Effect of Laser Annealing on Optical Properties of Ion-Implanted ZnO Nanorods

We report on the demonstration of the effectiveness of nanosecond laser annealing on optical properties of phosphorus ion (P)-implanted ZnO nanorods (NRs). Vertically-alligned ZnO NRs have been synthesized by nanoparticle-assisted pulsed laser deposition (NAPLD) on c-plane sapphire substrates. The pre-laser annealing was performed with the third harmonic (355 nm) of a Qwitched Nd:YAG laser at a fluence of 100mJ/cm for improving optical property and weakening ntype conduction of as-grown ZnO NRs. P-ions were implanted into the ZnO NRs followed by the post-laser annealing in the same way as the pre-laser annealing. The top part of the ZnO NRs were melted and recrystallized by laser annealing. The transitions of properties were investigated by the scanning electron microscope, the room temperature photoluminescence spectra, X-ray diffraction patterns, and I-V measurement. As a result, it turned out that laser annealing has potentiality for improving optical property and compensating donor-vacancies without reducing crystalline quality. Moreover, the effectiveness of post-laser annealing on recovering ion-implanted ZnO layer and activating acceptors was demonstrated. It is promising that straightforward and stable method of fabricating ZnO-based UV-LED is established by applications of nanosecond laser annealing process.