Supersaturation-controlled synthesis of two types of single-sided ZnO comb-like nanostructures by thermal evaporation at low temperature

Two types of ZnO single-sided nanocombs, namely the straight comb and the crescent comb, have been synthesized by simple evaporation of Zn powder in diluted O2 flow at 440 °C. Both combs have a common teeth growth direction of [0 0 0 1]. The backbone of the straight comb is a [21¯1¯0] oriented nanobelt, with combteeth distributed on its broader surface. The backbone of the crescent comb is a [011¯0] oriented nanobelt, with combteeth distributed on its narrower surface, and it is bent into an arc by stress. The crescent comb is interesting as it is not only a hierarchical assembly of one-dimensional nanostructures, but also folded into a secondary structure as well. The structures of our nanocombs are controlled by supersaturation. Taking advantage of our low-temperature synthesis, we studied the growth process by freezing the growth stages. A modified VS growth mechanism was proposed.