Tiniest Switches Promise Ultracompact Computer Memories

A unique organic molecule that my pave the way toward the design of incredibly compact digital storage devices or computer memories has been developed by Weizmann Institute scientists.

The researchers -- a team or organic chemists including graduate student Lior Zelikovich, senior staff scientist Dr. Jacqueline Libman, and group leader Prof. Abraham Shanzer -- have synthesized novel, triple-stranded complexes of iron that my serve as the basis for switches the size of a small molecule.

Adapting these molecular-sized switches for use as ultracompact electronic devices -- whose digital circuitry would contain tens of million of "on"-"off" elements -- will require the solution of several inherent problems. There are no known methods for turning individual molecular switches "on" and "off" (the so-called "addressing" problem), or for detecting whether a particular molecular switch is "on" or "off" (the "reading" problem), or for "wiring" individual molecules to the external world. Improved switching complexes that operate much more rapidly will also be needed.

"There is no way to predict when molecular switches will become integrated into functional devices," says Shanzer. "But because of the importance of further miniaturization of electronic components, research into the ultimate level of miniaturization -- the use of molecular components -- is now attracting increasing scientific interest. When this technology comes of age, it could result in digital storage elements and memories millions of times more compact than now available, and in novel devices with capabilities far beyond anything possible today."

Building on their experience in synthesizing metal-binding organic compounds for medical, industrial and agricultural applications, the Shanzer-Libman team turned to the design of similar complexes with switch-like properties. In this work, they engineered an organic molecule with two sites, each of which binds iron in differently charged states. Using simple chemical techniques, the charge on the iron can be raised or lowered, causing it to jump between the two molecular sites. This jump causes the complex to change its color from yellow-brown to purple, a change that is easily seen in the test tube.

The Shanzer-Libman team is now working on other molecules that may have a potential to be "switched," as well as on molecular structures that may be applicable for use as conductors or diodes. They are also examining ways of turning their molecular switches "on" and "off" by electrochemical and photochemical means, approaches that are closer to real-life, solid-state conditions than reaction chemistry in a test tube.

This research, which was undertaken at the Institute's Department of Organic Chemistry, was supported by the Israel Science Foundation (which is administered by the Israel Academy of Sciences and Humanities) and by the Consortium of German Chemical Companies.

Prof. Shanzer is the incumbent of the Siegfried and Irma Ullmann Professorial Chair.