Looking for all the world like an abacus, a newly invented computer memory chip has pushed the bounds of miniaturization nearly to the limit.

Unlike conventional hard drives and RAM chips, the new memory chip developed at University of Wisconsin-Madison uses individual atoms of silicon as its 1s and 0s. Like the memory storage in a normal computer, the chip is readable, writable and can be formattable.

In tiny grooves five atoms wide, strings of silicon atoms are displayed like eggs in a carton. When created the grooves are filled end-to-end with atoms, each of which representing a 1. By plucking out an atom here and an atom there, gaps are created which correspond to 0s. This results in a data density a million times greater than a DVD.

Of course, there aren't many home PCs equipped with a scanning tunneling microscope. The super-fine tip of the microscope is used to pluck or place the atoms into position. Luckily the microscope operator doesn't have to "hunt and peck" to grab the right atom. The atoms naturally line themselves up with nearly perfect precision, and the microscope can automatically scan to exactly the right spot.

Reading the chip is a simple matter of the microscope's tip running along to register the 1s and 0s on the chip. Writing is a bit more difficult however, which is why a new chip would start off full of 1s end to end. To accurately place individual atoms onto an entirely empty chip would require a temperature of about -452F -- the temperature of liquid helium. Any warmer and the atoms could stick to the microscope tip instead of to the chip. However, plucking ones from a lineup can be reliably done at room temperature.

http://uw.physics.wisc.edu/~himpsel/memory.html

-- Robert Myers