Morphology-controlled seed-assisted hydrothermal ZnO nanowires via critical concentration for nucleation and their photoluminescence properties

Here we demonstrate the controllability on morphology of hydrothermal ZnO nanowires through the critical concentration for nucleation. When Zn ion concentration is relatively low, the nucleation process preferentially occurs on the (0001) plane, promoting nanowire growth. In contrast, for relatively high Zn ion concentration, the (101<overbar></mml:mover>0) plane emerges, suppressing nanowire growth. The occurrence of this nucleation competition on the crystal planes as a function of concentration is caused by differences in the critical nucleation sizes between the (0001) plane and the (10<mml:mover accent="true">1<mml:mo><overbar></mml:mover>0) plane. Furthermore, we found that the density of ZnO nanowires trend to decrease with increasing the growth time due to the lateral growth effect. Photoluminescence measurement of ZnO nanowires exhibited that the near band emission peak of 380nm decreased with decreasing nanowire diameter while the broad emission peak below band gap appears the opposite trend because of surface to volume ratio effect.