Preparation of high quality Mg doped ZnO nanorod arrays with enhanced optical properties by MgO passivation
Mg doped ZnO (Mg:ZnO) nanrood (NR)-arrays have been successfully fabricated onto p-type Si substrate via hydrothermal method. The photoluminescence spectra of Mg:ZnO reveal the existence of residual surface defects as deep level in the visible range. Reliable approach was used to completely remove the surface defects in order to obtain high optical quality of Mg:ZnO NR-arrays in the UV region. RF sputtering was used to deposit MgO nanoparticles around the Mg:ZnO NRs to suppress the entire surface defects. Morphological observations reveal the formation of well-aligned nanorods grown perpendicularly to substrate surface. The hexagonal structure of Mg:ZnO NR-arrays oriented along c-axis favors the formation of core-shell Mg:ZnO/MgO NR-arrays. Photoluminescence spectra of the as-fabricated core-shell Mg:ZnO/MgO exhibit an intense peak near-band-edge (NBE) emission at 375nm which completely result in the disappearance of the deep level emission at around 580nm, achieving a maximum intensity ratio (∼140) of IUV/IVIS. The Raman E2 (high) mode of Mg:ZnO NR-arrays showed a blue shift compared to ZnO NR-arrays associated with the strain arising from Mg:ZnO core.