Fabrication of laser deposited high-quality multilayer zone plates for hard X-ray nanofocusing

Recently, we demonstrated unprecedented sub-5 nm point focusing of hard X-rays (at 7.9 keV) based on the combination of a high gain Kirkpatrick–Baez (KB) mirror system and a high resolution W/Si multilayer zone plate (MZP). This MZP was prepared by the combination of pulsed laser deposition (PLD) and focused ion beam (FIB). Despite the small focus size, the MZP's quality suffered from sufficient but comparatively low efficiency (2%). In this paper we discuss how to overcome limitations of MZP fabrication by PLD by investigating the material systems W/Si, W/ZrO2, and Ta2O5/ZrO2. We give a detailed description on the optimization processes for the deposition of smooth multilayers with highly precise layer thicknesses on a rotating wire. Furthermore, we present our latest results regarding a Ta2O5/ZrO2 MZP, which has been proven already to be a system of high potential in the very first experiments as the efficiency reached 6.9% (at 18 keV)

Two-dimensional sub-5-nm hard x-ray focusing with MZP

We present experiments carried out using a combined hard x-ray focusing set-up preserving the benefits of a large-aperture Kirckpatrick-Baez (KB) mirror system and a small focal length multilayer zone plane (MZP). The high gain KB mirrors produce a pre-focus of 400 nm × 200 nm; in their defocus, two MZP lenses of diameter of 1.6 μm and 3.7 μm have been placed, with focal lengths of 50 μm and 250 μm respectively. The lenses have been produced using pulsed laser deposition (PLD) and focused ion beam (FIB). Forward simulations including error models based on measured deviations, auto-correlation analysis and three-plane phase reconstruction support two-dimensional focus sizes of 4.3 nm × 4.7 nm (7:9 keV, W/Si)1 and 4.3 nm ×5.9 nm (13:8 keV, W/ZrO2), respectively. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only