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Lack of ferromagnetism in n-type cobalt-doped ZnO epitaxial thin films

Journal Article · · New Journal of Physics
 [1];  [1];  [2];  [1];  [1];  [1];  [3];  [3];  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Univ. of Washington, Seattle, WA (United States)
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Epitaxial thin films of cobalt-doped ZnO (Co:ZnO) were deposited by pulsed laser deposition (PLD) on both c-plane and r-plane sapphire (Al2O3). The films exhibited high structural quality with narrow x-ray diffraction (XRD) rocking curve peak widths. X-ray absorption spectroscopy (XANES and EXAFS) confirmed well-ordered Co substitution for Zn in ZnO without the formation of secondary phases. A wide range of n-type conductivities (10-4 – 105 Ω-cm) was achieved by controlling the deposition conditions, post-annealing in vacuum, and/or addition of Al during deposition. Despite the high structural quality of the Co:ZnO thin films, no significant room temperature ferromagnetism was observed under any processing or treatment conditions. The lack of ferromagnetism indicates that itinerant conduction band electrons alone are not sufficient to induce ferromagnetism in Co:ZnO, even when the carrier concentration is a significant fraction of the magnetic dopant concentration. The implications of this observation are discussed.
Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC05-76RL01830
OSTI ID:
937028
Report Number(s):
PNNL-SA--58534; 19856; KC0203020
Journal Information:
New Journal of Physics, Journal Name: New Journal of Physics Vol. 10; ISSN 1367-2630
Publisher:
IOP Publishing
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
COBALT
DOPED MATERIALS
EPITAXY
Environmental Molecular Sciences Laboratory
FERROMAGNETISM
N-TYPE CONDUCTORS
THIN FILMS
ZINC OXIDES