Synthesis of TiO2 Nanowires by Metallorganic Chemical Vapor Deposition

TiO2 nanowires were self-catalytically synthesized on bare Si(100) substrates using metallorganic chemical vapor deposition. The nanowire formation was critically affected by growth temperature. The TiO2 nanowires were grown at a high density on Si(100) at 510 degrees C, which is near the complete decomposition temperature (527 degrees C) of the Ti precursor (Ti(O-iPr) 2(dpm) 2). At 470 degrees C, only very thin (< 0.1 mu m) TiO2 film was formed because the Ti precursor was not completely decomposed. When growth temperature was increased to 550 degrees C and 670 degrees C, the nanowire formation was also significantly suppressed. A vaporsolid (V-S) growth mechanism excluding a liquid phase appeared to control the nanowire formation. The TiO2 nanowire growth seemed to be activated by carbon, which was supplied by decomposition of the Ti precursor. The TiO2 nanowire density was increased with increased growth pressure in the range of 1.2 to 10 torr. In addition, the nanowire formation was enhanced by using Au and Pt catalysts, which seem to act as catalysts for oxidation. The nanowires consisted of well-aligned similar to 20-30 nm size rutile and anatase nanocrystallines. This MOCVD synthesis technique is unique and efficient to self-catalytically grow TiO2 nanowires, which hold significant promise for various photocatalysis and solar cell applications.