Catálogo de publicaciones - revistas

<jats:p>Crystallization of diamond with different nitrogen concentrations was carried out with a FeNiCo–C system at pressure of 6.5 GPa. As the nitrogen concentration in diamond increased, the color of the synthesized diamond crystals changed from colorless to yellow and finally to atrovirens (a dark green). All the Raman peaks for the obtained crystals were located at about 1330 cm<jats:sup>−1</jats:sup> and contained only the sp<jats:sup>3</jats:sup> hybrid diamond phase. Based on Fourier transform infrared results, the nitrogen concentration of the colorless diamond was &lt; 1 ppm and absorption peaks corresponding to nitrogen impurities were not detected. However, the C-center nitrogen concentration of the atrovirens diamond reached 1030 ppm and the value of A-center nitrogen was approximately 180 ppm with a characteristic absorption peak at 1282 cm<jats:sup>−1</jats:sup>. Furthermore, neither the NV<jats:sup>0</jats:sup> nor the NV<jats:sup>−</jats:sup> optical color center existed in diamond crystal with nitrogen impurities of less than 1 ppm by photoluminescence measurement. However, Ni-related centers located at 695 nm and 793.6 nm were observed in colorless diamond. The NE8 color center at 793.6 nm has more potential for application than the common NV centers. NV<jats:sup>0</jats:sup> and NV<jats:sup>−</jats:sup> optical color centers coexist in diamond without any additives in the synthesis system. Importantly, only the NV<jats:sup>−</jats:sup> color center was noticed in diamond with a higher nitrogen concentration, which maximized optimization of the NV<jats:sup>−</jats:sup>/NV<jats:sup>0</jats:sup> ratio in the diamond structure. This study has provided a new way to prepare diamond containing only NV<jats:sup>−</jats:sup> optical color centers.</jats:p>

<jats:p>Vertically stacked heterostructures have received extensive attention because of their tunable electronic structures and outstanding optical properties. In this work, we study the structural, electronic, and optical properties of vertically stacked GaS–SnS<jats:sub>2</jats:sub> heterostructure under the frame of density functional theory. We find that the stacked GaS–SnS<jats:sub>2</jats:sub> heterostructure is a semiconductor with a suitable indirect band gap of 1.82 eV, exhibiting a type-II band alignment for easily separating the photo-generated carriers. The electronic properties of GaS–SnS<jats:sub>2</jats:sub> heterostructure can be effectively tuned by an external strain and electric field. The optical absorption of GaS–SnS<jats:sub>2</jats:sub> heterostructure is more enhanced than those of the GaS monolayer and SnS<jats:sub>2</jats:sub> monolayer in the visible light region. Our results suggest that the GaS–SnS<jats:sub>2</jats:sub> heterostructure is a promising candidate for the photocatalyst and photoelectronic devices in the visible light region.</jats:p>

<jats:p>We study the thermal and electronic transport properties as well as the thermoelectric (TE) performance of three two-dimensional (2D) <jats:italic>X</jats:italic>I<jats:sub>2</jats:sub> (<jats:italic>X</jats:italic> = Ge, Sn, Pb) bilayers using density functional theory and Boltzmann transport theory. We compared the lattice thermal conductivity, electrical conductivity, Seebeck coefficient, and dimensionless figure of merit (<jats:italic>ZT</jats:italic>) for the <jats:italic>X</jats:italic>I<jats:sub>2</jats:sub> monolayers and bilayers. Our results show that the lattice thermal conductivity at room temperature for the bilayers is as low as ∼1.1 W⋅m<jats:sup>−1</jats:sup>⋅K<jats:sup>−1</jats:sup>–1.7 W⋅m<jats:sup>−1</jats:sup>⋅K<jats:sup>−1</jats:sup>, which is about 1.6 times as large as the monolayers for all the three materials. Electronic structure calculations show that all the <jats:italic>X</jats:italic>I<jats:sub>2</jats:sub> bilayers are indirect-gap semiconductors with the band gap values between 1.84 eV and 1.96 eV at PBE level, which is similar as the corresponding monolayers. The calculated results of <jats:italic>ZT</jats:italic> show that the bilayer structures display much less direction-dependent TE efficiency and have much larger n-type <jats:italic>ZT</jats:italic> values compared with the monolayers. The dramatic difference between the monolayer and bilayer indicates that the inter-layer interaction plays an important role in the TE performance of <jats:italic>X</jats:italic>I<jats:sub>2</jats:sub>, which provides the tunability on their TE characteristics.</jats:p>

<jats:p>Thermoelectric devices (TEDs), including thermoelectric generators (TEGs) and thermoelectric coolers (TECs) based on the Seebeck and Peltier effects, respectively, are capable of converting heat directly into electricity and vice versa. Tough suffering from low energy conversion efficiency and relatively high capital cost, TEDs have found niche applications, such as the remote power source for spacecraft, solid-state refrigerators, waste heat recycling, and so on. In particular, on-chip integrable micro thermoelectric devices (μ-TEDs), which can realize local thermal management, on-site temperature sensing, and energy harvesting under minor temperature gradient, could play an important role in biological sensing and cell cultivation, self-powered Internet of Things (IoT), and wearable electronics. In this review, starting from the basic principles of thermoelectric devices, we summarize the most critical parameters for μ-TEDs, design guidelines, and most recent advances in the fabrication process. In addition, some innovative applications of μ-TEDs, such as in combination with microfluidics and photonics, are demonstrated in detail.</jats:p>

<jats:p>Lateral <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> Schottky barrier diodes (SBDs) each are fabricated on an unintentionally doped (-201) n-type <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> single crystal substrate by designing L-shaped electrodes. By introducing sidewall electrodes on both sides of the conductive channel, the SBD demonstrates a high current density of 223 mA/mm and low specific on-resistance of 4.7 mΩ⋅cm<jats:sup>2</jats:sup>. Temperature-dependent performance is studied and the Schottky barrier height is extracted to be in a range between 1.3 eV and 1.35 eV at temperatures ranging from 20 °C to 150 °C. These results suggest that the lateral <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> SBD has a tremendous potential for future power electronic applications.</jats:p>

<jats:p>With the widespread utilization of indium-phosphide-based high-electron-mobility transistors (InP HEMTs) in the millimeter-wave (mmW) band, the distributed and high-frequency parasitic coupling behavior of the device is particularly prominent. We present an InP HEMT extrinsic parasitic equivalent circuit, in which the conductance between the device electrodes and a new gate–drain mutual inductance term <jats:italic>L</jats:italic> <jats:sub>mgd</jats:sub> are taken into account for the high-frequency magnetic field coupling between device electrodes. Based on the suggested parasitic equivalent circuit, through HFSS and advanced design system (ADS) co-simulation, the equivalent circuit parameters are directly extracted in the multi-step system. The HFSS simulation prediction, measurement data, and modeled frequency response are compared with each other to verify the feasibility of the extraction method and the accuracy of the equivalent circuit. The proposed model demonstrates the distributed and radio-frequency behavior of the device and solves the problem that the equivalent circuit parameters of the conventional InP HEMTs device are limited by the device model and inaccurate at high frequencies when being extracted.</jats:p>

<jats:p>With a series of 1.0 wt%Bi<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>–<jats:italic>x</jats:italic> wt% CuO (<jats:italic>x</jats:italic> = 0.0, 0.2, 0.4, 0.6, and 0.8) serving as sintering additives, Ni<jats:sub>0.23</jats:sub>Cu<jats:sub>0.32</jats:sub>Zn<jats:sub>0.45</jats:sub>Fe<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub> ferrites are successfully synthesized at a low temperature (900 °C) by using the solid state reaction method. The effects of the additives on the phase formation, magnetic and dielectric properties as well as the structural and gyromagnetic properties are investigated. The x-ray diffraction (XRD) results indicate that the added Bi<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>–CuO can lower the synthesis temperature significantly without the appearing of the second phase. The scanning electron microscope (SEM) images confirm that Bi<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> is an important factor that determines the sintering behaviors, while CuO affects the grain size and densification. With CuO content <jats:italic>x</jats:italic> = 0.4 or 0.6, the sample shows high saturation magnetization, low coercivity, high real part of magnetic permeability, dielectric permittivity, and small ferromagnetic resonance linewidth (Δ<jats:italic>H</jats:italic>). The NiCuZn ferrites are a promising new generation of high-performance microwave devices, such as phase shifters and isolators.</jats:p>

<jats:p>Yttrium iron garnet (YIG) films possessing both perpendicular magnetic anisotropy (PMA) and low damping would serve as ideal candidates for high-speed energy-efficient spintronic and magnonic devices. However, it is still challenging to achieve PMA in YIG films thicker than 20 nm, which is a major bottleneck for their development. In this work, we demonstrate that this problem can be solved by using substrates with moderate lattice mismatch with YIG so as to suppress the excessive strain-induced stress release as increasing the YIG thickness. After carefully optimizing the growth and annealing conditions, we have achieved out-of-plane spontaneous magnetization in YIG films grown on sGGG substrates, even when they are as thick as 50 nm. Furthermore, ferromagnetic resonance and spin pumping induced inverse spin Hall effect measurements further verify the good spin transparency at the surface of our YIG films.</jats:p>

<jats:p>In real life, the rumor propagation is influenced by many factors. The complexity and uncertainty of human psychology make the diffusion model more challenging to depict. In order to establish a comprehensive propagation model, in this paper, we take some psychological factors into consideration to mirror rumor propagation. Firstly, we use the Ridenour model to combine the trust mechanism with the correlation mechanism and propose a modified rumor propagation model. Secondly, the mean-field equations which describe the dynamics of the modified SIR model on homogenous and heterogeneous networks are derived. Thirdly, a steady-state analysis is conducted for the spreading threshold and the final rumor size. Fourthly, we investigate rumor immunization strategies and obtain immunization thresholds. Next, simulations on different networks are carried out to verify the theoretical results and the effectiveness of the immunization strategies. The results indicate that the utilization of trust and correlation mechanisms leads to a larger final rumor size and a smaller terminal time. Moreover, different immunization strategies have disparate effectiveness in rumor propagation.</jats:p>

<jats:p>We present a self-error-rejecting multipartite entanglement purification protocol (MEPP) for <jats:italic>N</jats:italic>-electron-spin entangled states, resorting to the single-side cavity-spin-coupling system. Our MEPP has a high efficiency containing two steps. One is to obtain high-fidelity <jats:italic>N</jats:italic>-electron-spin entangled systems with error-heralded parity-check devices (PCDs) in the same parity-mode outcome of three electron-spin pairs, as well as <jats:italic>M</jats:italic>-electron-spin entangled subsystems (2 ≤ <jats:italic>M</jats:italic> &lt; <jats:italic>N</jats:italic>) in the different parity-mode outcomes of those. The other is to regain the <jats:italic>N</jats:italic>-electron-spin entangled systems from <jats:italic>M</jats:italic>-electron-spin entangled states utilizing entanglement link. Moreover, the quantum circuits of PCDs make our MEPP works faithfully, due to the practical photon-scattering deviations from the finite side leakage of the microcavity, and the limited coupling between a quantum dot and a cavity mode, converted into a failed detection in a heralded way.</jats:p>