Ultrathin epitaxial Al{sub 2}O{sub 3} films grown on Nb(110)/sapphire(0001) investigated by tunneling spectroscopy and microscopy

Journal Article · Fri Apr 15 04:00:00 EDT 2005 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.1876580· OSTI ID:20668306

Dietrich, Ch; Koslowski, B; Ziemann, P ^[1]

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1. Abteilung Festkoerperphysik, Universitaet Ulm, D-89069 Ulm (Germany)

Structural as well as electronic properties of ultrathin epitaxial Al{sub 2}O{sub 3} films prepared on Nb(110)/sapphire(0001) were analyzed in situ by applying scanning tunneling microscopy (STM) and spectroscopy as well as ultraviolet photoelectron spectroscopy, cathode luminescence, and low-energy electron diffraction. According to these experiments, the niobium base film is protected from oxidation, while the ultrathin Al film deposited onto the Nb is fully oxidized and (0001)-oriented with a very smooth surface. The STM-imaged topography of the oxide films in most cases reflects monatomic steps of the underlying Nb(110) film. In some cases (10% of all samples with low tunneling barriers) additional {approx}0.4-nm-high steps are observed characteristic of monatomic Al{sub 2}O{sub 3} steps. Furthermore, for growing tunneling voltages (>1 V), the STM-imaged topographies reveal an increasing density of small hillocks, which are attributed to localized defect states such as oxygen vacancies still present within the oxide layer.

• OSTI ID: 20668306
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 97; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CATHODES
CATHODOLUMINESCENCE
CRYSTALS
DEPOSITION
ELECTRIC POTENTIAL
ELECTRON DIFFRACTION
EPITAXY
LAYERS
NIOBIUM
OXIDATION
PHOTOELECTRON SPECTROSCOPY
SAPPHIRE
SCANNING TUNNELING MICROSCOPY
THIN FILMS
TOPOGRAPHY
TUNNEL EFFECT
ULTRAVIOLET RADIATION
VACANCIES