Plastic Deformation in Profile-Coated Elliptical KB Mirrors

Abstract

Profile coating has been successfully applied to produce elliptical Kirkpatrick-Baez (KB) mirrors using both cylindrical and flat Si substrates. Previously, focusing widths of 70 nm with 15-keV monochromatic and 80 nm with white beam were achieved using a flat Si substrate. Now, precision elliptical KB mirrors with sub-nm figure errors are produced with both Au and Pt coatings on flat substrates. Recent studies of bare Si-, Au-, and Pt-coated KB mirrors under prolonged synchrotron X-ray radiation and low-temperature vacuum annealing will be discussed in terms of film stress relaxation and Si plastic deformation.

Profile etching for prefiguring X-ray mirrors

“…A Kaufman KDC100 ion source was installed in a well of a large deposition system with linear transport as described previously (Liu et al, 2003). The ion source was originally supplied with divergent dished optics, which was later reversed to a more suitable focused one.…”

“…For the past 15 years, profile coating has been an essential technique in our laboratory for making laterally graded multilayers, monolithic and nested Kirkpatrick-Baez (KB) mirrors, multilayer Laue lenses, and X-ray gratings using multilayers grown on staircase substrates (Liu et al, 2001(Liu et al, , 2003(Liu et al, , 2012aKang et al, 2006;Wen et al, 2013). KB mirrors with sub-nanometre figure errors are routinely produced using flat Si substrates with only two profile-coating iterations (Kewish et al, 2010).…”

“…KB mirrors with sub-nanometre figure errors are routinely produced using flat Si substrates with only two profile-coating iterations (Kewish et al, 2010). When a flat substrate is converted into an elliptical mirror by coating alone, the substantial film thickness and gradient can produce non-uniform film stress and may fail under extreme X-ray irradiations, owing to possible film stress relaxation (Liu et al, 2012b). If a spherical substrate is used, the cross-section profiles will be different.…”