Development of a full-field reflective microscope in the water window for 10nm resolution cellular imaging (poster)
Résumé
In the context of the high-resolution cells imaging, we have started the study and the development of a new prototype of a full-field microscope in the water window. Imaging between the Carbon K edge (4.4 nm, 280 eV) and the Oxygen K edge (2.4 nm, 520 eV) is of interest for biological samples because the carbon skeleton of molecules can be visualized with a high contrast in aqueous media. However the spatial resolution achievable using mirrors is limited by diffraction, aberrations and surface roughness. Using superpolishing and aspherization techniques, diffraction-limited imaging has been attained in the extreme UV domain (10 to 40 nm) for plasma imaging [1], solar imaging and is being considered by the semiconductor industry as a serious candidate for microlithography. Depending on the exact wavelength and the spectral properties of materials that can be deposited, near-normal incidence reflectivity of single mirrors range typically between 15% and 70% [2].
We are currently exploring several optical design based on an Schwarzschild objective [4] with chromium-scandium coatings [3]. One of the interests of this scheme is to obtain a higher working distance than the typical Fresnel lenses that facilitates the insertion of the cryogenic sample holder. Designing the prototype faces unprecedented challenges in terms of mirror surface flatness (shaping and roughness control, ion beam etching for aspherisation [5]), multilayer manufacturing accuracy (deposition, thickness control, homogeneity control, roughness control) [6], and nanometer-scale instrument alignment (metrology at visible [7] and metrology at-wavelength [8]). We give an overview of all our skills and the techniques necessary to achieve the desired performances of the future instrument.
This work was supported by French State funds managed by the ANR within the Investissements d’Avenir programme under reference ANR-11-EQPX-29