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Free keywords:
molecular beam epitaxy; transmission electron microscopy; copper; crystalline oxides; interface structure
Abstract:
Transmission electron microscopy studies of oxygen-terminated
Cu(111)/alpha-Al2O3(0001) interfaces possessing two different
orientation relationships are reported. The oxygen-terminated
alpha-Al2O3(0001) surfaces were generated by utilizing an oxygen plasma
at different temperatures in ultrahigh vacuum, and then Cu thin films
were grown by molecular beam epitaxy on these surfaces. A clean
hydroxylated alpha-Al2O3(0001) surface could be obtained by room
temperature oxygen plasma cleaning. On this surface Cu films grew
following the conventional face-centered cubic/hexagonal close-packed
orientation relationship at room temperature, i.e., (111)Cu parallel
to(0001)(alpha) and +/-[1 (1) over bar0]Cu parallel to[10 (1) over
bar0](alpha), and were nearly incoherent to the substrate lattice. The
high-temperature (similar to 750 degrees C) oxygen plasma treatment
after a dehydroxylation process of alpha-Al2O3(001) generated an
oxygen-rich surface. On this surface, the Cu films showed a thermally
activated wetting by forming Cu2O-like bonding at the interface in an
orientation relationship rotated by 30 degrees from the conventional
orientation relationship around the interface normal: (111)Cu parallel
to(0001)(alpha), and +/- [2 (1) over bar(1) over bar ]Cu parallel to[10
(1) over bar0](alpha). (c) 2006 Acta Materialia Inc. Published by
Elsevier Ltd. All rights reserved.
