Under-surface observation of thin-film alumina on NiAl(100) with scanning tunneling microscopy

• Published in: Thin solid films Vol. 520; no. 11; pp. 3952 - 3959
• Main Authors: Wang, C.T., Lin, C.W., Hsia, C.L., Chang, B.W., Luo, M.F.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30-03-2012
• Subjects: Alumina; Density functional calculations; NiAl; Scanning tunneling microscopy; Thin films; Under-surface; Thin films; Scanning tunneling microscopy; Density functional calculations; NiAl; Under-surface; Alumina
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2012.01.011

Scanning tunneling microscopy (STM) was used to investigate the oxide structures underlying the surface of alumina thin-film grown on NiAl(100). At a bias voltage (on the sample) below 2.0V, STM topography images of the alumina layer beneath the surface were obtained. A probe with depth of 2–8Å was readily attained. The under-surface observation shows that the film consists of stacked layers of alumina whereas the layered alumina unnecessarily comprises entire θ-Al2O3 unit cells. The lattice orientation of the upper alumina layer differs from that of the lower one by 90° — the newly grown oxide structurally matching the horizontal oxide rather than the lower oxide. The results indicate a growth process competing with the typical mode of epitaxial growth for the growth of alumina film.
► STM images of alumina layers beneath the surface of alumina film/NiAl(100) obtained. ► A probe depth of 0.2–0.8nm is readily attained. ► The orientation of upper layer of alumina may differ from that of lower ones by 90°.