Influence of substrates and rutile seed layers on the assembly of hydrothermally grown rutile TiO2 nanorod arrays
Julian Kalb, James A. Dorman, Alena Folger, Melanie Gerigk, Vanessa Knittel, Claudia S. Plüisch, Bastian Trepka, Daniela Lehr, Emily Chua, Berit H. Goodge, Alexander Wittemann, Christina Scheu, Sebastian Polarz, Lukas Schmidt-Mende Journal of Crystal Growth, 494, 2018, 26.35 DOI: 10.1016/j.jcrysgro.2018.05.004
Abstract:
Rutile TiO2nanorod arrays (NRAs) are applicable in various prospective technologies. Hydrothermalmethods present a simple technique to fabricate such NRAs. In this report, we present the fabrication of seed layers for the hydrothermal growth of rutile TiO2 nanorods via sputter deposition, electron-beam evaporation, and sol-gel method and study the influence of each on the growth behavior. To satisfy the requirements of numerous applications, p-type silicon, platinum, levitating carbon membranes, a template made of polystyrene spheres, and commercial fluorine tin oxide (FTO) were employed as sub-strates. We document the structural properties of the TiO2 seed layers and describe the relationshipbetween the characteristics of the seed crystals, the growth evolution, and the appearance of as-grown nanorods. Various growth stages of rutile TiO2 nanorods are compared depending on whether they are grown on polycrystalline TiO2 or FTO seed layers. In both cases, a homogenous TiO2 bottom layer is formed at the seed layer/substrate interface, which is essential for electronic applications such as hybridsolar cells. Detached NRAs illustrate the effect of rutile FTO and TiO2 on the porosity of this bottom layer. Further details about the formation process of this layer are obtained from the growth on confined seedlayers fabricated by electron-beam lithography.