Zn-Vacancy Related Defects Identified in ZnO Films Grown by Pulsed Laser Deposition

Undoped and Cu-doped ZnO grown on sapphire using pulsed laser deposition (PLD) were studied by positron annihilation spectroscopy (PAS), photoluminescence (PL), high-resolution transmission electron microscopy (HRTEM) and secondary ion mass spectroscopy (SIMS). In the undoped samples, two kinds of VZn-related defects, namely VZn1 and VZn2 are identified. VZn1 was identified in as-grown samples grown at relatively low substrate (~300 °C). After annealing at 900 °C, VZn-2, the green luminescence (GL) peaking at 2.47 eV and the near band edge (NBE) emission at 3.23 eV in the low temperature photoluminescence (LT-PL) were simultaneously introduced. Another kind of VZn-related defect is identified in the Cu-doped ZnO sample, and is tentatively assigned to the VZn decorated with the Cu.