An array of nanotube transistors, which was printed in rotogravure printing on plastic film. (Nano Letters)
engineers at UC Berkeley working on a gravure printing process to produce cost-effective large areas of nanotube transistors and sensors.
Many obituaries have been already written in the “Gutenberg Galaxy”, the world of print products. As it stands, it was premature: the industrial production printing processes could dominate the coming decades – only a few letters that come in the future of printing machines, but increasingly everyday objects and electronics. Researchers at the University of California at Berkeley have developed a method with which they want to produce large areas of high-performance transistors on plastic films for novel wall-sized displays.
Transistors made of carbon nanotubes, which for ten years as a potential high-performance material apply for electronic applications. The advantage of these “nanotubes” you are mechanically extremely strong, both as a quality leader as well as semiconductors and are in principle allow transistors, which are much more energy efficient than their conventional counterparts of silicon. Placed in a solution, they also can be processed at low temperatures as electronic ink. So far, the performance of printed nanotube transistors but is still too low, says Ali Javey Berkeley computer scientist, who has led the work on the new method. His group has now managed to print a nanotube transistor film that brings a very high performance for the first time. It uses a nanotube mixture containing 99 percent of the variation of the semi-conductive tubular molecules. The method, researchers have recently presented in the journal Nano Letters : You work with the so-called rotogravure. In the laboratory version plastic films are stretched on a cylinder and unrolled on a flat surface, the depressions are filled in a certain pattern to the electronic ink. This mask is to be installed in the next stage of development to another role. As usual in rotogravure printing, the film could then be guided through an entire print line. First, the Berkeley researchers want to improve the printing mask to achieve a more uniform arrangement of transistors a! nd to increase their efficiency further. Then they want to tackle more complex patterns of circuits that contain sensors and other display componentsThe transistors show proved to be very robust. Even with the film curvature with a radius of only one millimeter, the engineers were able to not detect any significant deterioration of the transistor performance. Unlike previous attempts, the printed nanotube transistors are characterized by a high mobility of the electrons. Was the mobility of the charge carriers so far at 0.1 volts per square centimeter and second, the printed transistor films come to more than 9 cm2 / (V s) – however, values of 4000 cm2 / (V s) can be achieved in individual nanotubes.
The key is just for display, Javey says, because more mobile electrons can be produced with lower voltages, currents, which are needed for the operation of organic light emitting diodes (OLEDs) in screens. The multi-level printing process could lead to cheap displays that cover entire walls, so Javey. “Such large areas are not given the production costs with conventional methods feasible.” The Paper:Lau Pak Heng et al. ‘Fully Printed, High Performance Carbon Nanotube Thin-Film Transistors on Flexible Substrates “, Nano Letters August, 2013. <- AUTHOR MARKER DATA BEGIN -> ( Mike Orcutt ) / <- RSPEAK_STOP -> (nbo)
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