W/C Mirror Deposition Optimization
摘要
The reflectivity of grazing incidence W/C multilayer mirrors can be optimized by progressively refining structural features through sputter deposition parameter optimization. Beyond the configuration of system geometry, the deposition rate, substrate temperature and working gas pressure significantly affect the multilayer structure morphology. Of these parameters, working gas pressure has an overwhelming effect. The energy and distribution of sputtered adatoms, directly influenced by the sputtering gas pressure, affects the reactivity at and the reconstruction of vapor deposited surfaces. The interface abruptness is therefore affected by working gas pressure. The reduction in interfacial atomic intermixing (hence roughness) generally follows with decreased gas pressure. Correspondingly, the improved reflective efficiency becomes increasingly noticeable from hard to soft x-rays. Structural and reflectivity improvements in the W/C multilayer mirror system, characterized qualitatively using cross-section electron microscopy and quantitatively using x-ray diffraction, will be correlated to an optimization of the sputter deposition parameter - working gas pressure.