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<jats:p>A very long lifetime exciton emission with non-single exponential decay characteristics has been reported for single InA-s/GaAs quantum dot (QD) samples, in which there exists a long-lived metastable state in the wetting layer (WL) through radiative field coupling between the exciton emissions in the WL and the dipole field of metal islands. In this article we have proposed a new three-level model to simulate the exciton emission decay curve. In this model, assuming that the excitons in a metastable state will diffuse and be trapped by QDs, and then emit fluorescence in QDs, a stretched-like exponential decay formula is derived as <jats:italic>I</jats:italic>(<jats:italic>t</jats:italic>) = <jats:italic>A t</jats:italic> <jats:sup> <jats:italic>β</jats:italic> – 1</jats:sup> e<jats:sup>−(<jats:italic>rt</jats:italic>)<jats:sup> <jats:italic>β</jats:italic> </jats:sup> </jats:sup>, which can describe well the long lifetime decay curve with an analytical expression of average lifetime <jats:inline-formula> <jats:tex-math><?CDATA $\langle \tau \rangle =\displaystyle \frac{1}{r}\Gamma (\displaystyle \frac{1}{\beta }+1)$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo stretchy="false">〈</mml:mo> <mml:mi>τ</mml:mi> <mml:mo stretchy="false">〉</mml:mo> <mml:mo>=</mml:mo> <mml:mstyle displaystyle="true"> <mml:mfrac> <mml:mn>1</mml:mn> <mml:mi>r</mml:mi> </mml:mfrac> </mml:mstyle> <mml:mi>Γ</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mstyle displaystyle="true"> <mml:mfrac> <mml:mn>1</mml:mn> <mml:mi>β</mml:mi> </mml:mfrac> </mml:mstyle> <mml:mo>+</mml:mo> <mml:mn>1</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_9_097805_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> where Γ is the Gamma function. Furthermore, based on the proposed three-level model, an expression of the second-order auto-correlation function <jats:italic>g</jats:italic> <jats:sup>2</jats:sup>(<jats:italic>t</jats:italic>) which can fit the measured <jats:italic>g</jats:italic> <jats:sup>2</jats:sup>(<jats:italic>t</jats:italic>) curve well, is also obtained.</jats:p>

<jats:p>The electromagnetic wave enhanced transmission (ET) through the sub-wavelength aperture was an unconventional physical phenomenon with great application potential. It was important to find a general design method which can realize efficient ET for arbitrary-shaped apertures. For achieving ET with maximum efficiency at specific frequency through arbitrary-shaped subwavelength aperture, a topology optimization method for designing metamaterials (MTM) microstructure was proposed in this study. The MTM was employed and inserted vertically in the aperture. The description function for the arbitrary shape of the aperture was established. The optimization model was founded to search the optimal MTM microstructure for maximum enhanced power transmission through the aperture at the demanded frequency. Several MTM microstructures for ET through the apertures with different shapes at the demanded frequency were designed as examples. The simulation and experimental results validate the feasibility of the method. The regularity of the optimal ET microstructures and their advantages over the existing configurations were discussed.</jats:p>

<jats:p>Raman spectroscopy has been widely used to characterize the physical properties of two-dimensional materials (2DMs). The signal-to-noise ratio (SNR or S/N ratio) of Raman signal usually serves as an important indicator to evaluate the instrumental performance rather than Raman intensity itself. Multichannel detectors with outstanding sensitivity, rapid acquisition speed and low noise level have been widely equipped in Raman instruments for the measurement of Raman signal. In this mini-review, we first introduce the recent advances of Raman spectroscopy of 2DMs. Then we take the most commonly used CCD detector and IGA array detector as examples to overview the various noise sources in Raman measurements and analyze their potential influences on SNR of Raman signal in experiments. This overview can contribute to a better understanding on the SNR of Raman signal and the performance of multichannel detector for numerous researchers and instrumental design for industry, as well as offer practical strategies for improving spectral quality in routine measurement.</jats:p>

<jats:p>A hydrogen-plasma-etching-based plasma-enhanced chemical vapor deposition (PECVD) synthesis route without metal catalyst for preparing the graphene films on flexible glass is developed. The quality of the prepared graphene films is evaluated by scanning electron microscopy, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, ultraviolet-visible spectroscopy, and electrochemical measurements. In a radio frequency (RF) power range of 50 W–300 W, the graphene growth rate increases with RF power increasing, while the intensity ratio of D- to G-Raman peak (<jats:italic>I</jats:italic> <jats:sub>D</jats:sub>/<jats:italic>I</jats:italic> <jats:sub>G</jats:sub>) decreases. When the RF power is higher than 300 W, the <jats:italic>I</jats:italic> <jats:sub>D</jats:sub>/<jats:italic>I</jats:italic> <jats:sub>G</jats:sub> rises again. By optimizing experimental parameters of hydrogen plasma etching and RF power, the properties of as-prepared flexible graphene on glass are modulated to be able to achieve the graphene’s transparency, good electrical conductivity, and better macroscopic uniformity. Direct growth of graphene film without any metal catalyst on flexible glass can be a promising candidate for applications in flexible transparent optoelectronics.</jats:p>

<jats:p>We design a four-band terahertz metamaterial absorber that relied on the block Dirac semi-metal (BDS). It is composed of a Dirac material layer, a gold reflecting layer, and a photonic crystal slab (PCS) medium layer. This structure achieved perfect absorption of over 97% at 4.06 THz, 6.15 THz, and 8.16 THz. The high absorption can be explained by the localized surface plasmon resonance (LSPR). And this conclusion can be proved by the detailed design of the surface structure. Moreover, the resonant frequency of the device can be dynamically tuned by changing the Fermi energy of the BDS. Due to the advantages such as high absorption, adjustable resonance, and anti-interference of incident angle and polarization mode, the Dirac semi-metal perfect absorber (DSPA) has great potential value in fields such as biochemical sensing, information communication, and nondestructive detection.</jats:p>

<jats:p>The low-temperature magnetic order behaviors of perovskite oxide CaCu<jats:sub>3</jats:sub>Ti<jats:sub>4</jats:sub>O<jats:sub>12</jats:sub> (CCTO) ceramics prepared by different methods are discussed. X-ray diffraction, scanning electron microscope, x-ray photoelectron spectroscopy, and direct current (DC) magnetization are used to characterize the structures, microscopic morphologies, valence states, and magnetic properties of the samples. The results show that the magnetic behaviors of CCTO ceramics are very sensitive to the preparation process. The quenched CCTO ceramic and CCTO powders grown in a molten salt crystal, which contain much more oxygen vacancies and Ti<jats:sup>3+</jats:sup>, show the coexistence of weak ferromagnetic order and antiferromagnetic order below the Neel temperature. It suggests that the bound magnetopolaron formed by oxygen vacancies and Ti<jats:sup>3+</jats:sup> ion composite defects are responsible for the weak ferromagnetic order at low temperature.</jats:p>

<jats:p>Silicon-based carbon composites are believed as promising anodes in the near future due to their outstanding specific capacity and relatively lower volume effect compared to pure silicon anodes. Herein, a multilayer spherical core–shell (M-SCS) electrode with a graphite framework prepared with Si@O-MCMB/C nanoparticles is developed, which aims to realize chemically/mechanically stability during the lithiation/delithiation process with high specific capacity. An electrochemical-/mechanical-coupling model for the M-SCS structure is established with various chemical/mechanical boundary conditions. The simulation of finite difference method (FDM) has been conducted based on the proposed coupling model, by which the diffusion-induced stress along both the radial and the circumferential directions is determined. Moreover, factors that influence the diffusion-induced stress of the M-SCS structure have been discussed and analyzed in detail.</jats:p>

<jats:p>Optical superconducting transition-edge sensor (TES) has been widely used in quantum information, biological imaging, and fluorescence microscopy owing to its high quantum efficiency, low dark count, and photon number resolving capability. The temperature sensitivity (<jats:italic>α<jats:sub>I</jats:sub> </jats:italic>) and current sensitivity (<jats:italic>β<jats:sub>I</jats:sub> </jats:italic>) are important parameters for optical TESs, which are generally extracted from the complex impedance. Here we present a method to extract <jats:italic>α<jats:sub>I</jats:sub> </jats:italic> and <jats:italic>β<jats:sub>I</jats:sub> </jats:italic> based on a two-fluid model and compare the calculated current–voltage curves, pulse response, and theoretical energy resolution with the measured ones. This method shows qualitative agreement that is suitable for further optimization of optical TESs.</jats:p>

<jats:p>The damage effect characteristics of GaAs pseudomorphic high electron mobility transistor (pHEMT) under the irradiation of C band high-power microwave (HPM) is investigated in this paper. Based on the theoretical analysis, the thermoelectric coupling model is established, and the key damage parameters of the device under typical pulse conditions are predicted, including the damage location, damage power, <jats:italic>etc</jats:italic>. By the injection effect test and device microanatomy analysis through using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), it is concluded that the gate metal in the first stage of the device is the vulnerable to HPM damage, especially the side below the gate near the source. The damage power in the injection test is about 40 dBm and in good agreement with the simulation result. This work has a certain reference value for microwave damage assessment of pHEMT.</jats:p>

<jats:p>A novel hybrid structure with high responsivity and efficiency is proposed based on an L-shaped frame nano-antenna (LSFNA) array for solar energy harvesting application. So, two types of LSFNAs are designed and optimized to enhance the harvesting characteristics of traditional simple electric dipole nano-antenna (SEDNA). The LSFNA geometrical dimensions are optimized to have the best values for the required input impedance at three resonance wavelengths of <jats:italic>λ</jats:italic> <jats:sub>res</jats:sub> = 10 μm, 15 μm, and 20 μm. Then the LSFNAs with three different sizes are modeled like a planar spiral-shaped array (PSSA). Also, a fractal bowtie nano-antenna is connected with the PSSA in the array gap. This proposed hybrid structure consists of two main elements: (I) Three different sizes of the LSFNAs with two different material types are designed based on the thin-film metal–insulator–metal diodes that are a proper method for infrared energy harvesting. (II) The PSSA gap is designed based on the electron field emission proposed by the Fowler–Nordheim theory for the array rectification. Finally, the proposed device is analyzed. The results show that the PSSA not only has an averaged 3-time enhancement in the harvesting characteristics (such as return loss, harvesting efficiency, etc.) than the previously proposed structures but also is a multi-resonance wide-band device. Furthermore, the proposed antenna takes up less space in the electronic circuit and has an easy implementation process.</jats:p>