Microfabrication of saw-tooth refractive x-ray lenses in low-Zmaterials

Abstract

Saw-tooth x-ray refractive lenses have been fabricated in silicon, epoxy and diamond. Silicon lenses were made by anisotropic wet etching of single crystalline silicon. Epoxy lenses were moulded from silicon masters. Diamond lenses were replicated by chemical vapour deposition on silicon masters and subsequent sacrificial etching of silicon. Beryllium saw-tooth test structures were embossed using a diamond master. Silicon and epoxy lenses gave sub-micron focal lines and provided gains of up to 40 when tested in a synchrotron set-up. Focal lengths ranged from 0.33 to 0.61 m for x-ray energies between 14 and 30 keV.

Nano-ridge fabrication by local oxidation of silicon edges with silicon nitride as a mask

“…As an inherent feature of the process, the period of the structures has been decreased from one line per 8 µm to two ridges per 8 µm. This period doubling feature was also used by Ribbing et al to fabricate saw-tooth refractive x-ray lenses in 1 0 0 silicon [14].…”

Focusing with saw-tooth refractive lenses at a high-energy X-ray beamline

“…Significantly lowering the energy strongly increases (/ wavelength 2 ), in turn increasing ' f /v, and thereby coarsening the approximation to the parabola and increasing the refractive discreteness aberration h sin . This can be partially mitigated by making SRLs for low energies out of light elements, such as Be (Ribbing et al, 2003) or Li (Dufresne et al, 2001). Medium-Z materials like Si and Al are practical and well suited for the high photon energies of interest here.…”

“…Single-crystal Si SRLs have been fabricated through two processes -anisotropic etching (Ribbing et al, 2003) and dicing (Said & Shastri, 2010). The Si SRLs discussed in this article were produced by anisotropic etching, through the efforts of the former reference's authors.…”

Silicon saw-tooth refractive lens for high-energy X-rays made using a diamond saw

“…A previous article (Shastri et al, 2007) reported on the successful use of Si saw-tooth lenses at high energies (50-100 keV) for routine focusing (1-20 mm FWHM) and collimation optics applications at the 1-ID undulator beamline at the Advanced Photon Source (APS). Those lenses were fabricated by a process that involved subjecting single-crystal Si to a crystallographically anisotropic chemical etching process (Ribbing et al, 2003), yielding isosceles teeth of 100-200 mm height, depending on the device. This communication describes a different method of fabricating a Si saw-tooth lens using a thin diamond saw blade.…”