AVS 53rd International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThA

Paper SS1-ThA6
Substrate-controlled Limiting Thickness for Nanoscale Alumina Film Growth on Single Crystal Nickel Aluminides under non-UHV Conditions

Thursday, November 16, 2006, 3:40 pm, Room 2002

Session: Reactivity of Oxide Surfaces II
Presenter: J.A. Kelber, University of North Texas
Authors: J.A. Kelber, University of North Texas
N.P. Magtoto, University of North Texas
M. Jain, University of North Texas
C. Vamala, University of North Texas
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Nanothin ordered alumina films exposed to H@sub 2@O at partial pressures above UHV reach limiting thicknesses governed entirely by the structure of the nickel aluminide substrate (NiAl(110) vs. Ni@sub 3@Al(110)). This work provides a basis for developing quantitative predictive models of the Mott-Cabrera mechanism, and also indicates that such nanothin films have important differences from bulk oxides in non-UHV environments. Auger, LEED, and STM were used to characterize alumina films grown on single crystal substrates in UHV, and exposed to 10@super -7@ Torr < pH@sub 2@O < 10@super -3@ Torr/300 K in an adjacent environmental chamber. Film thickness was characterized by Auger spectroscopy. Films grown on NiAl(110) reach a limiting thickness of 17±1 angstroms independent of initial thickness or roughness, while films grown on Ni@sub 3@Al(110) displayed a limiting thickness of 12± 1 angstroms. The different thicknesses correspond to different energies for transfer of an Al atom from the substrate into the oxide, with the larger number of Ni-Al bonds for Ni@sub 3@Al leading to a higher barrier on that substrate. The implications of these results for ultrathin alumina films as model catalyst supports and in nanoelectronics will be discussed.