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In situ – Directed Growth of Organic Nanofibers and Nanoflakes: Electrical and Morphological Properties

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ABSTRACT

Organic nanostructures made from organic molecules such as para-hexaphenylene (p-6P) could form nanoscale components in future electronic and optoelectronic devices. However, the integration of such fragile nanostructures with the necessary interface circuitry such as metal electrodes for electrical connection continues to be a significant hindrance toward their large-scale implementation. Here, we demonstrate in situ–directed growth of such organic nanostructures between pre-fabricated contacts, which are source–drain gold electrodes on a transistor platform (bottom-gate) on silicon dioxide patterned by a combination of optical lithography and electron beam lithography. The dimensions of the gold electrodes strongly influence the morphology of the resulting structures leading to notably different electrical properties. The ability to control such nanofiber or nanoflake growth opens the possibility for large-scale optoelectronic device fabrication.

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a Ratio between average height and average width for the structures grown on electrodes with different widths are plotted as a solid line in the graph. ΔZ factor for the structures grown on electrodes with different widths are plotted as a dashed line in the graph. b Electrical characteristics for p-6P nanostructures grown on gold electrodes with w = 200 nm (nanoflakes) and w = 2 μm (nanofibers)
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Figure 3: a Ratio between average height and average width for the structures grown on electrodes with different widths are plotted as a solid line in the graph. ΔZ factor for the structures grown on electrodes with different widths are plotted as a dashed line in the graph. b Electrical characteristics for p-6P nanostructures grown on gold electrodes with w = 200 nm (nanoflakes) and w = 2 μm (nanofibers)

Mentions: A systematic investigation of the morphology of the organic nanostructures was made for different electrode widths w, by measuring the dimensions (width and height) of the grown nanostructures by SEM and AFM, respectively, and by calculating the aspect ratio, i.e. height-to-width ratio, as well as the difference between the maximum and minimum heights (ΔZ = Zmax - Zmin) along the long axis of each individual structure. Figure 3a shows how these factors change as a function of the electrode width w. The data are based on measurements on about 120 nanostructures. For wide electrodes, the ratio between the average height and the average width of the nanostructures is smaller than for structures grown on narrow electrodes. We propose the following explanation for the phenomenon: on wide electrodes, the surface diffusion area is large, and p-6P clusters can aggregate and form long and flat fibers. On narrow electrodes, the surface diffusion area, where clusters are formed, is smaller, and the growth is hindered by boundaries. As a consequence, the molecules grow preferentially side by side in the vertical direction since tail-to-tail growth for rod-like molecules is improbable. The structures grown on wide electrodes exhibit a more jagged morphology, as previously shown for p-6P nanofibers grown on gold surfaces [21,22]. This effect is also shown in Figure 3a, which shows an increase in ΔZ for structures grown on wider electrodes.


In situ – Directed Growth of Organic Nanofibers and Nanoflakes: Electrical and Morphological Properties
a Ratio between average height and average width for the structures grown on electrodes with different widths are plotted as a solid line in the graph. ΔZ factor for the structures grown on electrodes with different widths are plotted as a dashed line in the graph. b Electrical characteristics for p-6P nanostructures grown on gold electrodes with w = 200 nm (nanoflakes) and w = 2 μm (nanofibers)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211154&req=5

Figure 3: a Ratio between average height and average width for the structures grown on electrodes with different widths are plotted as a solid line in the graph. ΔZ factor for the structures grown on electrodes with different widths are plotted as a dashed line in the graph. b Electrical characteristics for p-6P nanostructures grown on gold electrodes with w = 200 nm (nanoflakes) and w = 2 μm (nanofibers)
Mentions: A systematic investigation of the morphology of the organic nanostructures was made for different electrode widths w, by measuring the dimensions (width and height) of the grown nanostructures by SEM and AFM, respectively, and by calculating the aspect ratio, i.e. height-to-width ratio, as well as the difference between the maximum and minimum heights (ΔZ = Zmax - Zmin) along the long axis of each individual structure. Figure 3a shows how these factors change as a function of the electrode width w. The data are based on measurements on about 120 nanostructures. For wide electrodes, the ratio between the average height and the average width of the nanostructures is smaller than for structures grown on narrow electrodes. We propose the following explanation for the phenomenon: on wide electrodes, the surface diffusion area is large, and p-6P clusters can aggregate and form long and flat fibers. On narrow electrodes, the surface diffusion area, where clusters are formed, is smaller, and the growth is hindered by boundaries. As a consequence, the molecules grow preferentially side by side in the vertical direction since tail-to-tail growth for rod-like molecules is improbable. The structures grown on wide electrodes exhibit a more jagged morphology, as previously shown for p-6P nanofibers grown on gold surfaces [21,22]. This effect is also shown in Figure 3a, which shows an increase in ΔZ for structures grown on wider electrodes.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Organic nanostructures made from organic molecules such as para-hexaphenylene (p-6P) could form nanoscale components in future electronic and optoelectronic devices. However, the integration of such fragile nanostructures with the necessary interface circuitry such as metal electrodes for electrical connection continues to be a significant hindrance toward their large-scale implementation. Here, we demonstrate in situ–directed growth of such organic nanostructures between pre-fabricated contacts, which are source–drain gold electrodes on a transistor platform (bottom-gate) on silicon dioxide patterned by a combination of optical lithography and electron beam lithography. The dimensions of the gold electrodes strongly influence the morphology of the resulting structures leading to notably different electrical properties. The ability to control such nanofiber or nanoflake growth opens the possibility for large-scale optoelectronic device fabrication.

No MeSH data available.