Investigation of initial growth of ZnO nanowires and their growth mechanism.

ZnO nanowires were synthesized on Si substrates by a simple metal vapor deposition method without any catalysts. The initial growth and the growth mechanism of the ZnO nanowires were studied using scanning and transmission electron microscopy. We found that the ZnO nanowires grew on the Si substrate via a self-seeding vapor-solid mechanism. The growth process of the ZnO nanowires consisted of four steps: self-seeding, one-dimensional epitaxial growth of the nanowires on the seeds by a base-growth mode, further acceleration of nanowire growth with additional seeding, and active formation of the nanowires.