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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.

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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.


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SEM observation of NW sidewalls for (a1) a <111>-oriented Si NWs and (b1) a <110>-oriented Ge NWs grown on a Si(111) surface by MBE. Some sidewall orientations are indicated for both types of NWs. Lattice-resolved TEM images showing the roughness of (a2) a {112} sidewall on a <111>-oriented Si NWs and (b2) a {111} sidewall on a <110>-oriented Ge NWs.
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Figure 4: SEM observation of NW sidewalls for (a1) a <111>-oriented Si NWs and (b1) a <110>-oriented Ge NWs grown on a Si(111) surface by MBE. Some sidewall orientations are indicated for both types of NWs. Lattice-resolved TEM images showing the roughness of (a2) a {112} sidewall on a <111>-oriented Si NWs and (b2) a {111} sidewall on a <110>-oriented Ge NWs.

Mentions: In order to understand the physical origin of the growth direction dependence on the NW length, we examined the sidewalls of both types of NWs, as shown in Figure 4. The <111>-oriented Si NWs consist of six sidewalls that exhibit small facets. It has been shown that these sidewalls correspond to {112} planes [9]. For <111>-oriented Si NWs grown by CVD at low silane partial pressure, that show similar sidewall orientations [10], gold is known to diffuse from the seed particle and to wet the sidewalls [11,12]. Adsorption of gold on Si(112) planes is also known to causes the faceting of these planes [13]. Similarly, Au diffusion from the seed particle is at the origin of the facet formation on the {112} planes, for which the crystallographic orientations alternate between {111} planes and high index planes [14]. HRTEM images of the sidewalls for the MBE grown Si NWs are consistent with the observations performed on <111>-oriented Si NWs grown by CVD. For example, Figure 4a2 reveals the rough morphology of one of the {112} sidewalls. Although the facets are rather rounded, probably due to the oxide layer that covered the sidewall, a corrugation of up to 2 nm is found when the height profile of the sidewall is measured.


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)

SEM observation of NW sidewalls for (a1) a <111>-oriented Si NWs and (b1) a <110>-oriented Ge NWs grown on a Si(111) surface by MBE. Some sidewall orientations are indicated for both types of NWs. Lattice-resolved TEM images showing the roughness of (a2) a {112} sidewall on a <111>-oriented Si NWs and (b2) a {111} sidewall on a <110>-oriented Ge NWs.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: SEM observation of NW sidewalls for (a1) a <111>-oriented Si NWs and (b1) a <110>-oriented Ge NWs grown on a Si(111) surface by MBE. Some sidewall orientations are indicated for both types of NWs. Lattice-resolved TEM images showing the roughness of (a2) a {112} sidewall on a <111>-oriented Si NWs and (b2) a {111} sidewall on a <110>-oriented Ge NWs.
Mentions: In order to understand the physical origin of the growth direction dependence on the NW length, we examined the sidewalls of both types of NWs, as shown in Figure 4. The <111>-oriented Si NWs consist of six sidewalls that exhibit small facets. It has been shown that these sidewalls correspond to {112} planes [9]. For <111>-oriented Si NWs grown by CVD at low silane partial pressure, that show similar sidewall orientations [10], gold is known to diffuse from the seed particle and to wet the sidewalls [11,12]. Adsorption of gold on Si(112) planes is also known to causes the faceting of these planes [13]. Similarly, Au diffusion from the seed particle is at the origin of the facet formation on the {112} planes, for which the crystallographic orientations alternate between {111} planes and high index planes [14]. HRTEM images of the sidewalls for the MBE grown Si NWs are consistent with the observations performed on <111>-oriented Si NWs grown by CVD. For example, Figure 4a2 reveals the rough morphology of one of the {112} sidewalls. Although the facets are rather rounded, probably due to the oxide layer that covered the sidewall, a corrugation of up to 2 nm is found when the height profile of the sidewall is measured.

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