Photoluminescent and Structural Properties of Precipitated ZnO Fine Particles

The correlation between photoluminescence (PL) and structural properties of ZnO crystals has been investigated using fine particles prepared by a precipitation method and subsequent heat treatment. The ZnO particles heat-treated at temperatures < 600 C exhibited red emission centered at 1.9 eV for a weak light excitation similar to that observed in ZnO thin films sputter-grown under thermally non-equilibrium conditions. Heat treatment at high temperatures reduced the red PL while it enhanced the green PL around 2.45 eV. Raman scattering and XRD measurements showed that the ZnO particles obtained at lower temperatures have a greater lattice disorder accompanied by a specific lattice expansion along the c-axis of the ZnO crystal which would introduce defect states in the band gap. In addition, electrical conductivity measurements suggested that the lattice disorder is associated with interstitial Zn. These results indicate that the lattice disorder along the c-axis of the ZnO crystal, i.e., the interst