Saturday, August 16, 2008

Buckyballs: C-60 to Flash Memory



Buckyballs were discovered in 1985 - the product of an experiment on carbon molecules in space. However, it was not until 1991 that buckyball science came into its own. Just how do buckyballs manage their chemical and physical feats? In C60, hexagons and pentagons of carbon link together in a coordinated fashion to form a hollow, geodesic dome with bonding strains equidistributed among 60 carbon atoms. Some of the electrons are delocalized over the entire molecule--a feature even more pronounced in that workhorse of organic chemistry, benzene. Benzene is flat and many of its derivatives also tend to stack in flatsheets. Spherical buckyballs literally add a new dimension to the chemistry of such aromatic compounds. Buckministerfullerine has been named the Molecule of the Year. In addition to opening up new fields on chemistry, C60 also shows interesting physical properties. It is resistant to shock and it has been suggested that as a lubricant, there is even evidence of superconductivity and it may provide the added ingredient that makes diamond films more practical.

Until a few years ago, there were two known forms of pure carbon, graphite and diamond. Then an improbable-seeming third form of carbon was discovered: a hollow cluster of 60 carbon atoms shaped like a soccer ball. Buckminsterfullerene or "buckyballs"--named for the American architect R. Buckminster Fuller, whose geodesic domes had a similar structure--is the roundest, most symmetrical large molecule known. It is exceedingly rugged and very stable, capable of surviving the temperature extremes of outer space. At first, however, the molecule was a mystery wrapped in an enigma. But when a convenient way of making this molecule, also known as C60, was discovered, it set off an explosion of research among chemists, physicists, and materials scientists to uncover the molecule's secrets. Investigators soon discovered a whole family of related molecules, including C70, C84 and other "fullerenes"--clusters as small as C28 and as large as a postulated C240.These unusual molecules turn out to have extraordinary chemical and physical properties.They react with elements from across the periodic table and with the chemical species known as free radicals--key to the polymerization processes widely used in industry--thus opening up the fullerenes to the manipulative magic of organic chemists. When a fullerene is "doped" by inserting just the right amount of potassium or cesium into empty spaces within the crystal, it becomes a superconductor--the best organic superconductor known.


The use of buckyballs in industry became the topic of discussion.With the growing technology and the want for a faster communicating medium,the bucky ball made its way to digital electronics. The flash memory was enhanced by the use of C60 in it. Flash memory consist of a transistor which has a gate ,drain and a source. The gate is separated from the transistor by a layer of insulation,the gate dielectric. The gate contains another ‘floating gate’ in the embedded dielectric. By varying the voltage on the gate the charge can be made to enter or leave the inner gate. The presence or absence of charge at the floating gate denotes the present bit. The flash memories have many such transistors and have followed the Moore’s law for years, but the power consumption is also high. The flash require about 11V-13V of supply for entering the charge or removing it from the dielectric. If the dielectric is made thinner then the charge can move faster but it may also result in leaking of charge. Buckyballs are now used to provide a path for charge to enter the dielectric and leave it faster. They are like the stepping stones in a river to cross from one side to another. Enough potential difference can cause them to show up and then the charge transfer can take place without disturbing the dielectric dynamics. This can enhance the speed of flash memories and bring down the power supply from 13V to 5V.

The cost of flash memories may increase due to it but may also be a very handy weapon to enervate the power consumption. Use of such technologies in DRAM’s can also prove to be effective.
More information on use of buckyballs through your comments would be appreciated.