A low-pass filtering Fresnel zone plate for soft x-ray microscopic analysis down to the lithium K-edge region

We have designed a new low-pass Fresnel zone plate (LPFZP) to extend soft x-ray absorption spectroscopy (XAS) to the lithium K absorption edge in a scanning transmission x-ray microscope (STXM). The performance of the LPFZP was evaluated in the STXM beamline at the UVSOR-III Synchrotron (Okazaki, Japan); the contribution of the higher-order harmonics is successfully suppressed to 0.1% of the fundamental energy, and a spatial resolution of 72 nm and an energy resolution (E/∆E) above 1000 are achieved as expected. XAS spectra of lithium are measured successfully in an electrode of a lithium-ion battery.