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

Abstract

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.

Authors:
; ;  [1]
  1. Abteilung Festkoerperphysik, Universitaet Ulm, D-89069 Ulm (Germany)
Publication Date:
OSTI Identifier:
20668306
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 97; Journal Issue: 8; Other Information: DOI: 10.1063/1.1876580; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Dietrich, Ch, Koslowski, B, and Ziemann, P. Ultrathin epitaxial Al{sub 2}O{sub 3} films grown on Nb(110)/sapphire(0001) investigated by tunneling spectroscopy and microscopy. United States: N. p., 2005. Web. doi:10.1063/1.1876580.
Dietrich, Ch, Koslowski, B, & Ziemann, P. Ultrathin epitaxial Al{sub 2}O{sub 3} films grown on Nb(110)/sapphire(0001) investigated by tunneling spectroscopy and microscopy. United States. https://doi.org/10.1063/1.1876580
Dietrich, Ch, Koslowski, B, and Ziemann, P. 2005. "Ultrathin epitaxial Al{sub 2}O{sub 3} films grown on Nb(110)/sapphire(0001) investigated by tunneling spectroscopy and microscopy". United States. https://doi.org/10.1063/1.1876580.
@article{osti_20668306,
title = {Ultrathin epitaxial Al{sub 2}O{sub 3} films grown on Nb(110)/sapphire(0001) investigated by tunneling spectroscopy and microscopy},
author = {Dietrich, Ch and Koslowski, B and Ziemann, P},
abstractNote = {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.},
doi = {10.1063/1.1876580},
url = {https://www.osti.gov/biblio/20668306}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 8,
volume = 97,
place = {United States},
year = {2005},
month = {4}
}