Scanning-X-ray-Microscopy (SXM)

During a measurement a sample is scanned through a small focused X-ray beam that generates microscopic images of a thin section of a sample. The best spatial resolution of ca. 20 nm can be achieved when Fresnel zone plates are used as the focusing elements. The microscopy has a variety of contrast mechanisms available, giving local information about the element distribution, the local chemical state of an atomic species, or the local mesoscopic and atomic structure. Therefore, it can also be applied to image the structure and the local chemical state of various materials. In the soft X-ray range, scanning transmission microscopy can be easily combined with X-ray fluorescence measurement to examine the elemental distribution across a studied material and with X-ray Absorption Spectroscopy (XAS), to identify different chemical species.

One of the main advantages of SXM is that the sample can be measured in air, under a He atmosphere, fixed between two Si3N4 windows to study wet samples such as hydrated polymers, biological materials, orused in conjunction with gas flow to study catalytic processes. In the soft X-ray region, elements like carbon, oxygen and nitrogen can be studied by exploiting the natural absorption contrast in the water window. Moreover, the L and M edges for some metals can be detected in the operation energy range of the SXM beamline. The radiation dose is much lower when compared to transmission electron microscope. Using the polarisation of light the information on the alignment of molecular orbitals and magnetic properties can be revealed.

SXM imaging can provide detailed morphology and chemical and physiological information at nanoscale spatial resolution. The SXM/XRF/XAS combined measurement is commonly used to solve problems in catalysis, energy storage, pharmaceutical research, medicine, polymer science, environmental chemistry, and biomaterials.