Microstructural, optical, and magnetic properties of (Zn1−xMnx)O thin films grown on (0 0 0 1) Al2O3 substrates

The microstructural, optical, and magnetic properties of (Zn1−xMnx)O thin films grown on (0 0 0 1) Al2O3 substrates by using a radio-frequency magnetron sputtering were investigated. X-ray diffraction, atomic force microscopy, and scanning electron microscopy measurements showed that the microstructural properties of the (Zn1−xMnx)O thin films were improved by increasing the thickness of the (Zn1−xMnx)O buffer layer, which might originate from the suppression of the columnar-growth mode at the initial growth stage because the (Zn1−xMnx)O buffer layer grown at a lower temperature had a relaxed c-axis preference. The photoluminescence peak at 419 nm from the (Zn0.91Mn0.09)O thin films could be attributed to the activation of Mn2+ ions substituting for Zn2+ ions, indicative of the existence of a diluted magnetic semiconductors. The magnetization curve as a function of the magnetic field at 15 K indicated that ferromagnetism existed in the (Zn0.91Mn0.09)O thin films, and the magnetization curve as a function of the temperature showed that the Tc value of the (Zn0.91Mn0.09)O thin films was 110 K. These results can help improve understanding of the effects of the microstructural properties on the magnetic properties of (Zn1−xMnx)O thin films grown on (0 0 0 1) Al2O3 substrates.