PAPER transistors could end the hunt for alternatives to silicon chips and herald the introduction of electronic devices cheap and bendy enough to use on disposable food cans.
鈥淧aper transistors were tested for two months without any deterioration鈥�
The transistors are the work of Elvira Fortunato of the New University of Lisbon in Portugal and colleagues, and were reported in this month鈥檚 IEEE Electron Device Letters. Fortunato and her team built the transistors by coating both sides of a sheet of ordinary paper with metal oxides. They then applied aluminium contacts onto the coated paper.
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The paper acts both as a flexible substrate and as an integral part of the semiconductor 鈥渟andwich鈥� at the heart of the transistor, helping to amplify the tiny currents that pass through the transistor. 鈥淯sing the interstrate is a clear advantage,鈥� says Professor Ioannis Kymissis of the Laboratory for Unconventional Electronics at Columbia University, New York.
The transistors were produced at room temperature and tested for two months without any deterioration in performance or stability. That makes it plausible that they could be used to make disposable microelectronics such as RFID tags and smart labels cheap enough to be used for everyday applications, such as labelling and tracking stock in supermarkets. Since they鈥檙e made of paper, they are liable to tear or become soggy if dampened, but this can be overcome by laminating the device.
Researchers have long sought ways of making electronic chips that don鈥檛 need multibillion-dollar manufacturing plants as silicon chips do. Inorganic alternatives such as germanium are at least as fiddly as silicon, so the search has focused on organic materials. But since most organic substances conduct electricity relatively poorly, the candidates so far have been too exotic.
It is not surprising then that practical transistors based on cellulose fibre have been enthusiastically received. It is the main ingredient of paper and one of the most common organic materials in the world. 鈥淭his may go a long way toward achieving a dream that many groups have pursued for very low-cost, flexible organic electronics,鈥� says Dick Slusher, director of the Georgia Tech Quantum Institute in Atlanta.
