Epitaxial Growth and Properties of Cobalt-doped ZnO on α-Al₂O₃ Single-Crystal Substrates

Journal Article · Mon Aug 30 00:00:00 EDT 2004 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.70.054424· OSTI ID:15010676

Tuan, Allan C. ^[1]; Bryan, John D. ^[1]; Pakhomov, Alexandre ^[1]; Shutthanandan, V. ^[2]; Thevuthasan, Suntharampillai ^[2]; McCready, David E. ^[2]; Gaspar, Dan J. ^[2]; Engelhard, Mark H. ^[2]; Rogers, J. W. ^[2]; Krishnan, Kannan M. ^[1]; Gamelin, Daniel R. ^[1]; Chambers, Scott A. ^[2]

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1. Univ. of Washington, Seattle, WA (United States)
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Co-doped ZnO (CoxZn₁-xO) is of potential interest for spintronics due to the prediction of room-temperature ferromagnetism. We have grown epitaxial CoxZn₁-xO films on Al₂O₃(012) substrates by metalorganic chemical vapor deposition using a liquid precursor delivery system. High concentrations of Co (x < 0.35) can be uniformly incorporated into the film without phase segregation. Co is found to be in the ⁺² oxidation state, independent of x. This material can be grown n type by the deliberate incorporation of oxygen vacancies, but not by inclusion of ~1 at. % Al. Semiconducting films remain ferromagnetic up to 350 K. In contrast films without oxygen vacancies are insulating and nonmagnetic, suggesting that exchange interaction is mediated by itinerant carriers. The saturation and remanent magnetization on a per Co basis was very small (< 0.1 μB/Co), even in the best films. The dependence of saturation magnetization, as measured by optical magnetic circular dichroism, on magnetic field and temperature, agrees with the theoretical Brillouin function, demonstrating that the majority of the Co(II) ions behave as magnetically isolated S = 3/2 spins.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 15010676
• Report Number(s): PNNL-SA-38883; 2097; TRN: US200502%%447
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 70, Issue 5; ISSN 1098-0121
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHEMICAL VAPOR DEPOSITION
EXCHANGE INTERACTIONS
FERROMAGNETISM
FORECASTING
MAGNETIC CIRCULAR DICHROISM
MAGNETIC FIELDS
MAGNETIZATION
OXYGEN
PRECURSOR
SATURATION
SEGREGATION
SUBSTRATES
VACANCIES
VALENCE
Environmental Molecular Sciences Laboratory