Structural, Optical and Magnetic Characterization of Highly Monodisperse Transition Metal-Doped ZnO Nanocrystals

Keywords:
diluted magnetic semiconductor, spintronics, monodisperse nanocrystall, ZnO

Abstract:
The recent finding of semiconductor materials with magnetic properties has attracted the attention due to its potential applications in spintronics. We present here the results on synthesis and characterization of (TM) doped-ZnO nanocrystals, (TM=Co, Ni, Fe, Cu and Cr). Stable suspensions of these materials were produced in ethanol at room-temperature. XRD characterization of doped systems confirmed the formation of ZnO. Ni in starting solutions delayed the formation of the oxide. ZnO host structure was fully developed after 6 days of aging when the fraction of Ni in solution, ‘x’, was 0.02. HRTEM analyses revealed the high monodispersity of the 6-8 nm nanocrystals. The blue shift in UV-Vis absorption peaks of doped nanocrystals with respect to bare ZnO evidenced the inhibition of crystal growth. Room-temperature PL spectra for aged bare ZnO showed a red shift in the position of the donor-acceptor pair and the broad band peaks. This shift is a confirmation of crystal growth during aging. PL measurements for doped ZnO evidenced the dependence of the visible emission intensity with dopant concentration. The visible emission was absent for x = 0.05 in Co-doped ZnO. Doped ZnO nanocrystals were paramagnetic or weakly ferromagnetic, in contrast with diamagnetic bare ZnO.

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Nanotech 2006 Conference Program Abstract