Catálogo de publicaciones - revistas

<jats:p>Degradation of a-InGaZnO thin-film transistors working under simultaneous DC gate and drain bias stress is investigated, and the corresponding degradation mechanism is proposed and verified. The maximum degradation occurs under the bias stress condition that makes the electric field and electron concentration relatively high at the same time. Trapping of hot electrons in the etching-stop layer under the extended drain electrode is proven to be the underlying mechanism. The observed degradation phenomena, including distortion in the transfer curve on a logarithmic scale and two-slope dependence on gate bias on a linear scale, current crowding in the output curve, and smaller degradation in transfer curves measured under large drain bias, can all be well explained with the proposed degradation mechanism.</jats:p>

<jats:p>We report a novel two-step ambient pressure chemical vapor deposition (CVD) pathway to grow high-quality MoS<jats:sub>2</jats:sub> monolayer on the SiO<jats:sub>2</jats:sub> substrate with large crystal size up to 110 μm. The large specific surface area of the pre-synthesized MoO<jats:sub>3</jats:sub> flakes on the mica substrate compared to MoO<jats:sub>3</jats:sub> powder could dramatically reduce the consumption of the Mo source. The electronic information inferred from the four-probe scanning tunneling microscope (4P-STM) image explains the threshold voltage variations and the n-type behavior observed in the two-terminal transport measurements. Furthermore, the direct van der Pauw transport also confirms its relatively high carrier mobility. Our study provides a reliable method to synthesize high-quality MoS<jats:sub>2</jats:sub> monolayer, which is confirmed by the direct 4P-STM measurement results. Such methodology is a key step toward the large-scale growth of transition metal dichalcogenides (TMDs) on the SiO<jats:sub>2</jats:sub> substrate and is essential to further development of the TMDs-related integrated devices.</jats:p>

<jats:p>The paper employs the principles of graph theory in nanobiophotonics, where the soot-assisted intra-pigmental energy transport in leaves is unveiled through the laser-induced thermal lens (TL) technique. Nanofluids with different soot concentrations are sprayed over Lablab purpureus (L) sweet leaves, and the extracted pigments are analyzed. The graph features of the constructed complex network from the TL signal of the samples are analyzed to understand their variations with optical absorbance. Besides revealing the presence of optimum soot concentration that can enhance photosynthesis, the study brings out the potential application of graph features in nanobiophotonics.</jats:p>

<jats:p>To reduce the energy demand and operation cost for circular electron positron collider (CEPC), the high efficiency klystrons are being developed at Institute of High Energy Physics, Chinese Academy of Sciences. A 800-kW continuous wave (CW) klystron operating at frequency of 650-MHz has been designed. The results of beam–wave interaction simulation with several different codes are presented. The efficiency is optimized to be 65% with a second harmonic cavity in three-dimensional (3D) particle-in-cell code CST. The effect of cavity frequency error and mismatch load on efficiency of klystron have been investigated. The design and cold test of reentrant cavities are described, which meet the requirements of RF section design. So far, the manufacturing and high-power test of the first klystron prototype have been completed. When the gun operated at DC voltage of 80 kV and current of 15.4 A, the klystron peak power reached 804 kW with output efficiency of about 65.3% at 40% duty cycle. The 1-dB bandwidth is ±0.8 MHZ. Due to the crack of ceramic window, the CW power achieved about 700 kW. The high-power test results are in good agreement with 3D simulation.</jats:p>

<jats:p>We use single-molecule FRET and newly-developed D-loop techniques to investigate strand displacement activity of Klenow fragment (exo-) of DNA polymerase I in DNA sequences rich in guanine and cytosine (GC) bases. We find that there exist in the FRET traces numerous ascending jumps, which are induced by the backsliding of Klenow fragment on DNA chains. Our measurements show that the probability of backsliding is closely related to the GC-richness and dNTP concentration: increasing the GC-richness leads to an increase in the backsliding probability, and increasing the dNTP concentration however leads to a decrease in the backsliding probability. These results provide a new insight into the mechanism of DNA polymerase I.</jats:p>

<jats:p>Monolithic perovskite/Si tandem solar cells (TSCs) have experienced rapid development in recent years, demonstrating its potential to exceed the Shockley–Queisser limit of single junction Si solar cells. Unlike typical organic-inorganic hybrid perovskite/silicon heterojunction TSCs, here we propose CsPbI<jats:sub>3</jats:sub>/TOPCon TSC, which is a promising architecture in consideration of its pleasurable thermal stability and good compatibility with current PERC production lines. The optical performance of CsPbI<jats:sub>3</jats:sub>/TOPCon TSCs is simulated by the combination of ray-tracing method and transfer matrix method. The light management of the CsPbI<jats:sub>3</jats:sub>/TOPCon TSC begins with the optimization of the surface texture on Si subcell, indicating that a bifacial inverted pyramid with a small bottom angle of rear-side enables a further minimization of the optical losses. Current matching between the subcells, as well as the parasitic absorption loss from the front transparent conductive oxide, is analyzed and discussed in detail. Finally, an optimized configuration of CsPbI<jats:sub>3</jats:sub>/TOPCon TSC with a 31.78% power conversion efficiency is proposed. This work provides a practical guidance for approaching high-efficiency perovskite/Si TSCs.</jats:p>

<jats:p>Iron oxides are widely found as ores in Earth’s crust and are also important constituents of its interiors. Their polymorphism, composition changes, and electronic structures play essential roles in controlling the structure and geodynamic properties of the solid Earth. While all-natural occurring iron oxides are semiconductors or insulators at ambient pressure, they start to metalize under pressure. Here in this work, we review the electronic conductivity and metallization of iron oxides under high-pressure conditions found in Earth’s lower mantle. We summarize that the metallization of iron oxides is generally controlled by the pressure-induced bandgap closure near the Fermi level. After metallization, they possess much higher electrical and thermal conductivity, which will facilitate the thermal convection, support a more stable and thicker D″ layer, and formulate Earth’s magnetic field, all of which will constrain the large-scale dynamos of the mantle and core.</jats:p>

<jats:p>Magnetic reconnection underlies the physical mechanism of explosive phenomena in the solar atmosphere and planetary magnetospheres, where plasma is usually collisionless. In the standard model of collisionless magnetic reconnection, the diffusion region consists of two substructures: an electron diffusion region is embedded in an ion diffusion region, in which their scales are based on the electron and ion inertial lengths. In the ion diffusion region, ions are unfrozen in the magnetic fields while electrons are magnetized. The resulted Hall effect from the different motions between ions and electrons leads to the production of the in-plane currents, and then generates the quadrupolar structure of out-of-plane magnetic field. In the electron diffusion region, even electrons become unfrozen in the magnetic fields, and the reconnection electric field is contributed by the off-diagonal electron pressure terms in the generalized Ohm’s law. The reconnection rate is insensitive to the specific mechanism to break the frozen-in condition, and is on the order of 0.1. In recent years, the launching of Cluster, THEMIS, MMS, and other spacecraft has provided us opportunities to study collisionless magnetic reconnection in the Earth’s magnetosphere, and to verify and extend more insights on the standard model of collisionless magnetic reconnection. In this paper, we will review what we have learned beyond the standard model with the help of observations from these spacecraft as well as kinetic simulations.</jats:p>

<jats:p>We employ the Dirac cone model to explore the high Chern number (<jats:italic>C</jats:italic>) phases that are realized in the magnetic-doped topological insulator (TI) multilayer structures by Zhao <jats:italic>et al.</jats:italic> [<jats:italic>Nature</jats:italic> <jats:bold>588</jats:bold> 419 (2020)]. The Chern number is calculated by capturing the evolution of the phase boundaries with the parameters, then the Chern number phase diagrams of the TI multilayer structures are obtained. The high-<jats:italic>C</jats:italic> behavior is attributed to the band inversion of the renormalized Dirac cones, along with which the spin polarization at the <jats:italic>Γ</jats:italic> point will get increased. Moreover, another two TI multilayer structures as well as the TI superlattice structures are studied.</jats:p>

<jats:p>Subcycle spectral structures and dynamics of high-order harmonic generation (HHG) processes of atoms and molecules driven by intense laser fields on the attosecond time scale have been originally studied theoretically and experimentally. However, the time scale of HHG dynamics in crystals is in the order of sub-femtosecond, and the carrier dynamics of HHG in crystals driven by subcycle laser pulses are largely unexplored. Here we perform a theoretical study of subcycle structures, spectra, and dynamics of HHG of crystals in mid-infrared laser fields subject to excitation by a subcycle laser pulse with a time delay. The HHG spectra as a function of time delay between two laser fields are calculated by using a single-band model for the intra-band carrier dynamics in crystal momentum space and by solving the time-dependent Schrödinger equation in velocity gauge for the treatment of multi-band crystal systems. The results exhibit a complex time-delay-dependent oscillatory pattern, and the enhancement and suppression of the HHG related to subcycle pulse are observed at the given time delay in either single-band or multi-band crystal systems. To understand oscillation structures with respect to the dependence for the subcycle laser fields, the time-frequency characteristics of the HHG as well as the probability density distribution of the radiation are analyzed in detail.</jats:p>