title: Gap states in pentacene thin film induced by inert gas exposure.
abstract: We studied gas-exposure effects on pentacene (Pn) films on SiO2 and Au(111) substrates by ultrahigh sensitivity photoelectron spectroscopy, which can detect the density of states of ∼10(16) states eV-1 cm-3 comparable to electrical measurements. The results show the striking effects for Pn/SiO2: exposure to inert gas (N2 and Ar) produces a sharp rise in gap states from ∼10(16) to ∼10(18) states eV-1 cm-3 and pushes the Fermi level closer to the valence band (0.15-0.17 eV), as does exposure to O2 (0.20 eV), while no such gas-exposure effect is observed for Pn/Au(111). The results demonstrate that these gap states originate from small imperfections in the Pn packing structure, which are induced by gas penetration into the film through the crystal grain boundaries.
authors.affiliation: Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan. fabio@restaff.chiba-u.jp
authors.forename: Fabio
authors.initials: F
authors.lastname: Bussolotti
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kera
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kudo
authors.forename: Antoine
authors.initials: A
authors.lastname: Kahn
authors.forename: Nobuo
authors.initials: N
authors.lastname: Ueno