Molecular Footprints And Memory Squeeze-Downs

Reported in the March and May issues of Advanced Materials, a team of Weizmann scientists headed by Prof. Jacob Sagiv of the Institute's Materials and Interfaces Department has developed a new strategy for high-density, long-term data storage using a unique molecular approach. Sagiv worked together with Dr. Rivka Maoz and Eli Frydman of the same department, as well as with Dr. Sidney Cohen of the Chemical Services Unit.

Current CD and microchip technologies are based on etching data onto existing materials -- the smaller the data-encryption markers used, the more information on a given surface. Engineers have excelled at this task over the last few decades -- with the bacchanalia of microelectronic gadgets on the market as ticking proof. However, it was clear that the party couldn't last. The race toward ever-smaller data-storage technologies on limited physical surfaces would eventually hit a stone wall.

The Institute scientists decided to skirt this obstacle, using a refreshing 'build from scratch' approach. Instead of etching data on existing surfaces, they actually construct it out of atoms and molecules, which they bind to one another much like a builder constructs a brick wall.

The construction work starts out with a smooth silicon surface covered with a one-molecule-thick layer, in which the exposed ends of these molecules are chemically inert. The researchers succeeded in activating a selected portion of these molecules while leaving others inert. Having different properties, the activated molecules can serve as minute footprints of information -- encoding diverse data, from text to images, or even music.

To achieve this, the researchers used an atomic force microscope (AFM) as their 'pencil.' Equipped with an ultra-sharp needle that can transmit electrical signals, the AFM 'writes' information by electrochemically modifying the ends of the molecules touched by the needle. Such modified molecules can later be detected by an AFM operated in its 'reading' mode. Using a computer, this molecular information is decoded to recreate the original letter, image, or sound. In a following study, the scientists took advantage of the same process to double-deck the information packs: once the molecular ends are activated, they are also capable of binding other atoms and molecules, thus enabling the researchers to add additional 'molecular floors' according to a predefined plan. This bottom-up approach could offer precise control over the structure and chemical composition of future nano-devices, thereby enabling dramatically increased data density, and potentially paving the way to breakthrough nano-electronic tools.

Prof. Jacob Sagiv's research is supported by the Verband der Chemischen Industrie and the German Society of Friends of the Weizmann Institute of Science, Germany.

The Weizmann Institute of Science is a major center of scientific research and graduate study located in Rehovot, Israel. Its 2,500 scientists, students and support staff are engaged in more than 1,000 research projects across the spectrum of contemporary science.