Interlayer charge transfer from contact electrification in conducting micro and nanoscale thin film heterostructures

Contact electrification (CE) give rise to charge accumulation at the interface when two materials are brought into contact with each other. The charge accumulation at the interface will diffuse to the interior of the conducting material if the dimensions of the contacting conducting material is of the order of an unknown critical length scale. This CE induced interlayer charge transfer will modify the fundamental physical properties of both the contacting materials. This review first discusses the reported experimental evidence of flexoelectricity induced CE and interlayer charge transfer in conducting thin film based heterostructures. The interlayer charge transfer creates a gradient of charge carrier in both the thin films constituting the heterostructure and also modifies the electron-electron interactions. Further, the interlayer charge transfer changes the electron-phonon coupling, spin-phonon coupling and magnetoelectronic coupling that give rise to new physical behavior, which did not exist prior to the interlayer charge transfer. The new physical behaviors from interlayer charge transfer and their mechanistic origins are reanalyzed and discussed, which include spin-Hall effect of charge carriers, topological Hall effect of magnetoelectronic electromagnon, inhomogeneous magnetoelectronic multiferroic effect, flexoelectronic proximity effect and topological spin texture. This review article presents a unified picture of current status and future directions that will provide the scientists a stepping stone for research in the field of flexoelectricity mediated CE and interlayer charge transfer mediated behavior in the micro/nanoscale heterostructures of the conducting materials.