Annealing Process-Induced Microstructural Variation in NiV/B4C Multilayers

The annealing process is one of the most common methods used to study the thermal stability of multilayers. To study the effect of the annealing process on the microstructural variation in NiV/B4C multilayers, different annealing experiments were performed on NiV/B4C multilayers with a d-spacing of 8 nm. This work provides a foundation for the fabrication of non-periodic NiV/B4C multilayers. The NiV/B4C multilayers were investigated by grazing-incidence X-ray reflectometry (GIXR), X-ray diffuse scattering (XRS), atomic force microscopy (AFM), X-ray diffraction (XRD), grazing-incidence small-angle X-ray scattering (GISAXS) and transmission electron microscopy (TEM). The temperature-dependent experiments showed that annealing at 70–290 °C slightly increased the period thickness and interface width. Annealing at higher temperatures resulted in significant structural changes and thickness ratio (Г = dNiV/d) changes from 0.4 to 1/3 at 340 °C. The time-dependent results showed that the microstructural variations primarily occurred after 60 min. The XRD, XRS, GISAXS and TEM were further used to study microstructural changes. It was found that the NiV/B4C multilayers exhibited a microcrystal structure after annealing, and that enhanced crystallinity and an increase in interface roughness were the main reasons for the microstructural changes.