D.C. conduction in Langmuir-Blodgett films with various electrode materials

Electrically insulating films of thickness from 2.5. to 40 nm were prepared by the technique of Langmuir and Blodgett. These films consist of long-chain molecules such as lead stearate arranged with the chains perpendicular to the electrode surface. Their d.c. electrical properties can be listed as follows. 1. (1) The current-voltage characteristics is linear for fields below 10 5 V cm -1 and exponential for high fields. 2. (2) The magnitude of the current depends strongly on the electrode material. We used Al, Hg, Si and SnO 2. Similar phenomena are observed in other insulators, although these effects were very pronounced in our films. It is likely that space charge plays a role, although we did not observe the usual space charge limited currents. The experiments point towards an explanation in terms of an electrode limited process acting in combination with space charge.