Relative permittivity and Hubbard U of pentacene extracted from scanning tunneling microscopy studies of p-doped films

Temperature-dependent I–V measurements determine that pentacene is effectively p-doped by tetrafluoro-tetracyanoquinodimethane (F4-TCNQ). It has been shown by scanning tunneling microscopy (STM) that the donated hole is localized by the ionized dopant counter potential, and that the hole can be visualized [4]. Here, it is argued that the effect of the localized hole on STM images should depend on distance as 1/ϵr, as per the Coulomb potential. By fitting line profiles of localized hole features to the Coulomb potential, it is shown that approximate values for the relative permittivity and Hubbard U of pentacene can be extracted.