激光刻蚀对镀金表面二次电子发射的有效抑制

An effective reduction on secondary electron emission yield of gold coated surfaces by laser etching

使用红外激光刻蚀技术在镀金铝合金表面制备了多种形貌的微孔及交错沟槽阵列.表征了两类激光刻蚀微阵列结构的三维形貌和二维精细形貌,分析了样品表面非理想二级粗糙结构的形成机制.研究了微阵列结构二次电子发射特性对表面形貌的依赖规律.实验结果表明:激光刻蚀得到的微阵列结构能够有效抑制镀金表面二次电子产额(secondary electron yield,SEY),且抑制能力明显优于诸多其他表面处理技术;微阵列结构对SEY的抑制能力与其孔隙率及深宽比呈现正相关,且孔隙率对SEY的影响更为显著.使用蒙特卡罗模拟方法并结合二次电子发射唯象模型和电子轨迹追踪算法,仿真了各微结构表面二次电子发射特性,模拟结果从理论上验证了微阵列结构孔隙率及深宽比对表面SEY的影响规律.本文获得了能够剧烈降低镀金表面SEY的微阵列结构,理论分析了SEY对微结构特征参数的依赖规律,对开发空间微波系统中低SEY表面及提高镀金微波器件性能有重要意义.

Multipactor is a frequent discharging phenomenon for space high-power microwave components, and this detrimental effect is mainly induced by secondary electron emission(SEE) and electron resonance in vacuum.Plenty of researches have verified that suppressing SEE is an efficient approach to mitigate the multipactor.Therefore, low SEE yield surfaces are urgently needed for mitigating the multipactor in the field of space science. In the past few decades, a number of technics have been developed to acquire low SEE yield surfaces,including surface coating, surfaces roughening, depositing coessential nanostructure, etc. Laser etching has been partly reported to be an advisable way to construct micro-or nano-structure on some materials surfaces, and able to further suppress the SEE yield. Whereas, employing laser etching to obtain the SEE yield reduction on gold coated surfaces is rarely investigated. In this work, by using the laser etching technic, we fabricate four micro hole arrays and three orthogonal groove arrays with various porosities and aspect ratios, and we also characterize their three-dimensional and accurate two-dimensional morphologies. In addition, we investigate the dependence of SEE yield on surface morphology. Experimental results indicate that the laser etched microstructures can effectively suppress the SEE yield from gold coated surfaces, and the suppression levels on SEE yield of these samples are superior to those of many other low SEE yield technics. Furthermore,experiments reveal that the ability to suppress the SEE yield is positively related to the porosity and aspect ratio, as well as that the porosity influences SEE yield more strongly than the aspect ratio does. To theoretically verify the experimental phenomena, we utilize the Monte Carlo method combining with the SEE phenomenological model and the electron trajectory tracking algorithm, to simulate the SEE characteristics of the fabricated microstructures. And the simulation results can qualitatively explain the experimental phenomena. This work digs out an advisable method to sharply reduce the SEE yield from gold coated surfaces by laser etching, which is of considerable importance for exploiting the low SEE yield surface engineering in space microwave systems, and for improving the performance of the space microwave components with gold coated surface.