A transmission-mode GaAs photocathode includes four layers of glass, Si3N4, Gal-xAlxAs and GaAs. A gradientdoping photocathode sample was obtained by molecular beam epitaxy and its transmittance was measured by spectr...A transmission-mode GaAs photocathode includes four layers of glass, Si3N4, Gal-xAlxAs and GaAs. A gradientdoping photocathode sample was obtained by molecular beam epitaxy and its transmittance was measured by spectrophotometer from 600 nm to 1100 nm. The theoretical transmittance is derived and simulated based on the matrix formula for thin film optics. The simulation results indicate the influence of the transition layers and the three thin-film layers except glass on the transmittance spectra. In addition, a fitting coefficient needed for error modification enters into the fitted formula. The fitting results show that the relative error in the full spectrum reduces from 19.51% to 4.35% after the formula is modified. The coefficient and the thicknesses are gained corresponding to the minimum relative error, meanwhile each layer and total thin-film thickness deviation in the module can be controlled within 73. The presence of glass layer roughness, layer interface effects and surface oxides is interpreted on the modification.展开更多
Two types of transmission-mode GaAs photocathodes grown by molecular beam epitaxy are compared in terms of activation process and spectral response, one has a gradient-doping structure and the other has a uniform-dopi...Two types of transmission-mode GaAs photocathodes grown by molecular beam epitaxy are compared in terms of activation process and spectral response, one has a gradient-doping structure and the other has a uniform-doping structure. The experimental results show that the gradient-doping photocathode can obtain a higher photoemission capability than the uniform-doping one. As a result of the downward graded band-bending structure, the cathode performance parameters, such as the electron average diffusion length and the surface electron escape probability obtained by fitting quantum yield curves, are greater for the gradient-doping photocathode. The electron diffusion length is within a range of from 2.0 to 5.4μm for doping concentration varying from 10^19 to 10^18 cm^-3 and the electron average diffusion length of the gradient-doping photocathode achieves 3.2 μm.展开更多
In order to develop the photodetector for effective blue-green response, the 18-mm-diameter vacuum image tube combined with the transmission-mode Alo.7Gao.3Aso.9Po.1/GaAso.9Po.1 photocathode grown by molecular beam ep...In order to develop the photodetector for effective blue-green response, the 18-mm-diameter vacuum image tube combined with the transmission-mode Alo.7Gao.3Aso.9Po.1/GaAso.9Po.1 photocathode grown by molecular beam epitaxy is tentatively fabricated. A comparison of photoelectric property, spectral characteristic and performance parameter be- tween the transmission-mode GaAsP-based and blue-extended GaAs-based photocathodes shows that the GaAsP-based photocathode possesses better absorption and higher quantum efficiency in the blue-green waveband, combined with a larger surface electron escape probability. Especially, the quantum efficiency at 532 nm for the GaAsP-based photocathode achieves as high as 59%, nearly twice that for the blue-extended GaAs-based one, which would be more conducive to the underwater range-gated imaging based on laser illumination. Moreover, the simulation results show that the favorable blue-green response can be achieved by optimizing the emission-layer thickness in a range of 0.4 μm-0.6 μm.展开更多
A 150-nm-thick CaN photocathode with a Mg doping concentration of 1.6 × 1017 cm-3 is activated by Cs/O in an ultrahigh vacuum chamber, and a quantum efficiency （QE） curve of the negative electron affinity trans...A 150-nm-thick CaN photocathode with a Mg doping concentration of 1.6 × 1017 cm-3 is activated by Cs/O in an ultrahigh vacuum chamber, and a quantum efficiency （QE） curve of the negative electron affinity transmission-mode （t-mode） of the GaN photocathode is obtained. The maximum QE reaches 13.0% at 290 nm. According to the t-mode QE equation solved from the diffusion equation, the QE curve is fitted. From the fitting results, the electron escape probability is 0.32, the back-interface recombination velocity is 5 ×104 cm. s^-1, and the electron diffusion length is 116 nm. Based on these parameters, the influence of CaN thickness on t-mode QE is simulated. The simulation shows that the optimal thickness of GaN is 90 nm, which is better than the 150-nm GaN.展开更多
目的考察复合式UCT-MBR对生活污水的脱氮除磷效果.方法针对生活污水特点,采用除磷能力较强的UCT(the University of Cape Town process)与膜生物反应器(Membrane Bioreactor,MBR)相结合的工艺,在反应器内投加立体弹性填料,构成复合式UCT...目的考察复合式UCT-MBR对生活污水的脱氮除磷效果.方法针对生活污水特点,采用除磷能力较强的UCT(the University of Cape Town process)与膜生物反应器(Membrane Bioreactor,MBR)相结合的工艺,在反应器内投加立体弹性填料,构成复合式UCT-MBR,形成悬浮污泥与附着污泥共存的复杂生物相体系.结果在HRT=8～12 h,SRT=30 d,膜出水量为10 L/h,气水比为40∶1条件下,经过42 d的污泥驯化,挂膜成功,其后60 d的稳定运行中,对CODCr、NH3-N平均去除率分别达到95.7%、97.7%,出水ρ(NH3-N)<2.4 mg/L.回流比为300%和400%时,TN去除效率分别为78.9%、84.1%,出水ρ(TN)<15 mg/L,并且由于生物膜的作用在好氧区发生了同步硝化反硝化.当硝化液回流比为300%时,TP的去除效果最佳,为83.2%,出水ρ(TP)<1 mg/L,满足一级B标准.结论采用该工艺处理生活污水运行稳定,具有较强的抗冲击负荷能力,出水水质良好,达到了国家生活杂用水的要求.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 60678043)the Research and Innovation Plan for Graduate Students of Jiangsu Higher Education Institutions of China (Grant No. CX09B-096Z)
文摘A transmission-mode GaAs photocathode includes four layers of glass, Si3N4, Gal-xAlxAs and GaAs. A gradientdoping photocathode sample was obtained by molecular beam epitaxy and its transmittance was measured by spectrophotometer from 600 nm to 1100 nm. The theoretical transmittance is derived and simulated based on the matrix formula for thin film optics. The simulation results indicate the influence of the transition layers and the three thin-film layers except glass on the transmittance spectra. In addition, a fitting coefficient needed for error modification enters into the fitted formula. The fitting results show that the relative error in the full spectrum reduces from 19.51% to 4.35% after the formula is modified. The coefficient and the thicknesses are gained corresponding to the minimum relative error, meanwhile each layer and total thin-film thickness deviation in the module can be controlled within 73. The presence of glass layer roughness, layer interface effects and surface oxides is interpreted on the modification.
基金supported by the National Natural Science Foundation of China(Grant Nos.60801036 and 61067001)the Key Science and Technology Project of Henan Province of China(Grant No.112102210202)the Research and Innovation Plan for Graduate Students of Jiangsu Higher Education Institutions of China(Grant No.CX09B_096Z)
文摘Two types of transmission-mode GaAs photocathodes grown by molecular beam epitaxy are compared in terms of activation process and spectral response, one has a gradient-doping structure and the other has a uniform-doping structure. The experimental results show that the gradient-doping photocathode can obtain a higher photoemission capability than the uniform-doping one. As a result of the downward graded band-bending structure, the cathode performance parameters, such as the electron average diffusion length and the surface electron escape probability obtained by fitting quantum yield curves, are greater for the gradient-doping photocathode. The electron diffusion length is within a range of from 2.0 to 5.4μm for doping concentration varying from 10^19 to 10^18 cm^-3 and the electron average diffusion length of the gradient-doping photocathode achieves 3.2 μm.
基金supported by the National Natural Science Foundation of China(Grant No.61301023)the Science and Technology on Low-Light-Level Nigh Vision Laboratory Foundation,China(Grant No.BJ2014001)
文摘In order to develop the photodetector for effective blue-green response, the 18-mm-diameter vacuum image tube combined with the transmission-mode Alo.7Gao.3Aso.9Po.1/GaAso.9Po.1 photocathode grown by molecular beam epitaxy is tentatively fabricated. A comparison of photoelectric property, spectral characteristic and performance parameter be- tween the transmission-mode GaAsP-based and blue-extended GaAs-based photocathodes shows that the GaAsP-based photocathode possesses better absorption and higher quantum efficiency in the blue-green waveband, combined with a larger surface electron escape probability. Especially, the quantum efficiency at 532 nm for the GaAsP-based photocathode achieves as high as 59%, nearly twice that for the blue-extended GaAs-based one, which would be more conducive to the underwater range-gated imaging based on laser illumination. Moreover, the simulation results show that the favorable blue-green response can be achieved by optimizing the emission-layer thickness in a range of 0.4 μm-0.6 μm.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60871012)the National Key Laboratory of Science and Technology Foundation on Low-Light-Level Night Vision,China (Grant No. J20110104)the Research and Innovation Plan for Graduate Students of Jiangsu Higher Education Institutions (Grant No. CXZZ11 0238)
文摘A 150-nm-thick CaN photocathode with a Mg doping concentration of 1.6 × 1017 cm-3 is activated by Cs/O in an ultrahigh vacuum chamber, and a quantum efficiency （QE） curve of the negative electron affinity transmission-mode （t-mode） of the GaN photocathode is obtained. The maximum QE reaches 13.0% at 290 nm. According to the t-mode QE equation solved from the diffusion equation, the QE curve is fitted. From the fitting results, the electron escape probability is 0.32, the back-interface recombination velocity is 5 ×104 cm. s^-1, and the electron diffusion length is 116 nm. Based on these parameters, the influence of CaN thickness on t-mode QE is simulated. The simulation shows that the optimal thickness of GaN is 90 nm, which is better than the 150-nm GaN.
文摘目的考察复合式UCT-MBR对生活污水的脱氮除磷效果.方法针对生活污水特点,采用除磷能力较强的UCT(the University of Cape Town process)与膜生物反应器(Membrane Bioreactor,MBR)相结合的工艺,在反应器内投加立体弹性填料,构成复合式UCT-MBR,形成悬浮污泥与附着污泥共存的复杂生物相体系.结果在HRT=8～12 h,SRT=30 d,膜出水量为10 L/h,气水比为40∶1条件下,经过42 d的污泥驯化,挂膜成功,其后60 d的稳定运行中,对CODCr、NH3-N平均去除率分别达到95.7%、97.7%,出水ρ(NH3-N)<2.4 mg/L.回流比为300%和400%时,TN去除效率分别为78.9%、84.1%,出水ρ(TN)<15 mg/L,并且由于生物膜的作用在好氧区发生了同步硝化反硝化.当硝化液回流比为300%时,TP的去除效果最佳,为83.2%,出水ρ(TP)<1 mg/L,满足一级B标准.结论采用该工艺处理生活污水运行稳定,具有较强的抗冲击负荷能力,出水水质良好,达到了国家生活杂用水的要求.
