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Dive into the research topics where Junju Zhang is active.

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Featured researches published by Junju Zhang.


international vacuum electron sources conference and nanocarbon | 2010

Higher quantum efficiency by optimizing GaN photocathode structure

Xiaoqian Fu; Bengkang Chang; Biao Li; Xiaohui Wang; Yujie Du; Junju Zhang

Higher quantum efficiency by optimizing GaN photocathode structure is reported. AlN was used to substitute for GaN as buffer layer, which could act as a potential barrier due to its higher energy gap and reflect electrons back toward the surface direction. Graded-doping structure was used to replace uniform-doping structure, which introduced three built-in electrical fields for the different doping concentrations.


Applied Optics | 2013

Attenuation performance of reflection-mode AlGaN photocathode under different preparation methods

Guanghui Hao; Mingzhu Yang; Benkang Chang; Xinlong Chen; Junju Zhang; Xiaoqian Fu

To research the attenuation performance of the AlGaN photocathode, three samples with the same structures grown by metalorganic chemical vapor deposition were activated with three different activation methods, which are called Cs-only, Cs-O, and Cs-O-Cs activation, respectively. The spectral responses and attenuated photocurrents of the three AlGaN photocathodes were measured. The results show that the Cs-O activated AlGaN photocathode exhibits the lowest attenuation speed in the first few hours, and the attenuation speed of the Cs-only activated one is fastest. After attenuating for 90 min, the attenuation photocurrent curve of the Cs-O-Cs activated sample is coincident with that of the Cs-O activated one. The main factor affecting the photocurrent attenuation is related to Cs atoms desorbed from the photocathode surface.


international vacuum electron sources conference and nanocarbon | 2010

Comparison of photoemission behavior between negative electron affinity GaAs and GaN photocathodes

Yijun Zhang; Jijun Zou; Xiaohui Wang; Benkang Chang; Yunsheng Qian; Junju Zhang; Pin Gao

In view of the important application of GaAs and GaN photocathodes in electron sources [1,2], the difference in the photoemission behavior, namely the activation process and quantum yield decay, between the two typical types of III-V compound photocathodes has been investigated using the multi-information measurement system. The reflection-mode GaAs and GaN photocathode samples both were grown by metal organic chemical vapor deposition, wherein the former is a substrate/AlGaAs/GaAs structure and the latter is a sapphire/AlN/GaN structure. The active layer in both structures was uniformly doped with p-type zinc and magnesium respectively.


Selected Papers from Conferences of the Photoelectronic Technology Committee of the Chinese Society of Astronautics: Optical Imaging, Remote Sensing, and Laser-Matter Interaction 2013 | 2014

Algorithm selective method of infrared/visual image fusion system based on air humidity

Bin Sun; Junju Zhang; Benkang Chang; Chaobo Min; Yingjie Li

To find out the best infrared and visible fusion system of fusion algorithm which has excellent target detection characteristics in different environment, we proposed a new fusion algorithm selective rule. We also defined new concepts: fusion algorithm coefficient and the equivalent transmissivity of system. Using local-target contrast, local-target articulation to calculate fusion algorithm coefficient, we can estimate the target detection performance of fusion system when it working in different air humidity environment. Also, we make use of infrared and visible fusion system designed by ourselves to verify this method. Besides fusion algorithm coefficient, we also use subjective evaluation to evaluate the target detection performance of fusion algorithm. At last, the best algorithm or the method which is most consistent with human visual in different conditions were found. Through this work, we can provide the basis for the algorithm of choice in the fusion system.


international vacuum electron sources conference and nanocarbon | 2010

Surface analysis for NEA GaAs photocathode

Junju Zhang; Benkang Chang; Rongguo Fu; Yafeng Qiu; Yunsheng Qian

To study the effect surface defects imposed on NEA GaAs photocathode, a surface analysis instrument shown in Fig. 1 has been designed, which is composed of a microimager, a 2-D displacement platform, an auto-focus equipment, a computer.


international vacuum electron sources conference and nanocarbon | 2010

Research of NEA GaN photocathode performance parameters on the effect of quantum efficiency

Yujie Du; Benkang Chang; Xiaoqian Fu; Biao Li; Junju Zhang

Research of negative electron affinity GaN ultraviolet photocathode performance parameters on the effect of quantum efficiency is reported. Electronic surface escaping probability is one of the important parameters in comprehensive measure the level of the preparation of GaN optoelectronic cathode.


international vacuum electron sources conference and nanocarbon | 2010

Electron emitting features and design of thermionic electron area emission sources

Qiu Yafeng; Benkang Chang; Junju Zhang; Qian Yunsheng; Fu Rongguo

In vacuum system, area source electron gun emits electrons to bombard the standard screen. With the first anode and the second anode in different potentials, the images show the features of divergent, uniform, convergence and submerge. Photos, images acquired by brightness meter, and the image gray values are listed in Table 1. By image gray value analysis, it can be seen that in item no. 1, the electrons emitted by area source electron gun are divergent ( not remarkable) ; in no. 2, it is uniform; in no. 3 it is convergence and in no. 4 it is submerged. It is deduced that when the voltage of first anode of electron gun is -4000 V and the second anode voltage is -2000 V, the fluorescence screen receives the uniformly distributed electrons. The difference is less than 5%. Based on this theory, the area source electron gun is developed. The electron gun is placed in a vacuum better than 1 x 10-4Pa to be tested and it is further verified that its electron emission is uniform. The successful development of hot-electron area source provide an effective guarantee for testing the fluorescence screen parameters such as uniformity, brightness, luminous efficiency and afterglow .


Applied Surface Science | 2012

Theoretical study of Cs adsorption on GaN(0 0 0 1) surface

Yujie Du; Benkang Chang; Xiaohui Wang; Junju Zhang; Biao Li; Mei-Shan Wang


Optik | 2012

Optimizing GaN photocathode structure for higher quantum efficiency

Xiaoqian Fu; Xiaohui Wang; Yongfu Yang; Benkang Chang; Yujie Du; Junju Zhang; Rongguo Fu


Chinese Optics Letters | 2012

First principle study of the influence of vacancy defects on optical properties of GaN

Yujie Du; Benkang Chang; Honggang Wang; Junju Zhang; Mei-Shan Wang

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Benkang Chang

Nanjing University of Science and Technology

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Yujie Du

Nanjing University of Science and Technology

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Xiaoqian Fu

Nanjing University of Science and Technology

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Biao Li

Nanjing University of Science and Technology

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Bin Sun

Nanjing University of Science and Technology

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Chaobo Min

Nanjing University of Science and Technology

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Xiaohui Wang

Nanjing University of Science and Technology

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Yingjie Li

Nanjing University of Science and Technology

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Bengkang Chang

Nanjing University of Science and Technology

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