Limits...
Structure-dependent growth control in nanowire synthesis via on-film formation of nanowires.

Shim W, Ham J, Noh JS, Lee W - Nanoscale Res Lett (2011)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, Yonsei University, 134 Shinchon, Seoul 120-749, Korea. wooyoung@yonsei.ac.kr.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Growth and X-ray diffraction (XRD) patterns of Bi sputtered films. (a) Schematic representation of the growth of Bi nanowires by OFF-ON. XRD patterns of Bi films before and after heat treatment at 270°C for 10 h. The films were deposited at a rate of (b) 2.7 Å/sec (RF power: 10 W) and (c) 32.7 Å/s (RF power: 100 W), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211252&req=5

Figure 1: Growth and X-ray diffraction (XRD) patterns of Bi sputtered films. (a) Schematic representation of the growth of Bi nanowires by OFF-ON. XRD patterns of Bi films before and after heat treatment at 270°C for 10 h. The films were deposited at a rate of (b) 2.7 Å/sec (RF power: 10 W) and (c) 32.7 Å/s (RF power: 100 W), respectively.

Mentions: Bi nanowires were fabricated by the OFF-ON method simply by annealing a Bi film at relevant temperatures without the use of conventional templates, catalysts, or starting materials (Figure 1a). Details related to the preparation of the substrates, deposition of the thin films, and annealing procedure are presented in [1]. In this study, the effect of several major parameters on Bi nanowire growth was examined. First, the effect of the Bi film microstructure, which can be modulated by film deposition rate, on the growth of nanowires was investigated. For this purpose, Bi thin films were deposited onto thermally oxidized Si (100) substrates at deposition rates of 2.7 Å/s (RF power: 10 W) and 32.7 Å/s (100 W), using UHV radio frequency (RF) sputtering. Second, the effect of Bi film areas, where the Bi nanowires are grown, on nanowire density was addressed. To study this, Bi films of various areas were fabricated using photolithography and lift-off. Four different Bi film areas were tested: (104 μm)2, (103 μm)2, (102 μm)2, and (10 μm)2. Third, we examined the effect of the magnitude of the compressive stress on the Bi film, which is modulated by the thermal expansion of the substrate, on Bi nanowire density. For this study, two different substrates, i.e., a thermally oxidized Si substrate and a Si substrate without SiO2 on top were used.


Structure-dependent growth control in nanowire synthesis via on-film formation of nanowires.

Shim W, Ham J, Noh JS, Lee W - Nanoscale Res Lett (2011)

Growth and X-ray diffraction (XRD) patterns of Bi sputtered films. (a) Schematic representation of the growth of Bi nanowires by OFF-ON. XRD patterns of Bi films before and after heat treatment at 270°C for 10 h. The films were deposited at a rate of (b) 2.7 Å/sec (RF power: 10 W) and (c) 32.7 Å/s (RF power: 100 W), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211252&req=5

Figure 1: Growth and X-ray diffraction (XRD) patterns of Bi sputtered films. (a) Schematic representation of the growth of Bi nanowires by OFF-ON. XRD patterns of Bi films before and after heat treatment at 270°C for 10 h. The films were deposited at a rate of (b) 2.7 Å/sec (RF power: 10 W) and (c) 32.7 Å/s (RF power: 100 W), respectively.
Mentions: Bi nanowires were fabricated by the OFF-ON method simply by annealing a Bi film at relevant temperatures without the use of conventional templates, catalysts, or starting materials (Figure 1a). Details related to the preparation of the substrates, deposition of the thin films, and annealing procedure are presented in [1]. In this study, the effect of several major parameters on Bi nanowire growth was examined. First, the effect of the Bi film microstructure, which can be modulated by film deposition rate, on the growth of nanowires was investigated. For this purpose, Bi thin films were deposited onto thermally oxidized Si (100) substrates at deposition rates of 2.7 Å/s (RF power: 10 W) and 32.7 Å/s (100 W), using UHV radio frequency (RF) sputtering. Second, the effect of Bi film areas, where the Bi nanowires are grown, on nanowire density was addressed. To study this, Bi films of various areas were fabricated using photolithography and lift-off. Four different Bi film areas were tested: (104 μm)2, (103 μm)2, (102 μm)2, and (10 μm)2. Third, we examined the effect of the magnitude of the compressive stress on the Bi film, which is modulated by the thermal expansion of the substrate, on Bi nanowire density. For this study, two different substrates, i.e., a thermally oxidized Si substrate and a Si substrate without SiO2 on top were used.

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, Yonsei University, 134 Shinchon, Seoul 120-749, Korea. wooyoung@yonsei.ac.kr.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus