Abstract:

Nanofocusing hard X-ray zone plates have been widely deployed at 3rd generation Synchrotron sources and will potentially play a much larger role at the upcoming generation of multi-bend achromat sources. Multiple beamlines at the APS use hard X-ray zone plates for focusing and imaging to probe information at sub-micron down to the tens of nanometer scale. Zone plates are diffractive focusing optics similar to circular diffraction gratings but with a period that changes as a function of radius. The outer zone width generally determines the numerical aperture of the optic, while the zone thickness determines the distribution between the foci and therefore the efficiency. Utilizing advanced nanofabrication methods developed at the Center for Nanoscale Materials (CNM) zone plates with outer zone width down to 16 nm have been deployed at the transmission X-ray microscope (TXM) at Sector 32 and the Sector 26 Nanoprobe. I will present the challenges, capabilities, and development that were part of delivering the sub-20 nm zone plates for the current APS. The next generation of APS-U beamlines will be capable of and are planning on using spot sizes down to 10 nm and below. Fabrication of these zone plates will require new generations of fabrication methods to meet the high aspect ratio, sub-10 nm zones required. I will summarize various strategies for fabricating zone plates with sub-10 nm outer zone width and spot sizes with reasonable efficiency at hard X-ray energy.