Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>First-principles evolutionary calculation was performed to search for all probable stable Ga–Te compounds at extreme pressure. In addition to the well-known structures of <jats:italic>P</jats:italic>6<jats:sub>3</jats:sub>/<jats:italic>mmc</jats:italic> and <jats:italic>Fm</jats:italic>-3<jats:italic>m</jats:italic> GaTe and <jats:italic>I</jats:italic>4/<jats:italic>m</jats:italic> Ga<jats:sub>2</jats:sub>Te<jats:sub>5</jats:sub>, several new structures were uncovered at high pressure, namely, orthorhombic <jats:italic>I</jats:italic>4/<jats:italic>mmm</jats:italic> GaTe<jats:sub>2</jats:sub> and monoclinic <jats:italic>C</jats:italic>2/<jats:italic>m</jats:italic> GaTe<jats:sub>3</jats:sub>, and all the Ga–Te structures stabilize up to a maximum pressure of 80 GPa. The calculation of the electronic energy band indicated that the high-pressure phases of the Ga–Te system are metallic, whereas the low-pressure phases are semiconductors. The electronic localization functions (ELFs) of the Ga–Te system were also calculated to explore the bond characteristics. The results showed that a covalent bond is formed at low pressure, however, this bond disappears at high pressure, and an ionic bond is formed at extreme pressure.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Quasi-elastic neutron scattering (QENS) has many applications that are directly related to the development of high-performance functional materials and biological macromolecules, especially those containing some water. The analysis method of QENS spectra data is important to obtain parameters that can explain the structure of materials and the dynamics of water. In this paper, we present a revised jump-diffusion and rotation-diffusion model (rJRM) used for QENS spectra data analysis. By the rJRM, the QENS spectra from a pure magnesium-silicate-hydrate (MSH) sample are fitted well for the <jats:italic>Q</jats:italic> range from 0.3 Å<jats:sup>−1</jats:sup> to 1.9 Å<jats:sup>−1</jats:sup> and temperatures from 210 K up to 280 K. The fitted parameters can be divided into two kinds. The first kind describes the structure of the MSH sample, including the ratio of immobile water (or bound water) <jats:italic>C</jats:italic> and the confining radius of mobile water <jats:italic>a</jats:italic> <jats:sub>0</jats:sub>. The second kind describes the dynamics of confined water in pores contained in the MSH sample, including the translational diffusion coefficient <jats:italic>D</jats:italic> <jats:sub>t</jats:sub>, the average translational residence time <jats:italic>τ</jats:italic> <jats:sub>0</jats:sub>, the rotational diffusion coefficient <jats:italic>D</jats:italic> <jats:sub>r</jats:sub>, and the mean squared displacement (MSD) <jats:inline-formula> <jats:tex-math><?CDATA $\langle {u}^{2}\rangle $?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">〈</mml:mo> <mml:msup> <mml:mrow> <mml:mi>u</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">〉</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_5_056105_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. The rJRM is a new practical method suitable to fit QENS spectra from porous materials, where hydrogen atoms appear in both solid and liquid phases.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The carrier behavior in CuInS<jats:sub>2</jats:sub> thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change in energy. The photo-generated charge carriers are extracted by a bias electric field <jats:italic>E</jats:italic> in the nanosecond transient photocurrent system. An applied <jats:italic>E</jats:italic> improves the efficiency of photon conversion to charge carriers and enhances the velocity of the extracted charge carriers. In addition, there exists a threshold of illumination intensity in the extraction process of charge carriers in the CuInS<jats:sub>2</jats:sub> thin film, above which carrier recombination occurs. The corresponding loss further increases with illumination intensity and the recombination rate is almost independent of <jats:italic>E</jats:italic>. Our results provide useful insights into the characteristics of carriers in the CuInS<jats:sub>2</jats:sub> thin film and are important for the operation of optoelectronic devices realized with these films.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Iridium is a promising substrate for self-limiting growth of graphene. However, single-crystalline graphene can only be fabricated over 1120 K. The weak interaction between graphene and Ir makes it challenging to grow graphene with a single orientation at a relatively low temperature. Here, we report the growth of large-scale, single-crystalline graphene on Ir(111) substrate at a temperature as low as 800 K using an oxygen-etching assisted epitaxial growth method. We firstly grow polycrystalline graphene on Ir. The subsequent exposure of oxygen leads to etching of the misaligned domains. Additional growth cycle, in which the leftover aligned domain serves as a nucleation center, results in a large-scale and single-crystalline graphene layer on Ir(111). Low-energy electron diffraction, scanning tunneling microscopy, and Raman spectroscopy experiments confirm the successful growth of large-scale and single-crystalline graphene. In addition, the fabricated single-crystalline graphene is transferred onto a SiO<jats:sub>2</jats:sub>/Si substrate. Transport measurements on the transferred graphene show a carrier mobility of about <jats:inline-formula> <jats:tex-math><?CDATA $3300\,{\mathrm{cm}}^{2}\cdot {{\rm{V}}}^{-1}\cdot {{\rm{s}}}^{-1}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>3300</mml:mn> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>·</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">V</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mo>·</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_5_056107_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. This work provides a way for the synthesis of large-scale, high-quality graphene on weak-coupled metal substrates.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report a comprehensive Raman scattering study on layered <jats:italic>M</jats:italic>PS<jats:sub>3</jats:sub> (<jats:italic>M</jats:italic>=Mn, Fe, Ni), a two-dimensional magnetic compound with weak van der Waals interlayer coupling. The observed Raman phonon modes have been well assigned by the combination of first-principles calculations and the polarization-resolved spectra. Careful symmetry analysis on the angle-dependent spectra demonstrates that the crystal symmetry is strictly described by C<jats:sub>2h</jats:sub> but can be simplified to D<jats:sub>3d</jats:sub> with good accuracy. Interestingly, the three compounds share exactly the same lattice structure but show distinct magnetic structures. This provides us with a unique opportunity to study the effect of different magnetic orders on lattice dynamics in <jats:italic>M</jats:italic>PS<jats:sub>3</jats:sub>. Our results reveal that the in-plane Néel antiferromagnetic (AF) order in MnPS<jats:sub>3</jats:sub> favors a spin–phonon coupling compared to the in-plane zig-zag AF in NiPS<jats:sub>3</jats:sub> and FePS<jats:sub>3</jats:sub>. We have discussed the mechanism in terms of the folding of magnetic Brillouin zones. Our results provide insights into the relation between lattice dynamics and magnetism in the layered <jats:italic>M</jats:italic>P<jats:italic>X</jats:italic> <jats:sub>3</jats:sub> (<jats:italic>M</jats:italic>=transition metal, <jats:italic>X</jats:italic>=S, Se) family and shed light on the magnetism of monolayer <jats:italic>M</jats:italic>P<jats:italic>X</jats:italic> <jats:sub>3</jats:sub> materials.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The variational and diffusion Monte Carlo approaches are used to study the ground-state properties of a hydrogen molecular ion in a spheroidal box. In this work, we successfully treat the zero-point motion of protons in the same formalism with as of electrons and avoid the Born–Oppenheimer approximation in density function theory. The study shows that the total energy increases with the decrease in volume, and that the distance between protons decreases as the pressure increases. Considering the motion of protons, the kinetic energy of the electron is higher than that of the fixed model under the same conditions and increases by 5%. The kinetic energy of the proton is found to be small under high pressure, which is only a fraction of the kinetic energy of the electron.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Inorganic halide perovskites CsPb<jats:italic>X</jats:italic> <jats:sub>3</jats:sub> (<jats:italic>X</jats:italic> = I, Br) have attracted tremendous attention in solar cell applications. However, the bulk form of the cubic phase CsPb<jats:italic>X</jats:italic> <jats:sub>3</jats:sub>, which offers moderate direct bandgaps, is metastable at room temperature and tends to transform into a tetragonal or orthorhombic phase. Here, our density functional theory calculation results found that the surface energies of the cubic phase are smaller than those of the orthorhombic phase, although the bulk counterpart of the cubic phase is less stable than that of the orthorhombic phase. These results suggest a surface stabilization strategy to maintain the stability of the cubic phase at room temperature that an enlarged portion of surfaces shall change the relative stability of the two phases in nanostructured CsPb<jats:italic>X</jats:italic> <jats:sub>3</jats:sub>. This strategy, which may potentially solve the long-standing stability issue of cubic CsPb<jats:italic>X</jats:italic> <jats:sub>3</jats:sub>, was demonstrated to be feasible by our calculations in zero-, one-, and two-dimensional nanostructures. In particular, confined sizes from few to tens of nanometers could keep the cubic phase as the most thermally favored form at room temperature. Our predicted values in particular cases, such as the zero-dimensional form of CsPbI<jats:sub>3</jats:sub>, are highly consistent with experimental values, suggesting that our model is reasonable and our results are reliable. These predicted critical sizes give the upper and lower limits of the confined sizes, which may guide experimentalists to synthesize these nanostructures and promote likely practical applications such as solar cells and flexible displays using CsPb<jats:italic>X</jats:italic> <jats:sub>3</jats:sub> nanostructures.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Low thermal expansion materials are mostly ceramics with low conductive property, which limits their applications in electronic devices. The poor conductive property of ceramic ZrV<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> could be improved by bi-substitution of Fe and Mo for Zr and V, accompanied with low thermal expansion. Zr<jats:sub>0.1</jats:sub>Fe<jats:sub>0.9</jats:sub>V<jats:sub>1.1</jats:sub>Mo<jats:sub>0.9</jats:sub>O<jats:sub>7</jats:sub> has electrical conductivity of 8.2×10<jats:sup>−5</jats:sup> S/cm and 9.41×10<jats:sup>−4</jats:sup> S/cm at 291 K and 623 K, respectively. From 291 K to 413 K, thermal excitation leads to the increase of carrier concentration, which causes the rapid decrease of resistance. At 413–533 K, the conductivity is unchanged due to high scattering probability and a slowing increase of carrier concentration. The conductivity rapidly increases again from 533 K to 623 K due to the intrinsic thermal excitation. The thermal expansion coefficient of Zr<jats:sub>0.1</jats:sub>Fe<jats:sub>0.9</jats:sub>V<jats:sub>1.1</jats:sub>Mo<jats:sub>0.9</jats:sub>O<jats:sub>7</jats:sub> is as low as 0.72×10<jats:sup>−6</jats:sup> K<jats:sup>−1</jats:sup> at 140–700 K from the dilatometer measurement. These properties suggest that Zr<jats:sub>0.1</jats:sub>Fe<jats:sub>0.9</jats:sub>V<jats:sub>1.1</jats:sub>Mo<jats:sub>0.9</jats:sub>O<jats:sub>7</jats:sub> has attractive application in electronic components.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the spatiotemporal Bloch states of a high-frequency driven two-component Bose–Einstein condensate (BEC) with spin–orbit coupling (SOC) in an optical lattice. By adopting the rotating-wave approximation (RWA) and applying an exact trial-solution to the corresponding quasistationary system, we establish a different method for tuning SOC via external field such that the existence conditions of the exact particular solutions are fitted. Several novel features related to the exact states are demonstrated; for example, SOC leads to spin–motion entanglement for the spatiotemporal Bloch states, SOC increases the population imbalance of the two-component BEC, and SOC can be applied to manipulate the stable atomic flow which is conducive to control quantum transport of the BEC for different application purposes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Two-dimensional (2D) materials provide a platform to exploit the novel physical properties of functional nanodevices. Here, we report on the formation of a new 2D layered material, a well-ordered monolayer TiTe<jats:sub>2</jats:sub>, on a Au(111) surface by molecular beam epitaxy (MBE). Low-energy electron diffraction (LEED) measurements of the samples indicate that the TiTe<jats:sub>2</jats:sub> film forms <jats:inline-formula> <jats:tex-math><?CDATA $(\sqrt{3}\times \sqrt{7})$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:msqrt> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_5_056801_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> superlattice with respect to the Au(111) substrate, which has three different orientations. Scanning tunneling microscopy (STM) measurements clearly show three ordered domains consistent with the LEED patterns. Density functional theory (DFT) calculations further confirm the formation of 2H-TiTe<jats:sub>2</jats:sub> monolayer on the Au(111) surface with Te as buffer layer. The fabrication of this 2D layered heterostructure expands 2D material database, which may bring new physical properties for future applications.</jats:p>