Surface polarization phenomena of organic monolayers and electron transport

Nano-electrostatic phenomena at the interfaces between metal/organic and organic/organic materials are discussed from the viewpoint of dielectrics physics. Focusing on two important origins of surface polarization phenomena, i.e., orientational ordering of polar molecules and displacement of excess charges, surface polarization phenomena of organic monomolecular films are discussed. Using orientational order parameters defined by Legendre polynomials, surface polarization due to the alignment of dipoles is discussed. The Maxwell displacement current (MDC) and optical second harmonic generation (SHG) measurements are shown to be effective for probing the spontaneous and nonlinear surface polarization phenomena of monolayers. On the one hand, the concept of surface Fermi level is introduced to discuss the nano-electrostatic phenomena due to displacement of excess electrons at the interface between metal and organic films. Experimental evidence of surface polarization due to displacement of excess charges is shown on the basis of single electron tunneling (SET) characteristics.