Spatial distribution of charges in heat-treated ultrathin polyimide Langmuir-Blodgett films

Organic ultrathin films are widely used as insulators in electronics, where the films are in contact with metal electrodes. It is essential to determine any electronic phenomena occurring at the metal/film interface. Information on the spatial distribution of charges in the films is very important. In this study, the spatial distribution of charges in heat-treated polyimide (PI) Langmuir-Blodgett (LB) films on various metals was determined on nanometer scale by measuring the potential across the films as a function of the number of deposited layers. The depth of penetration of excess charges displaced from metal electrodes into PI LB films was found to be about 3 nm, and an electric field of the order of 10⁶ V/cm is established at the interface owing to the excess charges displaced