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. 2010 Jun 4;22(21):2320-4.
doi: 10.1002/adma.200904410.

Curving nanostructures using extrinsic stress

Jeong-Hyun Cho  1 , Teena James, David H Gracias
Affiliations

Curving nanostructures using extrinsic stress

Jeong-Hyun Cho et al. Adv Mater. .
No abstract available

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Figures

Figure 1
Figure 1
Conceptual sketches and scanning electron microscopy (SEM) images showing the origin of the high extrinsic stress observed within the Sn film that caused Ni / Sn bilayers to curl up with nanoscale radii of curvature. a) The induction of grain coalescence in Sn films during plasma processing causes a large extrinsic stress. b) SEM images of Sn thin films deposited on bare Si before and after grain coalescence. Grain coalescence resulted in spontaneous curving of the released edges of the film due to the stress gradient generated. c) When deposited atop a Ni film, the stress generated within the Sn thin film due to grain coalescence was large enough to cause the Sn / Ni bilayer to curl up. d) SEM image of Ni / Sn bilayer curving into a nanoscale tubular structure with 20 nm radii of curvature. Also shown is a nanoscale ring.
Figure 2
Figure 2
Control experiment with a polymeric sacrificial layer demonstrating that the release of the structure from the underlying substrate and the self-assembly steps can be decoupled. a) Schematic showing the deposition of a Ni / Sn bilayer atop a polyvinyl alcohol (PVA) sacrificial layer. On dissolution of this sacrificial layer no curvature was observed in the released structure. Curvature was triggered only by inducing grain coalescence which could be achieved in a subsequent step. SEM images of a square patterned Ni 5 nm / Sn 5 nm film b) after release from the Si substrate showing no curvature and c) after Sn grain coalescence was induced.
Figure 3
Figure 3
Experimental results showing the variation of the radii of curvature with the cantilever geometry. a) Variation in thickness (L=300 and W= 50 nm). b) Variation in length (W=50 nm). c) Variation in width (L=1000 nm).
Figure 4
Figure 4
SEM images of the variation of curvature with varying widths showing that nanostructures with both homogeneous and varying radii of curvature can be self-assembled. a) SEM image of the curving of cantilevers with different widths (50, 100, 200, and 300 nm). All cantilevers have the same L= 1 μm and thickness (Ni 10 / Sn 2.5 nm). Cantilevers with the same width show the same radii of curvature, while those of larger widths have larger radii of curvature. This result highlights the reproducibility of the self-assembly process. b) SEM image of cantilevers with varying width along the length of the cantilever (i.e. W1V and FH of different magnitudes and directions. g) Tilted zoomed-in image of the nanoscroll shown in Figure 4f).
Figure 5
Figure 5
Demonstration of surface patterning a)-e), materials versatility f) and parallel nature of the assembly process. SEM images of single rolled nanotubes without a) patterning and b) with patterning of pores. c)-e) Nanostructures such as rings and scrolls with the letters JHU and NANOJHU patterns on them. f) Curving nanostructures composed of a dielectric material namely alumina (Al2O3 6 nm / Sn 5 nm).
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References

    1. Stoney GG. Pro R Soc London A. 1909;82:172.
    1. Nix WD. Metall Mater Trans A. 1989;20:2217.
    1. Freund LB, Suresh S. Thin film materials: stress, defect formation and surface evolution. Cambridge University Press; New York: 2009.
    1. Koch R. J Phys Condens Matter. 1994;6:9519.
    1. Hoffman RW. Thin Solid Films. 1976;34:185.

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