Gas spark switch is one of the key parts in pulsed power technology.Electrode erosion has great influence on the switch performance and lifetime.In this paper,a field distortion gas switch is selected for the experime...Gas spark switch is one of the key parts in pulsed power technology.Electrode erosion has great influence on the switch performance and lifetime.In this paper,a field distortion gas switch is selected for the experiment and a great deal of discharging experiments have been conducted in different test conditions.The forming process of etch pit as well as its influencing factors is discussed briefly and surface roughness coefficient(SRC) of the electrode is put forward to evaluate the state of electrode erosion.Experimental results show that current peak plays an important role in electrode erosion when waveforms of discharge current are the same,and electric charge and oscillation frequency of discharge current also have great effect on the electrode erosion when waveforms of discharge current are different.With the increase of discharge times,SRC decreases slowly at first and then decreases quickly after three thousand of discharge times.展开更多
A GaSb crystal incorporated with Mn has been grown by the Bridgman method on the Polizon facility onboard the FOTON-M3 spacecraft. Structural defects and growth striations have been successfully revealed by the chemic...A GaSb crystal incorporated with Mn has been grown by the Bridgman method on the Polizon facility onboard the FOTON-M3 spacecraft. Structural defects and growth striations have been successfully revealed by the chemical etching method. By calculating various parameters of the convection, the striation patterns can be explained, and the critical value of the Taylor number, which characterizes the convective condition of the rotating magnetic field induced azimuthal flow, was shown. The stresses generated during crystal growth can be reflected by the observations of etch pit distribution and other structural defects. Suggestions for improving the space experiment to improve the quality of the crystal are given.展开更多
Infrared(IR) detectors have important applications in numerous civil and military sectors. Hg Cd Te is one of the most important materials for IR detector manufacture. This review systematically discusses the progress...Infrared(IR) detectors have important applications in numerous civil and military sectors. Hg Cd Te is one of the most important materials for IR detector manufacture. This review systematically discusses the progress of Hg Cd Te materials grown via molecular-beam epitaxy(MBE) for IR detection in terms of material physics, structure design, and fabrication. The material physics of Hg Cd Te includes crystal information, band structure, and electrical and optical properties. The characterization methods of the As-grown Hg Cd Te materials are also summarized. Then, four design structures of Hg Cd Te for IR detectors, with multilayer, superlattice, double-layer heterojunction, and barrier properties, which significantly improve the device performance,are discussed. The third section summarizes the studies on Hg Cd Te MBE-grown on different substrates, including Cd Zn Te, Si,and Ga Sb, in recent decades. This review discusses the factors influencing the growth of the Hg Cd Te film and their relationships and optimal conditions. Finally, we present the prospects and challenges associated with the fabrication and applications of Hg Cd Te materials for IR detectors.展开更多
La2CuO4 and La1.86Sr0.14CuO4 single crystals were obtained by traveling solvent floating zone method. There were five kinds of defects in these single crystals: cracks, inclusions, gas bubbles, unhomogeneous distribut...La2CuO4 and La1.86Sr0.14CuO4 single crystals were obtained by traveling solvent floating zone method. There were five kinds of defects in these single crystals: cracks, inclusions, gas bubbles, unhomogeneous distribution of Sr2+, and substructures. CH3COOH aqueous solution was used to etch these single crystals, and the etch-pit density was calculated. The fort-nation mechanism of these defects was discussed. It is suggested that the good preparation of raw materials and the stringent growth conditions play an important role in growing high quality single crystals.展开更多
Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals tha...Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals that heat transfered by convection is greater than heat transfered by radiation. Considering the calculation results, Si spheres were dropped in the free-fall tower at low pressure state (0.2×105-0.5×105 Pa) to slow heat transfer by convection. After dash etching for 60 min, low pressure Si spheres have less etch pits, i.e., 80% for etch pit density and 8% for etch pit-area ratio compared to normal one. Furthermore, the conversion efficiency was improved from 6.57% (normal pressure spherical Si solar cell) to 9.56% (low one), which is 45% relative increase. The improvement is due to decrease of undercooling and increase of crystal growth duration. These results demonstrate that the dropping method at low pressure state is useful for fabricating high performance spherical Si solar cells.展开更多
基金Project Supported by National Natural Science Foundation of China(No.50637010)
文摘Gas spark switch is one of the key parts in pulsed power technology.Electrode erosion has great influence on the switch performance and lifetime.In this paper,a field distortion gas switch is selected for the experiment and a great deal of discharging experiments have been conducted in different test conditions.The forming process of etch pit as well as its influencing factors is discussed briefly and surface roughness coefficient(SRC) of the electrode is put forward to evaluate the state of electrode erosion.Experimental results show that current peak plays an important role in electrode erosion when waveforms of discharge current are the same,and electric charge and oscillation frequency of discharge current also have great effect on the electrode erosion when waveforms of discharge current are different.With the increase of discharge times,SRC decreases slowly at first and then decreases quickly after three thousand of discharge times.
基金supported by the Space Agency of China and the Chinese Academy of Sciences
文摘A GaSb crystal incorporated with Mn has been grown by the Bridgman method on the Polizon facility onboard the FOTON-M3 spacecraft. Structural defects and growth striations have been successfully revealed by the chemical etching method. By calculating various parameters of the convection, the striation patterns can be explained, and the critical value of the Taylor number, which characterizes the convective condition of the rotating magnetic field induced azimuthal flow, was shown. The stresses generated during crystal growth can be reflected by the observations of etch pit distribution and other structural defects. Suggestions for improving the space experiment to improve the quality of the crystal are given.
基金supported by the National Natural Science Foundation of China(Grant Nos.52072059,12274061,11774044,and 61971094)the Natural Science Foundation of Sichuan(Grant Nos.2022NSFSC0870,and2022NSFSC0485)+1 种基金the Foundation of Sichuan Excellent Young Talents(Grant No.2021JDJQ0015)the Fundamental Research Funds for the Central Universities(Grant No.ZYGX2020J023)。
文摘Infrared(IR) detectors have important applications in numerous civil and military sectors. Hg Cd Te is one of the most important materials for IR detector manufacture. This review systematically discusses the progress of Hg Cd Te materials grown via molecular-beam epitaxy(MBE) for IR detection in terms of material physics, structure design, and fabrication. The material physics of Hg Cd Te includes crystal information, band structure, and electrical and optical properties. The characterization methods of the As-grown Hg Cd Te materials are also summarized. Then, four design structures of Hg Cd Te for IR detectors, with multilayer, superlattice, double-layer heterojunction, and barrier properties, which significantly improve the device performance,are discussed. The third section summarizes the studies on Hg Cd Te MBE-grown on different substrates, including Cd Zn Te, Si,and Ga Sb, in recent decades. This review discusses the factors influencing the growth of the Hg Cd Te film and their relationships and optimal conditions. Finally, we present the prospects and challenges associated with the fabrication and applications of Hg Cd Te materials for IR detectors.
文摘La2CuO4 and La1.86Sr0.14CuO4 single crystals were obtained by traveling solvent floating zone method. There were five kinds of defects in these single crystals: cracks, inclusions, gas bubbles, unhomogeneous distribution of Sr2+, and substructures. CH3COOH aqueous solution was used to etch these single crystals, and the etch-pit density was calculated. The fort-nation mechanism of these defects was discussed. It is suggested that the good preparation of raw materials and the stringent growth conditions play an important role in growing high quality single crystals.
基金This work was partly financially supported by NEDO.
文摘Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals that heat transfered by convection is greater than heat transfered by radiation. Considering the calculation results, Si spheres were dropped in the free-fall tower at low pressure state (0.2×105-0.5×105 Pa) to slow heat transfer by convection. After dash etching for 60 min, low pressure Si spheres have less etch pits, i.e., 80% for etch pit density and 8% for etch pit-area ratio compared to normal one. Furthermore, the conversion efficiency was improved from 6.57% (normal pressure spherical Si solar cell) to 9.56% (low one), which is 45% relative increase. The improvement is due to decrease of undercooling and increase of crystal growth duration. These results demonstrate that the dropping method at low pressure state is useful for fabricating high performance spherical Si solar cells.
