Abstract Cr/Ti multilayers with moderate to low bi-layer thickness have been deposited by Ion beam sputtering system and have been investigated thoroughly by specular grazing incidence X-ray reflectivity (GIXR) and diffused X-ray scattering (both in coplanar and non-coplanar configurations) measurements. The investigation is important for development of Cr/Ti soft X-ray multilayer mirrors for “water window” applications in the wavelength regime of 2.2–4.4 nm. Initially few multilayers have been deposited and the highest reflectivity at first Bragg peak positions of the GIXR plots have been obtained for the Cr layer to bi-layer thickness ratio of 0.4. Subsequently, keeping the ratio fixed a set of five samples with bi-layer thickness varying from 3.8 nm to 2.1 nm have been prepared. For the all five ML samples reported in this communication, Ti layer thickness is greater than 1.3 nm, however, the Cr layer thickness varies from 1.5 to 0.8 nm in the above range of bi-layer thickness and it undergoes continuous-to-discontinuous transition. Cr films undergo significant change in morphology as the thickness changes and thus the interfaces are also evolved differently. Analysis of the diffused X-ray scattering data shows that interface imperfection of Ti-on-Cr interfaces is dominated by interface diffusion at low Cr thickness (discontinuous) regime and by interface roughness at high Cr thickness (continuous) regime, while in case of Cr-on-Ti interfaces, interface roughness dominates throughout the whole thickness regime. For the sample with highest bi-layer thickness of 3.8 nm high Bragg peak reflectivity value close to the ideal case is obtained manifesting high thickness uniformity, very low interface imperfection and high vertical correlation length across the interfaces for this sample which is also confirmed by cross-sectional Transmission Electron Microscopy. A 50 bi-layer sample prepared with the above bi-layer thickness shows high reflectivity of 5.6% at 2.84 nm water window soft X-ray wavelength.

中文翻译：

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Cr层连续到不连续过渡期间Cr/Ti多层膜的界面演变

摘要 具有中等至低双层厚度的 Cr/Ti 多层膜已通过离子束溅射系统沉积，并通过镜面掠入射 X 射线反射率 (GIXR) 和漫射 X 射线散射（共面和非共面）进行了彻底研究。共面配置）测量。该研究对于开发用于 2.2-4.4 nm 波长范围内的“水窗”应用的 Cr/Ti 软 X 射线多层反射镜很重要。最初沉积的多层膜很少，并且对于 0.4 的 Cr 层与双层厚度比，在 GIXR 图的第一个布拉格峰位置获得了最高反射率。随后，保持比率固定，制备了一组五个样品，其双层厚度从 3.8 nm 到 2.1 nm 不等。对于本次通信中报告的所有五个 ML 样本，Ti层厚度大于1.3nm，而Cr层厚度在上述双层厚度范围内从1.5到0.8nm变化，并且经历了连续到不连续的转变。随着厚度的变化，Cr 膜的形态发生显着变化，因此界面也发生了不同的演变。对扩散 X 射线散射数据的分析表明，Ti-on-Cr 界面的界面缺陷主要由低 Cr 厚度（不连续）区域的界面扩散和高 Cr 厚度（连续）区域的界面粗糙度支配，而在Cr-on-Ti 界面，界面粗糙度在整个厚度范围内占主导地位。对于具有最高双层厚度 3.8 nm 的样品，获得接近理想情况的高布拉格峰值反射率值，表现出高厚度均匀性，该样品的界面缺陷非常低，垂直相关长度高，这也得到了横截面透射电子显微镜的证实。用上述双层厚度制备的 50 双层样品在 2.84 nm 水窗软 X 射线波长下显示出 5.6% 的高反射率。