Dr. Chengwei Fang Profile

Dr. Chengwei Fang

at Nanjing Univ of Science and Technology

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Proceedings Article | 1 April 2020 Open Access

Application of scanning focused X-ray imaging positioning technique in preparation of GaAs photocathodes

Yijun Zhang, Chengwei Fang, Yunsheng Qian, Junju Zhang, Kaimin Zhang, Jingzhi Zhang, Minmin Rong, Feng Shi, Gangcheng Jiao, Xiaofeng Bai

Proceedings Volume 11367, 113671N (2020) https://doi.org/10.1117/12.2556086

KEYWORDS: Gallium arsenide, Chemical analysis, X-ray imaging, X-rays, Contamination

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Negative-electron-affinity GaAs-based photocathodes have already found widespread application in modern night vision detectors and vacuum electron sources. Considering the importance of surface micro-area analysis for cathode preparation, a new ultrahigh vacuum interconnection system for photocathode preparation and characterization was developed, wherein the scanning focused X-ray imaging positioning technique combined with the X-ray induced secondary electron image was applied to characterize the surface components in the specified micro region of semiconductor photocathodes. With the aid of the advanced characterization technique, the surface components of micro regions of interest for GaAs cathode samples after cleaning and Cs-O activation were analyzed. The experimental results show that the GaAs cathode samples would be subjected to secondary contamination from the metal sheet of sample holder, accompanied by a small amount of sodium and cesium. The subsequent heat treatment and Cs-O activation can hardly remove the sodium contamination, which can affect the arsenic desorption during heat treatment, hinder the Cs-O adsorption in the activation process, and finally reduce the photoemission performance of the activated cathode. Through the application of the X-ray induced secondary electron image, the optimal cleaning method for GaAs cathode was investigated. This surface characterization technique is of practical value to improving analysis accuracy and optimizing the cathode preparation process.

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