Growth Mechanism of Self-Assembled TiO2 Nanorod Arrays on Si Substrates Fabricated by Ti Anodization

Abstract

The growth rate and the growth mechanism are investigated by examining the results of scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) on TiO2 nanorods fabricated in the second anodization process through the nanopores of anodic aluminum oxide. Due to the strong electric field of 1.86 GV/m to 1.33 GV/m, the average ultra-fast growth rate of 250 nm/s is observed, and the abrupt increase of height reaches to 85.2% of its destined height in the early growth stage of 0.6 s. Then the growth rate decreases when the electric field decays with the increase of height, and it is interrupted by the dielectric breakdown under an electric field of 0.65 GV/m. According to the XPS analyzes, the TiO2 species on the outer shell of nanorods are observed, and the sub-oxides, Ti2O3 and TiO, are exhibited after Ar+ ions sputtering. It is proposed that the bottom growth mechanism is identified by the analyzes upon SEM and XPS results. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.034209jes] All rights reserved.