Structure-dependent growth control in nanowire synthesis via on-film formation of nanowires
- Equal contributors
1 Department of Materials Science and Engineering, Yonsei University, 134 Shinchon, Seoul 120-749, Korea
2 Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108, USA
Nanoscale Research Letters 2011, 6:196 doi:10.1186/1556-276X-6-196Published: 4 March 2011
On-film formation of nanowires, termed OFF-ON, is a novel synthetic approach that produces high-quality, single-crystalline nanowires of interest. This versatile method utilizes stress-induced atomic mass flow along grain boundaries in the polycrystalline film to form nanowires. Consequently, controlling the magnitude of the stress induced in the films and the microstructure of the films is important in OFF-ON. In this study, we investigated various experimental growth parameters such as deposition rate, deposition area, and substrate structure which modulate the microstructure and the magnitude of stress in the films, and thus significantly affect the nanowire density. We found that Bi nanowire growth is favored in thermodynamically unstable films that facilitate atomic mass flow during annealing. A large film area and a large thermal expansion coefficient mismatch between the film and the substrate were found to be critical for inducing large compressive stress in a film, which promotes Bi nanowire growth. The OFF-ON method can be routinely used to grow nanowires from a variety of materials by tuning the material-dependent growth parameters.