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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 Output curves for devices containing nanoflakes (w = 200 nm) and nanofibers (w = 2 μm). b Transfer curves for the nanoflakes device. The oxide thickness is 100 nm and the drain–source separation gap is 200 nm
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Figure 5: a Output curves for devices containing nanoflakes (w = 200 nm) and nanofibers (w = 2 μm). b Transfer curves for the nanoflakes device. The oxide thickness is 100 nm and the drain–source separation gap is 200 nm

Mentions: More elaborate results of the electrical characterization are shown in Figure 5a, which include output characteristics (IDS vs. VDS) for narrow (w = 200 nm) and wide (w = 2 μm) electrodes. These were measured by sweeping the drain–source voltage from 0 V to positive voltages, back to negative voltages, and returning and finishing the measurement at 0 V. Each sweep was performed with a constant gate voltage (0 or -10 V). The conductivity of the nanostructures increases when a negative voltage is applied to the gate electrode, showing that the nanofibres or nanoflakes are p-type semiconductors. It is seen from Figure 5a that a lower VDS is needed to conduct a current in the nanostructures grown on the wide electrodes (nanofibers) compared to the structures grown on the narrow electrodes (nanoflakes), as was also seen in Figure 3b. We explain this difference in turn-on voltage by the fact that the nanofibers have a larger contact area to the gold electrode surface compared to the nanoflakes and therefore have a smaller contact resistance. We have not observed any saturation behavior even when the drain–source voltage is swept up to 70 V (at this voltage, the fibers and flakes are destroyed); however, this is as expected since the electrode gap width to oxide thickness ratio is too small. Therefore, the field-effect mobility and the threshold voltage cannot be extracted from the data. The curves sweeping back to 0 V (Figure 5) show hysteresis. This effect is often observed for organic semiconductors [27] and is most likely due to charge trapping.


In situ – Directed Growth of Organic Nanofibers and Nanoflakes: Electrical and Morphological Properties
a Output curves for devices containing nanoflakes (w = 200 nm) and nanofibers (w = 2 μm). b Transfer curves for the nanoflakes device. The oxide thickness is 100 nm and the drain–source separation gap is 200 nm
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3211154&req=5

Figure 5: a Output curves for devices containing nanoflakes (w = 200 nm) and nanofibers (w = 2 μm). b Transfer curves for the nanoflakes device. The oxide thickness is 100 nm and the drain–source separation gap is 200 nm
Mentions: More elaborate results of the electrical characterization are shown in Figure 5a, which include output characteristics (IDS vs. VDS) for narrow (w = 200 nm) and wide (w = 2 μm) electrodes. These were measured by sweeping the drain–source voltage from 0 V to positive voltages, back to negative voltages, and returning and finishing the measurement at 0 V. Each sweep was performed with a constant gate voltage (0 or -10 V). The conductivity of the nanostructures increases when a negative voltage is applied to the gate electrode, showing that the nanofibres or nanoflakes are p-type semiconductors. It is seen from Figure 5a that a lower VDS is needed to conduct a current in the nanostructures grown on the wide electrodes (nanofibers) compared to the structures grown on the narrow electrodes (nanoflakes), as was also seen in Figure 3b. We explain this difference in turn-on voltage by the fact that the nanofibers have a larger contact area to the gold electrode surface compared to the nanoflakes and therefore have a smaller contact resistance. We have not observed any saturation behavior even when the drain–source voltage is swept up to 70 V (at this voltage, the fibers and flakes are destroyed); however, this is as expected since the electrode gap width to oxide thickness ratio is too small. Therefore, the field-effect mobility and the threshold voltage cannot be extracted from the data. The curves sweeping back to 0 V (Figure 5) show hysteresis. This effect is often observed for organic semiconductors [27] and is most likely due to charge trapping.

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.


Related in: MedlinePlus