Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
X-ray wave is a kind of electro-magnetic wave, which has a wavelength much shorter than that of visible light. It is therefore possible to construct an X-ray microscope with an X-ray lens. The spatial resolution of an X-ray microscope is limited by the wavelength of X-rays we use, so that, in the region of hard X-rays, a spatial resolution of 0.1 nm should be, in principle, realized. It is however difficult to fabricate an X-ray lens for such a spatial resolution because interaction of hard X-rays with matters is very weak. Spatial resolutions around 10 nm have been already realized for hard X-rays by virtue of recent progress in fabrication technology for hard X-ray lenses.
Using high penetration power of hard X-rays makes it possible to non-destructively observe structures in thick and opaque samples with high-spatial resolutions. However, , in general, there is a tradeoff between spatial resolution and sensitivity of a microscope. Hence, effort to increase the sensitivity should be made as well as to improve the spatial resolution. Using phase shift of X-rays is a solution to increase the sensitivity; especially for materials consisting of light elements, such as biomaterials and organic devices, X-ray phase microscopy provides us a sensitivity of three orders of magnitude higher than that of X-ray microscopy using X-ray absorption, which is commonly used for X-ray imaging.
Fig. 1 Experimental setup of our X-ray phase imaging microscope based on the Talbot effect.