Fabrication and multi-band photoluminescence of vertically aligned ZnO/ZnSe core/shell nanorod arrays

Vertically aligned ZnO/ZnSe core/shell nanorod (NR) arrays were fabricated on Si (100) using combined approach of hydrothermal growth of ZnO followed by pulsed laser deposition of ZnSe. The obtained ZnO/ZnSe core/shell NRs are composed of wurtzite ZnO cores and zinc blende ZnSe shells with the hydrothermally grown ZnO core nanorods preferentially c-axis oriented. Upon excitation by 325 nm light at room temperature, the ZnO/ZnSe core/shell NR arrays emit multi-band photoluminescence (PL) including the near-band-edge (NBE) emissions of ZnO and ZnSe as well as the defect-related emission and the emission associated with the effective band gap formed due to the staggered band alignment of the heterojunction constructed from ZnO and ZnSe, while the NBE emission of the ZnO cores is greatly suppressed by the ZnSe shells. The PL shows a strong dependence on temperature. Post-fabrication annealing of the samples in N₂ results in an improvement in crystal structure and an enhancement of PL intensity.