电子入射角度对聚酰亚胺二次电子发射系数的影响

采用具有负偏压收集极的二次电子发射系数测试系统, 对聚酰亚胺样品的二次电子发射系数与入射电子角度和入射电子能量的关系进行了测量. 测量结果表明, 在电子小角度入射样品的情况下, 随着入射角度的增加, 二次电子发射系数单调增加, 并符合传统的规律, 但是在电子大角度入射时, 却与此不符合. 测量显示, 出现偏差时对应的临界电子入射角度随着入射电子能量的降低而减小. 采用简化的电子弹性散射过程和卢瑟福弹性散射截面公式对这种偏差的出现进行了分析, 并推导出修正后的二次电子发射系数的计算公式. 修正后的二次电子发射系数的计算结果更加符合实验结果.

Effects of electron incident angle on the secondary electron yield for polyimide

Relationship between secondary electron yield (SEY) and electron incident angle has been measured for a polyimide sample. SEY as a function of incident angle at different incident electron energy is measured by use of a system with a single pulsed electron beam and a special surface charge neutralization technology based on the negatively biased collector. Measured results show that the SEY may deviate from the traditional law of monotonic increase with the incident angle when the angle is higher than a certain critical value. This deviation is even more obvious at lower incident electron energy. The critical incident angle decreases with decreasing incident energy. A theoretical analysis on the deviation is given in a simplified electron elastic scattering process. The distribution of the scattering region has an important effect on the relation of SEY versus incident angles. A sector region is introduced to describe the electron scattering region. Due to the limit of sample surface, the electron scattering region will decrease if the angle between the incident direction and the sample surface is smaller than half of the central angle of the sector. Corresponding SEY might no longer increase. Based on the Rutherford’s elastic scattering formula, a formula for the critical incident angle is derived as a function of incident electron energy, which is also confirmed by our measurement results. Finally, a revised SEY computation formula is developed which can give more accurate results at high incident electron angle.