Multilevel conductance and memory in ultrathin organic films

The present letter reports conductance switching in Langmuir-Blodgett films of an organic semiconductor. We have achieved multiple conducting levels in devices based on ultrathin films for increased density of memory bits in the same space. We have shown that multiple conducting levels in a device can be achieved by controlling the density of high-conducting molecules in the structures. We have observed one low- and three high-conducting states of the devices. All four states have associated memory for data-storage applications. Any of the four states, namely 00, 01, 10, and 11, can be read for several hours for read-only memory applications. We could erase a state, write another, and read the state for multibit random-access-memory applications. (C) 2004 American Institute of Physics.