Controlled growth of metal-free vertically aligned CNT arrays on SiC surfaces

► Metal-free CNT arrays can be obtained by high temperature decomposition of SiC(0 0 0 1¯) surface under oxygen-containing atmospheres, such as H2O. ► Formation of SiO nanoclusters at C/SiC interface via reaction between out-diffused Si nanoclusters and dissociated oxygen-containing species. ► The transient SiO nanoclusters are proposed to be the active sites for the continuous growth of CNTs on SiC surface.