Novel ZnO chessman-like and tower-like nanostructure arrays were synthesized by a simple thermal evaporation method. The morphology showed hierarchical structures which were believed to grow at different stages of the growth process. The growth mechanism of the nanostructures was discussed in detail. The difference between the chessman-like and tower-like structures was due to the different growth pressure during the cooling process. Various top morphologies were due to the different places relevant to the source. By keeping the other parameters the same, the chessman-like structures with sharp tops have the lowest turn-on electric field and threshold electric field. This superiority benefited from sharper top morphology and weaker field-screening effect as a consequence of the lower emitter density. (C) 2009 Elsevier B.V. All rights reserved.