Reproducible memory switching has been observed in metal/ Langmuir–Blodgett (LB) film/metal sandwich structures: LB films consist of organic molecules such as dyes having a number of conjugated bonds. The device switches from a nonconducting off state to a conducting on state via an intermediate state, and it switches directly from the on to the off state within less than 10 ns upon the application of a voltage. Both off-state and on-state resistances of the device depend linearly on the number of monolayers, the conduction being predominantly through the LB films.