Synthesis and characterization of some diluted magnetic semiconductors

Abstract

In the present work synthesis and characterization of undoped and Mn- doped ZnO nanoparticles are reported. Mn doped ZnO nanoparticles having composition (Zn1-xMnxO), where x = 0.00, 0.01, 0.03, 0.05, 0.07, 0.09, and 0.10 were synthesized by co-precipitation method, and sintered in Argon atmosphere. X-ray diffraction data revealed the formation of hexagonal wurtzite structure for both undoped and Mn-doped nanoparticles. Furthermore, no other impurity peak was observed in the XRD pattern showing the single phase sample formation of ZnO nanoparticles up to x=0.05, beyond which an impurity phase of MnO was detected in higher dopant concentration (x=0.07, 0.09, and 0.10). The lattice parameter, and crystal size slightly increase with the increase of dopant concentration up to x=0.05 after which they decrease for higher doping concentration. On contradictory, the strain curve has the opposite behavior. FTIR spectra of ZnO with Mn content have been measured in the range 1300-400 cm-1, and the results confirm the presence of a secondary phase (MnO) at the grain boundaries in higher dopant concentrations. TEM images of samples were spherical or elliptical nanoparticles showing that the grain size decreases for higher doping concentration which is consistent with the behavior that is shown by the XRD results. The ac conductivity and the dielectric constant of Mn-doped ZnO were investigated at temperatures from 320 to 515K in the frequency range from 102 to 106 Hz. The frequency dependence of dielectric constant, dielectric loss, and ac conductivity were discussed. The dielectric constant was found to increase with Mn substitution. It was found also that both the dielectric loss and the ac conductivity decrease with the increase in Mn content.