Fabrication of high-reflectance Mo–Si multilayer mirrors by planar-magnetron sputtering

TLDR

Molybdenum–silicon multilayer x‑ray mirrors were fabricated by direct‑current planar magnetron sputtering and characterized by X‑ray diffraction, high‑resolution electron microscopy, and synchrotron normal‑incidence reflectivity measurements. The mirrors show a pronounced dependence on sputtering gas pressure, with low‑pressure deposition producing columnar growth and a normal‑incidence reflectivity as high as 61 % at 132 Å, while higher pressures markedly reduce reflectivity.

Abstract

Molybdenum–silicon multilayer (ML) x-ray mirrors have been fabricated using a direct-current planar magnetron sputtering system. The ML structure has been characterized using x-ray diffraction and high-resolution electron microscopy, and the normal incidence x-ray reflectivity has been measured using synchrotron radiation. A striking dependence of the ML morphology on the sputtering gas pressure is observed, exhibiting a transition from layer growth at lower pressures to columnar growth at higher pressures. Correspondingly, the normal incidence x-ray reflectivity is found to decrease strongly with increasing gas pressure. By depositing Mo–Si ML at low sputtering gas pressures we have achieved a normal incidence reflectivity as high as 61% at 132 Å.