Fan-Yong Ran

Publications (3)5.16 Total impact

• Article: Ferromagnetism in Cu-doped AlN films

  Fan-Yong Ran, M. Subramanian, Masaki Tanemura, Yasuhiko Hayashi, Takehiko Hihara
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  ABSTRACT: AlN films doped with 3.2–8.2 at. % Cu were deposited by helicon magnetron sputtering. The films exhibited ferromagnetism with a Curie temperature above 360 K. The observed magnetic anisotropy and exclusion of ferromagnetic contamination indicated that the ferromagnetism was the intrinsic property of Cu-doped AlN films. Room-temperature (RT) saturation magnetization (Ms) tended to decrease with increasing Cu concentration and the maximum RT Ms obtained was about 8.5 emu/cm3 (0.6 μB/Cu). Vacuum annealing increased the RT Ms values and meanwhile reduced ratio of N/(Al+Cu), which suggested that Al interstitial and N vacancy might contribute to the observed ferromagnetic behavior.
  Applied Physics Letters 09/2009; 95(11):112111-112111-3. · 3.84 Impact Factor
• Article: Room‐temperature ferromagnetism of Cu‐doped ZnO films deposited by helicon magnetron sputtering

  Fan-Yong Ran, Masao Imaoka, Masaki Tanemura, Yasuhiko Hayashi, Tun-Seng Herng, Shu-Ping Lau
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  ABSTRACT: Wurtzite structure ZnO films doped with 0.5 and 1.7 at% Cu were deposited by helicon magnetron sputtering. The prepared films exhibited room-temperature (RT) ferromagnetism (FM). Maximum RT saturation magnetization of 2 emu/cm3 (∼0.3μB/Cu) was observed for ZnO film with 1.7 at% Cu. Cu ions were in a bivalent state as identified by X-ray photoelectron spectroscopy (XPS). In photoluminescence spectra, the green emission peak increased and redshifted due to the incorporation of Cu or defects induced by Cu incorporation. Since Cu and Cu-related oxides are not RT ferromagnetic, and no trace of ferromagnetic contamination was detected in XPS results, the observed FM is considered to be an intrinsic property of Cu-doped ZnO films. The FM was thought to originate from defect-related mechanisms. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
  physica status solidi (b) 03/2009; 246(6):1243 - 1247. · 1.32 Impact Factor
• Article: Effect of substrate temperature on the room-temperature ferromagnetism of Cu-doped ZnO films

  Fan-Yong Ran, Masaki Tanemura, Yasuhiko Hayashi, Takehiko Hihara
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  ABSTRACT: Wurtzite structure ZnO films doped with ~2 at% Cu were deposited at substrate temperatures (Ts) from 350 to 600 °C by helicon magnetron sputtering. All the films exhibited room-temperature (RT) ferromagnetism (FM) and the maximum saturation magnetization (Ms) was 1.2 emu/cm3 (~0.15 μB/Cu). Cu ions were mainly in a divalent state as identified by X-ray photoelectron spectroscopy. FM tended to increase with decreasing Ts, and vacuum annealing enhanced the Ms. These results suggested that oxygen vacancies and/or zinc interstitials might contribute to the ferromagnetic performance. Thus, the observed FM was explained in terms of the defect related mechanism.
  Journal of Crystal Growth.