Catálogo de publicaciones - revistas

<jats:p>Amorphous Ti–Cu–Zr–Ni alloys with minor addition of Sn and Al were prepared by melt spinning technique. The effects of Sn and Al additions on the microstructures and mechanical properties of glassy ribbons were investigated. The amorphous state of ribbons was confirmed by x-ray diffraction and transmission electron microscopy, where those ribbons with Sn addition exhibited a fully amorphous state. The characteristic temperature indicates that Ti<jats:sub>45</jats:sub>Cu<jats:sub>35</jats:sub>Zr<jats:sub>10</jats:sub>Ni<jats:sub>5</jats:sub>Sn<jats:sub>5</jats:sub> alloy has a stronger glass-forming ability, as proven by differential scanning calorimetry. Ti<jats:sub>45</jats:sub>Cu<jats:sub>35</jats:sub>Zr<jats:sub>10</jats:sub>Ni<jats:sub>5</jats:sub>Al<jats:sub>5</jats:sub> alloy showed a better hardness of 9.23 GPa and elastic modulus of 127.15 GPa and good wear resistance. Ti<jats:sub>45</jats:sub>Cu<jats:sub>35</jats:sub>Zr<jats:sub>10</jats:sub>Ni<jats:sub>5</jats:sub>Sn<jats:sub>5</jats:sub> alloy displayed a pop-in event related to discrete plasticity according to nanoindentation. When the temperature is below 560 K, Ti<jats:sub>45</jats:sub>Cu<jats:sub>35</jats:sub>Zr<jats:sub>10</jats:sub>Ni<jats:sub>5</jats:sub>Sn<jats:sub>5</jats:sub> alloy mainly exhibits elasticity. When the temperature rises between 717 K and 743 K, it shows a significant increase in elasticity but decrease in viscoelasticity after the ribbon experiences the main relaxation at 717 K. When the temperature is above 743 K, the ribbon shows viscoplasticity.</jats:p>

<jats:p>We report a catalyst-free growth of Cu nanocrystals on ionic liquid surfaces by thermal evaporation method at room temperature. After deposition of Cu on ionic liquid surfaces, ramified Cu aggregates form. It is found that the aggregates are composed of both granules and nanocrystals with triangular or hexagonal appearances. The sizes of the nanocrystals are in the range of tens to hundreds of nanometers and increase with the nominal deposition thickness. The growth mechanism of the Cu aggregates and nanocrystals is presented.</jats:p>

<jats:p>Few-layer two-dimensional (2D) semiconductor nanosheets with a layer-dependent band gap are attractive building blocks for large-area thin-film electronics. A general approach is developed to fast prepare uniform and phase-pure 2H-WSe<jats:sub>2</jats:sub> semiconducting nanosheets at a large scale, which involves the supercritical carbon dioxide (SC-CO<jats:sub>2</jats:sub>) treatment and a mild sonication-assisted exfoliation process in aqueous solution. The as-prepared 2H-WSe<jats:sub>2</jats:sub> nanosheets preserve the intrinsic physical properties and intact crystal structures, as confirmed by Raman, x-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscope (STEM). The uniform 2H-WSe<jats:sub>2</jats:sub> nanosheets can disperse well in water for over six months. Such good dispersivity and uniformity enable these nanosheets to self-assembly into thickness-controlled thin films for scalable fabrication of large-area arrays of thin-film electronics. The electronic transport and photoelectronic properties of the field-effect transistor based on the self-assembly 2H-WSe<jats:sub>2</jats:sub> thin film have also been explored.</jats:p>

<jats:p>Mg<jats:sub>3</jats:sub>Sb<jats:sub>1.5</jats:sub>Bi<jats:sub>0.5</jats:sub>-based alloys have received much attention, and current reports on this system mainly focus on the modulation of doping. However, there lacks the explanation for the choice of Mg<jats:sub>3</jats:sub>Sb<jats:sub>1.5</jats:sub>Bi<jats:sub>0.5</jats:sub> as matrix. Here in this work, the thermoelectric properties of Mg<jats:sub>3</jats:sub>Sb<jats:sub>2−<jats:italic>x</jats:italic> </jats:sub>Bi<jats:sub> <jats:italic>x</jats:italic> </jats:sub> (0.4 ≤ <jats:italic>x</jats:italic> ≤ 0.55) compounds are systematically investigated by using the first principles calculation combined with experiment. The calculated results show that the band gap decreases after Bi has been substituted for Sb site, which makes the thermal activation easier. The maximum figure of merit (<jats:italic>ZT</jats:italic>) is 0.27 at 773 K, which is attributed to the ultra-low thermal conductivity 0.53 W·m<jats:sup>−1</jats:sup>·K<jats:sup>−1</jats:sup> for <jats:italic>x</jats:italic> = 0.5. The large mass difference between Bi and Sb atoms, the lattice distortion induced by substituting Bi for Sb, and the nanoscale Bi-rich particles distributed on the matrix are responsible for the reduction of thermal conductivity. The introduction of Bi into Mg<jats:sub>3</jats:sub>Sb<jats:sub>2</jats:sub>-based materials plays a vital role in regulating the transport performance of thermoelectric materials.</jats:p>

<jats:p>The idea of replacing traditional silicon-based electronic components with the ones assembled by organic molecules to further scale down the electric circuits has been attracting extensive research focuses. Among the molecularly assembled components, the design of molecular logic gates with simple structure and high Boolean computing speed remains a great challenge. Here, by using the state-of-the-art nonequilibrium Green’s function theory in conjugation with first-principles method, the spin transport properties of single-molecule junctions comprised of two serially connected transition metal dibenzotetraaza[14]annulenes (TM(DBTAA), TM = Fe, Co) sandwiched between two single-walled carbon nanotube electrodes are theoretically investigated. The numerical results show a close dependence of the spin-resolved current-voltage characteristics on spin configurations between the left and right molecular kernels and the kind of TM atom in TM(DBTAA) molecule. By taking advantage of spin degree of freedom of electrons, NOR or XNOR Boolean logic gates can be realized in Fe(DBTAA) and Co(DBTAA) junctions depending on the definitions of input and output signals. This work proposes a new kind of molecular logic gates and hence is helpful for further miniaturization of the electric circuits.</jats:p>

<jats:p>We experimentally evaluated the interface state density of GaN MIS-HEMTs during time-dependent dielectric breakdown (TDDB). Under a high forward gate bias stress, newly increased traps generate both at the SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub>/AlGaN interface and the SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub> bulk, resulting in the voltage shift and the increase of the voltage hysteresis. When prolonging the stress duration, the defects density generated in the SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub> dielectric becomes dominating, which drastically increases the gate leakage current and causes the catastrophic failure. After recovery by UV light illumination, the negative shift in threshold voltage (compared with the fresh one) confirms the accumulation of positive charge at the SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub>/AlGaN interface and/or in SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub> bulk, which is possibly ascribed to the broken bonds after long-term stress. These results experimentally confirm the role of defects in the TDDB of GaN-based MIS-HEMTs.</jats:p>

<jats:p>We report capacitive coupling induced Kondo–Fano (K–F) interference in a double quantum dot (DQD) by systematically investigating its low-temperature properties on the basis of hierarchical equations of motion evaluations. We show that the interdot capacitive coupling <jats:italic>U</jats:italic> <jats:sub>12</jats:sub> splits the singly-occupied (S-O) state in quantum dot 1 (QD1) into three quasi-particle substates: the unshifted S-O<jats:sub>0</jats:sub> substate, and elevated S-O<jats:sub>1</jats:sub> and S-O<jats:sub>2</jats:sub>. As <jats:italic>U</jats:italic> <jats:sub>12</jats:sub> increases, S-O<jats:sub>2</jats:sub> and S-O<jats:sub>1</jats:sub> successively cross through the Kondo resonance state at the Fermi level (<jats:italic>ω</jats:italic> = 0), resulting in the so-called Kondo-I (KI), K–F, and Kondo-II (KII) regimes. While both the KI and KII regimes have the conventional Kondo resonance properties, remarkable Kondo–Fano interference features are shown in the K–F regime. In the view of scattering, we propose that the phase shift <jats:italic>η</jats:italic>(<jats:italic>ω</jats:italic>) is suitable for analysis of the Kondo–Fano interference. We present a general approach for calculating <jats:italic>η</jats:italic>(<jats:italic>ω</jats:italic>) and applying it to the DQD in the K–F regime where the two maxima of <jats:italic>η</jats:italic>(<jats:italic>ω</jats:italic> = 0) characterize the interferences between the Kondo resonance state and S-O<jats:sub>2</jats:sub> and S-O<jats:sub>1</jats:sub> substates, respectively.</jats:p>

<jats:p>We investigate the dynamic quantities: momentum, spin and orbital angular momenta (SAM and OAM), and their conversion relationship in the structured optical fields at subwavelength scales, where the spin–orbit interaction (SOI) plays a key role and determines the behaviors of light. Specifically, we examine a nanostructure of a Ag nanoparticle (Ag NP) attached on a cylindrical Ag nanowire (Ag NW) under illumination of elliptically polarized light. These dynamic quantities obey the Noether theorem, i.e., for the Ag nanoparticle with spherical symmetry, the total angular momentum consisting of SAM and OAM conserves; for the Ag NW with translational symmetry, the orbital momentum conserves. Meanwhile, the spin-to-orbital angular momentum conversion is mediated by SOI arising from the spatial variation of the optical potential. In this nanostructure, the conservation of momentum imposes a strict restriction on the propagation direction of the surface plasmon polaritons along the Ag NW. Meanwhile, the orbital momentum is determined by the polarized properties of the excitation light and the topography of the Ag NP. Our work offers insights to comprehend the light behaviors in the structured optical fields in terms of the dynamic quantities and benefits to the design of optical nano-devices based on interactions between spin and orbital degrees of freedom.</jats:p>

<jats:p>We investigate symmetrically coupled double quantum dots via the hierarchical equations of motion method and propose a novel zero-energy mode (ZEM) at a temperature above the spin singlet–triplet transition temperature. Owing to the resonance of electron quasi-particle and hole quasi-particle, ZEM has a peak at ω = 0 in the spectral density function. We further examine the effect of the magnetic field on the ZEM, where an entanglement of spin and charge has been determined; therefore, the magnetic field can split the ZEM in the spectra.</jats:p>

<jats:p>A single baffle metal–insulator–metal (MIM) waveguide coupled with a semi-circular cavity and a cross-shaped cavity is proposed based on the multiple Fano resonance characteristics of surface plasmon polaritons (SPPs) subwavelength structure. The isolated state formed by two resonators interferes with the wider continuous state mode formed by the metal baffle, forming Fano resonance that can independently be tuned into five different modes. The formation mechanism of Fano resonance is analyzed based on the multimode interference coupled mode theory (MICMT). The finite element method (FEM) and MICMT are used to simulate the transmission spectra of this structure and analyze the influence of structural parameters on the refractive index sensing characteristics. And the transmission responses calculated by the FEM simulation are consistent with the MICMT theoretical results very well. The results show that the figure of merit (FOM) can reach 193 and the ultra-high sensitivity is 1600 nm/RIU after the structure parameters have been optimized, and can provide theoretical basis for designing the high sensitive refractive index sensors based on SPPs waveguide for high-density photonic integration with excellent performance in the near future.</jats:p>