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Combinatorial growth of Si nanoribbons.

Park TE, Lee KY, Kim I, Chang J, Voorhees P, Choi HJ - Nanoscale Res Lett (2011)

Bottom Line: These twins appear to drive the lateral growth by a reentrant twin mechanism.These twins also create a mirror-like crystallographic configuration in the anisotropic surface energy state and appear to further drive lateral saw-like edge growth in the < 112 > direction.These outcomes indicate that the Si NRs are grown by a combination of the two mechanisms of a Pt-catalyst-assisted VLS mechanism for longitudinal growth and a twin-assisted VS mechanism for lateral growth.

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

ABSTRACT
Silicon nanoribbons (Si NRs) with a thickness of about 30 nm and a width up to a few micrometers were synthesized. Systematic observations indicate that Si NRs evolve via the following sequences: the growth of basal nanowires assisted with a Pt catalyst by a vapor-liquid-solid (VLS) mechanism, followed by the formation of saw-like edges on the basal nanowires and the planar filling of those edges by a vapor-solid (VS) mechanism. Si NRs have twins along the longitudinal < 110 > growth of the basal nanowires that also extend in < 112 > direction to edge of NRs. These twins appear to drive the lateral growth by a reentrant twin mechanism. These twins also create a mirror-like crystallographic configuration in the anisotropic surface energy state and appear to further drive lateral saw-like edge growth in the < 112 > direction. These outcomes indicate that the Si NRs are grown by a combination of the two mechanisms of a Pt-catalyst-assisted VLS mechanism for longitudinal growth and a twin-assisted VS mechanism for lateral growth.

No MeSH data available.


Cross-sectional TEM and HRTEM images of NR. (a) Cross-sectional TEM image of the saw-like edged NR. (b-d) Cross-sectional HRTEM images of the three regions (the end part of the saw-like edge, the middle part of the saw-like edge, and the part of the basal nanowire) indicated in panel (a). The insets of (b-d) show diffractograms of the Si region in the box in each part. These indicate that the basal nanowire was grown along < 110 > direction and that the Si nanosaw/NR is bi-crystalline containing a single {111} twin. (e) Schematic diagram of the projected shape and facets of the basal nanowire part. (f) Schematic showing the formation of the Si NR.
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Figure 4: Cross-sectional TEM and HRTEM images of NR. (a) Cross-sectional TEM image of the saw-like edged NR. (b-d) Cross-sectional HRTEM images of the three regions (the end part of the saw-like edge, the middle part of the saw-like edge, and the part of the basal nanowire) indicated in panel (a). The insets of (b-d) show diffractograms of the Si region in the box in each part. These indicate that the basal nanowire was grown along < 110 > direction and that the Si nanosaw/NR is bi-crystalline containing a single {111} twin. (e) Schematic diagram of the projected shape and facets of the basal nanowire part. (f) Schematic showing the formation of the Si NR.

Mentions: To investigate the structure of NRs in detail, cross-sectional samples of the saw-like edged NRs were prepared by focused ion beam (FIB) slicing and a lift-out process with a micromanipulator (Figure S1 in Additional file 1). This was then observed by TEM. Figure 4a shows a TEM cross-section image of the as-grown Si NRs. The right side of the TEM image in Figure 4a is the part of the basal nanowire, whereas the other side is the part of the saw-like edge. The width of the saw is approximately 1 μm, and its thickness is about 35 nm, as shown in Figure 1b and 4a-d. Further scrutiny of the morphology of the cross-sectional NRs shows no distinct interfaces, which confirms the epitaxial relationship between the basal nanowire and the saw-like edges. Figure 4b-d show cross-sectional high-resolution transmission electron microscopy (HRTEM) images of the NRs, indicating that the basal nanowires have hexagonal cross-sections. Indeed, < 110 > -oriented Si nanowires have been also shown to have hexagonal cross-sections [11,12].


Combinatorial growth of Si nanoribbons.

Park TE, Lee KY, Kim I, Chang J, Voorhees P, Choi HJ - Nanoscale Res Lett (2011)

Cross-sectional TEM and HRTEM images of NR. (a) Cross-sectional TEM image of the saw-like edged NR. (b-d) Cross-sectional HRTEM images of the three regions (the end part of the saw-like edge, the middle part of the saw-like edge, and the part of the basal nanowire) indicated in panel (a). The insets of (b-d) show diffractograms of the Si region in the box in each part. These indicate that the basal nanowire was grown along < 110 > direction and that the Si nanosaw/NR is bi-crystalline containing a single {111} twin. (e) Schematic diagram of the projected shape and facets of the basal nanowire part. (f) Schematic showing the formation of the Si NR.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 4: Cross-sectional TEM and HRTEM images of NR. (a) Cross-sectional TEM image of the saw-like edged NR. (b-d) Cross-sectional HRTEM images of the three regions (the end part of the saw-like edge, the middle part of the saw-like edge, and the part of the basal nanowire) indicated in panel (a). The insets of (b-d) show diffractograms of the Si region in the box in each part. These indicate that the basal nanowire was grown along < 110 > direction and that the Si nanosaw/NR is bi-crystalline containing a single {111} twin. (e) Schematic diagram of the projected shape and facets of the basal nanowire part. (f) Schematic showing the formation of the Si NR.
Mentions: To investigate the structure of NRs in detail, cross-sectional samples of the saw-like edged NRs were prepared by focused ion beam (FIB) slicing and a lift-out process with a micromanipulator (Figure S1 in Additional file 1). This was then observed by TEM. Figure 4a shows a TEM cross-section image of the as-grown Si NRs. The right side of the TEM image in Figure 4a is the part of the basal nanowire, whereas the other side is the part of the saw-like edge. The width of the saw is approximately 1 μm, and its thickness is about 35 nm, as shown in Figure 1b and 4a-d. Further scrutiny of the morphology of the cross-sectional NRs shows no distinct interfaces, which confirms the epitaxial relationship between the basal nanowire and the saw-like edges. Figure 4b-d show cross-sectional high-resolution transmission electron microscopy (HRTEM) images of the NRs, indicating that the basal nanowires have hexagonal cross-sections. Indeed, < 110 > -oriented Si nanowires have been also shown to have hexagonal cross-sections [11,12].

Bottom Line: These twins appear to drive the lateral growth by a reentrant twin mechanism.These twins also create a mirror-like crystallographic configuration in the anisotropic surface energy state and appear to further drive lateral saw-like edge growth in the < 112 > direction.These outcomes indicate that the Si NRs are grown by a combination of the two mechanisms of a Pt-catalyst-assisted VLS mechanism for longitudinal growth and a twin-assisted VS mechanism for lateral growth.

View Article: PubMed Central - HTML - PubMed

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

ABSTRACT
Silicon nanoribbons (Si NRs) with a thickness of about 30 nm and a width up to a few micrometers were synthesized. Systematic observations indicate that Si NRs evolve via the following sequences: the growth of basal nanowires assisted with a Pt catalyst by a vapor-liquid-solid (VLS) mechanism, followed by the formation of saw-like edges on the basal nanowires and the planar filling of those edges by a vapor-solid (VS) mechanism. Si NRs have twins along the longitudinal < 110 > growth of the basal nanowires that also extend in < 112 > direction to edge of NRs. These twins appear to drive the lateral growth by a reentrant twin mechanism. These twins also create a mirror-like crystallographic configuration in the anisotropic surface energy state and appear to further drive lateral saw-like edge growth in the < 112 > direction. These outcomes indicate that the Si NRs are grown by a combination of the two mechanisms of a Pt-catalyst-assisted VLS mechanism for longitudinal growth and a twin-assisted VS mechanism for lateral growth.

No MeSH data available.