Electronic Design

Molecular-Scale Electronics Grown Chemically In A Beaker

Lucent Technology's Bell Labs scientists Hendrik Schon, Zhenan Bao, and Hong Meng have created molecular-scale inverters using a class of organic semiconductor material known as thiols. This emerging technology can build transistor structures an order of magnitude smaller than those built with current technology. Using chemical means instead of high-precision lithography with attendant clean rooms, the Murray Hill, N.J., researchers have constructed basic amplifiers and switches in a glass beaker at room temperature. John Rogers, director of Nanotechnology Research, calls this process chemical self-assembly.

The new transistors have a channel thickness of only 1 to 2 nm. The active switching region may only consist of a single layer containing about 1000 molecules. Prior to this, the smallest reported thickness was 20 nm. Transistor structures were built using a clever approach that lets one layer of organic molecules self-assemble on an electrode. A shared electrode also simplifies the design of these self-assembled monolayer field-effect transistors (SEMFETs).

The SEMFETs created by the Bell Labs group have a switching ratio in excess of 105. The SEMFET is a p-channel device. Additional work is being done to create n-channel devices so more efficient CMOS-style devices can be created.

The technology may eventually be combined with plastic substrates. Flexible circuits could then be used in areas such as LCD drivers, thereby reducing size and weight in addition to making the device more resistant to damage.

This technology may take a decade to mature, and there are challenges to address. One such hurdle will be wiring when there are a large number of transistors as in a processor core. Another is the creation of complex but arbitrary structures needed to implement logic as in a processor core. Regular structure like memory or sensors may come first.

More information about Bell Labs' work on molecular-scale electronics can be found at www.bell-labs.com.

See associated figure.

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