Scanning tunnelling microscope studies of angstrom-scale Co ₃O₄ nanowires

We report the bottom-up assembly of an atomic-scale building block, which consists of four Co₃₊ cations, two Co₂₊ cations, and eight O^2- anions, for generating one-dimensional Co₃O ₄ nanostructures with diameters ranging from 0.5 to 3 nm. Controlled experiments were carried out and the growth mechanism of the Co ₃O₄ nanowires was investigated. The effects of a single cation defect on the epitaxial growth of the one-dimensional nanostructures were investigated. We proposed a self-rectifying growth mechanism on the basis of direct experimental observations. This mechanism will help us to understand synthesized crystals usually exhibiting homogeneous composition and uniform morphology, though the existence of defects is inevitable in the growth process.