Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>In this work, diamond crystals were synthesized with different doping proportions of N-H-O at 5.5-7.1GPa and 1370-1450℃. With the increase of N-H-O doping ratio, the crystal growth rate decreases, a more serve temperature and pressure condition are required for diamond nucleation process and the crystalline process for diamond are affected. [111] becomes dominant plane of diamonds, and the surface morphology is blocked, more growth texture, stacking fault and etch pit were appeared. Diamond crystals own a two-dimensional growth habit. Increasing the doping concentration also leading more nitrogen enter into diamond crystals, which is confirmed by FTIR. However, the quality of the crystal gradually deteriorates which could be ascertained by the red shift of Raman peak position and the widening of Raman full width at half maximum. With the increase of doping ratio, the photoluminescence property of diamond crystal also drastically changed. The intensity of NV center of diamond crystal changes, and several Ni-related defect center such as NE1 center and NE3 center appear. Synthesis of diamond in N-H-O bearing fluid provides important information for a deeper understanding of the growth characteristics of diamond in complex system and the formation mechanism of natural diamond as nature diamonds are almost nitrogen rich and full of various defect centers. Meanwhile, this work proves that the type of defect center in diamond crystal could be regulated by controlling the N-H-O impurities content in the synthesis system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A comprehensive investigation on CrAlGe indicates this compound to be an itinerant ferromagnet with strong tunability of the Curie temperature $T_C$ and the spontaneous moment $μ_0$ depending on annealing heat treatment. While the value of $T_C$ was previously reported to be 80 K with $μ_0$ $\approx$ 0.41 $\mu_B$, the two quantities attain values as high as 170 K and 0.66 $\mu_B$ in this work, respectively. Heat treatment does not cause changes of the lattice parameters and symmetry, but results in a slight narrowing of the Bragg peaks. The strong tunability of the itinerant ferromagnetism indicates significantly tunable hybridization between the Cr 3$d$ electrons and the conduction bands, in consistent with the dominant Cr$-$Al/Ge bonds of this compound. Further tuning along the same line towards even stronger or weaker itinerant ferromagnetism promises an interesting follow-up to clarify the localized$-$itinerant duality of the 3$d$ electrons in this compound.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Multiferroic (BFO) nanoparticles doped with strontium with general formula, Bi<jats:sub>1‐x</jats:sub>Sr<jats:sub>x</jats:sub>FeO<jats:sub>3</jats:sub> (x=0.0,0.3,0.5, 0.7 ) have been synthesized by modified Sol‐gel auto‐combustion process. The structural, electrical, optical, and magnetic properties of the samples are discussed. The structural analysis carried out by X‐ray powder diffraction technique shows a structural transition from rhombohedral (R‐3c) to cubic(Pm‐3m) for the doping amount of strontium(Sr) equal to x=0.3. Morphological analyses of the prepared samples are carried out using scanning electron microscopy (SEM). Frequency‐dependent dielectric constant and ac conductivity have been studied. The doped samples, having improved dielectric properties, can be used to fabricate different optoelectronic devices. Strong dielectric dispersion and broad relaxation were exhibited by all samples. Cole‐Cole plots were employed as an effective tool to study the dispersion parameters namely optical dielectric constant, static dielectric constant, relaxation time, and spreading factor. The activation energy was calculated from relaxation peaks and Cole‐Cole plots and found to be compatible with each other. The bandgap of the samples was calculated using Diffuse reflectance spectral (DRS) analysis. The sharp and strong photoluminescence in the IR region is observed in the samples similar to ZnO, which is reported for the first time. The room temperature and low‐temperature magnetization studies point towards the superparamagnetic nature of the samples with an improvement of magnetic properties with doping. Antiferromagnetic behavior of bulk bismuth ferrite transforms to superparamagnetic nature for both pure and Sr‐substituted bismuth ferrite nanoparticles due to close dimension of crystallite size with magnetic domains leading to break‐down of the frustrated spin cycloidal moment.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Cold atom physics in space station attract a lot of interest of scientists. We investigate the dynamical output process of the space continuous atom laser by solving non-linear Gross-Pitaevksii equations numerically. Slow-moving continuous atom beams in two directions are observed simultaneously. The slow-moving coherent atom beams can be used as a source of atom interferometer to do long-time measurements. We also control the output of space atom laser by adjusting the output coupling strength.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The authors demonstrate a Bull’s eye cavity design that is composed of circular Bragg gratings and micropillar optical cavity in 4H silicon carbide (4H-SiC) for single photon emission. Numerical calculations are used to investigate and optimize the emission rate and directionality of emission. Thanks to the optical mode resonances and Bragg reflections, the radiative decay rates of a dipole embedded in the cavity center is enhanced by 12.8 times as compared to that from a bulk 4H-SiC. In particular, a convergent angular distribution of the emission in far field is simultaneously achieved, which remarkably boost the collection efficiency. The findings of this work provide an alternative architecture to manipulate light-mater interactions for achieving high-efficient SiC single photon sources towards applications in quantum information technologies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Two-dimensional (2D) semiconductors, such as lead selenide (PbSe), locate at the key position of next-generation devices. However, the ultrathin PbSe is still rarely reported experimentally, particularly on metal substrates. Here, we report the ultrathin PbSe synthesized via sequential molecular beam epitaxy on Ag(111). The scanning tunneling microscopy is used to resolve the atomic structure and confirms the selective formation of ultrathin PbSe through the reaction between Ag<jats:sub>5</jats:sub>Se<jats:sub>2</jats:sub> and Pb, as further evidenced by the theoretical calculation. It is also found that the increased accumulation of Pb leads to the improved quality of PbSe with larger and more uniform films. The detailed analysis reveals the bilayer structure of synthesized PbSe, which could be deemed to achieve the 2D limit. The differential conductance spectrum reveals a metallic feature of the PbSe film, indicating a certain interaction between PbSe and Ag(111). Moreover, the moiré pattern originated from the lattice mismatch between PbSe and Ag(111) is observed, and this moiré system provides the opportunity for studying physics under periodical modulation and for device applications. Our work illustrates a pathway to selectively synthesize ultrathin PbSe on metal surfaces and suggests a 2D experimental platform to explore PbSe-based opto-electronic and thermoelectric phenomena.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Natural gas hydrate is estimated to contain huge reserves. Its exploitation can solve the global oil and gas shortage problem. Hydrates decompose into water and methane, and methane molecules are supersaturated to form nanobubbles. Methane nanobubbles can affect the decomposition efficiency of hydrates. They can provide abundant methane sources for the re-nucleation of hydrates. Molecular dynamics is employed in this study to investigate the decomposition process of type I methane hydrate and the formation of methane nanobubbles generated during decomposition under different methane mole fraction, pressures, and temperatures. The results indicate that external pressure inhibits the diffusion of methane molecules, thereby preventing the formation of nanobubbles. A higher mole fraction of methane molecules in the system requires a higher external pressure to generate stable nanobubbles after the decomposition of the hydrate structure. At 330 K, it is easy to form a nanobubble structure. Results of this study can help provide ideas for the study of efficient extraction and secondary nucleation of hydrates.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A self-powered solar-blind ultraviolet (UV) photodetector (PD) was successfully constructed on Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/Bi<jats:sub>2</jats:sub>WO<jats:sub>6</jats:sub> heterojunction, which was fabricated by spin-coating the hydrothermally-grown Bi<jats:sub>2</jats:sub>WO<jats:sub>6</jats:sub> onto MOCVD-grown Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> film. The results show that a typical type-I heterojunction is formed at the interface of Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> film and clustered Bi<jats:sub>2</jats:sub>WO<jats:sub>6</jats:sub>, which demonstrates a distinct photovoltaic effect with an open-circuit voltage of 0.18 V under the irradiation of 254 nm UV light. Moreover, the Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/Bi<jats:sub>2</jats:sub>WO<jats:sub>6</jats:sub> PD displays excellent photodetection performance with an ultralow dark current of ~6 fA, and a high light-to-dark current ratio (PDCR) of 3.5×10<jats:sup>4</jats:sup> in self-powered mode (0 V), as well as a best responsivity of 2.21 mA/W in power supply mode (5 V). Besides, the PD possesses a stable and fast response speed under different light intensities and voltages. At zero voltage, the PD exhibits a fast rise time of 132 ms and 162 ms, as well as a quick decay time of 69 ms and 522 ms, respectively. In general, the newly attempted Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/Bi<jats:sub>2</jats:sub>WO<jats:sub>6</jats:sub> heterojunction may become a potential candidate for realizing self-powered and high-performance UV photodetectors.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Multi-links networks are universal in real world such as relationship networks, transportation networks and communication networks. It is significant to investigate the synchronization of the network with multi-links. In this paper, considering the complex network with uncertain parameters, new adaptive controller and update laws are proposed to ensure that complex-valued multi-links network realizes finite-time complex projective synchronization (FTCPS). In addition, based on fractional-order Lyapunov functional method and finite-time stability theory, the criteria of FTCPS are derived and synchronization time is given which is associated with fractional order and control parameters. Meanwhile, numerical example is given to verify the validity of proposed finite-time complex projection strategy and analyze the relationship between synchronization time and fractional order and control parameters. Finally, the network is applied to image encryption and security analysis is carried out to verify the correctness of this method.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, the refractive index (RI) sensor based on surface plasmon resonance effect is proposed using the truncated cladding negative curvature fiber (TC-NCF). The influences of the TC-NCF structure parameters on the sensing performances are investigated and compared with the traditional NCF. The simulation results show that the proposed TC-NCF RI sensor has an ultra-wide detection range from 1.16 to 1.43. The maximum wavelength sensitivity is up to 12400 nm/RIU, and the corresponding R<jats:sup>2</jats:sup> of the polynomial fitting equation is 0.9999. The maximum and minimum resolutions are 2.56×10<jats:sup>-5</jats:sup> and 8.06×10<jats:sup>-6</jats:sup>, respectively. In addition, the maximum amplitude sensitivity can be up to -379.1 RIU<jats:sup>-1</jats:sup> when the RI is chosen as 1.43. The proposed TC-NCF RI sensor could be useful in biochemical medicine, environmental monitoring, and food safety.</jats:p>