Effect of the nanofilm thickness on the properties of the two-dimensional electron gas at the interface between two dielectrics

Abstract

The mechanism of formation of the two-dimensional conductivity along the interface between two polymer dielectrics is experimentally studied. The idea of “polar catastrophe,” which was successfully used earlier to explain the electronic properties of the interface between two perovskites LaAlO₃/SrTiO₃, is chosen as a base hypothesis. Piezoelectric response microscopy is used to reveal the presence of spontaneous polarization on the surface of a polymer film, and the remanent polarization is found to decrease with increasing film thickness. As in the case of perovskites, the polymer film thickness is found to strongly affect the electrical conductivity along the interface. Substantial differences between these phenomena are detected. The change in the electrical conductivity is shown to be caused by a significant increase in the charge carrier mobility when the film thickness decreases below a certain critical value. The relation between the change in the carrier mobility and the change in the spontaneous surface polarization of the polymer film when its thickness decreases is discussed.