Patterned growth of carbon nanotubes through AFM nano-oxidation

Carbon nanotubes have been grown on a patterned silicon oxide using an AFM nano-oxidation technique. A nano oxide pattern with a height of 1.0-5.0 nm was fabricated oil a Si substrate by applying a bias voltage of +8 V while rastering a grounded conductive cantilever over the surface at scan speeds of 0.5-4.0 mu m/s. An iron film with a thickness of I nm was then coated as a catalyst by arc plasma deposition. By annealing the substrate, Fe on the bare Si area was transformed into iron silicide through an interfacial reaction, while the reaction was inhibited on the oxide patterned area. Thus, Fe nanoparticles, which are essential as catalysts for CNT growth. can be formed only on the oxide area. CNTs, which selectively grow only on these nano oxide areas, tend to cluster together to form column-like arrays, presumably due to van der Waals forces. A single CNT has been successfully grown on a 50 nm-wide Si oxide dot. The dependence of the width and height of the initial oxide lines to the morphology and density of CNTs is also discussed. (C) 2008 Elsevier B.V. All rights reserved.