Electrostatic phenomena of ultrathin electrically insulating polyimide films: Space charge distribution and electronic density of states at the nanometric interface

Nanometric electrostatic phenomena in ultrathin insulator films at the metal-film interface are described. The space charge distribution in Langmuir-Blodgett (LB) films on metal electrodes is determined on the order of nanometer film thickness scale from the surface potential method, and the distribution of electron density of states, electron acceptor and donor states, is calculated from the temperature dependence of the space charge distribution, assuming that electronic charges are displaced from metals to LB films until a thermodynamic equilibrium is established at the metal-film interface. Using three kinds of polyimide (PI) LB films deposited on various kinds of metal electrodes, surface potential of these films have been examined as a function of the number of deposited layers at a temperature between -100°C and +150°C. Then the space charge distribution and electronic density of states in these films were determined, and the presence of electron acceptor-states was revealed