Growth behavior of Al-doped zinc oxide microrods with times

Abstract

We investigated the growth behavior of Al-doped zinc oxide (ZnO) microrods grown on ZnO seed layers at various growth times. During the initial 3h (region I), the randomly oriented microrods grew on the surface of the substrate because of the weak acidity of the initial solution (pH ∼5.5). Between 3h and 6h (region II), when the pH was close to neutrality, a dominant growth of Al-doped ZnO (AZO) microrods with tapered shape occurred. After that the vertical growth of the microrods reached a certain equilibrium, a selective etching of the side nonpolar plane, rather than the top polar plane, dominantly occurred between 6h and 12h (region III), thus leading to the formation of the microrods of cylindrical shape. From 12h to 24h (region IV), the pH value was saturated, and the morphology of the microrods did not significantly change. As a result, owing to the change of the pH value, the growth behavior of the AZO microrods appeared significantly different when increasing the time.