posted on 2021-09-23, 14:07authored byKeitaro Eguchi, Hideyuki Murata
The
ionization energy (IE) of pentacene in two- and three-dimensional
(2D and 3D) thin films and its evolution with coverage were studied
via photoelectron yield spectroscopy in ambient conditions. In the
2D thin films, the IE of pentacene was found to be nearly constant
at 4.91 eV, irrespective of its island size, for an average island
size exceeding 1.6 × 104 nm2. In the 3D
thin films, however, a reduction in IE by 0.04 eV was clearly observed
upon stacking an additional molecular layer on top of the monolayer
film, and the IE decreased to 4.73 eV at 20 monolayers. These experimental
findings demonstrate the IE evolution in the buried layers of the
3D thin films and the significant impact of the neighboring molecular
layers on the IE in layered systems with molecular aggregation.