Bonded Multilayer Laue Lens for focusing hard X-rays

We have fabricated partial Multilayer Laue Lens (MLL) linear zone plate structures with thousands of alternating WSi2 and Si layers and various outermost zone widths according to the Fresnel zone plate formula. Using partial MLL structures, we were able to focus hard X-rays to line foci with a width of 30 nm and below. Here, we describe challenges and approaches used to bond these multilayers to achieve line and point focusing. Bonding was done by coating two multilayers with AuSn and heating in a vacuum oven at 280–300 °C. X-ray reflectivity measurements confirmed that there was no change in the multilayers after heating to 350 °C. A bonded MLL was polished to a 5–25 μm wedge without cracking. SEM image analyses found well-positioned multilayers after bonding. These results demonstrate the feasibility of a bonded full MLL for focusing hard X-rays.