Studies on sub-100 nm fluorite-derivative oxide films

This dissertation presents detailed studies on the relationship between oxygen stoichiometry, microstructure, and functional properties of the sub-100nm fluorite derivative thin film oxides, utilizing novel experimental methods such as in-situ electron microscopy, ultraviolet photon irradiation, and electrical conductivity relaxation studies. Microstructure evolution in undoped and yttria-doped-zirconia (YDZ) films grown by electron beam evaporation at room temperature was studied by in-situ transmission electron microscopy. We found that phase stability in nanoscale zirconia is remarkably different from that in bulk. The results suggest that the phase and microstructural stability in zirconia thin films are very sensitive to minute differences in doping concentration, oxygen stoichiometry and synthesis methods. CeO 2 and Y 2 O 3 films grown on sapphire c-plane substrate by molecular beam synthesis were directed in [111] direction with large lattice misfit. The CeO 2 /Al 2 O 3 interface had high density of misfit dislocations to accommodate large misfit, while the Y 2 O 3 /Al 2 O 3 interface was nearly defect free and misfit was accommodated by defects within the Y 2 O 3 films. The electrical conductivity relaxation kinetics have studied in ceria films and the relaxation time was found to be much slower in highly textured ceria films compared to that in polycrystalline thin films. Ultraviolet photon synthesis has been introduced as a unique approach to control various difficult properties in nanoscale oxide thin films. It has been shown that this technique enables near-room temperature modification of structure and interfacial chemistry with atomic-level control. The UV process is versatile; it can be used post-growth or during oxidation. We demonstrated UV irradiation can introduce significant structural change at room temperature in nanoscale YDZ films grown on silicon substrates. We also demonstrated that the oxygen concentration in YDZ grown on germanium can be controllably tuned using this approach in a self-limiting manner. Metal alloy oxidation under UV was studied and shown to be very promising way to grow conformal oxide thin films at room temperature. High temperature properties, such as grain size and oxygen diffusivity, are slightly different in UV grown films compared to that in conventional thermally grown films.