Fabrication of Mirror Surfaces for Polarizing Neutron Optics

Advanced Cooling Technologies, Inc. (ACT) proposes to develop a scalable method for the fabrication of polarizing neutron supermirrors. Polarized neutron beams are a powerful probe for investigating a breadth of material properties ranging from the atomic level structure of magnetic materials to the structure of biological and soft matter materials. The implementation of polarized neutron beams requires sophisticated experimental setups which rely on critical optical elements, such as polarizing neutron supermirrors. ACT’s method will involve an automated hot wire-assisted atomic layer deposition (HW-ALD) process to grow irons (Fe) and silicon (Si) thin films and develop the multi-bilayer film structure characteristic of polarizing neutron supermirrors. During Phase I, automated deposition processes will be developed for Fe and Si thin film growth, using commercially available Fe-containing and Si-containing precursors and molecular hydrogen (H2) as a reducing agent. A new gas supply system will be assembled and installed to deliver the process gases to the reactor by interfacing with the existing gas injection system. Using the HW-ALD reactor systems, Fe and Si films will be grown on quartz substrates and characterized to determine the chemical composition, thickness, crystallinity, and areal uniformity of the films. These data will drive an iterative feedback loop to develop successful automated Fe and Si coating processes, which can be subsequently leveraged to grow multi-bilayered structures necessary for supermirror prototype fabrication in Phase II.