Crystallinity and thickness control of well-ordered ultra-thin Al sub 2 O sub 3 film on NiAl(110)

In the past decade, considerable effort has been made to study the growth of alumina films on nickel aluminides. NiAl is one of the heat-resistant nickel alloys, and an aluminum oxide layer formed on the surface contributes to resistance to heat and corrosion. Epitaxial film of well-ordered ultra-thin (0.5 nm) Al sub 2 O sub 3 is known to grow on NiAl(110) by 1200 L oxygen introduction. We found that the crystallinity of the epitaxial film was improved by introducing 1200 L oxygen at lower pressure. Control of the thickness of the epitaxial Al sub 2 O sub 3 film was also achieved, by multiple-oxidation, for the first time. Successful thickness control of epitaxial Al sub 2 O sub 3 film in the range of 0.5-1.4 nm is considered an important step toward a tunneling electron emitter device, as well as basic research for model catalysts.