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

• 作者: 封国宝 曹猛 王芳 胡天存
• 来源期刊: 中国物理B（英文版）
• 关键词: charge and discharge PMMA numerical simulation electron irradiation
• 年，卷（期）: 2015,（11）
• 页码范围: 117901-1-117901-7
• 页数: 1页
• 语种: 英文
• DOI: 10.1088/1674-1056/24/11/117901

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.