Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The silicon heterojunction (SHJ) solar cell has long been considered as one of the most promising candidates for the next-generation PV market. Transition metal oxides (TMOs) shows good carrier selectivity when combined with c-Si solar cells. This has led to the rapid demonstration of the remarkable potential of TMOs (especially MoO<jats:sub>x</jats:sub>) with high work function to replace the p-type a-Si:H emitting layer. MoO<jats:sub>x</jats:sub> can induce a strong inversion layer on the interface of n-type c-Si, which is beneficial to the extraction and conduction of holes. In this paper, the radio-frequency magnetron sputtering was used to deposit MoO<jats:sub>x</jats:sub> films. The optical, electrical and structural properties of MoO<jats:sub>x</jats:sub> films are measured and analyzed, with focus on the inherent compositions and work function. Then the MoO<jats:sub>x</jats:sub> films are applied into SHJ solar cells. When the MoO<jats:sub>x</jats:sub> works as a buffer layer between ITO/p-a-Si:H interface in the reference SHJ solar cell, a conversion efficiency of 19.1% can be obtained. When the MoO<jats:sub>x</jats:sub> is used as a hole transport layer (HTL), the device indicates a desirable conversion efficiency of 17.5%. To the best of our knowledge, this current efficiency is the highest one for the MoO<jats:sub>x</jats:sub> film as HTL by RF sputtering.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The adsorption dynamics of double-stranded DNA (dsDNA) molecules on a graphene oxide (GO) surface are important for applications of the DNA/GO functional structures in biosensors, biomedicine, and materials science. In this work, molecular dynamics simulations were used to examine the adsorption of different length dsDNA molecules (from 4bp to 24bp) on the GO surface. The dsDNA molecules could be adsorbed on the GO surface through the terminal bases and stand on the GO surface. For short dsDNA (4bp) molecules, the double helix structure was partially or totally broken, and the adsorption dynamic process was affected by the structural fluctuation of short dsDNA and the distribution of the oxidized groups on the GO surface. For long dsDNA molecules (from 8bp to 24bp), it is a stable adsorption. By nonlinear fitting the contact angle between the axis of dsDNA molecule and GO surface, we found that dsDNA molecule adsorbed on GO surface has the chance parallel to the GO surface if the length of dsDNA molecule is longer than 54 bp. We attributed this behavior to the flexibility of dsDNA molecule. With the length increasing, the flexibility of dsDNA molecule is also increasing and the increasing flexibility gives the adsorbed dsDNA molecule more chance to reach the GO surface by the free terminal. This work provides a whole picture of dsDNA molecule adsorption on GO surface, and would be benefit to the design of DNA/GO based biosensors.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>As a special order of electronic correlation induced by spatial modulation, the charge density wave (CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in various temperatures, we discover a hidden incommensurate stripe-like CDW order besides the ($\sqrt 7 $×$\sqrt 3 $) CDW phase at low-temperature of 4 K in the epitaxial monolayer 1T-VSe<jats:sub>2</jats:sub> film. Combining the variable-temperature angle-resolved photoemission spectroscopic (ARPES) measurements, we discover a two-step transition of an anisotropic CDW gap structure that consists of two parts Δ<jats:sub>1</jats:sub> and Δ<jats:sub>2</jats:sub>. The gap part Δ<jats:sub>1</jats:sub> that closes around ~150 K is accompanied with the vanish of the ($\sqrt 7 $×$\sqrt 3 $) CDW phase. While another momentum-dependent gap part Δ<jats:sub>2</jats:sub> can survive up to ~340 K, and is suggested to the result of the incommensurate CDW phase. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure Δ<jats:sub>1</jats:sub>+Δ<jats:sub>2</jats:sub>, which suggests the different forming mechanism between the ($\sqrt 7 $×$\sqrt 3 $) and the incommensurate CDW phases. Our findings provide significant information and deep understandings on the CDW phases in monolayer 1T-VSe<jats:sub>2</jats:sub> film as a 2D material.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>With the development of Moore's Law, the future trend of devices will inevitably be shrinking and integration to further achieve size reduction. The emergence of new two-dimensional non-layered materials (2DNLMs) not only enriches the 2D material family to meet future development, but also stimulates the global enthusiasm for basic research and application technologies in the 2D field. Van der Waals (vdW) heterostructures, in which two-dimensional layered materials (2DLMs) are physically stacked layer by layer, can also occur between 2DLMs and 2DNLMs hybrid heterostructure, providing an alternative platform for nanoelectronics and optoelectronic applications. Here, we outline the recent developments of 2DLMs/2DNLMs hybrid heterostructures, with particular emphasis on major advances in synthetic methods and applications. And the categories and crystal structures of 2DLMs and 2DNLMs are also shown. We highlight some promising applications of the heterostructures in electronics, optoelectronics, and catalysis. Finally, we provide conclusions and future prospects in the 2D materials field.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We systematically investigated the Ni and Co thickness-dependent perpendicular magnetic anisotropy (PMA) coefficient, magnetic domain structures, and magnetization dynamics of Pt(5 nm)/[Co(<jats:italic>t</jats:italic> <jats:sub>Co</jats:sub> nm)/Ni(<jats:italic>t</jats:italic> <jats:sub>Ni</jats:sub> nm)]<jats:sub>5</jats:sub>/Pt(1 nm) multilayers by combining the four standard magnetic characterization techniques. The magnetic-related hysteresis loops obtained from the field-dependent magnetization <jats:italic>M</jats:italic> and anomalous Hall resistivity (AHR) <jats:italic>ρ</jats:italic> <jats:sub>xy</jats:sub> found that the two serial multilayers with <jats:italic>t</jats:italic> <jats:sub>Co</jats:sub> = 0.2 and 0.3 nm have the optimum PMA coefficient <jats:italic>K</jats:italic> <jats:sub>U</jats:sub> well as the highest coercivity <jats:italic>H</jats:italic> <jats:sub>C</jats:sub> at the Ni thickness <jats:italic>t</jats:italic> <jats:sub>Ni</jats:sub> = 0.6 nm. Additionally, the magnetic domain structures obtained by Magneto-optic Kerr effect (MOKE) microscopy also significantly depend on the thickness and <jats:italic>K</jats:italic> <jats:sub>U</jats:sub> of the films. Furthermore, the thickness-dependent linewidth of ferromagnetic resonance is inversely proportional to <jats:italic>K</jats:italic> <jats:sub>U</jats:sub> and <jats:italic>H</jats:italic> <jats:sub>C</jats:sub>, indicating that inhomogeneous magnetic properties dominate the linewidth. However, the intrinsic Gilbert damping constant determined by a linear fitting of frequency-dependent linewidth does not depend on Ni thickness and <jats:italic>K</jats:italic> <jats:sub>U</jats:sub>. Our results could help promote the PMA [Co/Ni] multilayer applications in various spintronic and spin-orbitronic devices.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Laterally-coupled ridge-waveguide distributed feedback lasers fabricated without epitaxial regrowth steps have the advantages of process simplification and low cost. We present a laterally coupled grating with slots. The slots etched between the ridge and grating area are designed to suppress the lateral diffusion of carriers and to reduce the influence of ARDE effect on the grating morphology in the etching process. Moreover, the grating height in this structure can be decreased to lower the aspect ratio significantly, which is advantageous over the conventional laterally coupled ridge waveguide gratings. The effects of five main structural parameters on the coupling characteristics of gratings are studied by MODE Solutions. It is found that varying the lateral width of the grating can be used as an effective way to tune coupling strength; Narrow slots (100 and 300 nm) and wide ridge (2-4 μm) promote the stability of grating coupling coefficient and device performance; It's important to note that the grating bottom should be fabricated precisely. The comparative study of carrier distribution and mode field distribution shows that the introduction of narrow slots can strengthen the competitive advantage and stability of fundamental mode.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Diffusion in narrow curved channels with dead-ends as in extracellular space in the biological tissues, e.g. brain, tumors, muscles, etc. is a geometrically induced complex diffusion and is relevant to different kinds of biological, physical, and chemical systems. In this paper, we study the effects of geometry and confinement on the diffusion process in an elliptical comb-like structure and analyze its statistical properties. The ellipse domain whose boundary has the polar equation: <jats:italic>ρ</jats:italic>(<jats:italic>θ</jats:italic>)=$\frac{b}{{\sqrt {1 - {e^2}{{\cos }^2}\theta } }}$ with 0&amp;#60;<jats:italic>e</jats:italic>&amp;#60;1, <jats:italic>θ</jats:italic>∈[0,2<jats:italic>π</jats:italic>], and <jats:italic>b</jats:italic> is constant, can be obtained through stretched radius <jats:italic>r</jats:italic> such that Υ=<jats:italic>r</jats:italic> <jats:italic>ρ</jats:italic>(<jats:italic>θ</jats:italic>) with <jats:italic>r</jats:italic>∈[0,1]. We suppose that, for fixed radius <jats:italic>r</jats:italic>=<jats:italic>R</jats:italic>, an elliptical motion takes place and interspersed with a radial motion inward and outward of the ellipse. The probability distribution function (PDF) in the structure and the marginal PDF and mean square displacement (MSD) along the backbone are obtained numerically. Results show a transient sub-diffusion behavior dominates the process for a time followed by a saturating state. The sub-diffusion regime and saturation threshold are affected by the length of the elliptical channel lateral branch and its curvature.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Continuous-wave cavity ring-down spectroscopy (CW-CRDS) is an important technical means to monitor greenhouse gases in atmospheric environment. In this paper, a continuous-wave cavity ring-down spectroscopy system is built to meet the needs of atmospheric methane monitoring. The problem of mode matching is explained from the perspective of transverse mode and longitudinal mode, and the influence of laser injection efficiency on measurement precision is further analyzed. The results of cavity ring-down time measurement show that the measurement precision is higher when the laser is coupled with the fundamental mode. In the experiment, DFB laser is used to calibrate the system with standard methane concentration, and a measurement error of 1.1% is obtained. The methane concentration in the air is monitored in real time for two days. The results show the consistency of the concentration changes over the two days, which further demonstrate the reliability of the system for the measurement of trace methane. By analyzing the influence of mode matching, it not only assists the adjustment of the optical path, but also further improves the sensitivity of the system measurement.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Based on the density functional theory calculations, we have investigated the feasibility of two-dimensional <jats:italic>β</jats:italic>-GeS monolayer as high-performance anodes for alkali metal ion batteries. The results show that the electrical conductivity of <jats:italic>β</jats:italic>-GeS monolayer can be enhanced after adsorbing the alkali metal atoms owing to the semiconductor-to-metal transition. The low diffusion barriers of alkali metal atoms on the <jats:italic>β</jats:italic>-GeS surface indicate a rapid charge/discharge rate without metal clustering. Moreover, the low average open-circuit voltage (0.211 V) and a high theoretical capacity (1024 mAh g<jats:sup>-1</jats:sup>) for Na suggest that the <jats:italic>β</jats:italic>-GeS monolayer is a promising anode material for Na-ion batteries with high performance.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In a quantum Hall effect, flat Landau levels may be broadened by disorder. However, it has been found that in the thermodynamic limit,all extended (or current carrying) states shrink to one single energy value within each Landau level. On the other hand, a quantum anomalous Hall effect consists of dispersive bands with finite widths. We numerically investigate the picture of current carrying states in this case. With size scaling, the spectrum width of these states in each bulk band still shrinks to a single energy value in the thermodynamic limit, in a power law way. The magnitude of the scaling exponent at the intermediate disorder is close to that in the quantum Hall effects. The number of current carrying states obeys similar scaling rules, so that the density of states of current carrying states is finite. Other states in the bulk band are localized and may contribute to the formation of a topological Anderson insulator.</jats:p>