Abstract: GaN-based light-emitting diode (LED) thin films grown on Si(111) substrates are successfully detached and transferred to copper and silicon submounts, and then become 40mil high power vertical structure LED chips. Electroluminescence properties of the two kinds of chips with the same expitaxial structure are investigated at different forward current densities and ambient temperatures. The obtained results are as follows. 1) at the same temperature, the EL peak wavelength of the chip with copper submount is longer than that of the chip with silicon submount. Under 13 K, the EL peak wavelength of the chip with copper submount is about 6 nm longer than that of chip with silicon submount as the driving current increases from 0.01 mA to 400 mA. While under 300 K, the difference in EL peak wavelength between the two kinds of chips at 0.01 mA is only about 3 nm; as the current increases to 400 mA, the difference will tend to zero and the spectra will coincide. 2) At the same current density, as the temperature increases from 13 K to 320 K, the EL peak wavelengths of the two kinds of chips are S-shaped, and the spectra tend to coincide. 3)When the temperature is below 100 K, the current density droop effect of the chips with copper submount is more abvious than that of chips with silicon submount, while above 100 K, the results are just inverse. Perhaps, it is due to the fact that the differences in thermal expansion coefficient and thermal conductivity between the two kinds of submounts lead to the diffrent EL properties.

Abstract: With the effective Thomson scattering diagnostic of the laser plasmas produced under different laser conditions, the distinct asymmetry of the two peaks of the ion-acoustic waves are measured 150 μm in front of the target surface. The more intense peak appears at shorter wavelength when the electron temperature is higher, and switches to longer wavelength when the electron temperature is lower. The two-peak strcture, the asymmetry and the position of the more intensity peak of the ion-acoustic waves can be well interpreted with the Raman scattering effect. This paper, for the first time, establishes the corresponding relationship between Raman scattering of light and Thomson scattering of electons in laser plasmas.

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: By using multi-frame optical probing photography, we have discovered and investigated the large-scale "Horn Tip" plasma jet structures in the coronal region of line-focused laser-produced plasmas. These plasma jets always appear at the boundary between the hot plasma and the cold target material, or between two plasmas with different Z-numbers.

Abstract: The band structure and dielectric properties of the pure ZnO and the Al-doped ZnO were studied by using a first-principle ultrasoft pseudopotential approach of the plane wave based on the density functional theory. The pure ZnO and the Al-doped ZnO powders were prepared via the solid state reaction at 600°C with holding time of 1.5 h. The prepared powders were characterized by X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）. The dielectric parameters were determined by the vector network analyzer in the frequency range of 8.2—12.4 GHz. Results show that the volume of super-cell has no obvious change and the Fermi energy level is introduced into conduction band through introducing Al ions. XRD patterns indicate that all the samples have pure wurtzite structure of ZnO. It is found that Al ions form the substitutional impurity in ZnO crystal according to the result of XPS. The experimental results show that both the real part ε′ and imaginary part ε″ of permittivity of the samples are increased by Al doping, in agreement with the result of calculation.

Abstract: Grain boundary (GB) research is always the most fundamental and active study field in interface science. Grain boundary premelting (GBPM) is induced as a consequence of local inner strain around defects in material at high temperature. When GB premelting is under an external stress, it is referred to as stress induced GBPM (SIGBPM). Owing to the fact that the width of a GB usually is a few atoms thick, it is difficult to observe the GBPM directly in experiment, thus the development of computational simulation experiment can make up for the shortcomings in experiment. For this reason, a new method which is named phase field crystal (PFC) model based on density functional theory is proposed. Because the method can be used to simulate the evolution of macroscopic structure of polycrystalline material on a diffusive time and atomic scale, therefore, PFC has a great advantage in simulating the evolution of microstructure. In this paper, PFC method is used to investigate the annihilation process of dislocation pairs of premelted grain boundary under strain at high temperature. Simulated results show that the essence of separation process of sub-GB (SGB) from original GB is that sub-grain structures are generated. The SGB migration is the process of the new grain swallowing up the old one. The annihilation process of GBPM under applied strain at high temperature can be divided into two stage features. The first stage is the stage of system energy increasing, which is corresponding to the process of SGB migration, dislocation gliding; the second stage is the energy decreasing, which corresponds to the interaction of SGBs and annihilation of dislocations, while the speed of annihilation in this process is slow and the peak of energy curve is wide and smooth. According to the changing process of the atomic density distribution projected along the directions of x and y axis with strain increasing, we can reveal that the nature of annihilation of double dislocation pairs at high temperature is the process of two-step annihilations, of which the detailed process is not easy to observe at low temperature due to its fast annihilating speed of dislocation pairs.

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: The 1.06 μm laser with irradiance 3.5×1013W/cm2 was injected into Mg microtube target with lateral jet nozzle. The temporal evolution of X-ray spectra emitted from Mg10+ and Mg11+ ion along the side-blow direction was recorded by using X-ray streak camera. The results demonstrate that three-body recombination is the main mechanism to realize the strong population inversion between the excited state energy levels Is4p and Is3p of Mg10+ ion. The electron density in lateral jet nozzle measured by a 2660? UV laser probe coincides with density results deduced from the spectrum information.

Abstract: Germanium based metal oxide semiconductor (MOS) device has been a research hotspot and considered as a potential candidate for future complementary MOS (CMOS) technology due to its high and symmetric carrier mobility. However, the poor quality of gate dielectric/channel interface significantly restricts the performances of germanium based MOS devices. Besides, the solid-solubility and activation concentration of dopants in Ge are both quite low, and the dopants diffuse fast in Ge, which makes it difficult to achieve ultra-shallow junction with high dopant concentration, especially for Ge NMOS devices.To solve these problems, different techniques are proposed and overviewed. The proposed nitrogen-plasma-passivation method can effectively suppress the regrowth of germanium sub-oxide and reduce the interface state density. Thus the performance of the fabricated Ge NMOS device is significantly improved. To enhance the n-type dopant activation in Ge, the multiple implantation technique and the multiple annealing technique are proposed. High electrical activation over 1 1020 cm-3 is achieved, and the corresponding contact resistivity is reduced to 3.8 10-7 cm2. Besides, the implantation after germanide (IAG) technique is first proposed to modulate the Schottky barrier height (SBH). The record-low electron SBH of 0.10 eV is obtained by IAG technique, and the optimized process window is given. In addition, the poor thermal stability of NiGe restricts the further improvement in performance of Ge MOS device. P and Sb co-implantation technique and novel ammonium fluoride pretreatment method are proposed to improve the thermal stability of NiGe. The electrical characteristic of NiGe/Ge diode is also improved simultaneously. The results provide the guidelines for further enhancing the performances of germanium-based MOS devices.

Abstract: Based on the semi-classical theory，the pulsed-laser pumped D2O gas tera-Hz laser was theoretically analyzed，the relation between the intensity of pumping laser and the output tera-Hz laser light was studied and numerically calculated. According to the result of calculation，the intensity of the output tera-Hz laser light increased approximately linearly with that of the input laser in a certain range，but gradually decreased because of the bottleneck effect when the intensity of the input laser exceeded a fixed value，and for given gas pressure，cavity length and operating temperature，an optimal intensity of pumping laser exists. A frequency tuning range of the output signal occurred when the intensity of the input laser was strong enough.