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<jats:p>Tandem cell with structure of indium tin oxide (ITO)/molybdenum oxide (MoO<jats:sub>3</jats:sub>)/fullerene (C60)/copper phthalocyanine (CuPc)/C60/tris-8-hydroxy-quinolinato aluminum (Alq<jats:sub>3</jats:sub>)/Al was fabricated to study the effect of net carriers at the interconnection layer. The open circuit voltage and short circuit current were found to be 1.15 V and 0.56 mA/cm<jats:sup>2</jats:sup>, respectively. Almost the same performance (1.05 V, 0.58 mA/cm<jats:sup>2</jats:sup>) of tandem cell with additional recombination layer (ITO/MoO<jats:sub>3</jats:sub>/C60/Alq<jats:sub>3</jats:sub>/Al/Ag/MoO<jats:sub>3</jats:sub>/CuPc/C60/Alq<jats:sub>3</jats:sub>/Al) demonstrates that the carrier balance is more crucial than carrier recombination. The net holes at the interconnection layer caused by more carrier generation from the back cell on one hand would enhance the recombination with electrons from the front cell and on the other hand would quench the excitons produced in CuPc of the back cell.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Because of the wide selectivity of ferromagnetic and ferroelectric (FE) components, electric-field (E-field) control of magnetism with via strain mediation can be easily realized through composite multiferroic heterostructures. Here, an MgO-based magnetic tunnel junction (MTJ) is chosen rationally as ferromagnetic constitution and a high-activity (001)-Pb(Mg<jats:sub>1/3</jats:sub>Nb<jats:sub>2/3</jats:sub>)<jats:sub>0.7</jats:sub>Ti<jats:sub>0.3</jats:sub>O<jats:sub>3</jats:sub> (PMN-0.3PT) single crystal is selected as FE component to create a multiferroic MTJ/FE hybrid structure. The shape of tunneling magnetoresistance (TMR) vs. <jats:sup>in situ</jats:sup> E-fields imprints the butterfly loop of piezo-strain of the FE without magnetic field biasing. The E-field-controlled change of the TMR ratio is up to -0.27% without magnetic-field bias. Moreover, when a typical magnetic field (~±10-Oe) is applied along the minor axis of the MTJ, the butterfly loop is changed significantly by E-fields relative to that without magnetic field biasing. This suggests that the E-field-controlled junction resistance is spin-dependent and correlated with magnetization switching in the free layer of the MTJ. In addition, based on such a multiferroic heterostructure, a strain-gauge factor up to approximately 40 is achieved, which decreases further with a sign change from positive to negative with increasing magnetic fields. This multiferroic hybrid structure is a promising avenue to control TMR through E-fields in low-power-consumption spintronic and straintronic devices at room temperature.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, carbon ion irradiation and precise diamond blade dicing are applied for Nd:GdCOB ridge waveguide fabrication. The propagation properties of the fabricated Nd:GdCOB waveguides are investigated through experiments and theoretical analysis. The micro-Raman analysis reveals that the lattice of Nd:GdCOB crystal expands during the irradiation process. The micro-second harmonic spectroscopic analysis suggests that the original nonlinear properties of the Nd:GdCOB crystal are greatly enhanced within the waveguide volume. Under a pulsed 1064-nm laser pumping, second harmonic generation (SHG) at 532 nm have been achieved in the fabricated waveguides. The maximum SHG conversion efficiencies are determined to be ~8.32%W<jats:sup>-1</jats:sup> and ~22.36%W<jats:sup>-1</jats:sup> for planar and ridge waveguides, respectively.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Temperature and strain sensitivities of surface acoustic wave (SAW) and hybrid acoustic wave (HAW) Brillouin scattering (BS) in 1-1.3 μm diameter optical microfibers are simulated. In contrast to stimulated Brillouin scattering (SBS) from bulk acoustic wave in standard optical fiber, SAW and HAW BS, due to SAWs and HAWs induced by the coupling of longitudinal and shear waves and propagating along the surface and core of microfiber respectively, facilitate innovative detection in optical microfibers sensing. The highest temperature and strain sensitivities of the hybrid acoustic modes (HAMs) are 1.082 MHz/℃ and 0.0289 MHz/µ<jats:italic>ε</jats:italic>, respectively, which is suitable for microfiber sensing application of high temperature and strain resolutions. Meanwhile, the temperature and strain sensitivities of the SAMs are less affected by fiber diameter changes, ranging from 0.05 to 0.25 MHz/℃/µm and 0.0001 to 0.0005 MHz/µ<jats:italic>ε</jats:italic>/µm, respectively. It can be found that that SAW BS for temperature and strain sensing would put less stress on manufacturing constraints for optical microfibers. Besides, the simultaneous sensing of temperature and strain can be realized by SAW and HAW BS, with temperature and strain errors as low as 0.30-0.34 ℃ and 14.47-16.25 µ<jats:italic>ε</jats:italic>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Sideband cooling is a key technique for improving the performance of optical atomic clocks by preparing cold atoms and single ions into the ground vibrational state. In this work, we demonstrate detailed experimental research on pulsed Raman sideband cooling in a <jats:sup>171</jats:sup>Yb optical lattice clock. A sequence comprised of interleave 578 nm cooling pulses resonant on the 1st-order red sideband and 1388 nm repumping pulses is carried out to transfer atoms into the motional ground state. We successfully decrease the axial temperature of atoms in the lattice from 6.5 µK to less than 0.8 µK in the trap depth of 24 µK, corresponding to an average axial motional quantum number &amp;#60;<jats:italic>n</jats:italic> <jats:sub> <jats:italic>z</jats:italic> </jats:sub>&amp;#62; &amp;#60; 0.03. Rabi oscillation spectroscopy is measured to evaluate the effect of sideband cooling on inhomogeneous excitation. The maximum excitation fraction is increased from 0.8 to 0.86, indicating an enhancement in the quantum coherence of the ensemble. Our work will contribute to improving the instability and uncertainty of Yb lattice clocks.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, we present an efficient strategy, that is the co-substitution of Fe<jats:sup>3+</jats:sup> and Ta<jats:sup>5+</jats:sup> ions with large radius for Ti<jats:sup>4+</jats:sup> ion, to enhance energy storage performance of Ba<jats:sub>2</jats:sub>Bi<jats:sub>4</jats:sub>Ti<jats:sub>5</jats:sub>O<jats:sub>18</jats:sub> film. For the films co-doped with Fe<jats:sup>3+</jats:sup> and Ta<jats:sup>5+</jats:sup> ions, the maximum polarization under the same external electric field is improved because the radius of Fe<jats:sup>3+</jats:sup> and Ta<jats:sup>5+</jats:sup> ions is larger than that of Ti<jats:sup>4+</jats:sup> ion. Moreover, due to the composition and chemical disorder, the relaxor properties are also slightly improved, which can not be achieved by the film doped with Fe<jats:sup>3+</jats:sup> ions only. What’s more, for the films doped with Fe<jats:sup>3+</jats:sup> ion only, the leakage current density increases greatly due to the charge imbalance, resulting in a significant decrease in breakdown strength. It is worth mentioning that the breakdown strength of Fe<jats:sup>3+</jats:sup> and Ta<jats:sup>5+</jats:sup> ions co-doped film does not decrease due to the charge balance. Another important point is the recoverable energy storage density of the films co-doped with Fe<jats:sup>3+</jats:sup> and Ta<jats:sup>5+</jats:sup> ions have been greatly improved based on the fact that the maximum external electric field does not decrease and the maximum polarization under the same external electric field increases. On top of that, the hysteresis of the polarization has also been improved. Finally, the co-doped films with Fe<jats:sup>3+</jats:sup> and Ta<jats:sup>5+</jats:sup> ions have good frequency and temperature stability.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Anisotropic electrical transport and magnetic properties of FeSe<jats:sub>0.5</jats:sub>Te<jats:sub>0.5</jats:sub> single crystals, which are grown by the self-flux method, have been investigated. The in-plane resistivity shows a metallic-like temperature-dependence, while the out-of-plane resistivity shows a broad lump with maximum at around 64 K. The magnetization loops for <jats:italic>H</jats:italic>//c-axis and <jats:italic>H</jats:italic>//ab-plane are also different, for example, there is a typical second peak for <jats:italic>H</jats:italic>//c-axis. The in-plane critical current density is larger than the out-of-plane one. The coherence length and penetration depth are estimated by the Ginzburg-Landau theory. The anisotropic parameter <jats:italic>γ</jats:italic> depends on the applied magnetic field and the temperature. The coupling of superconducting FeSe(Te)-layers and the flux pinning mechanism relevant to anisotropy are also discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Structural, magnetic properties, critical behaviors and magnetic entropy changes of La<jats:sub>0.7-<jats:italic>x</jats:italic> </jats:sub>Gd<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Ca<jats:sub>0.3</jats:sub>MnO<jats:sub>3</jats:sub> (x=0, 0.05, 0.1) polycrystalline manganites have been investigated. The X-ray diffraction characterization shows that all the samples can be well indexed on an orthorhombic structure with Pnma space group. Magnetic measurements show that polycrystalline samples sequentially display the characteristics of cluster spin glass states, ferromagnetic states, ferromagnetic paramagnetic coexistence states and pure paramagnetic states with increasing temperature. The Curie temperature (T<jats:sub>c</jats:sub>) increases with increasing doping concentration x, and the ferromagnetic paramagnetic transform into a second-order phase transitions near the T<jats:sub>c</jats:sub>. Critical behaviors have been studied through the modified Arrott plots and the Kouvel-Fisher method. The critical exponents of polycrystalline samples are determined to be close to the critical exponents of the tricritical mean field model (x=0), 3D Ising model (x=0.05) and 3D Heisenberg model (x=0.1), indicating that their ferromagnetic coupling may be the result of the short-range interactions between spins in this system. The maximum magnetic entropy changes reach values of 3.99 J/(kg·K), 2.81 J/(kg·K) and 4.20 J/(kg·K) at the magnetic field of 7T, and the relative cooling power (RCP) values of La<jats:sub>0.7-<jats:italic>x</jats:italic> </jats:sub>Gd<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Ca<jats:sub>0.3</jats:sub>MnO<jats:sub>3</jats:sub> (x=0, 0.05, 0.1) are 478.8 J/kg, 431.1 J/kg and 536.98 J/kg respectively.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>a-IGZO thin films are prepared by pulsed laser deposition and fabricated into thin film transistors (TFTs) devices. <jats:italic>In-situ</jats:italic> X-ray photoelectron spectroscopy (XPS) illustrates that weakly bonded oxygen (O) atoms exist in a-IGZO thin films deposited under high O<jats:sub>2</jats:sub> pressure, but can be eliminated by vacuum annealing. The threshold voltage (V<jats:sub>th</jats:sub>) of the a-IGZO TFTs is shifted under positive gate bias, and the V<jats:sub>th</jats:sub> shift is positively related with the deposition pressure. A temperature varying experiment in the range of 20-300 K demonstrates that an activation energy of 144 meV is required for the V<jats:sub>th</jats:sub> shift, which is close to the activation energy for the migration of weakly bonded O atoms in a-IGZO thin films. Accordingly, the V<jats:sub>th</jats:sub> shift is attributed to the acceptor-like states induced by the accumulation of weakly bonded O atoms at the a-IGZO/SiO<jats:sub>2</jats:sub> interface under positive gate bias. The results provide insight into the mechanism for the V<jats:sub>th</jats:sub> shift of the a-IGZO TFTs, and are helpful to the reliability design.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>To discover the microcosmic mechanism of cavitation nucleation in pure water, the nucleation processes in pure water are simulated using the molecular dynamics method. Cavitation nucleation is generated by uniformly stretching of the system under isothermal conditions, and the formation and development of cavitation nuclei are simulated and discussed at the molecular level. The process of energy, pressure, and density are analyzed, and the tensile strength of the pure water and the critical volume of the bubble nuclei are investigated. The results show that critical states exist in the process of cavitation nucleation. In the critical state, the energy, density, and pressure of the system would change abruptly, and the steady cavitation nucleus would be produced if the energy barrier and critical volume has been broken through. System pressure and water density are the key factors in generating cavitation nuclei. When the critical state is broken through, the liquid is completely ruptured, and the volume of the cavitation nucleus increases rapidly to more than 100 nm<jats:sup>3</jats:sup> and then the surface tension of the bubble dominates the cavitation nucleus instead of intermolecular forces. The negative critical pressure of bubble nucleation is -198.6MPa, the corresponding critical volume is 13.84nm<jats:sup>3</jats:sup> and the nucleation rate is 2.42×10<jats:sup>32</jats:sup> m<jats:sup>-3</jats:sup> s<jats:sup>-1</jats:sup> in pure water at 300K. Temperature has a significant effect on nucleation, as temperature rises, nucleation thresholds decrease, and cavitation nucleation occurs earlier.</jats:p>