tailieunhanh - Báo cáo hóa học: " Structure-dependent growth control in nanowire synthesis via on-film formation of nanowires"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Structure-dependent growth control in nanowire synthesis via on-film formation of nanowires | Shim et al. Nanoscale Research Letters 2011 6 196 http content 6 1 196 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Structure-dependent growth control in nanowire synthesis via on-film formation of nanowires Wooyoung Shim1 2t Jinhee Ham1t Jin-Seo Noh1 Wooyoung Lee1 Abstract On-film formation of nanowires termed OFF-ON is a novel synthetic approach that produces high-quality singlecrystalline 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. Introduction Recently we reported a new nanowire growth method termed on-film formation of nanowires OFF-ON that combines the advantages of simple thin film deposition and whisker formation to achieve highly crystalline nanowires 1 . OFF-ON is a template- and catalyst-free synthetic approach that utilizes thermally induced compressive stress within a polycrystalline thin film to obtain nanowires as small as tens of nanometers in diameter. Because of its direct growth capability via atomic mass flow and .