Atom-level Memory Pointing to the Speed Limit

Physicists at the University of Wisconsin-Madison in the US and the University of Basel in Switzerland have developed a memory that stores information by detecting the presence or absence of a single silicon atom.

Professor Franz Himpsel, group leader and principal investigator on the project, said that we have produced a memory right at the atomic density limit, where a bit is stored by the presence or absence of a single atom. This is achieved by coating a silicon surface with a touch of gold so that the atoms assemble themselves into tracks that are exactly five atoms wide. They can format the memory by depositing extra atoms, write it by removing atoms with a scanning tunneling microscope, and read it on-the-fly by scanning along the tracks.

One of the major improvements the system offers over previous atom manipulation devices is that the system is stable at room temperature. Another advantage is that the position of the atoms, at well-defined distances along tracks, allows conventional magnetic hard-disk readout techniques to be used.

Two problems that still need to be addressed in the system are the fact that the writing and reading functions in the device are relatively slow and that the memory needs to be prepared and preserved in a vacuum. According to Prof. Himpsel, the team's next step will be to address one of these problems and increase the system's speed. He said that an obvious next step is the use of fast scanning electronics to speed up the readout to its theoretical limit, and that is 100,000 times faster than what our simple electronics allowed us to do.