Three growth modes and mechanisms for highly structure-tunable SnO2 nanotube arrays of template-directed atomic layer deposition

This article presents a vapor-phase strategy to synthesize highly structure-tunable SnO2 nanotube arrays of high aspect ratio, which features atomic layer deposition of SnO2 on anodic aluminium oxide templates using SnCl4 and H2O as precursors. This systematic study disclosed that there are three distinctive temperature-dependent growth modes, i.e., layer-by-layer, layer-by-particle, and evolutionary particles contributing to the structural uniqueness of the resultant SnO2 nanotubes. The layers were identified in an amorphous phase while the particles in a crystalline phase. As a consequence, the synthesized SnO2 nanotubes are not only phase-controllable but also morphology-transferable with growth temperatures. In a following effort to explore the underlying mechanisms, as another contribution of this study, three growth models were proposed and clarified. Thus, this study offers not just a precise alternative for synthesizing structurally novel nanotubes but scientific insights into fundamentals as well.