Characterization of chemical speciation in ultrathin uranium oxide layered films.

A unique approach to detect chemical speciation and distribution on nanometer-scale nuclear materials has been achieved by the combination of neutron reflectometry and shell-isolated surface-enhanced Raman spectroscopy. Both surface and underlying layers of the uranium oxide materials were determined with angstrom-level resolution. Our results reveal that the UOx film is composed of three sublayers: an ∼38 A thick layer of U3O8 formed along the UOx/substrate interface; the adjacent sublayer consists of an ∼900 A thick single phase of α-UO3, and the top layer is γ-UO3 with a thickness of ∼115 A.