High X-ray Reflectivity Research Articles

A high quality surface finish grinding process to produce total reflection mirror for x-ray fluorescence analysis

Total reflection x-ray fluorescence analysis is applied to trace element detection in liquid for effective environmental monitoring. This analytical approach requires x-ray total reflection mirrors. In order to achieve high sensitivity element detection, the mirrors require high surface quality for high x-ray reflectivity. Surface finishing for x-ray mirrors is typically conducted through a series of abrasive processes, such as grinding and polishing, and is thus time consuming. The purpose of this study is to streamline and enhance the surface finishing process based on unique high quality grinding techniques for the production of x-ray total reflection mirrors.

Optimization of the design of a multilayer X-ray mirror for Cu-Kα energy

A method for optimizing the design of a multilayer X-ray mirror to obtain a high X-ray reflectivity at a specific angle and for a specific energy, based on quarter-wave layer thickness, is described. The quarter-wave design method is widely used for designing optical multilayers, and there is extensive experience in applying this method, which can be useful when designing multilayer X-ray mirrors. The purpose of this paper is to investigate if the quarter-wave design method can be adapted to designing X-ray multilayers. The method is demonstrated for the case of reflectivity from a multilayer structure, of the Cu Kα line (8.04 keV) at 5.5°. Theoretical reflectivity higher than 50% can be achieved with the proposed design by using 500 layers.

Diamond brilliance

Most materials either absorb or transmit X-rays. This is useful for imaging but makes it notoriously difficult to build mirrors for reflective X-ray optics. A demonstration of the high X-ray reflectivity of diamond could provide a timely solution to make the most of the next generation of free-electron lasers.

Optimization and Structural Characterization of W/Al2O3 Nanolaminates Grown Using Atomic Layer Deposition Techniques

W/Al2O3 nanolaminates were fabricated using atomic layer deposition (ALD) techniques. ALD of tungsten was performed using alternating exposures of WF6 and Si2H6. ALD of Al2O3 was performed using alternating exposures of Al(CH3)3 and H2O. The fabrication of optimum nanolaminates was very dependent on nucleation during the ALD of each layer. The nucleation of Al2O3 ALD on W surfaces and W ALD on Al2O3 surfaces was examined using quartz crystal microbalance investigations. Al2O3 ALD on W nucleated easily during the first Al(CH3)3/H2O reaction cycle. In contrast, W ALD nucleation on Al2O3 required multiple WF6/Si2H6 reaction cycles and was very sensitive to the Si2H6 exposure. The W ALD nucleation required at least six or seven WF6/Si2H6 reaction cycles. The optimum reaction parameters for nucleation were utilized to fabricate W/Al2O3 nanolaminates with a total targeted thickness of ∼1000 Å that were composed of various numbers of bilayers. Transmission electron microscopy (TEM) images revealed very well defined two-bilayer and four-bilayer W/Al2O3 nanolaminates grown at 177 °C. Depth-profile secondary ion mass spectrometry (SIMS) measurements confirmed the composition of the W/Al2O3 nanolaminates. Both the TEM and SIMS results showed that sharper interfaces were observed when W ALD nucleates on Al2O3, and rougher interfaces were observed when Al2O3 ALD nucleates on W. X-ray reflectivity (XRR) investigations indicated that the W/Al2O3 nanolaminates were much thicker than the ∼1000 Å target for the total thickness when the W/Al2O3 nanolaminates were composed of a larger number of bilayers. These results were consistent with much lower than expected film densities for the thin Al2O3 ALD nanolayers. Atomic force microscope studies revealed that the surface roughness of W/Al2O3 nanolaminates was lower at lower growth temperatures and lower at higher interfacial densities. XRR investigations also revealed a pronounced Bragg peak with a high X-ray reflectivity from 64-bilayer W/Al2O3 nanolaminates grown at 177 °C. The X-ray reflectivity of the 64-bilayer W/Al2O3 nanolaminates grown at 177 °C was constant versus annealing up to 500 °C. The reflectivity then dropped rapidly for annealing at ≥600 °C. This thermal instability will place some limits on the application of W/Al2O3 nanolaminates as thermal barrier coatings and X-ray mirrors.

The microstructure and X-ray reflectivity of Mo/Si multilayers

We have studied microstructure Mo/Si multilayers grown by RF and DC sputtering at different deposition parameters by cross-sectional transmission electron microscopy and X-ray reflectivity for the wavelength 13.4 nm and 0.154 nm. It is shown experimentally that reflection properties of mirrors are determined by the crystalline state of molybdenum layers. The results are compared for the different samples and discussed in view of the choice an optimal deposition parameters to produce multilayers with a high X-ray reflectivity for the λ=13.4 nm.