ZnO nanostructures have been synthesized using a catalyst-assisted carbothermal reduction approach on Si substrate. By analyzing SEM images, two different growth mechanisms were found to grow ZnO nanostructures. At low growth temperature (900 and 950 degreesC), vapor-solid mode is dominant in the growth process. With increasing the growth temperature to 1000 degreesC, ZnO nanorods grow followed vapor-liquid-solid process. The role of catalyst in these two growth processes is discussed. In room-temperature photoluminescence measurement a strong excitonic emission located at 3.25 eV was observed for ZnO obtained at the growth temperature of 1000 degreesC. (C) 2004 Elsevier B.V. All rights reserved.