Micro-Raman investigation of transition-metal-doped ZnO nanoparticles

We measured the Raman spectra of ZnO nanoparticles (ZnO‐NPs), as well as transition‐metal‐doped (5% Mn(II), Fe(II) or Co(II)) ZnO nanoparticles, with an average size of 9 nm. A typical Raman peak at 436 cm−1 is observed in the ZnO‐NPs, whereas Zn1−xMnxO, Zn1−xFexO and Zn1−xCoxO presented characteristic peaks at 661, 665 and 675 cm−1, respectively. These peaks can be related to the formation of Mn3O4, Fe3O4 and Co3O4 species in the doped ZnO‐NPs. Moreover, these samples were analyzed at various laser powers. Here, we observed new vibrational modes (512, 571 and 528 cm−1), which are specific to Mn, Fe and Co dopants, respectively, and ZnO‐NPs did not reveal any additional modes. The new peaks were interpreted either as disorder activated phonon modes or as local vibrations of Mn‐, Fe‐ and Co‐related complexes in ZnO. Copyright © 2007 John Wiley & Sons, Ltd.