Interfacial electrostatic phenomena and capacitance-voltage characteristics of ultra-thin polyimide Langmuir-Blodgett films

In this study, we investigated the capacitance-voltage (C-V) characteristics of ultra-thin polyimide (PI) Langmuir-Blodgett (LB) films with taking into account the charge exchange phenomena at the metal/PI LB film. From the theoretical analysis, it was concluded that the capacitance of the film changes by the application of the voltage, because the thickness of charge exchange layer changes and the charge exchange phenomena at the interfacial electronic states reduce the apparent film thickness of the device. From our experiment, it was found that the apparent film thickness decreases as the applied field increases at the positive bias, whereas the decrease is very small at the negative bias, due to the formation of very high electrostatic electric field at the PI LB film/Al interface