Search for magnetism in Co and Fe-doped HfO 2 thin films for potential spintronic applications
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D6.13.1
Search for magnetism in Co and Fe-doped HfO2 thin films for potential spintronic applications
M.S.R. Rao, Darshan C. Kundaliya, S. Dhar, C.A. Cardoso, A. Curtin Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742 S.J. Welz, R. Erni, N.D. Browning1 Department of Chemical Engineering and Materials Science, University of California at Davis, California 95616 and 1Lawrence Berkeley National Laboratory, NCEM, One Cyclotron Road, Berkeley, California 94720 S.E. Lofland and C.J. Metting Department of Chemistry and Physics, Rowan University, Glassboro, New Jersey 080281701 S.B. Ogale1 and T. Venkatesan Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742, USA and 1Department of Materials Science, University of Maryland, College Park, Maryland 20742
D6.13.2
We studied the structural and magnetic properties of dilutely (5 mol%) doped 3d elements (Co and Fe) in PLD grown HfO2 high-k dielectric thin films. Monoclinic phase of HfO2 was stabilized by Co- and Fe- substitution at significantly low growth temperature (~725 oC). No magnetic moment was observed in Co-doped HfO2 films. On the other hand, 5 mol% Fe-doped HfO2 films grown at different oxygen partial pressures (10-6 torr to 10 mtorr) showed interesting magnetization behavior with varying coercive field due to the segregation of Fe2O3 and Fe3O4 phases. Magnetic force microscopy (MFM) study revealed magnetic impurity phase segregation. Films grown at 1 x 10-4 torr of oxygen partial pressure (O2pp) showed oriented Fe3O4 impurity line (220) and the coercive field (Hc) ~ 350 Oe. Films grown at higher oxygen partial pressure (1x10-2 torr) showed no impurities and magnetization was absent. Coercive field varied as a function of oxygen partial pressure. This property will be of great interest from the view point of magneto-optic applications.
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Hafnia (HfO2) is a high-k dielectric material with a wide band-gap of ~ 4.5 eV. It has high thermal stability and the potential to replace SiO2 gate dielectric in microelectronic devices.1 The oxygen vacancy and stoichiometry issues play an important role in tuning the properties of HfO2-based devices.2 Not much work has been available in literature on HfO2 films as has been the case with its isostructural ZrO2 (zirconia) films.3 Moreover, the recent spur in research activity in wide band gap oxide films such as ZnO, TiO2 and SnO2,4-11 of which TiO2 has a high-k dielectric character, has prompted us to search for magnetism in dilutely (5 mol%) Co and Fe doped HfO2 thin films grown using the pulsed laser deposition (PLD) thin film growth technique. Magnetism in such high k-dielectric thin films, if realized, should be useful in non-linear optical and quantum computation applications.12,13 High Purity (>99.9%) HfO2, CoO and Fe2O3 powders were mixed thoroughly in the required ratios for 5mol% Co and Fe doping in HfO2. The mixtures were heated at 1100 oC for 18h followed by grinding. The resulting powd
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