Reflectometry on curved interfaces

Reflectometry is known since long as an interferometric method which can be used to characterize surfaces and thin films regarding their structure and, to a certain degree, composition as well. Properties like layer structures, layer thickness, density, and interface roughness can be determined by fitting the obtained reflectivity data with an appropriate model using a recursive fitting routine. However, one major drawback of the reflectometric method is its restriction to planar surfaces. In this article we demonstrate an approach to apply X-ray and neutron reflectometry to curved surfaces by means of the example of bent bare and coated glass slides. We prove the possibility to observe all features like Fresnel decay, Kiessig fringes, Bragg peaks and off-specular scattering and are able to interpret the data using common fitting software and to derive quantitative results about roughness, layer thickness and internal structure. The proposed method has become practical due to the availability of high quality 2D-detectors. It opens up the option to explore many kinds and shapes of samples, which, due to their geometry, have not been in the focus of reflectometry techniques until now.