电子轰击下MgO薄膜的二次电子效应的衰减机理

摘要

以MgO薄膜、MgO/Au复合薄膜作为二次电子发射材料的研究对象,利用持续电子束轰击薄膜的方式,研究了二次电子效应与时间的变化规律.通过测试样品时间的指数衰减,电导率和介电常数对衰减速率的影响,建立模型假设来研究二次电子发射的机理,提出了潜在电子的概念及平板电容模型;以此模型为基础进行分析推导,建立了二次电子发射过程理论模型,得出了诱导电流和二次电子发射系数实验值的表达式,与实际样品测试结果的趋势一致,二次电子发射材料性能的衰减速率与薄膜电导率正相关,验证了所提理论模型能很好地解释介质薄膜二次电子发射的衰减机理,有助于提高二次电子发射材料的衰减性能,为改进工艺和研发新型介质薄膜材料提供了一定的理论指导.%To improve the secondary electron emission coefficient and attenuation characteristic becomes the key to the application technology.Taking MgO film and MgO/Au composite films as the research objects of secondary electron emission materials,the change law of secondary electron effect over time is revealed by continuous electron beam bombardment on the film.The exponential decay of the sample time was tested and the influence of conductivity and dielectric constant on attenuation rate was explored.The mechanism of secondary electron emission was discussed under model hypothesis.The concept of potential electron and tablet capacitance model were put forward,and the theory model of the secondary electron emission process was then established.The expression of experimental value of the induced current and the secondary electron emission coefficient was obtained and coincided with the test result trend of actual sample,namely,the attenuation rate of secondary electron emission material properties was positively correlated to the film conductivity.It is concluded that the proposed theoretical model effectively explains the attenuation mechanism of the dielectric film secondary electron emission,and facilitates improving the attenuation performance of secondary electron emission material.