The STM as an information storage device

Abstract

SUMMARYThe high spatial resolution of the scanning tunnelling microscope (STM) makes its use as an information storage device very attractive. However, even without specifying the means of information storage, several limits can be placed on the characteristics of these devices. One would expect that a bit of information could not be stored in a dimension smaller than an atom. This limits the storage density to 1015 bits/cm2. Present‐day STM have fields of view that range up to 2times10−6cm2 yielding a total potential capacity of 2times109 bits. This capacity would be expected to grow as STM design becomes more refined. At 1 nA, shot noise will limit the read rate to 20 Mbits/s. This limit can only be overcome by using larger currents. The write rate may also be limited by this phenomenon if the writing mechanism demands that a certain charge threshold be reached to write a bit. For a particular device structure, operating conditions will be identified where the above limitations will become important. The above analysis leads to the conclusion that an STM storage device with reasonable read/write rates and a large storage capacity should be possible.