PREPARATION AND CHARACTERIZATION OF GAMMA-ALUMINA ON ALUMINUM (AUGER SPECTROSCOPY, TRANSMISSION ELECTRON, ALUMINUM)

Gamma alumina is a high surface area, catalytically active material used as a catalyst, a co-catalyst, a catalyst support, and an adsorbent, and in the microelectronics industry as an isolator. The electronic and geometric properties causing the material to be catalytically active are not well understood. A combination of ultrahigh vacuum surface spectroscopies and transmission electron microscopy has been used to study the kinetics of aluminum oxidation and the morphology and crystallographic orientation of planar (gamma)-alumina grown on aluminum substrates.;The oxidation of Al{111} by oxygen is a two stage process. The chemisorption of oxygen occurs by a first order kinetic process in oxygen gas and aluminum metal, followed by the formation of aluminum oxide by a zero order kinetic process in oxygen gas chemisorbed aluminum oxide. Planar (gamma)-alumina, 80 nm thick, was formed on crystallographically distinct substrates by heating in air for 3 h at 863 K. The oxide was epitactically oriented when grown on single crystal aluminum substrates, but not preferentially oriented when grown on polycrystalline substrates. The oxide grain size was always much smaller than the aluminum substrate grain size, and nucleation of the oxide was homogeneous on the surface of the aluminum substrate.;The kinetics of the oxidation reaction for dry oxygen on Al{111} were studied using Auger electron spectroscopy. A chemical analysis of the top two monolayers of the sample is acquired as an adsorption reaction occurs. Transmission electron microscopy was used to directly image oxides that were chemically removed from the aluminum substrates in order to establish the crystallography and morphology of the oxides as a function of the substrate type and preparation conditions. High resolution electron microscopy was used to form lattice fringes giving detailed information about the molecular regularity within a small area of the oxide. Rutherford backscattering was used to determine the oxide thickness based on the oxide and substrate preparation conditions.