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Synthesis of long group IV semiconductor nanowires by molecular beam epitaxy.

Xu T, Sulerzycki J, Nys JP, Patriarche G, Grandidier B, Stiévenard D - Nanoscale Res Lett (2011)

Bottom Line: Structural studies of both types of NWs performed with electron microscopies reveal a marked difference between the roughnesses of their respective sidewalls.As the investigation of their length dependence on their diameter indicates that the growth of the NWs predominantly proceeds through the diffusion of adatoms from the substrate up along the sidewalls, difference in the sidewall roughness qualitatively explains the length variation measured between both types of NWs.The formation of atomically flat {111} sidewalls on the <110>-oriented Ge NWs accounts for a larger diffusion length.

View Article: PubMed Central - HTML - PubMed

Affiliation: Département ISEN, Institut d'Electronique, de Microélectronique et de Nanotechnologie, IEMN (CNRS, UMR 8520), 41 bd Vauban, 59046 Lille Cedex, France. bruno.grandidier@isen.fr.

ABSTRACT
We report the growth of Si and Ge nanowires (NWs) on a Si(111) surface by molecular beam epitaxy. While Si NWs grow perpendicular to the surface, two types of growth axes are found for the Ge NWs. Structural studies of both types of NWs performed with electron microscopies reveal a marked difference between the roughnesses of their respective sidewalls. As the investigation of their length dependence on their diameter indicates that the growth of the NWs predominantly proceeds through the diffusion of adatoms from the substrate up along the sidewalls, difference in the sidewall roughness qualitatively explains the length variation measured between both types of NWs. The formation of atomically flat {111} sidewalls on the <110>-oriented Ge NWs accounts for a larger diffusion length.

No MeSH data available.


Related in: MedlinePlus

Evolution of the <110>-oriented Ge NW morphology. The NWs initially show (a) an irregular hexagonal cross-section, then (b) a reduction of the gold seed particle and a lateral overgrowth on the {111} sidewall that is exposed to the Ge flux, and finally (c) the disappearance of both the gold seed particle and the {100} sidewalls, giving rise to Ge NW with a rhombohedral cross-section.
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Figure 6: Evolution of the <110>-oriented Ge NW morphology. The NWs initially show (a) an irregular hexagonal cross-section, then (b) a reduction of the gold seed particle and a lateral overgrowth on the {111} sidewall that is exposed to the Ge flux, and finally (c) the disappearance of both the gold seed particle and the {100} sidewalls, giving rise to Ge NW with a rhombohedral cross-section.

Mentions: When L becomes larger than λf, then the length growth rate depends mainly on the diffusion of adatoms that adsorb directly onto the NW sidewalls or on the seed particle. Therefore, the NWs with the smallest diameters grew slower while the NWs with the biggest diameters keep on growing with the same length growth rate. The effect of a limited diffusion length is readily visible in Figure 6. While the <110>-oriented Ge NWs appear cylindrical at the beginning of the growth (Figure 6a), some of the {111} sidewalls may show a change of their morphology, as the growth proceeds. Such an example is seen in Figure 6b, where a strong overgrowth occurs at the base of the NW indicating that the adatoms from the substrate are rather incorporated onto the sidewalls than diffusing up to the top of the NWs. Finally, when the growth duration approaches tens of minutes, Au may have completely diffused away from the original seed particle. As a result, the NW cannot grow in length any more, but overgrowth on the sidewalls occurs. The {100} sidewalls, for which the surface tension is higher [15,23], disappear through the lateral growth of the {111} sidewalls, giving rise to a typical rhombohedral cross-section (Figure 6c).


Synthesis of long group IV semiconductor nanowires by molecular beam epitaxy.

Xu T, Sulerzycki J, Nys JP, Patriarche G, Grandidier B, Stiévenard D - Nanoscale Res Lett (2011)

Evolution of the <110>-oriented Ge NW morphology. The NWs initially show (a) an irregular hexagonal cross-section, then (b) a reduction of the gold seed particle and a lateral overgrowth on the {111} sidewall that is exposed to the Ge flux, and finally (c) the disappearance of both the gold seed particle and the {100} sidewalls, giving rise to Ge NW with a rhombohedral cross-section.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211158&req=5

Figure 6: Evolution of the <110>-oriented Ge NW morphology. The NWs initially show (a) an irregular hexagonal cross-section, then (b) a reduction of the gold seed particle and a lateral overgrowth on the {111} sidewall that is exposed to the Ge flux, and finally (c) the disappearance of both the gold seed particle and the {100} sidewalls, giving rise to Ge NW with a rhombohedral cross-section.
Mentions: When L becomes larger than λf, then the length growth rate depends mainly on the diffusion of adatoms that adsorb directly onto the NW sidewalls or on the seed particle. Therefore, the NWs with the smallest diameters grew slower while the NWs with the biggest diameters keep on growing with the same length growth rate. The effect of a limited diffusion length is readily visible in Figure 6. While the <110>-oriented Ge NWs appear cylindrical at the beginning of the growth (Figure 6a), some of the {111} sidewalls may show a change of their morphology, as the growth proceeds. Such an example is seen in Figure 6b, where a strong overgrowth occurs at the base of the NW indicating that the adatoms from the substrate are rather incorporated onto the sidewalls than diffusing up to the top of the NWs. Finally, when the growth duration approaches tens of minutes, Au may have completely diffused away from the original seed particle. As a result, the NW cannot grow in length any more, but overgrowth on the sidewalls occurs. The {100} sidewalls, for which the surface tension is higher [15,23], disappear through the lateral growth of the {111} sidewalls, giving rise to a typical rhombohedral cross-section (Figure 6c).

Bottom Line: Structural studies of both types of NWs performed with electron microscopies reveal a marked difference between the roughnesses of their respective sidewalls.As the investigation of their length dependence on their diameter indicates that the growth of the NWs predominantly proceeds through the diffusion of adatoms from the substrate up along the sidewalls, difference in the sidewall roughness qualitatively explains the length variation measured between both types of NWs.The formation of atomically flat {111} sidewalls on the <110>-oriented Ge NWs accounts for a larger diffusion length.

View Article: PubMed Central - HTML - PubMed

Affiliation: Département ISEN, Institut d'Electronique, de Microélectronique et de Nanotechnologie, IEMN (CNRS, UMR 8520), 41 bd Vauban, 59046 Lille Cedex, France. bruno.grandidier@isen.fr.

ABSTRACT
We report the growth of Si and Ge nanowires (NWs) on a Si(111) surface by molecular beam epitaxy. While Si NWs grow perpendicular to the surface, two types of growth axes are found for the Ge NWs. Structural studies of both types of NWs performed with electron microscopies reveal a marked difference between the roughnesses of their respective sidewalls. As the investigation of their length dependence on their diameter indicates that the growth of the NWs predominantly proceeds through the diffusion of adatoms from the substrate up along the sidewalls, difference in the sidewall roughness qualitatively explains the length variation measured between both types of NWs. The formation of atomically flat {111} sidewalls on the <110>-oriented Ge NWs accounts for a larger diffusion length.

No MeSH data available.


Related in: MedlinePlus