Two-step gas flow controlled evaporation process was introduced as a simple technique to fabricate aligned ZnO nano wires via the VLS growth mode. Using this method, well-aligned single crystalline ZnO nanowires was successfully synthesized on Au coated Si substrates. The diameter of ZnO nanowires was controlled from 40 to 150 nm and the ratio of length to diameter was observed to be larger than 30. Tetrapod-shaped ZnO nanostructures were formed using a mixture of Ar and O-2 gases, and it indicated that the partial pressure of oxygen during the synthesis is crucial for the growth of ZnO nanowire structures. Green emission induced from singly ionized oxygen vacancies was generated from ZnO nanowires with the excitonic emission in UV range. Higher intensity of the green emission was observed in thinner nanowires, which is attributed to their higher surface-to-volume ratio. Patterned structure of ZnO nanowires with a high fidelity was achieved by pattering the Au catalyst films.' (C) 2003 Elsevier B.V. All rights reserved.