Synthesis and growth mechanism of catalyst free ZnO nanorods with enhanced aspect ratio by high flow additional carrier gas at low temperature

This paper reports an effective catalyst free metal–organic chemical vapour deposition method for obtaining vertically well-aligned ZnO nanorods with enhanced aspect ratio at relatively low temperature (300 °C) by supplying additional Ar carrier gas at high flow rates. An increase in the flow rate of Ar gas through a by-pass line caused remarkable changes in the surface morphology from film-like to nanorods at the same growth temperature. These nanorods exhibited superior optical properties due to the elimination of grain boundaries and increase in emissive area. The enhanced aspect ratio of the nanorods was attributed to the increase in adsorption efficiency and the high directionality of the deposited atoms through the enhanced transfer velocity of the reactive gas. A schematic growth model for the formation of nanorods is also proposed.