Detection on the nanoscale

Don’t throw away that old ink-jet printer just yet, it might be needed to print the transistors for your flat-screen TV. 

Researchers in Japan have made a liquid form of silicon and ink-jet printed polycrystalline thin-film transistors, which will be a boost for manufacturers of large flexible screens and other displays, they claim. 

Tatsuya Shimoda and colleagues at the Seiko Epson Corporation took a carbon-free and oxygen-free silicon compound, cyclopentasilane, Si₅H₁₀, polymerised it, and redissolved and filtered it to produce silicon ’ink’. The ink was used to print islands of silicon as thin films. The islands were not completely crystalline, and the films’ electrical properties were not good enough to compete with thin films already available. But Shimoda is hopeful that once microdroplets of the liquid silicon material are better understood, processing problems will be overcome and a competitive material will be produced. 

Ink-jetting films will allow ’unprecedented control over the size and placement of semiconducting silicon in future generations of high-performance electronic equipment,’ said Lisa Rosenberg, from the University of Victoria, Canada. 

Engineering professor John Canny, at University of California, Berkeley, US, told Chemistry World that Shimoda’s work was an ’interesting development, but a bit esoteric’. Ink-jet printed silicon will never be used to print microchips, Canny said. The main applications of the technology are likely to be in transistors for use in displays, sensors, and possibly keypads for mobile phones, but won’t be seen for at least five years, he predicted. 

Shimodas’ team are now working to improve the materials and processes they used, and plan to make other liquid materials. Shimoda aims to develop the technology to print large volumes of cheap, high performance thin film transistors. 

Katharine Sanderson