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<jats:p>The electronic structures of lead-free piezoceramic (K<jats:sub>0.5</jats:sub>Na<jats:sub>0.5</jats:sub>)NbO<jats:sub>3</jats:sub> (KNN) and La-doped KNN ((K<jats:sub>0.5</jats:sub>Na<jats:sub>0.5</jats:sub>)<jats:sub>0.994</jats:sub>La<jats:sub>0.006</jats:sub>NbO<jats:sub>3</jats:sub>) are studied by using first principles calculation on the basis of density functional theory (DFT). The results reveale that the piezoelectricity stems from strong hybridization between the Nb atom and the O atom. At the same time, the K or Na atoms are replaced by the La doping atoms, which brings about the anisotropic relaxation. The La doping reduces the forbidden band, at the same time it makes Fermi surfaces shift toward the energetic conduction band (CB) of KNN. With the increase of La-doping intent, the phase structure of KNN extends from O-phase to T-phase and improves the piezoelectric properties of KNN.</jats:p>

<jats:p>The surface plasmon polaritons of the topological insulator Bi<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> can be excited by using etched grating or grave structures to compensate the wave vector mismatch of the incident photon and plasmon. Here, we demonstrate novel gold grating/Bi<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> thin film/sapphire hybrid structures, which allow the excitation of surface plasmon polaritons propagating through nondestructive Bi<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> thin film with the help of gold diffractive gratings. Utilizing periodic Au surface structures, the momentum can be matched and the normal-incidence infrared reflectance spectra exhibit pronounced dips. When the width of the gold grating <jats:italic>W</jats:italic> (with a periodicity 2<jats:italic>W</jats:italic>) increases from 400 nm to 1500 nm, the resonant frequencies are tuned from about 7000 cm<jats:sup>−1</jats:sup> to 2500 cm<jats:sup>−1</jats:sup>. In contrast to the expected <jats:inline-formula> <jats:tex-math> <?CDATA $\sqrt{q}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msqrt> <mml:mi>q</mml:mi> </mml:msqrt> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_6_067801_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> dispersion for both massive and massless fermions, where <jats:italic>q</jats:italic> ∼ <jats:italic>π</jats:italic>/<jats:italic>W</jats:italic> is the wave vector, we observe a sound-like linear dispersion even at room temperature. This surface plasmon polaritons with linear dispersion are attributed to the unique noninvasive fabrication method and high mobility of topological surface electrons. This novel structure provides a promising application of Dirac plasmonics.</jats:p>

<jats:p>We have investigated the electronic states of clean Fe(001) and oxygen adsorbed Fe(001)–<jats:italic>p</jats:italic>(1 × 1)-O films epitaxially grown on MgO(001) substrates by means of polarization-dependent angle-resolved photoemission spectroscopy (ARPES) and extensive density-functional theory (DFT) calculations. The observed Fermi surfaces and band dispersions of pure Fe near the Fermi level were modified upon oxygen adsorption. By the detailed comparison of ARPES and DFT results of the oxygen adsorbed Fe surface, we have clarified the orbital-dependent p–d hybridization in the topmost and second Fe layers. Furthermore, the observed energy levels and Fermi wave numbers for the oxygen adsorbed Fe surface were deviated from the DFT calculations depending on the orbital characters and momentum directions, indicating an anisotropic interplay of the electron correlation and p–d hybridization effects in the surface region.</jats:p>

<jats:p>Five-fold twinned nanostructures are intrinsically strained or relaxed by extended defects to satisfy the space-filling requirement. Although both of metallic and semiconductor five-fold twinned nanostructures show inhomogeneity in their cross-sectional strain distribution, the evident strain concentration at twin boundaries in the semiconductor systems has been found in contrast to the metallic systems. Naturally, a problem is raised how the chemical bonding characteristics of various five-fold twinned nanosystems affects their strain-relieving defect structures. Here using three-dimensional (3D) electron diffraction mapping methodology, the intrinsic strain and the strain-relieving defects in a pentagonal Ag nanowire and a star-shaped boron carbide nanowire, both of them have basically equal radial twin-plane width about 30 nm, are non-destructively characterized. The non-uniform strain and defect distribution between the five single crystalline segments are found in both of the five-fold twinned nanowires. Diffraction intensity fine structure analysis for the boron carbide five-fold twinned nanowire indicates the presence of high-density of planar defects which are responsible for the accommodation of the intrinsic angular excess. However, for the Ag five-fold twinned nanowire, the star-disclination strain field is still present, although is partially relieved by the formation of localized stacking fault layers accompanied by partial dislocations. Energetic analysis suggests that the variety in the strain-relaxation ways for the two types of five-fold twinned nanowires could be ascribed to the large difference in shear modulus between the soft noble metal Ag and the superhard covalent compound boron carbide.</jats:p>

<jats:p>Recently, ZrTe<jats:sub>5</jats:sub> has received a lot of attention as it exhibits various topological phases, such as weak and strong topological insulators, a Dirac semimetal, a three-dimensional quantum Hall state, and a quantum spin Hall insulator in the monolayer limit. While most of studies have been focused on the three-dimensional bulk material, it is highly desired to obtain nanostructured materials due to their advantages in device applications. We report the synthesis and characterizations of ZrTe<jats:sub>5</jats:sub> nanoribbons. Via a silicon-assisted chemical vapor transport method, long nanoribbons with thickness as thin as 20 nm can be grown. The growth rate is over an order of magnitude faster than the previous method for the bulk crystals. Moreover, transport studies show that the nanoribbons are of low unintentional doping and high carrier mobility, over 30000 cm<jats:sup>2</jats:sup>/V⋅s, which enable reliable determination of the Berry phase of <jats:italic>π</jats:italic> in the <jats:italic>ac</jats:italic> plane from quantum oscillations. Our method holds great potential in growth of high quality ultra-thin nanostructures of ZrTe<jats:sub>5</jats:sub>.</jats:p>

<jats:p>Although the lithium-ion batteries (LIBs) have been increasingly applied in consumer electronics, electric vehicles, and smart grid, they still face great challenges from the continuously improving requirements of energy density, power density, service life, and safety. To solve these issues, various studies have been conducted surrounding the battery design and management methods in recent decades. In the hope of providing some inspirations to the research in this field, the state of the art of design and management methods for LIBs are reviewed here from the perspective of process systems engineering. First, different types of battery models are summarized extensively, including electrical model and multi-physics coupled model, and the parameter identification methods are introduced correspondingly. Next, the model based battery design methods are reviewed briefly on three different scales, namely, electrode scale, cell scale, and pack scale. Then, the battery model based battery management methods, especially the state estimation methods with different model types are thoroughly compared. The key science and technology challenges for the development of battery systems engineering are clarified finally.</jats:p>

<jats:p>In anode free batteries (AFBs), the current collector acts as anode simultaneously and has large volume expansion which is generally considered as a negative effect decreasing the structural stability of a battery. Moreover, despite many studies on the fast lithium diffusion in the current collector materials of AFB such as copper and aluminum, the involved Li diffusion mechanism in these materials remains poorly understood. Through first-principles calculation and stress-assisted diffusion equations, here we study the Li diffusion mechanism in several current collectors and related alloys and clarify the effect of volume expansion on Li diffusion respectively. It is suggested that due to the lower Li migration barriers in aluminum and tin, they should be more suitable to be used as AFB anodes, compared to copper, silver, and lead. The Li diffusion facilitation in copper with a certain number of vacancies is proposed to explain why the use of copper with a thickness ⩽ 100 nm as the protective coating on the anode improves the lifetime of the batteries. We show that the volume expansion has a positive effect on Li diffusion via mechanical–electrochemical coupling. Namely, the volume expansion caused by Li diffusion will further induce stress which in turn affects the diffusion. These findings not only provide in-depth insight into the operating principle of AFBs, but also open a new route toward design of improved anode through utilizing the positive effect of mechanical–electrochemical coupling.</jats:p>

<jats:p>The cluster-shaped plasmonic nanostructures are used to manage the incident light inside an ultra-thin silicon solar cell. Here we simulate spherical, conical, pyramidal, and cylindrical nanoparticles in a form of a cluster at the rear side of a thin silicon cell, using the finite difference time domain (FDTD) method. By calculating the optical absorption and hence the photocurrent, it is shown that the clustering of nanoparticles significantly improves them. The photocurrent enhancement is the result of the plasmonic effects of clustering the nanoparticles. For comparison, first a cell with a single nanoparticle at the rear side is evaluated. Then four smaller nanoparticles are put around it to make a cluster. The photocurrents of 20.478 mA/cm<jats:sup>2</jats:sup>, 23.186 mA/cm<jats:sup>2</jats:sup>, 21.427 mA/cm<jats:sup>2</jats:sup>, and 21.243 mA/cm<jats:sup>2</jats:sup> are obtained for the cells using clustering conical, spherical, pyramidal, cylindrical NPs at the backside, respectively. These values are 13.987 mA/cm<jats:sup>2</jats:sup>, 16.901 mA/cm<jats:sup>2</jats:sup>, 16.507 mA/cm<jats:sup>2</jats:sup>, 17.926 mA/cm<jats:sup>2</jats:sup> for the cell with one conical, spherical, pyramidal, cylindrical NPs at the backside, respectively. Therefore, clustering can significantly improve the photocurrents. Finally, the distribution of the electric field and the generation rate for the proposed structures are calculated.</jats:p>

<jats:p>Measurement of shipborne radar sea echo is instrumental in collecting the sea clutter data in open sea areas. However, the ship movement would introduce an extra Doppler component into the spectrum of the sea clutter, so the sea clutter inherent spectrum must be estimated prior to investigating the sea clutter Doppler characteristics from the shipborne radar sea echo. In this paper we show some results about a shipborne sea clutter measurement experiment that was conducted in the South China Sea in a period between 2017 and 2018; abundant clutter data have been collected by using a shipborne S-band clutter measurement radar. To obtain the sea clutter inherent Doppler spectrum from these data, an estimation method, based on the mapping relationship between the shipborne clutter spectrum and the inherent clutter spectrum, is proposed. This method is validated by shipborne clutter data sets under the same measuring conditions except for the ship speed. Using this method, the characteristics of the Doppler spectrum lineshapes in the South China Sea are calculated and analyzed according to different sea states, wave directions, and radar resolutions, which can be instrumental in designing the radar target detection algorithms.</jats:p>

<jats:p>we report nBn photodetectors based on InAs<jats:sub>0.91</jats:sub>Sb<jats:sub>0.09</jats:sub> with a 100% cut-off wavelength of 4.75 μm at 300 K. The band of an nBn detector is similar to that of a standard pin detector, but there is special wide bandgap AlAs<jats:sub>0.08</jats:sub>Sb<jats:sub>0.92</jats:sub> barrier layer in the nBn detector, in which the depletion region of nBn detector exists. The nBn design has many advantages, such as low dark current and high quantum efficiency, because the nBn design can suppress the generation–recombination (GR) current that is the main composition of standard pin detector dark current. The constant slope of the Arrhenius plot of <jats:italic>J</jats:italic> <jats:sub>0</jats:sub>–1/<jats:italic>T</jats:italic> indicates the absence of the generation–recombination dark current. We fabricate an nBn detector with a quantum efficiency (QE) maximum of ∼ 60% under −0.2-V bias voltage. The InAsSb nBn detectors may be a competitive candidate for midwavelength infrared detector.</jats:p>