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IBM's future molecular switch

In another attempt to extend the validity of Moore's Law, IBM researchers are turning to molecules. They have demonstrated how a single molecule measuring only about 1.5 nanometers in length can be switched between two distinct 'on' and 'off' states. This discovery could lead to better memory and logic applications, but not before a dozen years.
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Written by Roland Piquepaille, Inactive on

In another attempt to extend the validity of Moore's Law, IBM researchers are turning to molecules. According to Red Herring in IBM Sees a Dip in Chip Size, they have demonstrated how a single molecule can be switched between two distinct 'on' and 'off' states. They've used specially designed organic molecules measuring only about 1.5 nanometers in length. This is much smaller than the 10 nanometers limits of CMOS technology, which could be reached in 10 to 15 years. This discovery could lead to better memory and logic applications, but not before a dozen years. Read more...

Here are the opening paragraphs of the Red Herring article.

Researchers at IBM’s Zurich Laboratory said Friday they’ve discovered a new way to manipulate molecules within semiconductor chips to help scale down their size while increasing their function.
Heike Riel and Emanuel Lörtscher said they found an individual molecule within semiconductor chips that can be turned 'on' and 'off.' The discovery is part of their goal to explore molecules that could lead to better memory and logic applications.

As this article is more oriented towards business than technology, let's move to this IBM Zurich Research Laboratory news release (August 4, 2006) for more details.

Using a sophisticated mechanical method, they were able to establish electrical contact with an individual molecule to demonstrate reversible and controllable switching between two distinct conductive states. This investigation is part of their work to explore and characterize molecules to become possible building blocks for future memory and logic applications. With dimensions of a single molecule on the order of one nanometer (one millionth of a millimeter), molecular electronics redefines the ultimate limit of miniaturization far beyond that of today's silicon-based technology.

Below is a sketch showing "the switching molecule 'caught' between the electrodes by closing the bridge gradually with picometer accuracy until one molecule 'reaches' both electrodes" (Credit: IBM Zurich Research Laboratory).

IBM's switching molecule

One thing is to obtain this switching effect a single time. But is this effect repeatable?

The results show that these molecules exhibit properties that can be utilized to perform the same logic operations as used in today's information technology. Namely, by applying voltage pulses to the molecule, it can be controllably switched between two distinct "on" and "off" states. These correspond to the "0" and "1" states on which data storage is based.
Moreover, both conductive states are stable and enable non-destructive read-out of the bit state—a prerequisite for nonvolatile memory operation—which the IBM researchers demonstrated by performing repeated write-read-erase-read cycles. With this single-molecule memory element, Riel and Lörtscher have documented more than 500 switching cycles and switching times in the microsecond range.

IBM is not really talkative about the molecule that was used for these experiments. The company just says that "the switching molecule is BPDN-DT, a specially designed organic molecule with dimensions of typically 1.5 nm" and that it was "designed and synthesized by Professor James M. Tour and co-workers of Rice University, Houston, USA."

I'm sure that the name of James Tour rings a bell for some of you. Just to refresh your memory, he's the guy behind the Nanokids and the NanoPutians projects. He's also behind the first 'nanocar' with buckyball wheels.

For more information about IBM future molecular switches, this research work has been published by SMALL under the title "Reversible and Controllable Switching of a Single-Molecule Junction" (Volume 2, Issue 8-9, Pages 973-977, August 4, 2006). Here is a link to the abstract.

Sources: Red Herring, August 4, 2006; and various web sites

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