Fabrication of ZnO Crystals by UV-Laser Annealing on ZnO Nanoparticles Prepared by Laser Ablation Method

Various zinc oxide (ZnO) nanocrystals are expected as new building blocks for optoelectronic devices. Among them, we have studied about fabricating ZnO nanowires using nanoparticle-assisted pulsed laser deposition (NAPLD). Recently, we achieved to fabricate the periodically-aligned ZnO nanowires with a period of from 4 to 5 mu m using interfering four-beams of nanosecond ultraviolet (UV) laser processing. ZnO nanowires with diameters of several dozen nanometers were grown on the ZnO buffer layer prepared by pulsed laser deposition at the low-chamber pressure of 3 Pa. Additionally, crystallization of ZnO nanoparticles collected on a sapphire substrate was achieved by UV-laser annealing. In this method, ZnO nanoparticles were collected at room temperature, then they were laser-annealed with a KrF excimer laser. The particle size increased by instantaneous melting and aggregation of ZnO nanoparticles because of the high absorption efficiency of ZnO in the UV spectral region. It was found that the optical property was improved by UV-laser annealing process. Additionally, their x-ray diffraction peaks of wurtzite ZnO crystals had narrower full width half maximum than those before laser annealing.