Fabrication of ultrashort sub-meter-radius x-ray mirrors using dynamic stencil deposition with figure correction

This paper presents nanometer-scale production and metrology methods for elliptic-cylindrical x-ray mirrors with an unprecedentedly small tangential radius of curvature of 160 mm. Sub-millimeter-scale figure correction is conducted based on dynamic stencil deposition. The deposition flux through one or two shadow masks is examined by a comparison to a simple model. The masked deposition flux distribution is improved, leading to film thickness profiles that are 50 times sharper in terms of aspect ratio than those obtained using existing differential deposition approaches. Surface roughness deterioration is also effectively suppressed. A 2-mm-long 160-mm-radius mirror is produced with a width of 10 mm and measured using simple interferometry. The results are confirmed by conventional mirror metrology, contact profilometry, and x-ray ptychography. The x-ray focusing profile is diffraction-limited with a 142-nm focus size at a photon energy of 300 eV. The proposed methods have the potential to enhance the ultraprecise fabrication of highly curved mirrors, thus benefiting nanoscale photon-hungry x-ray techniques.