Promoted growth of Bi single-crystalline nanowires by sidewall-induced compressive stress in on-film formation of nanowires.

To increase the density of Bi nanowires grown by our unique on-film formation of nanowires (OFF-ON) method, we introduced a technique for enhancing compressive stress, which is the driving force for the nanowire growth. The compressive stress could be controlled by modifying the substrate structure. A combination of photolithography and a reactive ion etching technique was used to fabricate patterns on a thermally oxidized Si(100) substrate. It was found that the density of Bi nanowires grown from Bi films in 100 x 100 microm2-sized SiO2 patterns increases by a factor of seven over that from non-patterned substrates. Our results indicate that the density of Bi nanowires can be increased by enhanced compressive stress arising from a sidewall effect in the optimized pattern size and array.