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The first (sequential) logic circuit has been built using carbon nanotubes. The fast manufacturing process has been developed to print these circuits on TFT with a plastic sub straight resulting in a flexible circuit board. Professors Yutaka Ohno from Nagoya University in Japan and Esko I. Kauppinen explained, nanotube networks contain both metallic and semiconducting nanotubes. While a greater amount of metallic nanotubes increases the transistor’s charge-carrier mobility, it also decreases the on/off ratio. Since both of these characteristics are important for overall transistor performance, the researchers in the new study found a way to optimize both characteristics by fabricating a nanotube network with certain unique properties. For instance, the network’s morphology consists of straight, relatively long (10 micrometers) nanotubes (30% of which are metallic) compared to other nanotube networks. The new network also uses more Y-junctions than X-junctions between nanotubes. Since Y-junctions have a larger junction area than X-junctions, they also have lower junction resistance. Using this nanotube network, the researchers fabricated TFTs that simultaneously demonstrate a high charge-carrier mobility and on/off ratio, offering significantly better performance than previous nanotube-based transistors. After building the transistors, the researchers fabricated an IC capable of sequential logic, the first such circuit based on carbon nanotube transistors to date. This is the first step towards building similar circuits with memory.


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