Paper AC+TF-ThA4
Solution Route to High Quality Epitaxial Actinide Films Form Oxides to Carbides

Thursday, November 3, 2011, 3:00 pm, Room 207

We report on the solution based synthesis of epitaxial thin films of neptunium oxide and plutonium oxide. Actinides represent a tremendous challenge to first principle calculations of orbital energies due to the complicating features that arise from f orbital interactions. Theoretical development from first principle calculations relies on predictions of continuous materials with no boundaries. To test these theories requires experimental results using high quality single crystals. For many materials this can be a straight forward process. For actinide oxides the experimental work is complicated by the radioactivity that makes CVD processes challenging from a safety perspective and by the recalcitrant nature of the oxides. The challenge of modeling actinide oxides is best represented in Mott insulators such as UO₂. Theoretical calculations that worked with transition metals predict UO₂ to be a metal as opposed to an insulator with a 2.3 eV band gap. Recent reports predict the same metallic behavior for NpO₂. Many theoretical reports have highlighted the need for experimental work on single crystals. In the absence of single crystals they rely on work done on powders as in the case of PuO_2. We report here on epitaxial films of PuO₂ that are thin enough to measure the optical band gap directly. XRD has been used to determine the alignment of the PuO₂ relative to the substrate and EXAFS confirm the stoichiometry.