Formation and dissociation of Zn nanoclusters in MgO

Zinc nanoclusters were created in MgO by implantation of 1 x 1017 Zn ions cm-2 at an energy of 140 keV and subsequent thermal annealing. The defect evolution was investigated by means of optical absorption spectroscopy, Rutherford backscattering spectrometry and channeling, Doppler broadening positron beam analysis, and with cross-sectional transmission electron microscopy (XTEM). After annealing at 1150 K, an optical absorption band appears due to plasmon resonance. TEM investigations confirm that metallic Zn nanoclusters with sizes of 5-10 nm are formed at this temperature. The nanoclusters have the hcp Zn crystal structure and the c-axis is aligned with one of the cubic MgO axes, i.e. MgO(0 0 1) parallel Zn(0 0 0 1). The nanoclusters dissociate during annealing at 1550 K. At this temperature, the Zn is dissolved and diffuses into the MgO matrix