Determination of layer structure in Mo/Si multilayers using soft X-ray reflectivity

The soft X-ray reflectivity characterization of Mo/Si multilayer deposited by electron beam evaporation is discussed. The measurements are performed on Indus-1 synchrotron storage ring. The interdiffusion of two-layer materials in multilayer leads to the formation of interlayers. To understand the influence of interlayers and interfacial roughness on soft X-ray reflectivity profile, simulation studies are performed. The roughness parameter leads to reduction in peak reflectivity whereas the interlayers significantly change the reflectivity profile. For fitting the angle-dependent soft X-ray reflectivity profile, a four-layer model accounts for the interlayers formed at the interfaces. Asymmetry at the two interfaces, viz. Si-on-Mo and Mo-on-Si needs to be considered for a good model fitting of the soft X-ray reflected profile. The mechanism, which could lead to the formation of interlayers in Mo/Si multilayer is discussed