title: Photoexcited State Confinement in Two-Dimensional Crystalline Anthracene Monolayer at Room Temperature.
abstract: Organic thin film electronics place a high demand on bottom-up technology to form a two-dimensionally (2D) functional unit consisting of a single molecular crystalline layer bound to a layered structure. As the strong interaction between a substrate and molecules makes it difficult to evaluate the electronic properties of organic films, the nature of electronic excited states has not been elucidated. Here, we study a 2D crystalline anthracene monolayer electronically decoupled by alkanethiolates on a gold substrate using scanning tunneling microscopy and time-resolved two-photon photoemission spectroscopy and unravel the geometric/electronic structures and excited electron dynamics. Our data reveal that dispersive 2D excited electrons on the surface can be highly coupled with an annihilation of nondispersive excitons that facilitate electron emission with vibronic interaction. Our results provide a fundamental framework for understanding photoexcited anthracene monolayer and show how the coupling between dispersive and nondispersive excited states may assist charge separation in crystalline molecular layers.
authors.affiliation: Keio Institute of Pure and Applied Science (KiPAS), Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Shibuta
authors.affiliation: Nakajima Designer Nanocluster Assembly Project, ERATO, Japan Science and Technology Agency (JST) , 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan.|Department of Chemistry, Faculty of Science and Technology, Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Hirata
authors.affiliation: Nakajima Designer Nanocluster Assembly Project, ERATO, Japan Science and Technology Agency (JST) , 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan.|Department of Chemistry, Faculty of Science and Technology, Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Eguchi
authors.affiliation: Keio Institute of Pure and Applied Science (KiPAS), Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.|Nakajima Designer Nanocluster Assembly Project, ERATO, Japan Science and Technology Agency (JST) , 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan.|Department of Chemistry, Faculty of Science and Technology, Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors.forename: Atsushi
authors.identifier: 0000-0003-2650-5608
authors.initials: A
authors.lastname: Nakajima
keywords: electron dynamics; excitons; organic devices; self-assembled monolayer; two-dimensional crystal; two-photon photoemission