Room Temperature Ferromagnetism in Transition Metal Doped CVD-Grown ZnO Films and Nanostructures

We have characterized the chemical, compositional, and magnetic properties of Mn- and Fe-ion implanted epitaxial ZnO films and single crystal nanostructures grown by MOCVD as candidate room temperature diluted magnetic semiconductors. X-ray absorption spectroscopy (SXAS) shows that Mn-implanted films contain Mn$^{2+}$ ions which convert to a mixture of Mn$^{3+}$ and Mn$^{4+}$ upon annealing. Fe-implanted films contain a mixture of Fe$^{2+}$ and Fe$^{3+}$ which converts to a higher concentration of Fe$^{3+}$ upon annealing. XAS and preliminary analysis of EXAFS data indicate that the TM ions are substitutional for Zn. SQUID magnetometry shows that as-implanted films are ferromagnetic at 5K and the annealed films are ferromagnetic at room temperature. X-ray diffraction shows that the annealed films remain epitaxial with excellent long range order. Rutherford backscattering spectrometry indicates a substantial recovery of local order upon annealing as well. The properties of in-situ Fe-doped MOCVD-grown ZnO epitaxial films and nanostructures will also be discussed.