X-ray reflectivity characterization of atomic layer deposition Al ₂O₃/TiO₂ nanolaminates with ultrathin bilayers

Nanolaminate structures have many prospective uses in mechanical, electrical, and optical applications due to the wide selection of materials and precise control over layer thicknesses. In this work, ultrathin Al 2O3/TiO2 nanolaminate structures deposited by atomic layer deposition from Me3Al, TiCl4, and H 2O precursors with intended bilayer thicknesses ranging from 0.1 to 50 nm were characterized by x-ray reflectivity (XRR) measurements. The measurements were simulated to obtain values for thickness, density, and roughness of constituting layers. XRR analysis shows that the individual layers within the nanolaminate remain discrete for bilayers as thin as 0.8 nm. Further reduction in bilayer thickness produces a composite of the two materials.