Growth Mechanism and Photoluminescence Properties of In2O3 Nanotowers

To elucidate the growth mechanism of In2O3 nanotowers synthesized via a Au-catalyzed vapor transport process, the structural evolution of In2O3 nanotowers was carefully examined during the synthesis process. It was found that Au catalysts only play a role at the initial stage, where they facilitate the formation of In2O3 nanoparticles and nanorods. After the Au atoms are consumed by the formation of Au-In compound(s), the liquid In droplets will form on the tips of In2O3 nanoparticles or nanorods, and the self-catalytic vapor-liquid-solid (VLS) growth mechanism will dominate the subsequent one-dimensional (1D) growth of In2O3 nanopillars. Since the supply of In2O may not be sufficient for the continuous 1D growth, the lateral growth of In2O3 nanopillars governed by the vapor-solid (VS) mechanism will occur. The periodical axial and continuous lateral growth leads to the formation of In2O3 nanotowers with a truncated octahedron structure of 4-fold symmetry {111} accumulated planes along the [100] direction. The photoluminescence (PL) spectrum of In2O3 nanotowers exhibited an intense green-yellow luminescence at the wavelength of 580 nm, which can be ascribed to the possible recombination of electrons on singly ionized oxygen vacancies and holes on the valence band or doubly ionized oxygen vacancies.