Large-scale synthesis of high-purity, one-dimensional α-Al2O3 structures

Nanostructures of alpha-Al2O3 were successfully synthesized by simple evaporation of the commercial high-purity oxide powders, followed by vapour condensation onto a sapphire substrate under controlled conditions of supersaturation without the presence of a catalyst. Synthesis was carried out in a specially designed reactor equipped with a laser set-up that allows monitoring of the growth process in situ. Detailed in situ interferometric and high-resolution substrate curvature measurements revealed, for the first time, that the growth of these one-dimensional structures is driven by a mechanical stress, which develops in an initially continuous, two-dimensional layer. This interaction between chemical activity and mechanical stress is shown to provide an important additional parameter to actively control the large-scale synthesis of one-dimensional oxide structures.