Shortest transistor makes its debut

In a transistor, electrons scurry along a channel whose length partly determines the device’s speed. Chip makers have devised clever schemes to shrink circuitry, including transistors and their channels, thereby speeding up electronic processing.

Now, using a novel method of making transistors, Jan Hendrik Schön and his colleagues at Lucent Technologies’ Bell Labs in Murray Hill, N.J., have built prototype devices with channels the length of a single molecule, about 2 nanometers.

The new channels span less than a fiftieth the length of the channels typical in chips today, Schön says. They’re also shorter than the channels of other single-molecule transistors made from tubular strands called carbon nanotubes (SN: 11/10/01, p. 294: Wiring teensy tubes, strands into circuits).

To make the devices, the Lucent scientists etched notches into silicon and deposited gold into them. The researchers then coated the gold with a one-molecule-thick layer of conductive organic molecules called thiols. Finally, they capped that layer with another film of gold. The area of each transistor measures 100 nm by 800 nm, the researchers report in the Oct. 18 Nature.

At first, the scientists made devices that conducted current through thousands of thiol molecules at once. According to a report in an upcoming Science, they later made transistors in which apparently a single thiol molecule was the channel. They achieved this by diluting the thiols with nonconductive molecules.

The new transistors have a long way to go before they can compete with conventional devices, Schön says. However, the extremely short channels bode well for making faster devices, he claims. Moreover, the fabrication technique avoids high temperatures, the need for vacuum chambers, and other drawbacks of conventional chip making. By the time current electronics fabrication reaches its limits in the next decade or so, these new types of chips may be ready to keep the miniaturization momentum going.