Probing motion of electric dipoles and carriers in organic monolayers by Maxwell Displacement Current and optical second harmonic generation

Probing and modeling of surface polarization phenomena originating from dipoles and electrons in organic materials are studied. We use an electrical measurement that can directly probe orientational dipolar motion in monolayers by Maxwell Displacement Current, and show that a two-dimensional domain shape is dependent on electrostatic energy stored in the domain owing to the polar orientational alignment of permanent dipoles. Also, we demonstrate a novel optical second harmonic generation technique that allows carrier motion in active layers of organic field-effect transistors to be directly probed as the migration of electric field. We conclude that probing of electric field generated from moving charged particles, e.g., dipoles and electrons, at the interface is a common concept for studying dielectric polarization and its related two-dimensional interfacial phenomena in organic materials.