Sarkar Piyali, Biswas Arup, De Rajnarayan, Divakar Rao K, Ghosh Subir, Modi M H, John Siju, Barshilia H C, Bhattacharyya Dibyendu, Sahoo Naba Kishor
Appl Opt. 2017 Sep 20;56(27):7525-7532. doi: 10.1364/AO.56.007525.
The DC magnetron sputter grown Co/Ti multilayers, with ultra-low bi-layer thicknesses and with Co layers deposited under mixed ambience of argon and dry air, have been investigated for use in the water window soft x-ray regime of 23-44 Å. Initially, deposition parameters have been optimized for obtaining smooth and continuous low thickness Co and Ti single-layer films, and, then, multilayers with five bi-layers of various bi-layer thicknesses were deposited. The samples have been primarily characterized by the grazing incidence x-ray reflectivity (GIXR) measurements with a hard x-ray laboratory source. Subsequently, a set of multilayers with an increasing number of bi-layers has been deposited with a constant bi-layer thickness of 42 Å. GIXR results show that hard x-ray reflectivity at the first Bragg peak is maximum for the 20 bi-layer sample, beyond which the reflectivity decreases. Finally, the samples with the most promising hard x-ray GIXR have been used for soft x-ray reflectivity measurement with synchrotron radiation, and ∼2.5% peak reflectivity has been obtained in the multilayer sample at a 30.7 Å wavelength for a 21.5° grazing angle of incidence. The fitting results for both hard and soft x-ray reflectivities have been thoroughly investigated to find out the cause of the saturation of reflectivity with the increase in the number of bi-layers.
对采用直流磁控溅射生长的Co/Ti多层膜进行了研究，这些多层膜具有超低的双层厚度，且Co层是在氩气和干燥空气的混合气氛下沉积的，用于23 - 44 Å的水窗软X射线波段。首先，对沉积参数进行了优化，以获得光滑、连续的低厚度Co和Ti单层膜，然后沉积了具有五种不同双层厚度的双层膜的多层膜。这些样品主要通过使用硬X射线实验室源的掠入射X射线反射率（GIXR）测量进行表征。随后，沉积了一组双层数量不断增加、双层厚度恒定为42 Å的多层膜。GIXR结果表明，对于20双层样品，第一布拉格峰处的硬X射线反射率最大，超过此值反射率会降低。最后，将具有最有前景的硬X射线GIXR的样品用于同步辐射软X射线反射率测量，在波长为30.7 Å、掠入射角为21.5°时，多层膜样品获得了约2.5%的峰值反射率。对硬X射线和软X射线反射率的拟合结果进行了深入研究，以找出反射率随双层数量增加而饱和的原因。
