Preparation and characterization of ZnO nanorods, nanowalls, and nanochains

The vertically aligned zinc oxide (ZnO) nanorods were synthesized on silicon (Si) substrate using high-pressure pulsed laser deposition (HPPLD). The aligned ZnO nanorods were obtained at the substrate temperature of 650 °C, oxygen partial pressure of 7 Torr, and the target-substrate distance of 25 mm. The influence of substrate lattice mismatch including gallium nitride (GaN-2%), sapphire (Al₂O₃-18%), and Si (40%) on the growth of ZnO nanowalls was examined. The interlinked ZnO nanowalls were obtained on GaN substrate, whereas ZnO nanorods were obtained on Al₂O₃ and Si substrates. The magnesium (Mg) doping has influenced the morphological transition of ZnO from nanorods to nanochains. The chain-like structures were obtained for Mg-doped ZnO target. The growth mechanism has been proposed for the formation of ZnO nanorods, nanowalls, and nanochains. The strong (0002) peak and E_2H mode confirmed that the ZnO nanorods, nanowalls, and nanochains are preferentially oriented along c-axis and have good crystalline quality. The near band edge emission (NBE) at 3.27 eV revealed the good optical properties of ZnO nanorods, nanowalls, and nanochains.