Microstructure analysis of low electron density contrast metallic multilayers using resonant X-ray reflectivity

Resonant X-ray reflectivity (RXRR) was employed to investigate the microstructural properties, such as layer thicknesses, densities and interface widths, of metallic multilayers with low electron density contrast. Cu/Nb multilayers were chosen as a model system to demonstrate the enhanced sensitivity of RXRR. These multilayers, consisting of ten bilayers with varying period thicknesses, were deposited using magnetron sputtering. X-ray reflectivity measurements were performed at the K-absorption edges of both Cu and Nb, as well as using conventional Cu Kα radiation. A pronounced difference was observed between reflectivity profiles acquired at these different energies. The enhanced contrast near the absorption edges enabled an effective means to extract microstructural information. The results demonstrate that RXRR is a powerful technique for characterizing metallic multilayers with low electron density contrast.