In-situ observation of structural and chemical transitions in B4C based layered systems

Abstract In the context of multilayer based X-ray optics developments, thin layered systems of C/[Pt/B4C] multilayers and C/Pt/B4C/Cr stacks with variable cap layer thicknesses were deposited on Si wafers using DC magnetron sputtering. The samples were studied with in-situ X-ray reflectivity techniques during annealing in air up to temperatures of 300°C. Simulated X-ray spectra of B4C/Cr reveal a considerable thickness loss of the B4C layer at elevated temperatures. The effect is amplified and accelerated when a thin Pt top layer is added but attenuated and slowed down by an additional C cap layer. Energy dispersive X-ray spectroscopy data indicate the overall depletion of B in samples after the annealing process. In-depth studies using X-ray photoelectron spectroscopy techniques show clear evidence of chemical modifications in the original B4C layer and confirm the structural modifications derived from the X-ray reflectivity data. This study demonstrates the catalyzing role of Pt in the degradation of B4C based layered structures in air and the potential protective function of C cap layers.