AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS2-ThA

Paper SS2-ThA5
Evolution of Surface Morphology and Growth Modes for Epitaxial alpha-Fe@sub 2@O@sub 3@ on alpha-Al@sub 2@O@sub 3@

Thursday, November 5, 1998, 3:20 pm, Room 309

Session: Oxide Growth and Structure
Presenter: I. Yi, Pacific Northwest National Laboratory
Authors: I. Yi, Pacific Northwest National Laboratory
A. Chambers, Pacific Northwest National Laboratory
Correspondent: Click to Email
We have investigated how the surface morphology of epitaxial alpha-Fe@sub 2@O@sub 3@ evolves with film thickness on alpha-Al@sub 2@O@sub 3@ as a function of growth rate and surface orientation. The lattice mismatch of this materials system is 5.7%. The growth technique used was oxygen-plasma-assisted molecular beam epitaxy. Film surfaces were characterized as a function of thickness in situ using reflection high-energy electron diffraction, low-energy electron diffraction, x-ray photoelectron spectroscopy and diffraction, and non-contact atomic force microscopy. Island formation is observed upon relaxation of the Fe@sub 2@O@sub 3@ film to its bulk lattice spacing. Relaxation begins at coverages of only ~1 full monolayer. Furthermore, the shape and size distributions of the islands are critically dependent on growth rate during the early stages of film growth. Sparsely populated, high-aspect-ratio islands form at higher growth rates, whereas more densely populated islands with lower aspect ratios form at lower growth rates. The former surface morphology is found to be a very poor template for further epitaxy, and gives rise to poorly ordered material, whereas subsequent epitaxy on the latter morphology produces very well ordered films and surfaces. The low-aspect-ratio islands formed at the initial stages of film growth coalesce within the first 50 Å. With a reduced number of islands, the surface becomes smoother. With additional growth, the surface morphology is greatly improved and the island-to-island height variation is reduced to few Ångstroms.@footnote 1@ @FootnoteText@ @footnote 1@Work supported by the U.S. Department of Energy, Offices of Basic Energy Sciences and Biological and Environmental Research Environmental Management Science Program.