氮气反应溅射制备软X射线Co/Ti多层膜

针对"水窗"波段(280~540eV)对多层膜反射镜的应用需求,在Ti的L吸收边(452.5eV)附近,优化设计了Co/Ti多层膜的膜系结构。计算了不同界面粗糙度条件下的反射率,结果显示,界面粗糙度对多层膜反射率有较大影响。采用直流磁控溅射方法在超光滑硅基片上制备了Co/Ti多层膜,通过将氮气引入原有的溅射气体氩气中作为反应气体,明显减小了制备的多层膜的界面粗糙度。利用X射线掠入射反射实验和透射电子显微镜测试了多层膜结构,并在北京同步辐射装置(BSRF)3W1B实验站测量了不同氮气浓度下多层膜的反射率。结果显示,氮气含量为5%的溅射气体制备的多层膜样品反射率最高,即将纯氩气溅射制备得到的反射率9.5%提高到了12.0%。得到的结果表明,将氮气加入反应溅射气体可以有效改善Co/Ti多层膜的性能。

Preparation of Co/Ti multilayer in soft X-ray region by nitrogen reactive sputtering

The film system structures of Co/Ti multilayer film were designed optimally at the L-absorption edge of Ti(452.5 eV) to meet the requirements of a multilayer mirror at the ‘water window’ energy region between 280 eV and 540 eV. The reflectivity of the multilayer film was calculated at different interface roughness conditions and it shows that the interface roughness has greater effect on the reflectivity of the multilayer film. Co/Ti multilayer films were deposited on a Si substrate by DC magnetron sputtering method and the quality of these films was improved by adding nitrogen gas into original argon gas in magnetron sputtering. Finally, the multilayer film structure was measured by a Grazing Incident X-ray Reflection (GIXRR) method and a Transmission Electron Microscope(TEM), and the reflectivities in different nitrogen concentrations were measured by Soft X-ray Reflectivity(SXR) at Beijing Synchrotron Radiation Facility(BSRF). The results show that the reflectivity of the Co/Ti multilayer with nitrogen gas fraction of 5% is the highest among the samples, by which the reflectivity has been improved from 9.5% to 12.0%. The results demonstrate that the reaction sputtering with nitrogen gas improves the quality of Co/Ti multilayer films effectively.