The limits of pushing storage density to the atomic scale are explored with a memory that stores a bit by the presence or absence of one silicon atom. These atoms are positioned at lattice sites along self-assembled tracks with a pitch of five atom rows. The memory can be initialized and reformatted by controlled deposition of silicon. The writing process involves the transfer of Si atoms to the tip of a scanning tunneling microscope. The constraints on speed and reliability are compared with data storage in magnetic hard disks and DNA.
In 1959 physics icon Richard Feynman estimated that ?all of the information that man has carefully accumulated in all the books in the world, can be written in a cube of material one two-hundredth of an inch wide?. Thereby, he uses a cube of 5?5?5 = 125 atoms to store one bit, which is comparable to the 32 atoms that store one bit in DNA. Such a simple, back-of-the-envelope calculation gave a first glimpse into how much room there is for improving the density of stored data when going down to the atomic level.
???????? In the meantime, there has been great progress towards miniaturizing electronic devices all the way down to single molecules or nanotubes as active elements. Memory structures have been devised that consist of crossed arrays of nanowires linked by switchable organic molecules or crossed arrays of carbon nanotubes with electro statically switchable intersections.
??????? Now, a little more than 40 years after Feynman's prescient estimate, scientists have created an atomic-scale memory using atoms of silicon in place of the 1s and 0s that computers use to store data. The feat represents a first crude step toward a practical atomic-scale memory where atoms would represent the bits of information that make up the words, pictures and codes read by computers.
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