abstract
A series of chemically prepared Co(2+)-doped ZnO colloids has been surface modified either by growing shells of ZnSe or by the in situ encapsulation in poly(styrene). The surface modification effects using these two distinct chemical strategies on the magnetic properties of the nanocrystals were probed by electron paramagnetic resonance (EPR). Structural characterization by means of x-ray diffraction and transmission electron microscopy gave no evidence of second phase formation within the detection limits of the used equipment. The EPR analysis was carried out by simulations of the powderlike EPR spectra. The results confirm that in the core of these nanocrystals Co was incorporated as Co(2+), occupying the Zn(2+) sites in the wurtzite structure of ZnO. Additionally we identify two Co signals stemming from the nanocrystals' shell. The performed surface modifications clearly change the relative intensity of the EPR spectrum components, revealing the core and shell signals. (c) 2008 American Institute of Physics.
keywords
THIN-FILMS; FERROMAGNETIC PROPERTIES; ELECTRIC PROPERTIES; QUANTUM DOTS; ZN1-XMNXO; EPR
subject category
Physics
authors
Pereira, AS; Ankiewicz, AO; Gehlhoff, W; Hoffmann, A; Pereira, S; Trindade, T; Grundmann, M; Carmo, MC; Sobolev, NA
our authors
Angela Sofia dos Santos Pereira
Post-doc Fellowship
Sérgio Manuel de Sousa Pereira
Principal Researcher
Tito Trindade
Full professor