries of form A<jats:sub>n</jats:sub>B<jats:sub>m</jats:sub> or A<jats:sub>n</jats:sub>B<jats:sub>m</jats:sub>C<jats:sub>k</jats:sub> . Among the discovered structures, we find examples that can be built by decorating nearly all Platonic and Archimedean tesselations as well as their dual Laves or Catalan tilings. We also obtain a rich, and unexpected, polymorphism for some specific compounds. We further accelerate the exploration of the chemical space of two-dimensional materials by employing machine-learning-accelerated prototype search, based on the structural types discovered in the systematic search. In total, we obtain around 6500 compounds, not present in previous available databases of 2D materials, with a distance to the convex hull of thermodynamic stability smaller than 250 meV/atom.</jats:p>