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Title: Surface layer of SrRuO{sub 3} epitaxial thin films under oxidizing and reducing conditions

Abstract

Imperfect stoichiometry and heterogeneity of a surface layer of SrRuO{sub 3} epitaxial thin films, grown on SrTiO{sub 3} substrates, are presented with the help of various methods. Rutherford backscattering spectroscopy, x-ray photoemission spectroscopy (XPS), and time of flight secondary ion mass spectrometry are used to obtain information about the stoichiometry and uniformity of the SrRuO{sub 3} structure. The temperature of chemical decomposition is first determined for polycrystalline samples under different conditions using thermogravimetry analysis. Then the determined values are used for thin film annealings in high and low oxygen pressure ambients, namely, air, vacuum, and hydrogen. The surface deterioration of the thin film together with changes in its electronic structure is investigated. O1s and Sr3d core lines measured by XPS for as-made samples obviously consist of multiple components indicating different chemical surroundings of atoms. Thanks to different incident beam angle measurements it is possible to distinguish between interior and surface components. Valence band spectra of the interior of the film are consistent with theoretical calculations. After annealing, the ratio of the different components changes drastically. Stoichiometry near the surface changes, mostly due to ruthenium loss (RuO{sub X}) or a segregation process. The width and position of the Ru3p line formore » as-made samples suggest a mixed oxidation state from metallic to fully oxidized. Long annealing in hydrogen or vacuum ambient leads to a complete reduction of ruthenium to the metallic state. Local conductivity atomic force microscopy scans reveal the presence of nonconductive adsorbates incorporated in the surface region of the film. Charge transport in these measurements shows a tunneling character. Scanning tunneling microscopy scans show some loose and mobile adsorbates on the surface, likely containing hydroxyls. These results suggest that an adequate description of a SrRuO{sub 3} thin film should take into account imperfections and high reactivity of its surface region.« less

Authors:
; ; ; ; ; ;  [1];  [2];  [3]
  1. Institut fuer Festkoerperforschung, Forschungszentrum Juelich, 52425 Juelich (Germany)
  2. (Germany)
  3. (Poland)
Publication Date:
OSTI Identifier:
20982639
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 2; Other Information: DOI: 10.1063/1.2408382; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANNEALING; ATOMIC FORCE MICROSCOPY; CHARGE TRANSPORT; DECOMPOSITION; ELECTRONIC STRUCTURE; EPITAXY; HYDROXIDES; MASS SPECTRA; MASS SPECTROSCOPY; OXIDATION; RUTHENIUM COMPOUNDS; RUTHERFORD BACKSCATTERING SPECTROSCOPY; SCANNING TUNNELING MICROSCOPY; STOICHIOMETRY; STRONTIUM TITANATES; THERMAL GRAVIMETRIC ANALYSIS; THIN FILMS; TIME-OF-FLIGHT METHOD; TUNNEL EFFECT; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Mlynarczyk, M., Szot, K., Petraru, A., Poppe, U., Breuer, U., Waser, R., Tomala, K., Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Juelich, 52425 Juelich, and M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow. Surface layer of SrRuO{sub 3} epitaxial thin films under oxidizing and reducing conditions. United States: N. p., 2007. Web. doi:10.1063/1.2408382.
Mlynarczyk, M., Szot, K., Petraru, A., Poppe, U., Breuer, U., Waser, R., Tomala, K., Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Juelich, 52425 Juelich, & M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow. Surface layer of SrRuO{sub 3} epitaxial thin films under oxidizing and reducing conditions. United States. doi:10.1063/1.2408382.
Mlynarczyk, M., Szot, K., Petraru, A., Poppe, U., Breuer, U., Waser, R., Tomala, K., Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Juelich, 52425 Juelich, and M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow. Mon . "Surface layer of SrRuO{sub 3} epitaxial thin films under oxidizing and reducing conditions". United States. doi:10.1063/1.2408382.
@article{osti_20982639,
title = {Surface layer of SrRuO{sub 3} epitaxial thin films under oxidizing and reducing conditions},
author = {Mlynarczyk, M. and Szot, K. and Petraru, A. and Poppe, U. and Breuer, U. and Waser, R. and Tomala, K. and Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Juelich, 52425 Juelich and M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow},
abstractNote = {Imperfect stoichiometry and heterogeneity of a surface layer of SrRuO{sub 3} epitaxial thin films, grown on SrTiO{sub 3} substrates, are presented with the help of various methods. Rutherford backscattering spectroscopy, x-ray photoemission spectroscopy (XPS), and time of flight secondary ion mass spectrometry are used to obtain information about the stoichiometry and uniformity of the SrRuO{sub 3} structure. The temperature of chemical decomposition is first determined for polycrystalline samples under different conditions using thermogravimetry analysis. Then the determined values are used for thin film annealings in high and low oxygen pressure ambients, namely, air, vacuum, and hydrogen. The surface deterioration of the thin film together with changes in its electronic structure is investigated. O1s and Sr3d core lines measured by XPS for as-made samples obviously consist of multiple components indicating different chemical surroundings of atoms. Thanks to different incident beam angle measurements it is possible to distinguish between interior and surface components. Valence band spectra of the interior of the film are consistent with theoretical calculations. After annealing, the ratio of the different components changes drastically. Stoichiometry near the surface changes, mostly due to ruthenium loss (RuO{sub X}) or a segregation process. The width and position of the Ru3p line for as-made samples suggest a mixed oxidation state from metallic to fully oxidized. Long annealing in hydrogen or vacuum ambient leads to a complete reduction of ruthenium to the metallic state. Local conductivity atomic force microscopy scans reveal the presence of nonconductive adsorbates incorporated in the surface region of the film. Charge transport in these measurements shows a tunneling character. Scanning tunneling microscopy scans show some loose and mobile adsorbates on the surface, likely containing hydroxyls. These results suggest that an adequate description of a SrRuO{sub 3} thin film should take into account imperfections and high reactivity of its surface region.},
doi = {10.1063/1.2408382},
journal = {Journal of Applied Physics},
number = 2,
volume = 101,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}