We have prepared under ultrahigh vacuum conditions a NiAl(110) wedge w
hich was oxidized such that, after oxidation, small support-free Al2O3
crystallites were formed at the edge of the wedge, and the remaining
part of the wedge was covered by a thin well-ordered Al2O3 film. This
film, which has been characterized in great detail in earlier studies
[J. Libuda et al., Surf. Sci. 318 (1994) 61], was transferred in air t
o a transmission electron microscope (TEM) and studied with respect to
its geometric structure. The particular sample preparation allows for
a direct comparison between the structure of the film and the bulk al
uminum oxide. We find that the supported oxide exhibits a gamma-Al2O3-
like structure similar to that observed previously under UHV condition
s, indicating that exposure to air has only a limited influence on the
film. The lattice constant of the oxide film agrees within similar to
2% with that reported for bulk Al2O3. The domain structure of the alu
mina film as found in the ultrahigh vacuum experiments was also identi
fied using TEM of the supported layer. The support-free oxide formed a
t the edge of the wedge exhibits the structure of the supported film f
ormed under UHV conditions with deviations of the lattice constants of
similar to 7% in one direction and similar to 1% in the other. (C) 19
97 Elsevier Science B.V.