Molecules and silicon devices can work together, as can chemists and engineers.

Building a molecular computer is a challenge that calls for expertise in a variety of different disciplines. James Tour, a chemist at Rice University in Texas, was already collaborating with John Reif, a computer scientist at North Carolina State University, on such a project when he realized that he needed help from someone who knew about the packaging and fabricating of electronic devices. Reif put Tour in contact with Paul Franzon, an electrical engineer at North Carolina, and they have now shown that organic molecules can control the electronic characteristics of silicon field-effect transistors (J. Am. Chem. Soc. 128, 14537–14541).

Tour, Franzon and co-workers fabricated a pseudo-MOSFET — a form of field-effect transistor that serves as a proof-of-concept device — that consisted of boron-doped source and drain electrodes with a channel in between. After Franzon prepared the devices, Tour grafted organic molecules with different electronic properties onto the channel region of the transistors. Electron-poor molecules increased the conductance of the channel, whereas electron-rich molecules had the opposite effect. Grafting molecules in this way is similar to doping, which is central to all semiconductor devices, and this approach could prove to be useful when electronic devices become so small that the traditional methods of doping no longer work.

What has Tour learned from the collaboration? “Be prepared to learn a new language and explain yourself very simply,” he says. “Even simple terms like 'hole mobility' can cause a synthetic chemist to scratch his head, but once he realizes that we are simply talking about the flow of cations, then discussions become easy.” The two sides also had different approaches to laboratory chemicals. “Engineers are sometimes skittish about using solvents like dichloromethane,” says Tour, “but they will use terribly dangerous compounds such as silane without batting an eye”.