Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The phase transitions among the high-pressure polymorphic forms of CaCO<jats:sub>3</jats:sub> (cc-I, -II, -III, and -IIIb) were investigated by dynamic diamond anvil cell (dDAC) and <jats:italic>in situ</jats:italic> Raman spectroscopy. Experiments were carried out at room temperature and high pressures up to 12.8 GPa with the pressurizing rate varied from 0.006 to 0.056 GPa/s. <jats:italic>In situ</jats:italic> observation shows that with the increase of pressure, calcite transforms from cc-I to cc-II at ~1.5 GPa and from cc-II to cc-III at ~2.5 GPa, and transitions are independent of the pressurizing rate. Further, as the pressure continues to increase, cc-IIIb begins to appear and coexists with cc-III within a pressure range that is inversely correlated to the pressurizing rate. At the pressurizing rates of 0.006, 0.012, 0.021, and 0.056 GPa/s, the coexistence pressure ranges of cc-III and cc-IIIb are 2.8-9.8, 3.1-6.9, 2.7-6.0, and 2.8-4.5 GPa, respectively. The dependence of the coexistence on pressurizing rate may result from the influence of pressurizing rate on activation process of transition by reducing energy barrier. The higher the pressurizing rate, the lower the energy barrier, and the easier it is to pull the system out of the coexistence state. The results of this <jats:italic>in situ</jats:italic> study provide new insights into understanding the phase transition of calcite.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-quality Sr<jats:sub>2</jats:sub>CrWO<jats:sub>6</jats:sub> (SCWO) films have been grown on SrTiO<jats:sub>3</jats:sub> (STO) substrate by pulsed laser deposition under low oxygen pressure. With decrease of the film thickness, a drastic conductivity increase is observed. The Hall measurements show that the thicker the film, the lower the carrier density. An extrinsic mechanism of charge doping due to the dominance of oxygen vacancies at SCWO/STO interfaces is proposed. The distribution and gradient of carrier concentration in SCWO films are considered to be related to this phenomenon. Resistivity behavior observed in these films is found to follow the variable range hopping model. It is revealed that with increase of the film thickness, the extent of disorder in the lattice increases, which gives a clear evidence of disorder-induced localization charge carriers in these films. Magnetoresistance measurements show that there is a negative magnetoresistance in SCWO films, which is considered to be caused by the magnetic scattering of magnetic elements Cr<jats:sup>3+</jats:sup> and W<jats:sup>5+</jats:sup>. In addition, a sign reversal of anisotropic magnetoresistance (<jats:italic>AMR</jats:italic>) in SCWO film is observed for the first time, when the temperature varies across a characteristic value, <jats:italic>T</jats:italic> <jats:sub> <jats:italic>M</jats:italic> </jats:sub>. Magnetization-temperature measurements demonstrate that this <jats:italic>AMR</jats:italic> sign reversal is caused by the direction transition of easy axis of magnetization from the in-plane ferromagnetic order at <jats:italic>T</jats:italic> &amp;#62; <jats:italic>T</jats:italic> <jats:sub> <jats:italic>M</jats:italic> </jats:sub> to the out-of-plane at <jats:italic>T</jats:italic> &amp;#60; <jats:italic>T</jats:italic> <jats:sub> <jats:italic>M</jats:italic> </jats:sub>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The important applications of quantum dot system are to implement logic operations and achieve universal quantum computing based on different quantum nonlocalities. Here, we characterize the quantum steering, Bell nonlocality, and nonlocal advantage of quantum coherence (NAQC) of quantum dot system suffering from nonunital and unital channels. The results reveal that quantum steering, Bell nonlocality, and NAQC can display the traits of dissipation, enhancement and freezing. One can achieve the detections of quantum steering, Bell nonlocality, and NAQC of quantum dot system in different situations. Among these quantum nonlocalities, NAQC is the most fragile, and it is most easily influenced by different system parameters. Furthermore, considering quantum dot system coupling with amplitude damping channel and phase damping channel, these quantum nonlocalities degenerate with the enlargement of the channel parameters <jats:italic>t</jats:italic> and Γ. Remarkably, measurement reversal can effectively control and enhance quantum steering, Bell nonlocality, and NAQC of quantum dot system suffering from decoherence, especially in the scenarios of the amplitude damping channel and strong operation strength.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A high-performance terahertz Schottky Barrier Diode (SBD) with an inverted trapezoidal epitaxial cross-section structure featuring high varactor characteristics and reverse breakdown characteristics is reported in this paper. Inductively coupled plasma dry etching and dissolution wet etching are used to define the profile of the epitaxial layer, by which the voltage-dependent variation trend of the thickness of the metal-semiconductor contact depletion layer is modified. The simulation of the inverted trapezoidal epitaxial cross-section SBD is also proposed, to explain the physical mechanism of electric field and space charge region area. Compared with the normal structure, the grading coefficient <jats:italic>M</jats:italic> increased from 0.47 to 0.52, and the capacitance modulation ratio (<jats:italic>C</jats:italic> <jats:sub>max</jats:sub>/<jats:italic>C</jats:italic> <jats:sub>min</jats:sub>) increased from 6.70 to 7.61. Inverted trapezoidal epitaxial cross-section structure is a promising approach to improve the Variable-capacity ratio by eliminating the accumulation of charge at the Schottky electrode edge. A 190 GHz frequency doubler based on inverted trapezoidal epitaxial cross-section SBD also shows a doubling efficiency of 35% compared to a normal SBD of 30%.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The repetitive unclamped inductive switching (UIS) avalanche stress are conducted to investigate the degradation and breakdown behaviors of conventional shield gate trench MOSFET (C-SGT) and P-ring SGT MOSFETs (P-SGT). It is found that the static and dynamic parameters of both devices show different degrees of degradation. Combining experimental and simulation results, the hot holes trapped into the Si/SiO<jats:sub>2</jats:sub> interface and the increase of crystal lattice temperature should be responsible for the degradation and breakdown behaviors. Moreover, under repetitive UIS avalanche stress, the reliability of P-SGT overcomes that of C-SGT, benefitting from the decreasing of the impact ionization rate at bottom of field oxide caused by the existence of P-ring.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this article, a novel 1200 V SiC super-junction (SJ) MOSFET with a partially widened pillar structure is proposed and investigated by using the two-dimensional numerical simulation tool. Based on the SiC SJ MOSFET structure, a partially widened P-region is added at the SJ pillar region to improve the short-circuit (SC) ability. After investigating the position and doping concentration of the widened P-region, an optimal structure is determined. From the simulation results, the SC withstand times (<jats:italic>SCWT</jats:italic>) of the conventional trench MOSFET (CT-MOSFET), the SJ MOSFET, and the proposed structure at 800 V DC bus voltage are 15 μs, 17 μs, and 24 μs, respectively. The <jats:italic>SCWT</jats:italic> of the proposed structure increased by 60 % and 41.2 % in comparison with that of the other two structures. The main reason for the proposed structure with an enhanced SC capability is related to the effective suppression of saturation current at the high DC bias conditions by using a modulated P-pillar region. Meanwhile, a good <jats:italic>Baliga’s FOM</jats:italic> (<jats:italic>BV</jats:italic> <jats:sup>2</jats:sup>/<jats:italic>R</jats:italic> <jats:sub>on</jats:sub>) also can be achieved in the proposed structure due to the advantage of the SJ structure. In addition, the fabrication technology of the proposed structure is compatible with the standard epitaxy growth method used in the SJ MOSFET. As a result, the SJ structure with this feasible optimization skill presents an effect on improving the SC reliability of the SiC SJ MOSFET without the degeneration of the <jats:italic>Baliga’s FOM</jats:italic>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Microplastic pollution has already been a global environmental concern. It was reported that microplastics are easily accessible to a wide range of aquatic organisms and ultimately enter the human body along the food chain. They pose a severe threat to ecosystems, organisms, even human health due to their durability and persistence. However, how to reduce the microplastic pollution still remains a challenge in terms of scientific techniques and policy-making. There is still a lack of effective methods for microplastic recycling and removing currently. Luckily, a new technique of micro-nanobubbles (MNBs) may provide a possible and highly effective method to enrich the microplastic pollution via their great advantages<jats:sup>[1]</jats:sup>: higher specific surface area, longer lifetime and easier to absorb microplastics of the same size and hydrophobicity. Then they further absorb on larger bubbles such as microbubbles or millimeter bubbles, to float on the water surface together. In this study, we presented a new method, using MNBs to enrich the microplastic pollution with higher efficiency. Two types of microplastics, millimeter-scale plastic fragments and microplastic particles, were chosen as the model systems of microplastic pollution to study the enrichment efficiency of MNBs on the microplastics. Results showed that MNBs can efficiently enrich the microplastics. The enrichment efficiency would increase with the flotation time until reaching the maximum value. It was proved that MNBs not only collect the microplastic pollution but also reduce the detergent used in domestic laundry sewage. This is because detergent as a surfactant easily absorbs on the surface of micro-nanobubbles and could be collected together with microplastic pollution. Our research demonstrated that MNBs technique could be a promising candidate for microplastic recycling and reduce the pollution of detergent in daily life.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using an improved Bridgman method, 0.3 mol%Tm<jats:sup>3+</jats:sup>/0.6 mol%Tb<jats:sup>3+</jats:sup>/y mol%Eu<jats:sup>3+</jats:sup>(y=0, 0.4, 0.6, 0.8) doped Na<jats:sub>5</jats:sub>Y<jats:sub>9</jats:sub>F<jats:sub>32</jats:sub> single crystals were prepared. The X-ray diffractions, excitation spectra, emission spectra and fluorescence decay curves were used to explore crystal structure and optical performance of the obtained samples. When excited by 362 nm light, the cool white emission was realized from Na<jats:sub>5</jats:sub>Y<jats:sub>9</jats:sub>F<jats:sub>32</jats:sub> single crystal triply-doped 0.3 mol% Tm<jats:sup>3+</jats:sup>/0.6 mol% Tb<jats:sup>3+</jats:sup>/0.8 mol% Eu<jats:sup>3+</jats:sup>, in which the CIE coordinate was (0.2995, 0.3298) and the correlated color temperature (CCT) was 6586 K. The integrated normalized emission intensity of the tri-doped single crystal at 448 K can keep 62% of that 298 K. The internal quantum yield (QY) was calculated to be ~ 15.16% by integrating spheres. These results suggested that the single crystals tri-doped Tm<jats:sup>3+</jats:sup>, Tb<jats:sup>3+</jats:sup> and Eu<jats:sup>3+</jats:sup>ions have a promising potential application for white light-emitting diodes (w-LEDs).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>To alleviate the greenhouse effect and maintain sustainable development, it is of great significance to find an efficient and low-cost catalyst to reduce carbon dioxide (CO<jats:sub>2</jats:sub>) and generate formic acid (FA). In this work, based on the first-principles calculation, the catalytic performance of a single transition metal (TM) (TM = Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Ir, Pt, Au, Hg) atom anchored on C<jats:sub>9</jats:sub>N<jats:sub>4</jats:sub> monolayer (TM@C<jats:sub>9</jats:sub>N<jats:sub>4</jats:sub>) for the hydrogenation of CO<jats:sub>2</jats:sub> to FA is calculated. The results show that single TM atom doping in C<jats:sub>9</jats:sub>N<jats:sub>4</jats:sub> can form a stable TM@C<jats:sub>9</jats:sub>N<jats:sub>4</jats:sub> structure, and Cu@C<jats:sub>9</jats:sub>N<jats:sub>4</jats:sub> and Co@C<jats:sub>9</jats:sub>N<jats:sub>4</jats:sub> show better catalytic performance in the process of CO<jats:sub>2</jats:sub> hydrogenation to FA (the corresponding maximum energy barriers are 0.41 eV and 0.43 eV, respectively). The partial density of states (PDOS), projected crystal orbital Hamilton population (pCOHP), difference charge density analysis and Bader charge analysis demonstrate that the TM atom plays an important role in reaction. The strong interaction between the 3<jats:italic>d</jats:italic> orbitals of TM atom and the non-bonding orbitals (1<jats:italic>π</jats:italic> <jats:sub> <jats:italic>g</jats:italic> </jats:sub>) of CO<jats:sub>2</jats:sub> allows the reaction to proceed under mild conditions. In general, our results show that Cu@C<jats:sub>9</jats:sub>N<jats:sub>4</jats:sub> and Co@C<jats:sub>9</jats:sub>N<jats:sub>4</jats:sub> are a promising single-atom catalyst and can be used as the non-precious metals electrocatalyst for CO<jats:sub>2</jats:sub> hydrogenation to formic acid.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, by optimizing the V/III beam-equivalent pressure ratio, a high-quality InAs/GaSb type-II superlattice material for the long-wavelength infrared range is achieved by molecular beam epitaxy (MBE). High-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectrometer were used to characterize the material growth quality. The results show that the full width at half maximum (FWHM) of the superlattice zero-order diffraction peak, the mismatching of the superlattice zero-order diffraction peak between the substrate diffraction peaks, and the surface roughness get the best results when the BEP ratio reach the optimal value, which are 28 arcsec, 13 arcsec and 1.63 Å, respectively. The intensity of the zero-order diffraction peak is strongest at the optimal value. The relative spectral response of the LWIR detector shows that it exhibits a 100% cut-off wavelength of 12.6 μm at 77 K. High-quality epitaxial materials have laid a good foundation for preparing high-performance LWIR detector.</jats:p>