Characterizing Nanoscale Thin-film Residual Stresses for Stress Mitigation and Engineering in Next-generation X-ray Optics

Reflection gratings, are critical components to successful X-ray spectroscopes and represent important priorities for future NASA observatories. As such, significant research efforts have been invested to improve mirror and grating fabrication, resulting in increased collecting area and improved mirror performance. However, residual stresses induced by reflective coatings continue to present challenges, causing mirror deformation, degradation of spectral resolution, and decreased scientific performance. Additionally, stress distributions and the stress response of nanoscale layers (5-30nm) are not well understood and can be difficult to measure. This study demonstrates methods to better characterize and minimize the stress of single and bi-layered reflective thin films at nanoscale thicknesses (5-30 nm) and to more fully understand the stress response of these coatings to deposition conditions. High-Z materials (Pt, Au) have been chosen for this study due to their favorable reflectivity over X-ray wavelengths of interest in the soft X-ray regime.