Charges at the heterogeneous interface of dielectrics

Abstract

Abstract The heterogeneous interface of two different dielectrics is commonly observed in diverse electronic devices. Charge emerging will take place at the heterogeneous interface and may greatly influence the device performance. Typically, charge emerging behavior is attributed to the Maxwell–Wagner effect. The emerged charge by the Maxwell–Wagner effect is unipolar. Nevertheless, bipolar phenomena are also frequently observed. This paper reports the change characteristic of accumulated charge between unipolar and bipolar at the heterogeneous interface composed of two different dielectrics. A theoretical analysis is proposed. As an illustration, the laminated membrane is formed by thermally pressing two non-polar polymers, fluorinated ethylene propylene (FEP) and polypropylene (PP). Its interfacial charge nature is studied by means of electret research. It is found that the bipolar charge derives from contact electrification and is determined by the electronegativity of the atoms at two dielectrics’ interface. The unipolar charge originates from the Maxwell–Wagner effect and is determined by the dielectric constant and conductivity of dielectrics. In the absence of external electric field, the charge nature shows bipolar in the form of dipole electric double-layer. In the presence of external electric field, the change of charge nature from bipolarity to unipolarity will occur depending on the electric field and temperature. Its regulation is closely related to the connection mode of external electric field with the heterogeneous interface of dielectrics. When negative electrode is connected with FEP, the charge nature at the interface evolves from bipolarity to positive polarity. When positive electrode is connected with FEP, the charge nature transforms from bipolarity to negative polarity. A critical point exists for a polarizing voltage to induce the change of charge nature.