Abstract: Laboratory astrophysics is a rapid developing field studying astrophysical or astronomical processes on a high-power pulsed facility in laboratory. It has been proved that with the similarity criteria, the parameters in astrophysical processes can be transformed into those under laboratory conditions. With appropriate experimental designs the astrophysical processes can be simulated in laboratory in a detailed and controlled way. Magnetic fields play an important role in many astrophysical processes. Recently, the generation of strong magnetic fields and their effects on relevant astrophysics have attracted much interest. According to our previous work, a strong magnetic field can be induced by a huge current formed by the background cold electron flow around the laser spot when high power laser pulses irradiate a metal wire. In this paper we use this scheme to produce a strong magnetic field and observe its effect on a bow shock on the Shenguang II (SG II) laser facility. The strength of the magnetic field is measured by B-dot detectors. With the measured results, the magnetic field distribution is calculated by using a three-dimension code. Another bunch of lasers irradiates a CH planar target to generate a high-speed plasma. A bow shock is formed in the interaction of the high-speed plasma with the metal wire under the strong magnetic condition. The effects of the strong magnetic field on the bow shock are observed by shadowgraphy and interferometry. It is shown that the Mach number of the plasma flow is reduced by the magnetic field, leading to an increase of opening angle of the bow shock and a decrease of the density ratio between downstream and upstream. In addition, according to the similarity criteria, the experimental parameters of plasma are scaled to those in space. The transformed results show that the magnetized plasma around the wire, produced by X-ray emitted from the laser-irradiated planar target in the experiment, is suitable for simulating solar wind in astrophysics. In this paper, we provide another method to produce strong magnetic field, apply it to a bow shock laboratory astrophysical study, and also generate the magnetized plasma which can be used to simulate solar wind in the future experiments.

Abstract: One-dimensional (1D) graphene superlattices were formed on a prototypical high index surface-Cu(410)-O. Atomic hydrogen adsorption on the superlattice was studied by using Raman spectroscopy, low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Selective H adsorption due to the 1D modulation from the Cu substrate was observed in defect-free graphene area. Most H adatoms occupy the same positions in the 1D graphene superlattice stripes, as revealed by STM. This opens the possibility for further graphene property tuning through 1D superlattices. In addition to H monomers and dimers, a new type of trimer configuration was also observed.

Abstract: As an ideal single-photon source, quantum dots (QDs) can play a unique role in the field of quantum information. Controlling QD exciton spontaneous emission can be achieved by anti-phase coupling between QD exciton dipole field and Au dipole field after QD film has been transferred onto the Si substrate covered by Au nanoparticles. In experiment, the studied InAs/GaAs QDs are grown by molecular beam epitaxy (MBE) on a (001) semi-insulation substrate. The films containing QDs with different GaAs thickness values are separated from the GaAs substrate by etching away the AlAs sacrificial layer and transferring the QD film to the silicon wafer covered by Au nanoparticles with a diameter of 50 nm. The distance 〈i〉D〈/i〉 (thickness of GaAs) from the surface of the Au nanoparticles to the QD layer is 10, 15, 19, 25, and 35 nm, separately. A 640-nm pulsed semiconductor laser with a 40-ps pulse length is used to excite the QD samples for measuring QD exciton photoluminescence and time-resolved photoluminescence spectra at 5 K. It is found that when the distance 〈i〉D〈/i〉 is 15–35 nm the spontaneous emission rate of exciton is suppressed. And when 〈i〉D〈/i〉 is close to 19 nm, the QD spontaneous emission rate decreases to 〈inline-formula〉〈tex-math id="M2"〉\begin{document}$ ~{10}^{-3} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211863_M2.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211863_M2.png"/〉〈/alternatives〉〈/inline-formula〉, which is consistent with the theoretical calculations. The physical mechanism of long-lived exciton luminescence observed in experiment lies in the fact that Au nanoparticles scatter the light field of the exciton radiation in the QD wetting layer, and the phase of the scattered field is opposite to the phase of the exciton radiation field. Therefore, the destructive interference between the exciton radiation field and scattering field of Au nanoparticles results in long-lived exciton emission observed in experiment.

Abstract: In the past few decades, the studies of exciton emissions coupled with the metal nanoparticles have mainly focused on the enhancing exciton radiation and reducing exciton lifetime by near-field coupling interactions between excitons and metal nanoparticles. Only in recent years has the plasmon-field-induced to extend exciton lifetime (inhibition of the exciton emission) been reported. Experimentally, for observing a long-lifetime exciton state it needs to satisfy a condition of 〈inline-formula〉〈tex-math id="M8"〉\begin{document}$kz\sim1$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M8.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M8.png"/〉〈/alternatives〉〈/inline-formula〉, instead of near-field condition of 〈inline-formula〉〈tex-math id="M9"〉\begin{document}$ kz\ll 1 $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M9.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M9.png"/〉〈/alternatives〉〈/inline-formula〉, where 〈inline-formula〉〈tex-math id="M10"〉\begin{document}$k=2{\pi }n/\lambda$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M10.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M10.png"/〉〈/alternatives〉〈/inline-formula〉 is the wavevector, 〈inline-formula〉〈tex-math id="M11"〉\begin{document}$ n $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M11.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M11.png"/〉〈/alternatives〉〈/inline-formula〉 is the refractive index, 〈inline-formula〉〈tex-math id="M12"〉\begin{document}$ \lambda $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M12.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M12.png"/〉〈/alternatives〉〈/inline-formula〉 is the wavelength, and 〈inline-formula〉〈tex-math id="M13"〉\begin{document}$ z $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M13.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M13.png"/〉〈/alternatives〉〈/inline-formula〉 is the separation distance between the emitter and metal nanoparticle. Thus, in this paper, we tune the exciton emission wavelength by applying hydrostatic pressure to achieve the condition of 〈inline-formula〉〈tex-math id="M14"〉\begin{document}$kz\sim1$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M14.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M14.png"/〉〈/alternatives〉〈/inline-formula〉 in order to in detail investigate the coupling between excitons and metal nanoparticles. The studied InAs/GaAs quantum dot (QD) sample is grown by molecular beam epitaxy on a (001) semi-insulating GaAs substrate. After the AlAs sacrificial layer is etched with hydrofluoric acid, the QD film sample is transferred onto an Si substrate covered with Ag nanoparticles. Then the sample is placed in the diamond anvil cell device combined with a piezoelectric ceramic. In this case we can measure the photoluminescence and time-resolved photoluminescence spectra of the QD sample under different pressures. It is found that the observed longest exciton lifetime is 〈inline-formula〉〈tex-math id="M15"〉\begin{document}$(120\pm 4)\times 10~\rm{n}\rm{s}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M15.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M15.png"/〉〈/alternatives〉〈/inline-formula〉 at a pressure of 〈inline-formula〉〈tex-math id="M16"〉\begin{document}$ 1.38\;\rm{G}\rm{P}\rm{a} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M16.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M16.png"/〉〈/alternatives〉〈/inline-formula〉, corresponding the exciton emission wavelength of 〈inline-formula〉〈tex-math id="M17"〉\begin{document}$ 797.49\;\rm{n}\rm{m} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M17.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M17.png"/〉〈/alternatives〉〈/inline-formula〉〈i〉,〈/i〉 which is about 〈inline-formula〉〈tex-math id="M18"〉\begin{document}$ 1200 $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M18.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M18.png"/〉〈/alternatives〉〈/inline-formula〉 times longer than the exciton lifetime of 〈inline-formula〉〈tex-math id="M19"〉\begin{document}$\sim 1\;\rm{n}\rm{s} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M19.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221344_M19.png"/〉〈/alternatives〉〈/inline-formula〉 in QDs without the influence of Ag nanoparticles. The experimental results can be understood based on the destructive interference between the quantum dot exciton radiation field and the scattering field of metal nanoparticles. This model proposes a convenient way to increase the emission lifetime of dipoles on a large scale, and is expected to be applied to quantum information processing, optoelectronic applications, fundamental physics researches such as Bose-Einstein condensates.

Abstract: Flexible organic field-effect transistors (OFETs) have revealed wide prospect in their applications to the flexible display, flexible sensor, flexible radio frequency tag and flexible integrated circuit due to their advantages such as foldability, light weight of device and low-cost fabrication process. On the basis of the introduction of advancement in the study of flexible OFETs in this paper, a broad overview about device structures of flexible OFETs, substrate materials, gate insulating layer materials, active layer materials and electrode materials used for flexible OFETs is given, the fabricating process of flexible OFETs is explained, and the effect of bending pattern on the performance of flexible OFETs is discussed. Finally, the application areas of flexible OFETs are summarized and prospected.

Abstract: Flexible organic non-volatile memory field-effect transistors (ONVMFETs) are promising candidates in the field of flexible organic electronic devices, which can be used in flexible radio frequency tags, memories, integrated circuits and large-area displays, because of their remarkable advantages such as flexibility, lightweight, low cost and large-area organic electronics. On the basis of the introduction of the development of flexible ONVMFETs in terms of substrates, structures and characteristics, the classification of flexible ONVMFETs is summarized. Meanwhile, we discuss the effects of mechanical stress and temperature on the performance of flexible ONVMFET. Finally, some prospects as well as the challenges are pointed out.

Abstract: Materials can be experimentally characterized up to terapascal pressures by sending a laser-induced shock wave through a sample that is pre-compressed inside a diamond-anvil cell. Pre-compression expands the ability to control the initial condition, allowing access to thermodynamic states from the principal Hugoniot and enter into the 10 TPa to 100 TPa (0.1-1 Gbar) pressure range that is relevant to planetary science. We demonstrate here a laser-driven shock wave in a water sample that is pre-compressed in a diamond anvil cell. The compression factors of the dynamic and static techniques are multiplied. This approach allows access to a family of Hugoniot curves which span the P-T phase diagram of fluid water to high density. According to the loading characteristics of the SG-Ⅱ high-power laser, the traditional diamond anvil cell is improved and optimized, and a new diamond anvil cell target adapting to high power laser loading is developed. In order to adapt to laser shock, the diamond window should be thin (100 μm) enough so that the shock can propagate to the sample before the side rarefaction erodes too much the shock planarity. With a thickness of 100 mm over an aperture of 600 μm diameter, a pre-compressed water sample at 0.5 GPa can be obtained. The water is pre-compressed to 0.5 GPa by using the diamond anvil cell. Hugoniot curve is partially followed starting from pre-compression at a pressure of 0.5 GPa. Pressure, density, and temperature data for pre-compressed water are obtained in a pressure range from 150 GPa to 350 GPa by using the laser-driven shock compression technique. Our P-ρ-T data totally agree with the results from the model based on quantum molecular dynamics calculations. These facts indicate that this water model can be used as the standard for modeling interior structures of Neptune, Uranus, and exoplanets in the liquid phase in the multi-Mbar range and should improve our understanding of these types of planets.

Abstract: In this paper, we study the electrical resistance of nonmagnetic amorphous alloy Cu60Zr20Hf10Ti10 and amorphous ferromagnet Fe61Co7Zr10Mo5W2B15. We fit the c urve in the light of special models, and analyze the origination of the minima which occurs in both of the samples. The contributions both from the disorder structure and magnetic status are discussed.