Influence of Mn doping on structural and vibrational properties of self-assembled Mn doped ZnO nanocrystals

Nanocrystallites (15-25 nm) of Mn doped ZnO prepared by refluxing their acetate precursors in the presence of diethylene glycol, self-assemble into polydisperse spheres of broad size distributation (100-400 nm). The center of X-ray diffraction peaks shifts towards lower angle and the line gets broadened on increasing Mn concentration. Compared to the vibration modes of wurtzite ZnO, one additional vibration mode is observed in the range of 522-518 cm(-1) in Raman spectra of Mn doped ZnO whose intensity increases on increasing the Mn concentration. The origin of this peak could be related to the incorporation of Mn2+ in Zn2+ lattice site. Further, on increasing Mn concentration, infrared band red shifted and surface phonon mode absorption get pronounced due to the incorporation of Mn2+ in Zn2+ lattice site resulting changes in the local structure parameters (effective mass, force constant, bond length).