Polarity determined growth of carbon nanotubes of different alignments

Growing carbon nanotubes (CNTs) of different alignments, including surface-bounded and vertically aligned arrays, on metallic electrodes was achieved by applying electric voltages of different polarities on metallic electrodes during the laser-assisted chemical vapor deposition process. Surface-bounded CNTs were found to crawl out from the positively charged electrodes. In contrary, vertically aligned CNTs dominated the negatively charged electrodes. The alignment control was ascribed to the movement of catalyst-nanoparticles (NPs) under the influence of external electric field. The surface-bounded CNTs were ascribed to the repulsive forces between the catalyst NPs and the anodes. The vertically aligned CNTs were ascribed to the joint interactions of catalyst-cathode interactions and tube-tube interactions. This investigation suggests a convenient approach to control the alignment of CNT arrays for applications in different fields.