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

C. T. Wang, C. W. Lin, C. L. Hsia, B. W. Chang, M. F. Luo

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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 2.0 V, STM topography images of the alumina layer beneath the surface were obtained. A probe with depth of 2-8 Å 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-Al 2O 3 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.

Original languageEnglish
Pages (from-to)3952-3959
Number of pages8
JournalThin Solid Films
Issue number11
StatePublished - 30 Mar 2012


  • Alumina
  • Density functional calculations
  • NiAl
  • Scanning tunneling microscopy
  • Thin films
  • Under-surface


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