A Model for the Characterization of the Polarizability of Thin Films Independently of the Thickness of the Film

Abstract

The dielectric properties of thin films can be modified relative to the bulk material because the interaction between film and substrate influences the mobility of the atoms or molecules in the first layers. Here we show that a strong scale effect occurs in nanometer size octadecylammine thin films. This effect is attributed to the different distribution of molecules depending on the size of the film. To accurately describe this effect, we have developed a model which is a reinterpretation of the linearized Thomas-Fermi approximation. Within this model, we have been able to characterize the polarizability of thin films independently of the thickness of the film.

Electric Field Control of Molecular Charge State in a Single-Component 2D Organic Nanoarray

“…These values are similar to those reported for NaCl/Au(111) and NaCl/Ag(100) and are consistent with the weak DCA–Ag(111) interaction observed and the fact that DCA behaves effectively on Ag(111) as on a thin insulator. For NaCl/Au(111), ϵ r increases with increasing film thickness due to size effects in the ultrathin material, , consistent with DCA/Ag(111) where ϵ r increases with d . The relative dielectric constant ϵ r is a measure of the local out-of-plane polarizability of DCA/Ag(111).…”

“…These values are similar to those reported for NaCl/Au(111) 54 and NaCl/ Ag(100) 55 and are consistent with the weak DCA−Ag(111) interaction observed and the fact that DCA behaves effectively on Ag(111) as on a thin insulator. For NaCl/Au(111), ϵ r increases with increasing film thickness due to size effects in the ultrathin material, 56,57 and larger d eff (due to a smaller ϵ r ); whereas an electron injected into the LUMO is easier to screen by the metal for M 0 than for M 10 , it is not so for an external electric field applied perpendicular to the molecule−surface system. These effects are responsible for the substantial variations in the susceptibility of charging observed for the different molecules.…”