Researchers in Japan have come up with a new transistor manufacturing technique that they claim will squeeze the best performance enhancements out of carbon nanotubes, without losing the on/off ratio of a good semiconductor.
The Nagoya University researchers say they have demonstrated flexible integrated circuits that "are capable of sequential logic" - a first for a transistor made from carbon nanotubes. They are also optimistic that the process will be scalable, and are aiming to commercialise their work inside five years.
Carbon nanotubes have been the focus of much research as scientists look for ways to make thin, flexible computer devices, like electronic paper, and flexible RFID tags.
But as we know, sheets of carbon don’t have the best on/off ratio. Carbon nanotubes alone will not do, they have to be mixed with semiconducting companions so that the transistors they form can be switched off. More carbon equals better charge/carrier mobility, but it also decreases the on/off ratio, and vice-versa.
So the researchers at Nagoya University developed a way of arranging a lower (and controllable) density of carbon nanotubes so as to maximise their charge/carrier mobility boost.
From the article abstract in Nature Nanotechnology: We report the fabrication of high-performance thin-film transistors and integrated circuits on flexible and transparent substrates using floating-catalyst chemical vapour deposition followed by a simple gas-phase filtration and transfer process. The resulting nanotube network has a well-controlled density and a unique morphology, consisting of long (~10 µm) nanotubes connected by low-resistance Y-shaped junctions.
Co-author Yutaka Ohno told PhysOrg: "Our near-future plan is to demonstrate roll-to-roll fabrication of carbon nanotube-transistor-based TFT arrays and integrated circuits. To do so, we need to replace all the lithographic techniques by high-throughput printing techniques. For commercialization [sic], we have to improve the uniformity of TFT characteristics more, but we are aiming at commercializing [sic] within five years."