氦离子辐照对钨表面形貌的影响及其光学性质的变化

Influence of Helium Ion Irradiation on Surface Microstructures and Optical Property of Tungsten Surface

采用空心阴极法产生高密度氦等离子体对纯钨进行辐照实验,并对氦辐照后钨表面形貌及其性能的变化进行了研究。辐照实验参数:辐照时间分别为0.5,2以及3 h,氦离子注入能量约100 eV,束流密度约10^(22)/m^2·s,温度约1850 K。实验中分别使用光学显微镜、扫描电子显微镜及X射线衍射手段对氦离子轰击后的纯钨表面进行分析表征,发现在经历一定剂量的氦离子(0.5 h,1.8×10^(25)/m^2)辐照后,原本光滑的钨表面产生了三种不同的形貌,分别为波纹状、三角锥状和纳米绒毛层。同时实验结果表明:表面形貌的变化与氦离子的辐照剂量密切相关,随着辐照剂量的增多,光滑表面逐渐减少,波纹状、三角锥状以及纳米绒毛层的区域逐渐增多,并且前两种形貌最终向纳米绒毛结构层转变。本文还研究了钨的表面形貌与散射率之间的关系,结果表明:散射率随着绒毛结构的增多而下降。

The impact of beam energy,beam fluence and irradiation time of the high density helium ion beam, generated by a hollow cathodeplasma source, on the mierostructures and optical properties of highly pure tungsten surfaces was investigated with optical microscope, scanning electron microscope and X-ray diffraction. The prelimi- nary results show that depending on the implantation dose, the He-ion irradiation significantly affected the micro- structures and optical properties of the tungsten surfaces. To be specific, as the He-ion dose increasedto higher than 1.8×10^25/m2（ irradiated at 100 eV for 0. 5 h） ,the triangular pyramids,ripples and nano-fluff increasingly invaded the smooth tungsten surfaces, till nano-fluff dominated the entire tungsten surfaces. In addition, we found that the highly porous nano-fluff surface strongly absorbs but weakly scatters light in the ultraviolet and visible bands. Possi- ble mechanisms responsible for the observation were also tentatively discussed