sports molecule-thin layer
Technology Research News
note: this research has been withdrawn by the scientists.
It's going to be a long time before anyone builds a computer with components
made out of individual molecules. The big obstacle is figuring out how to
wire billions of molecules together without having to connect them one by
Short of that lofty goal, however, making parts of components only one molecule
thick could make for faster computers.
Researchers at Lucent Technologies' Bell Labs have made a transistor that
uses a single layer of molecules as a semiconductor.
"We have demonstrated that such tiny devices can act as a transistor [to]
switch and amplify signals," said Hendrik Schön, a physicist at Bell Labs.
The researchers also connected two of the transistors to form an inverter,
which reverses a signal.
Transistors are microscopic electronic switches that channel electrical
current; there are millions of them on computer processor and memory chips.
The most common way to make faster chips is to use smaller transistors,
shortening the path electrons have to travel to switch the devices on and
The Bell Labs' transistors are not especially small. While the semiconductor
is only a molecule thick, each transistor uses 1,000 of the semiconducting
molecules and is about 800 nanometers wide, said Schön. But they set the
stage for smaller transistors and are a step toward the ultimate goal of
making a transistor from a single molecule.
"The [semiconductor layer] of the device can be as small as a molecule,
about 1 nanometer," said Schön. "This is more than a factor of a hundred
smaller than state-of-the-art silicon devices in, for example, a Pentium
Transistors usually have five parts: a semiconducting channel that carries
the flow of electrons, a source electrode that puts electrons into the channel,
a drain electrode that takes electrons out of the channel, a gate electrode
that turns the flow on and off, and an insulator that separates the gate
electrode and the channel.
In field-effect transistors like the Bell Labs' device, when current is
applied to the gate electrode it produces an electric field that lowers
the resistance of the semiconducting channel, causing current to flow from
the source electrode through the channel to the drain electrode. Computers
use this flow and absence of flow to represent the ones and zeros of binary
The semiconductor portion of the Bell Labs' device is also organic, or carbon-based,
rather than silicon. This means the layer can be formed using simple, room-temperature
chemical processes and does not require the expensive facilities and equipment
ordinarily used to make computer chips, said Schön.
The other components of the Bell Labs' transistor were made from more traditional
computer chip materials: silicon for the gate electrode, silicon oxide for
the insulator, and metal for the source and drain electrodes.
The researchers are also working toward replacing these with organic --
and smaller -- components that assemble chemically, said Schön. "We want
to make use of more complex schemes of self-assembly. For example, not only
defining the active material but also [making the] insulator and contacts
by similar techniques," he said.
Other researchers have built the insulator portion of field-effect transistors
using self-assembled single-molecule layers. Building all of the components
of the transistor out of organic materials would also make it flexible,
which means it could be used to make electronic devices on sheets of plastic.
The researchers' long-term goal is to make an entire transistor out of a
single molecule, said Schön. "[One] goal is to design and synthesize more
complex molecules, which combine the different transistor functionalities
-- semiconductor, insulator, electrodes -- on a single molecule," he said.
What the researchers have done so far "is a very nice science result," said
Mark Reed, a professor of engineering and applied science at Yale University.
There's a lot of work to be done before the layers can be used in practical
It will be at least ten years before manufacturers can produce transistors
using single-molecule semiconductor layers, said Schön.
Schön's research colleagues were Hong Meng and Zhenan Bao. They published
the research in the October 18, 2001 issue of the journal Nature. The research
was funded by Lucent Technologies.
Timeline: >10 years
TRN Categories: Semiconductors; Integrated Circuits; Materials
Science and Engineering
Story Type: News
Related Elements: Technical paper, "Self-Assembles Monolayer
Organic Field-Effect Transistors," Nature, October 18, 2001
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