Design, development and applications of etched multilayers for soft X-ray spectroscopy

An etched multilayer, a 2D structure fabricated by etching a periodic multilayer according to the pattern of a laminar grating, is applied in the soft X-ray range to improve the spectral resolution of wavelength dispersive spectrometers. The present article gathers all the successive stages of the development of such a device optimized to analyze the characteristic emission of light elements: design, structural and optical characterization and applications to X-ray spectroscopy. The evolution of the shape of the C K alpha emission band of highly oriented pyrolytic graphite (HOPG), as a function of the angle between the emission direction and the (0 0 0 1) planes, is measured. These results, compared to those with a grating, demonstrate that the achieved spectral resolution enables disentangling sigma -> 1s and pi -> 1s transitions within the C K emission band.