Optical, chemical, and depth characterization of Al/SiC periodic multilayers

Abstract

We present the characterization of Al/SiC periodic multilayers designed for optical applications. In some samples, a thin layer of W or Mo is added at the SiC-on-Al interfaces. We use x-ray reflectivity (XRR) in order to determine the parameters of the stacks, i.e. thickness and roughness of all the layers. We have performed x-ray emission spectroscopy (XES) to identify the chemical state of the Al and Si atoms present within the structure from an analysis of the shape of the Al Kβ and Si Kβ emission bands. Finally, time of flight secondary ion mass spectrometry (ToF-SIMS) is used to obtain the depth profile of the different elements present within the studied stacks. A fit of the XRR curves shows that the Al/SiC multilayer present large interfacial roughness (up to 2.8 nm), which is decreased considerably (down to 1 nm or less) when the refractory metal layers are introduced in the periodic structure. The combination of XES and ToFSIMS allows us to conclude that in these systems the roughness is a purely geometrical parameter and not related to chemical interfacial reactions.