中国物理B ›› 2015, Vol. 24 ›› Issue (11): 117901-117901.doi: 10.1088/1674-1056/24/11/117901

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

Characteristics of charge and discharge of PMMA samples due to electron irradiation

封国宝a, 王芳a, 胡天存b, 曹猛a   

  1. a Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Department of Electronic Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China;
    b National Key Laboratory of Science and Technology on Space Microwave, Xi’an 710000, China
  • 收稿日期:2015-05-12 修回日期:2015-06-04 出版日期:2015-11-05 发布日期:2015-11-05
  • 通讯作者: Wang Fang E-mail:wangfang@mail.xjtu.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11175140 and 11004157) and the Foundation of National Key Laboratory of Space Microwave Technology of China (Grant No. 9140C530101130C53013).

Characteristics of charge and discharge of PMMA samples due to electron irradiation

Feng Guo-Bao (封国宝)a, Wang Fang (王芳)a, Hu Tian-Cun (胡天存)b, Cao Meng (曹猛)a   

  1. a Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Department of Electronic Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China;
    b National Key Laboratory of Science and Technology on Space Microwave, Xi’an 710000, China
  • Received:2015-05-12 Revised:2015-06-04 Online:2015-11-05 Published:2015-11-05
  • Contact: Wang Fang E-mail:wangfang@mail.xjtu.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11175140 and 11004157) and the Foundation of National Key Laboratory of Space Microwave Technology of China (Grant No. 9140C530101130C53013).

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摘要： In this study, using a comprehensive numerical simulation of charge and discharge processes, we investigate the formation and evolution of negative charge and discharge characteristics of a grounded PMMA film irradiated by a non-focused electron beam. Electron scattering and transport processes in the sample are simulated with the Monte Carlo and the finite-different time-domain (FDTD) methods, respectively. The properties of charge and discharge processes are presented by the evolution of internal currents, charge quantity, surface potential, and discharge time. Internal charge accumulation in the sample may reach saturation by primary electron (PE) irradiation providing the charge duration is enough. Internal free electrons will run off to the ground in the form of leakage current due to charge diffusion and drift during the discharge process after irradiation, while trapped electrons remain. The negative surface potential determined by the charging quantity decreases to its saturation in the charge process, and then increases in the discharge process. A larger thickness of the PMMA film will result in greater charge amount and surface potential in charge saturation and in final discharge state, while the electron mobility of the material has little effects on the final discharge state. Moreover, discharge time is less for smaller thickness or larger electron mobility. The presented results can be helpful for estimating and weakening the charging of insulating samples especially under the intermittent electron beam irradiation in related surface analysis or measurement.

关键词: charge and discharge, PMMA, numerical simulation, electron irradiation

Abstract: In this study, using a comprehensive numerical simulation of charge and discharge processes, we investigate the formation and evolution of negative charge and discharge characteristics of a grounded PMMA film irradiated by a non-focused electron beam. Electron scattering and transport processes in the sample are simulated with the Monte Carlo and the finite-different time-domain (FDTD) methods, respectively. The properties of charge and discharge processes are presented by the evolution of internal currents, charge quantity, surface potential, and discharge time. Internal charge accumulation in the sample may reach saturation by primary electron (PE) irradiation providing the charge duration is enough. Internal free electrons will run off to the ground in the form of leakage current due to charge diffusion and drift during the discharge process after irradiation, while trapped electrons remain. The negative surface potential determined by the charging quantity decreases to its saturation in the charge process, and then increases in the discharge process. A larger thickness of the PMMA film will result in greater charge amount and surface potential in charge saturation and in final discharge state, while the electron mobility of the material has little effects on the final discharge state. Moreover, discharge time is less for smaller thickness or larger electron mobility. The presented results can be helpful for estimating and weakening the charging of insulating samples especially under the intermittent electron beam irradiation in related surface analysis or measurement.

Key words: charge and discharge, PMMA, numerical simulation, electron irradiation

中图分类号:  (Theory of impact phenomena; numerical simulation)

  • 79.20.Ap
72.20.Dp (General theory, scattering mechanisms) 02.70.Uu (Applications of Monte Carlo methods) 72.80.Le (Polymers; organic compounds (including organic semiconductors))