Watching bismuth nanowires grow

We report real-time high temperature scanning electron microscopy observations of the growth of bismuth nanowires via the on-film formation of nanowires (OFF-ON) method. These observations provide experimental evidence that thermally induced-stress on a Bi film is the driving force for the growth of Bi nanowires with high aspect ratios, uniform diameter, and high-quality crystallinity. Our results show that immobile grain boundaries in the Bi film are required for the growth of nanowires so that grain broadening resulting in hillock formation can be prevented. This study not only provides an understanding of the underlying mechanism, but also affords a strategy for facilitating nanowire growth by OFF-ON.